claude / claude-fable-5 session: 3797c0bb-21bf-4ce4-9897-446e9d3626a7 cwd: /workspace/problems/05_topk_bitonic
INCOMPLETE SESSION. hit wall-clock budget (SIGTERM). The transcript below is usable but may be missing the agent's final tool calls or summary. Don't score this run as a clean failure or success.
harness
claude
model
claude-fable-5
turns
57
tools called
33
events
104
input toks
4,154
output toks
4,448
cache hit
3,204,466
solution.py
final answer
benchmark.log
check.log
result.json
"""Single-kernel top-k for SM120 (RTX PRO 6000).

Strategy: one fused CUDA kernel per forward. Each row is split across one or
more blocks; each warp streams its span keeping a register-resident sorted
top-K (Faiss WarpSelect-style threshold + per-lane candidate queue, bitonic
networks via warp shuffles). Warps merge through shared memory. Multi-split
rows publish packed (key|idx) candidates to a scratch buffer; the last block
per row (device-scope acq-rel counter) merges them and writes the output.

Values travel as a monotonic fp32->u32 key packed with the source index into
a u64, so all comparisons are single integer compares and the exact fp32 bits
round-trip on output.
"""
import os

import torch
from torch.utils.cpp_extension import load_inline

_CPP_SRC = r"""
#include <cstdint>
int64_t topk_configure(int64_t batch, int64_t n, int64_t k, int64_t splits,
                       int64_t threads, int64_t vals_ptr, int64_t idx_ptr);
void topk_run(int64_t handle, int64_t x_ptr);
void topk_run_cached(int64_t handle);
"""

_CUDA_SRC = r"""
#include <cuda_runtime.h>
#include <cuda/atomic>
#include <c10/cuda/CUDAStream.h>
#include <c10/cuda/CUDAGuard.h>
#include <ATen/cuda/CUDAContext.h>
#include <torch/extension.h>
#include <vector>

using u32 = unsigned int;
using u64 = unsigned long long;

#define FULL_MASK 0xffffffffu

// Monotonic transform: descending float order == descending u32 key order.
__device__ __forceinline__ u32 fkey(u32 bits) {
    return bits ^ (u32(int(bits) >> 31) | 0x80000000u);
}
__device__ __forceinline__ float unkey(u32 key) {
    u32 b = key ^ ((key & 0x80000000u) ? 0x80000000u : 0xFFFFFFFFu);
    return __uint_as_float(b);
}
__device__ __forceinline__ u64 umax(u64 a, u64 b) { return a > b ? a : b; }
__device__ __forceinline__ u64 umin(u64 a, u64 b) { return a < b ? a : b; }

// Descending bitonic merge of 32 elements held one-per-lane.
__device__ __forceinline__ void bmerge32(u64 &v, int lane) {
    #pragma unroll
    for (int d = 16; d >= 1; d >>= 1) {
        u64 o = __shfl_xor_sync(FULL_MASK, v, d);
        v = ((lane & d) == 0) ? umax(v, o) : umin(v, o);
    }
}

// Descending bitonic merge of 64 elements: element e = j*32+lane in regs a0,a1.
__device__ __forceinline__ void bmerge64(u64 &a0, u64 &a1, int lane) {
    u64 lo = umin(a0, a1);
    a0 = umax(a0, a1);
    a1 = lo;
    bmerge32(a0, lane);
    bmerge32(a1, lane);
}

// Full descending sort of 32 elements one-per-lane.
__device__ __forceinline__ void sort32(u64 &v, int lane) {
    #pragma unroll
    for (int s = 2; s <= 32; s <<= 1) {
        #pragma unroll
        for (int d = s >> 1; d >= 1; d >>= 1) {
            u64 o = __shfl_xor_sync(FULL_MASK, v, d);
            bool i_low = (lane & d) == 0;
            bool asc = (lane & s) != 0;   // gives overall descending
            bool take_max = i_low ^ asc;
            v = take_max ? umax(v, o) : umin(v, o);
        }
    }
}

// ---------- Warp-resident top-K buffer -------------------------------------
// R registers per lane; element e = j*32 + lane; sorted descending by e.

template <int R> struct WarpBuf;

template <> struct WarpBuf<1> {
    u64 b0;
    __device__ __forceinline__ void init() { b0 = 0; }
    // Merge a descending-sorted 32-vector (one per lane) into the buffer.
    __device__ __forceinline__ void merge_sorted32(u64 v, int lane) {
        u64 r = __shfl_xor_sync(FULL_MASK, v, 31);  // reversed
        b0 = umax(b0, r);
        bmerge32(b0, lane);
    }
    __device__ __forceinline__ u32 kth_key(int k, int lane) {
        u64 e = __shfl_sync(FULL_MASK, b0, (k - 1) & 31);
        return (u32)(e >> 32);
    }
    __device__ __forceinline__ void store(u64 *dst, int lane) { dst[lane] = b0; }
    __device__ __forceinline__ void load(const u64 *src, int lane) { b0 = src[lane]; }
    // Merge another descending list of 32 (in shared, reversed addressing).
    __device__ __forceinline__ void merge_list(const u64 *src, int lane) {
        b0 = umax(b0, src[31 - lane]);
        bmerge32(b0, lane);
    }
};

template <> struct WarpBuf<2> {
    u64 b0, b1;
    __device__ __forceinline__ void init() { b0 = 0; b1 = 0; }
    __device__ __forceinline__ void merge_sorted32(u64 v, int lane) {
        // positions 32..63 paired with reversed v
        u64 r = __shfl_xor_sync(FULL_MASK, v, 31);
        b1 = umax(b1, r);
        bmerge64(b0, b1, lane);
    }
    __device__ __forceinline__ u32 kth_key(int k, int lane) {
        u64 e = (k <= 32) ? __shfl_sync(FULL_MASK, b0, (k - 1) & 31)
                          : __shfl_sync(FULL_MASK, b1, (k - 1) & 31);
        return (u32)(e >> 32);
    }
    __device__ __forceinline__ void store(u64 *dst, int lane) {
        dst[lane] = b0; dst[32 + lane] = b1;
    }
    __device__ __forceinline__ void load(const u64 *src, int lane) {
        b0 = src[lane]; b1 = src[32 + lane];
    }
    __device__ __forceinline__ void merge_list(const u64 *src, int lane) {
        b0 = umax(b0, src[63 - lane]);
        b1 = umax(b1, src[31 - lane]);
        bmerge64(b0, b1, lane);
    }
};

// ---------- Streaming select: queue + flush ---------------------------------

template <int R, int T> struct WarpSelect {
    WarpBuf<R> buf;
    u64 q[T];
    int cnt;
    u32 thresh;
    int k;
    int lane;

    __device__ __forceinline__ void init(int k_, int lane_) {
        buf.init();
        cnt = 0;
        thresh = 0;
        k = k_;
        lane = lane_;
    }

    __device__ __forceinline__ void flush() {
        #pragma unroll
        for (int j = 0; j < T; ++j) {
            // skip slots empty across the whole warp
            if (!__ballot_sync(FULL_MASK, cnt > j)) break;
            u64 v = (j < cnt) ? q[j] : 0ULL;
            sort32(v, lane);
            buf.merge_sorted32(v, lane);
        }
        cnt = 0;
        thresh = buf.kth_key(k, lane);
    }

    __device__ __forceinline__ void push(u32 key, u32 idx) {
        if (key > thresh) {
            q[cnt++] = ((u64)key << 32) | (u64)idx;
        }
        if (__ballot_sync(FULL_MASK, cnt == T)) flush();
    }

    // Fast path: check 4 candidates with one ballot when none pass.
    __device__ __forceinline__ void push4(u32 k0, u32 k1, u32 k2, u32 k3, u32 i0) {
        u32 m = max(max(k0, k1), max(k2, k3));
        if (__ballot_sync(FULL_MASK, m > thresh)) {
            push(k0, i0);
            push(k1, i0 + 1);
            push(k2, i0 + 2);
            push(k3, i0 + 3);
        }
    }

    __device__ __forceinline__ void finish() {
        if (__ballot_sync(FULL_MASK, cnt > 0)) flush();
    }
};

// ---------- Kernel -----------------------------------------------------------

template <int R, int T, int W>
__global__ void __launch_bounds__(W * 32) topk_kernel(
    const float *__restrict__ x,
    float *__restrict__ out_vals,
    long *__restrict__ out_idx,
    u64 *__restrict__ scratch,   // batch * splits * k
    int *__restrict__ counters,  // batch
    int n, int k, int splits, int chunk, int per_warp, int vec_ok)
{
    constexpr int K32 = 32 * R;
    __shared__ u64 smem[W * K32];
    __shared__ int s_last;

    const int row = blockIdx.y;
    const int split = blockIdx.x;
    const int w = threadIdx.x >> 5;
    const int lane = threadIdx.x & 31;

    const float *xr = x + (size_t)row * n;

    WarpSelect<R, T> sel;
    sel.init(k, lane);

    // ---- Phase A: stream this block's chunk --------------------------------
    {
        const int cbeg = split * chunk;
        const int cend = min(cbeg + chunk, n);
        const int wbeg = cbeg + w * per_warp;
        const int wend = min(wbeg + per_warp, cend);
        if (wbeg < wend) {
            const int span = wend - wbeg;
            const int nfull = vec_ok ? (span >> 7) : 0;  // full 128-elem warp steps
            const float4 *base = reinterpret_cast<const float4 *>(xr + wbeg);
            for (int s = 0; s < nfull; ++s) {
                float4 v = __ldcs(base + s * 32 + lane);
                u32 i0 = (u32)(wbeg + ((s * 32 + lane) << 2));
                sel.push4(fkey(__float_as_uint(v.x)), fkey(__float_as_uint(v.y)),
                          fkey(__float_as_uint(v.z)), fkey(__float_as_uint(v.w)), i0);
            }
            for (int ib = wbeg + (nfull << 7); ib < wend; ib += 32) {
                const int i = ib + lane;
                const bool act = i < wend;
                u32 key = act ? fkey(__float_as_uint(__ldg(xr + i))) : 0u;
                if (__ballot_sync(FULL_MASK, act && key > sel.thresh)) {
                    if (act && key > sel.thresh) sel.q[sel.cnt++] = ((u64)key << 32) | (u64)(u32)i;
                    if (__ballot_sync(FULL_MASK, sel.cnt == T)) sel.flush();
                }
            }
        }
        sel.finish();

        // block merge
        sel.buf.store(smem + w * K32, lane);
        __syncthreads();
        if (w == 0) {
            #pragma unroll 1
            for (int ow = 1; ow < W; ++ow) sel.buf.merge_list(smem + ow * K32, lane);
        }
    }

    if (splits == 1) {
        if (w == 0) {
            u64 e0 = sel.buf.b0;
            if (lane < k) {
                out_vals[(size_t)row * k + lane] = unkey((u32)(e0 >> 32));
                out_idx[(size_t)row * k + lane] = (long)(u32)e0;
            }
            if constexpr (R == 2) {
                u64 e1 = sel.buf.b1;
                int e = 32 + lane;
                if (e < k) {
                    out_vals[(size_t)row * k + e] = unkey((u32)(e1 >> 32));
                    out_idx[(size_t)row * k + e] = (long)(u32)e1;
                }
            }
        }
        return;
    }

    // ---- publish candidates to scratch --------------------------------------
    u64 *srow = scratch + (size_t)row * splits * k;
    if (w == 0) {
        u64 e0 = sel.buf.b0;
        if (lane < k) srow[(size_t)split * k + lane] = e0;
        if constexpr (R == 2) {
            u64 e1 = sel.buf.b1;
            int e = 32 + lane;
            if (e < k) srow[(size_t)split * k + e] = e1;
        }
    }
    __syncthreads();
    if (threadIdx.x == 0) {
        cuda::atomic_ref<int, cuda::thread_scope_device> c(counters[row]);
        int prev = c.fetch_add(1, cuda::memory_order_acq_rel);
        s_last = (prev == splits - 1) ? 1 : 0;
    }
    __syncthreads();
    if (!s_last) return;

    // ---- Phase B: last block merges all candidates --------------------------
    {
        const int C = splits * k;
        sel.init(k, lane);
        const int per_w = (C + W - 1) / W;
        const int beg = w * per_w;
        const int end = min(beg + per_w, C);
        for (int i = beg + lane; ; i += 32) {
            bool act = i < end;
            u64 it = act ? __ldg(srow + i) : 0ULL;
            if (!__ballot_sync(FULL_MASK, act)) break;
            u32 key = (u32)(it >> 32);
            if (__ballot_sync(FULL_MASK, act && key > sel.thresh)) {
                if (act && key > sel.thresh) sel.q[sel.cnt++] = it;
                if (__ballot_sync(FULL_MASK, sel.cnt == T)) sel.flush();
            }
        }
        sel.finish();

        __syncthreads();  // smem reuse
        sel.buf.store(smem + w * K32, lane);
        __syncthreads();
        if (w == 0) {
            #pragma unroll 1
            for (int ow = 1; ow < W; ++ow) sel.buf.merge_list(smem + ow * K32, lane);
            u64 e0 = sel.buf.b0;
            if (lane < k) {
                out_vals[(size_t)row * k + lane] = unkey((u32)(e0 >> 32));
                out_idx[(size_t)row * k + lane] = (long)(u32)e0;
            }
            if constexpr (R == 2) {
                u64 e1 = sel.buf.b1;
                int e = 32 + lane;
                if (e < k) {
                    out_vals[(size_t)row * k + e] = unkey((u32)(e1 >> 32));
                    out_idx[(size_t)row * k + e] = (long)(u32)e1;
                }
            }
        }
        if (threadIdx.x == 0) counters[row] = 0;
    }
}

// ---------- Host side --------------------------------------------------------

struct Cfg {
    const float *x;
    float *vals;
    long *idx;
    u64 *scratch;
    int *counters;
    int batch, n, k, splits, chunk, per_warp, threads;
    int R;
};

static std::vector<Cfg> g_cfgs;

static void launch(const Cfg &c, cudaStream_t st) {
    dim3 grid(c.splits, c.batch);
    dim3 block(c.threads);
    const int W = c.threads / 32;
    const int vec_ok = (c.n % 4 == 0) ? 1 : 0;
    #define LAUNCH(RR, WW) topk_kernel<RR, 4, WW><<<grid, block, 0, st>>>( \
        c.x, c.vals, c.idx, c.scratch, c.counters, c.n, c.k, c.splits, c.chunk, c.per_warp, vec_ok)
    if (c.R == 1) {
        switch (W) {
            case 4: LAUNCH(1, 4); break;
            case 8: LAUNCH(1, 8); break;
            case 16: LAUNCH(1, 16); break;
            default: TORCH_CHECK(false, "bad W");
        }
    } else {
        switch (W) {
            case 4: LAUNCH(2, 4); break;
            case 8: LAUNCH(2, 8); break;
            case 16: LAUNCH(2, 16); break;
            default: TORCH_CHECK(false, "bad W");
        }
    }
    #undef LAUNCH
}

int64_t topk_configure(int64_t batch, int64_t n, int64_t k, int64_t splits,
                       int64_t threads, int64_t vals_ptr, int64_t idx_ptr) {
    Cfg c{};
    c.batch = (int)batch;
    c.n = (int)n;
    c.k = (int)k;
    c.splits = (int)splits;
    c.threads = (int)threads;
    c.R = (k > 32) ? 2 : 1;
    c.chunk = (int)(((n + splits - 1) / splits + 3) & ~3LL);
    // recompute splits so last chunk is non-empty
    c.splits = (c.n + c.chunk - 1) / c.chunk;
    int W = c.threads / 32;
    c.per_warp = ((c.chunk + W - 1) / W + 3) & ~3;
    c.vals = (float *)vals_ptr;
    c.idx = (long *)idx_ptr;
    c.scratch = nullptr;
    c.counters = nullptr;
    if (c.splits > 1) {
        cudaMalloc(&c.scratch, (size_t)c.batch * c.splits * c.k * sizeof(u64));
        cudaMalloc(&c.counters, (size_t)c.batch * sizeof(int));
        cudaMemset(c.counters, 0, (size_t)c.batch * sizeof(int));
    }
    g_cfgs.push_back(c);
    return (int64_t)g_cfgs.size() - 1;
}

void topk_run(int64_t handle, int64_t x_ptr) {
    Cfg &c = g_cfgs[handle];
    c.x = (const float *)x_ptr;
    launch(c, c10::cuda::getCurrentCUDAStream().stream());
}

void topk_run_cached(int64_t handle) {
    const Cfg &c = g_cfgs[handle];
    launch(c, c10::cuda::getCurrentCUDAStream().stream());
}
"""


def _build():
    os.environ.setdefault("TORCH_CUDA_ARCH_LIST", "12.0")
    return load_inline(
        name="topk_sm120_v1",
        cpp_sources=_CPP_SRC,
        cuda_sources=_CUDA_SRC,
        functions=["topk_configure", "topk_run", "topk_run_cached"],
        extra_cuda_cflags=["-O3", "--use_fast_math", "-gencode=arch=compute_120,code=sm_120"],
        verbose=False,
    )


_ext = _build()

# (splits, threads) per (batch, n, k); fallback heuristic otherwise.
_TUNE = {
    (1, 131072, 64): (128, 256),
    (64, 8192, 8): (2, 256),
    (32, 16384, 32): (4, 256),
    (16, 12000, 16): (8, 256),
    (128, 4096, 1): (1, 256),
}


def _pick_cfg(batch: int, n: int, k: int):
    if (batch, n, k) in _TUNE:
        return _TUNE[(batch, n, k)]
    target = 256
    splits = max(1, min(target // max(batch, 1), (n + 255) // 256))
    return splits, 256


class Model(torch.nn.Module):
    def __init__(self, batch: int, n: int, k: int):
        super().__init__()
        self.batch, self.n, self.k = batch, n, k
        self.register_buffer("_dummy", torch.zeros(1))
        dev = torch.device("cuda")
        self._vals = torch.empty(batch, k, dtype=torch.float32, device=dev)
        self._idx = torch.empty(batch, k, dtype=torch.int64, device=dev)
        splits, threads = _pick_cfg(batch, n, k)
        self._handle = _ext.topk_configure(
            batch, n, k, splits, threads, self._vals.data_ptr(), self._idx.data_ptr()
        )
        self._ret = (self._vals, self._idx)
        self._last_ptr = -1
        self._run = _ext.topk_run
        self._run_cached = _ext.topk_run_cached

    def forward(self, x: torch.Tensor):
        p = x.data_ptr()
        if p == self._last_ptr:
            self._run_cached(self._handle)
        else:
            self._last_ptr = p
            self._run(self._handle, p)
        return self._ret

    __call__ = forward


# Module-level shims rebuilt by check.py / benchmark.py per shape.
batch = 64
n = 8192
k = 8


def get_inputs():
    x = torch.randn(batch, n, dtype=torch.float32)
    return [x]


def get_init_inputs():
    return [batch, n, k]
Now a quick scratch correctness test against torch.topk (allowed in scratch files, not in solution.py).
warning: `VIRTUAL_ENV=/home/infatoshi/benchmarks/KernelBench-Hard/.venv` does not match the project environment path `/home/infatoshi/benchmarks/KernelBench-Hard/outputs/runs/20260610_174700_claude_claude-fable-5_05_topk_bitonic/repo/.venv` and will be ignored; use `--active` to target the active environment instead
benchmark_event event=variant_start shape=0 variant=solution ts=2026-06-11T00:34:42.891807+00:00
benchmark_event event=variant_end shape=0 variant=solution ts=2026-06-11T00:34:42.903325+00:00 elapsed_s=0.012 ms=0.024384
shape=0 variant=solution tflops=0.022 gbps=21.533 ms=0.024
shape=0 solution_peak_fraction=0.0120
benchmark_event event=variant_start shape=1 variant=solution ts=2026-06-11T00:34:42.905305+00:00
benchmark_event event=variant_end shape=1 variant=solution ts=2026-06-11T00:34:42.910618+00:00 elapsed_s=0.005 ms=0.014192
shape=1 variant=solution tflops=0.148 gbps=148.203 ms=0.014
shape=1 solution_peak_fraction=0.0823
benchmark_event event=variant_start shape=2 variant=solution ts=2026-06-11T00:34:42.912376+00:00
benchmark_event event=variant_end shape=2 variant=solution ts=2026-06-11T00:34:42.917678+00:00 elapsed_s=0.005 ms=0.015696
shape=2 variant=solution tflops=0.134 gbps=134.393 ms=0.016
shape=2 solution_peak_fraction=0.0747
benchmark_event event=variant_start shape=3 variant=solution ts=2026-06-11T00:34:42.918314+00:00
benchmark_event event=variant_end shape=3 variant=solution ts=2026-06-11T00:34:42.923479+00:00 elapsed_s=0.005 ms=0.011872
shape=3 variant=solution tflops=0.065 gbps=64.949 ms=0.012
shape=3 solution_peak_fraction=0.0361
benchmark_event event=variant_start shape=4 variant=solution ts=2026-06-11T00:34:42.924813+00:00
benchmark_event event=variant_end shape=4 variant=solution ts=2026-06-11T00:34:42.929925+00:00 elapsed_s=0.005 ms=0.010560
shape=4 variant=solution tflops=0.199 gbps=198.739 ms=0.011
shape=4 solution_peak_fraction=0.1104
peak_fraction: 0.0494
RESULT: LOW
warning: `VIRTUAL_ENV=/home/infatoshi/benchmarks/KernelBench-Hard/.venv` does not match the project environment path `/home/infatoshi/benchmarks/KernelBench-Hard/outputs/runs/20260610_174700_claude_claude-fable-5_05_topk_bitonic/repo/.venv` and will be ignored; use `--active` to target the active environment instead
warning: Ignoring existing virtual environment linked to non-existent Python interpreter: /home/infatoshi/benchmarks/KernelBench-Hard/outputs/runs/20260610_174700_claude_claude-fable-5_05_topk_bitonic/repo/.venv/bin/python3 -> python
Using CPython 3.11.15
Removed virtual environment at: /home/infatoshi/benchmarks/KernelBench-Hard/outputs/runs/20260610_174700_claude_claude-fable-5_05_topk_bitonic/repo/.venv
Creating virtual environment at: /home/infatoshi/benchmarks/KernelBench-Hard/outputs/runs/20260610_174700_claude_claude-fable-5_05_topk_bitonic/repo/.venv
   Building kernelbench-hard @ file:///home/infatoshi/benchmarks/KernelBench-Hard/outputs/runs/20260610_174700_claude_claude-fable-5_05_topk_bitonic/repo
      Built kernelbench-hard @ file:///home/infatoshi/benchmarks/KernelBench-Hard/outputs/runs/20260610_174700_claude_claude-fable-5_05_topk_bitonic/repo
Installed 56 packages in 70ms
PASS
{
    "run_id": "20260610_174700_claude_claude-fable-5_05_topk_bitonic",
    "run_group": "",
    "problem": "05_topk_bitonic",
    "harness": "claude",
    "model": "claude-fable-5",
    "reasoning_effort": "max",
    "started_at": "2026-06-10T17:47:00-06:00",
    "harness_finished_at": "2026-06-10T18:32:01-06:00",
    "finished_at": "2026-06-10T18:34:43-06:00",
    "start_epoch": 1781135220,
    "harness_end_epoch": 1781137921,
    "end_epoch": 1781138083,
    "has_solution": true,
    "correct": true,
    "failure_reason": "pass",
    "retryable_infra_failure": false,
    "minimum_useful_output_tokens": 5000,
    "peak_fraction": 0.0494,
    "template_mutated": false,
    "elapsed_seconds": 2701,
    "total_elapsed_seconds": 2863,
    "check_elapsed_seconds": 29,
    "benchmark_elapsed_seconds": 133,
    "check_timeout_seconds": 180,
    "benchmark_timeout_seconds": 1800,
    "check_exit_code": 0,
    "benchmark_exit_code": 0,
    "harness_exit_code": 124,
    "session_complete": false,
    "agent_cuda_disabled": false,
    "agent_container": true,
    "agent_container_image": "nvcr.io/nvidia/tensorrt-llm/release:latest",
    "agent_container_network": "bridge",
    "gpu_queue_mode": "agent_container_native_profiling_path_wrapper_gpu_lock",
    "output_tokens_per_second": 1.6467974824139209,
    "usage": {"input_tokens": 4154, "output_tokens": 4448, "cache_read_tokens": 3204466, "cache_creation_tokens": 358376, "reasoning_tokens": null, "total_cost_usd": null}
}

timeline (104 events)

system — init
session start cwd=/workspace/problems/05_topk_bitonic model=claude-fable-5 permissions=bypassPermissions
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I'll start by exploring the workspace to understand the problem setup.
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Bash
args
{
  "command": "ls -la /workspace/problems/05_topk_bitonic/",
  "description": "List files in problem workspace"
}
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assistant
Read /workspace/problems/05_topk_bitonic/reference.py
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/reference.py"
}
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tool
stdout (1711 chars) — TRUNCATED
1	"""Naive top-k reference: torch.topk over the last dim.
2	
3	This is the correctness oracle. The agent's solution must produce the same
4	top-k values (and equivalent indices modulo ties) within the tolerance
5	declared in problem.yaml. Note that solution.py is FORBIDDEN from calling
6	torch.topk / torch.sort / torch.kthvalue (see problem.yaml).
7	"""
8	import torch
9	import torch.nn as nn
10	
11	OP_TYPE = "topk"
12	SUPPORTED_PRECISIONS = ["fp32"]
13	HARDWARE_REQUIRED = ["RTX_PRO_6000", "H100", "B200"]
14	
15	
16	class Model(nn.Module):
17	    """Top-k over the last dim of a 2D tensor.
18	
19	    Input:
20	        x: (batch, n) fp32
21	    Output:
22	        values:  (batch, k) fp32, sorted descending
23	        indices: (batch, k) int64, into the last dim of x
24	    """
25	
26	    def __init__(self, batch: int, n: int, k: int):
27	        super().__init__()
28	        self.batch, self.n, self.k = batch, n, k
29	        # No learned parameters, but declare a dummy buffer so state_dict
30	        # is non-empty and load_state_dict(strict=True) is meaningful.
31	        self.register_buffer("_dummy", torch.zeros(1))
32	
33	    def forward(self, x: torch.Tensor):
34	        values, indices = torch.topk(x, k=self.k, dim=-1, largest=True, sorted=True)
35	        return values, indices
36	
37	
38	# Module-level shims rebuilt by check.py / benchmark.py per shape.
39	batch = 64
40	n = 8192
41	k = 8
42	
43	
44	def get_inputs():
45	    # fp32 input drawn from a roughly Gaussian dist

... (211 more chars)
subagent · 0 events · 0 tools
tool
stdout (459 chars)
total 44
drwxrwxr-x 2 1002 1002 4096 Jun 10 23:47 .
drwxrwxr-x 3 1002 1002 4096 Jun 10 23:47 ..
-rw-rw-r-- 1 1002 1002 2084 Apr 27 09:21 PROMPT.txt
-rw-rw-r-- 1 1002 1002 5078 Jun  1 21:05 benchmark.py
-rw-rw-r-- 1 1002 1002 6288 Jun  2 01:09 check.py
-rw-rw-r-- 1 1002 1002 2199 Apr 26 04:20 problem.yaml
-rw-rw-r-- 1 1002 1002 1561 Apr 26 04:19 reference.py
-rw-rw-r-- 1 1002 1002  933 Apr 26 04:19 shapes.py
-rw-rw-r-- 1 1002 1002  945 Apr 26 04:20 sota.py
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Read /workspace/problems/05_topk_bitonic/check.py
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/check.py"
}
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tool
stdout (6810 chars) — TRUNCATED
1	"""Correctness runner for TopK.
2	
3	Runs solution.Model vs reference.Model across all shapes in shapes.py, 3 seeds
4	each. Top-k correctness has two parts:
5	
6	  1. VALUES: sol_values must match ref_values within fp32 tol. Both are
7	     returned sorted descending, so positional comparison is well-defined.
8	  2. INDICES: lenient — we do NOT require sol_indices == ref_indices because
9	     ties in x can yield multiple valid index sets. Instead we gather x at
10	     sol_indices and check those values match ref_values within tol. This
11	     catches "wrong indices" without false-failing on legitimate tie-breaks.
12	
13	Also rejects forbidden ops by grep.
14	"""
15	import re
16	import sys
17	from pathlib import Path
18	
19	import torch
20	import yaml
21	
22	REPO_ROOT = Path(__file__).resolve().parents[2]
23	sys.path.insert(0, str(REPO_ROOT))
24	
25	from src.eval.correctness import check_correctness  # noqa: E402
26	from src.eval.numeric_stress import (  # noqa: E402
27	    numeric_stress_cases,
28	    numeric_stress_context,
29	    tolerance_for_case,
30	)
31	
32	
33	def main():
34	    try:
35	        import reference
36	        import shapes
37	        import solution
38	    except Exception as e:
39	        print(f"FAIL: import error: {e}")
40	        sys.exit(1)
41	
42	    problem_yaml = Path("problem.yaml")
43	    meta = yaml.safe_load(problem_yaml.read_text()) if problem_yaml.exists() else {}
44	
45	    # --- Forbidden-op check --------------------------------------

... (5310 more chars)
assistant
Read /workspace/problems/05_topk_bitonic/benchmark.py
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/benchmark.py"
}
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tool
stdout (5552 chars) — TRUNCATED
1	"""Roofline benchmark for TopK.
2	
3	For each shape: times eager reference (torch.topk), compiled reference, SOTA
4	(also torch.topk — see sota.py), and the agent's solution. Reports achieved
5	TFLOPS, GB/s, and peak_fraction (vs DRAM bandwidth, since this is memory-bound).
6	
7	Output lines the harness picks up:
8	  shape=<idx> variant=<name> tflops=<N> gbps=<N> ms=<N>
9	  peak_fraction: <N>  (geomean over shapes of solution's peak_fraction)
10	"""
11	import sys
12	from math import exp, log
13	from pathlib import Path
14	
15	import torch
16	import yaml
17	
18	REPO_ROOT = Path(__file__).resolve().parents[2]
19	sys.path.insert(0, str(REPO_ROOT))
20	
21	from src.eval.roofline import compute_gbps, compute_tflops, peak_fraction  # noqa: E402
22	from src.eval.timing import benchmark_baselines_enabled, time_variant  # noqa: E402
23	from src.hardware import get as get_hw  # noqa: E402
24	
25	
26	def _eval_formula(expr: str, vars: dict) -> float:
27	    return float(eval(expr, {"__builtins__": {}}, vars))
28	
29	
30	def main():
31	    import reference
32	    import shapes
33	    import solution
34	
35	    meta = yaml.safe_load(Path("problem.yaml").read_text())
36	    hw = get_hw(meta["hardware"][0])
37	    peak_tflops = hw.peak_tflops_dense.get(meta["peak_tflops_key"], 0.0)
38	    peak_gbps = hw.peak_bandwidth_gb_s
39	    regime = meta.get("regime", "memory")
40	    flops_formula = meta["flops_formula"]
41	    bytes_formula = meta["bytes_formula"]
42	    num_perf_trials = int(meta.

... (4052 more chars)
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Read /workspace/problems/05_topk_bitonic/shapes.py
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/shapes.py"
}
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tool
stdout (976 chars)
1	"""Canonical shape sweep for TopK.
2	
3	Mix of:
4	  - decoder vocab top-k (single sequence, very large n, moderate k) — pure
5	    bandwidth test; the input read dominates everything.
6	  - prefill / batched attention top-k (many rows, moderate n, small k) — tests
7	    per-row parallelism and shared-memory bitonic networks.
8	  - non-power-of-2 n stress case — bitonic sort networks naturally want
9	    powers of two; this forces the agent to handle padding or partial sorts.
10	  - small-k limit — k=1 (argmax) is a degenerate but useful sanity case.
11	"""
12	
13	SHAPES = [
14	    {"batch": 1,   "n": 131072, "k": 64},   # decoder vocab top-k (Llama vocab ~128k)
15	    {"batch": 64,  "n": 8192,   "k": 8},    # prefill / attention top-k
16	    {"batch": 32,  "n": 16384,  "k": 32},   # mid-size batched
17	    {"batch": 16,  "n": 12000,  "k": 16},   # non-power-of-2 n stress
18	    {"batch": 128, "n": 4096,   "k": 1},    # batched argmax (k=1 corner case)
19	]
20	
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Read /workspace/problems/05_topk_bitonic/problem.yaml
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/problem.yaml"
}
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tool
stdout (2359 chars) — TRUNCATED
1	name: 05_topk_bitonic
2	display_name: "TopK via Bitonic Sort"
3	precision: fp32
4	regime: memory
5	
6	# Top-k is dominated by the input read (small output, no reduction over k).
7	# Comparator-network FLOPs are not the bottleneck on real hardware, so we
8	# track them but score on bandwidth.
9	flops_formula: "batch * n * 4"            # ~O(n log^2 n) compares total, but the
10	                                          # bitonic network is so cheap relative
11	                                          # to memory that a coarse 4*n estimate
12	                                          # is fine for telemetry only.
13	bytes_formula: "batch * n * 4 + batch * k * (4 + 8)"  # fp32 input read + (fp32 value + int64 idx) output
14	
15	hardware: [RTX_PRO_6000]
16	peak_tflops_key: fp32
17	peak_bandwidth_key: dram
18	
19	# Top-k correctness:
20	#   - VALUES must match within fp32 atol/rtol (the kth largest value is
21	#     well-defined modulo float-equal ties, so we use a loose-ish tol).
22	#   - INDICES are checked leniently: for each row, the multiset of returned
23	#     indices must select values that match ref values within tol. Direct
24	#     index equality is NOT required (ties in x can yield different valid
25	#     index sets).
26	tolerance:
27	  float32: 1.0e-4
28	
29	# Forbidden ops — using any of these in solution.py fails correctness post-hoc.
30	# This problem is about IMPLEMENTING the selection, not dispatching to PyTorch's
31	# tuned top-k. torch.sort is also banned b

... (859 more chars)
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Read /workspace/problems/05_topk_bitonic/sota.py
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/sota.py"
}
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tool
stdout (1012 chars)
1	"""SOTA reference for TopK: torch.topk itself.
2	
3	torch.topk dispatches to a CUB-backed kernel that uses radix-select for
4	moderate k and a tuned bitonic sort for small n. It is the bar the agent's
5	hand-rolled bitonic kernel must beat. There is no obvious vendor library that
6	does better on the (batch, n, k) shape mix we evaluate — Faiss BlockSelect is
7	specialized for k>=32 with much larger n, and CUB's DeviceSegmentedRadixSort
8	sorts the full row (overkill for top-k).
9	
10	This file is INTENTIONALLY allowed to call torch.topk because it is the SOTA
11	oracle, not the agent's submission. The agent's solution.py is forbidden from
12	using torch.topk (see problem.yaml.forbidden).
13	"""
14	from __future__ import annotations
15	
16	import torch
17	
18	
19	def sota_forward(x: torch.Tensor, k: int):
20	    """Best-available top-k reference. x: (batch, n) fp32."""
21	    return torch.topk(x, k=k, dim=-1, largest=True, sorted=True)
22	
23	
24	def is_available() -> bool:
25	    return True
26	
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Now let me look at the evaluation harness code to understand how timing is measured.
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Bash
args
{
  "command": "ls /workspace/ && ls /workspace/src/eval/ 2>/dev/null",
  "description": "List workspace and eval source directories"
}
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subagent · 0 events · 0 tools
tool
stdout (134 chars)
problems
pyproject.toml
src
uv.lock
__init__.py
__pycache__
correctness.py
numeric_stress.py
report.py
roofline.py
shapes.py
timing.py
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Read /workspace/src/eval/timing.py
args
{
  "file_path": "/workspace/src/eval/timing.py"
}
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tool
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1	"""Centralized GPU timing for benchmark.py files.
2	
3	All problems' benchmark.py should call `time_fn` from here so we have one
4	implementation of warmup, L2 flush, and CUDA event capture to maintain.
5	
6	Methodology:
7	  - 10 warmup calls absorb Triton autotune (typical ~7 configs) and
8	    torch.compile reduce-overhead CUDA-graph capture.
9	  - Between each timed call, `_l2_flush()` writes 128 MB to evict L2
10	    (Blackwell L2 is 96 MB; we want any prior L2 contents flushed so
11	    we measure HBM-load bandwidth, not L2-cached bandwidth).
12	  - GPU timing via cuda.Event with synchronize() AFTER record() but
13	    BEFORE elapsed_time() — the canonical NVIDIA pattern.
14	  - Reported value is the median of `iters` trials, robust to outliers.
15	
16	Notes / known biases not addressed here:
17	  - torch.compile(mode="reduce-overhead") gets CUDA graphs which eliminate
18	    launch overhead. Custom Triton/CUDA kernels do NOT get this treatment.
19	    On small shapes where launch overhead matters, this gives compile an
20	    artificial advantage. We accept this as the cost of using the agreed
21	    "compiled" baseline policy.
22	  - cuBLAS / cuDNN allocate workspaces on first call. 10 warmup absorbs.
23	  - Median over a fairly small number of trials (default 30) is fine for
24	    headline numbers but won't catch bimodal distributions. Use --extra
25	    instrumentation if you ever care.
26	"""
27	from __future__ import annotations
28	
29	import os
30	import re
31	

... (3182 more chars)
assistant
Read /workspace/src/eval/numeric_stress.py
args
{
  "file_path": "/workspace/src/eval/numeric_stress.py"
}
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tool
stdout (6656 chars) — TRUNCATED
1	"""Numeric distribution stress cases for correctness checks.
2	
3	These cases are not hidden shapes. They rerun the same shape/seed validation
4	under a few scale regimes that catch kernels that only work for the nominal
5	N(0, 1)-ish inputs.
6	"""
7	from __future__ import annotations
8	
9	import os
10	from collections.abc import Iterator, Mapping, Sequence
11	from contextlib import contextmanager
12	from dataclasses import dataclass, field
13	
14	import torch
15	
16	ToleranceOverride = Mapping[str, float | Mapping[str, float]]
17	
18	
19	@dataclass(frozen=True)
20	class NumericStressCase:
21	    name: str
22	    input_scales: Mapping[int, float] = field(default_factory=dict)
23	    state_scales: Mapping[str, float] = field(default_factory=dict)
24	    tolerance: ToleranceOverride | None = None
25	
26	
27	NOMINAL_CASE = NumericStressCase("nominal")
28	
29	_SMALL_BF16 = {"bfloat16": {"atol": 1e-4, "rtol": 5e-2}}
30	_MED_BF16 = {"bfloat16": {"atol": 5e-4, "rtol": 5e-2}}
31	_LARGE_BF16 = {"bfloat16": {"atol": 2e-1, "rtol": 5e-2}}
32	_TINY_FP32 = {"float32": {"atol": 1e-7, "rtol": 1e-4}}
33	_LARGE_FP32 = {"float32": {"atol": 1e-1, "rtol": 1e-4}}
34	
35	_CASES: dict[str, tuple[NumericStressCase, ...]] = {
36	    "01_fp8_gemm": (
37	        NumericStressCase("small_input", input_scales={0: 1e-3}, tolerance=_SMALL_BF16),
38	        NumericStressCase("large_input", input_scales={0: 64.0}, tolerance=_LARGE_BF16),
39	        NumericStressCase(
40	            "small_weight",
41	      

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Bash
args
{
  "command": "nvidia-smi && uv run python -c \"import torch; print(torch.__version__, torch.version.cuda); print(torch.cuda.get_device_name(0)); print(torch.cuda.get_device_properties(0))\"",
  "description": "Check GPU and torch environment"
}
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subagent · 0 events · 0 tools
tool
stdout (2543 chars) — TRUNCATED
Wed Jun 10 23:58:51 2026       
+-----------------------------------------------------------------------------------------+
| NVIDIA-SMI 610.43.02              KMD Version: 610.43.02     CUDA UMD Version: 13.3     |
+-----------------------------------------+------------------------+----------------------+
| GPU  Name                 Persistence-M | Bus-Id          Disp.A | Volatile Uncorr. ECC |
| Fan  Temp   Perf          Pwr:Usage/Cap |           Memory-Usage | GPU-Util  Compute M. |
|                                         |                        |               MIG M. |
|=========================================+========================+======================|
|   0  NVIDIA RTX PRO 6000 Blac...    On  |   00000000:01:00.0 Off |                  Off |
| 32%   45C    P0             90W /  600W |      15MiB /  97887MiB |      0%      Default |
|                                         |                        |                  N/A |
+-----------------------------------------+------------------------+----------------------+

+-----------------------------------------------------------------------------------------+
| Processes:                                                                              |
|  GPU   GI   CI              PID   Type   Process name                        GPU Memory |
|        ID   ID                                                               Usage      |
|======================================================================================

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Bash
args
{
  "command": "cat /workspace/src/eval/roofline.py /workspace/src/eval/correctness.py | head -120 && grep -rn \"RTX_PRO_6000\" /workspace/src/hardware* 2>/dev/null | head; ls /workspace/src/",
  "description": "Read roofline, correctness, hardware specs"
}
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subagent · 0 events · 0 tools
tool
stdout (4595 chars) — TRUNCATED
"""Roofline math: achieved TFLOPS / GB/s, peak fraction.

FLOPS and bytes formulas come from the problem's `problem.yaml`. They are the
dense-equivalent algorithmic work; kernels that skip work (sparsity, early
exit) are still measured against the dense cost.
"""
from __future__ import annotations


def compute_tflops(flops: float, time_ms: float) -> float:
    """flops per invocation and wall time in ms -> TFLOPS."""
    if time_ms <= 0:
        return 0.0
    return flops / (time_ms * 1e-3) / 1e12


def compute_gbps(bytes_moved: float, time_ms: float) -> float:
    """bytes per invocation and wall time in ms -> GB/s."""
    if time_ms <= 0:
        return 0.0
    return bytes_moved / (time_ms * 1e-3) / 1e9


def peak_fraction(
    achieved: float,
    peak: float,
) -> float:
    """Return achieved / peak, clamped to [0, infinity)."""
    if peak <= 0:
        return 0.0
    return max(0.0, achieved / peak)
"""Per-dtype correctness tolerance.

Stanford's KernelBench uses 1e-4 atol/rtol for fp32 and 1e-2 for fp16/bf16.
We extend to fp8 (0.1, permissive) and int (exact).
"""
from __future__ import annotations

import torch

DEFAULT_TOLERANCE = {
    torch.float32: {"atol": 1e-4, "rtol": 1e-4},
    torch.float16: {"atol": 1e-2, "rtol": 1e-2},
    torch.bfloat16: {"atol": 1e-2, "rtol": 1e-2},
    torch.float8_e4m3fn: {"atol": 1e-1, "rtol": 1e-1},
    torch.float8_e5m2: {"atol": 1e-1, "rtol": 1e-1},
    torch.int8: {"atol": 0, "rtol": 0},
    torch.int32: {"atol": 0, "rtol": 0},

... (3095 more chars)
assistant
Read /workspace/src/hardware/rtx_pro_6000.py
args
{
  "file_path": "/workspace/src/hardware/rtx_pro_6000.py"
}
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tool
stdout (987 chars)
1	"""RTX PRO 6000 Blackwell Workstation — SM120, consumer-lineage Blackwell.
2	
3	Peak tensor-core throughputs are dense-matrix advertised peaks. Actual kernels
4	will see 60-85% of peak on well-tuned code.
5	"""
6	from dataclasses import dataclass
7	
8	
9	@dataclass(frozen=True)
10	class HardwareTarget:
11	    name: str
12	    sm: str
13	    vram_gb: int
14	    peak_bandwidth_gb_s: float  # DRAM
15	    peak_tflops_dense: dict[str, float]  # dtype -> TFLOPS
16	
17	
18	RTX_PRO_6000 = HardwareTarget(
19	    name="RTX PRO 6000 Blackwell Workstation",
20	    sm="sm_120a",
21	    vram_gb=96,
22	    peak_bandwidth_gb_s=1800.0,
23	    peak_tflops_dense={
24	        "fp4": 800.0,
25	        "nvfp4": 800.0,
26	        "mxfp4": 800.0,
27	        "fp6": 800.0,
28	        "fp8": 400.0,
29	        "bf16": 200.0,
30	        "fp16": 200.0,
31	        "tf32": 100.0,
32	        "fp32": 12.0,  # non-tensor-core SIMT fp32
33	        "int8": 400.0,
34	        "int4": 800.0,
35	    },
36	)
37	
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Bash
args
{
  "command": "which nvcc; nvcc --version 2>/dev/null | tail -2; echo \"---\"; ls /usr/local/ | head",
  "description": "Check nvcc availability"
}
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subagent · 19 events · 8 tools
tool
stdout (284 chars)
Command running in background with ID: bjz2w3tbp. Output is being written to: /tmp/claude-1002/-workspace-problems-05-topk-bitonic/3797c0bb-21bf-4ce4-9897-446e9d3626a7/tasks/bjz2w3tbp.output. You will be notified when it completes. To check interim output, use Read on that file path.
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Read /tmp/claude-1002/-workspace-problems-05-topk-bitonic/3797c0bb-21bf-4ce4-9897-446e9d3626a7/tasks/bjz2w3tbp.output
args
{
  "file_path": "/tmp/claude-1002/-workspace-problems-05-topk-bitonic/3797c0bb-21bf-4ce4-9897-446e9d3626a7/tasks/bjz2w3tbp.output"
}
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tool
stdout (18 chars)
1	/kbh/bin/nvcc
2	
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nvcc exists at /kbh/bin/nvcc. Now I'll write a floor-measurement experiment: an empty kernel and a pure-read kernel timed exactly like the harness does.
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Write /workspace/problems/05_topk_bitonic/scratch/floor.py
diff (81 lines)
--- /dev/null
+++ b//workspace/problems/05_topk_bitonic/scratch/floor.py
@@ -0,0 +1,78 @@
+"""Measure the timing floor under harness methodology: empty kernel, pure-read kernel."""
+import statistics
+import sys
+
+import torch
+from torch.utils.cpp_extension import load_inline
+
+src = r"""
+#include <torch/extension.h>
+#include <cuda_runtime.h>
+
+__global__ void empty_kernel() {}
+
+__global__ void read_kernel(const float4* __restrict__ x, float* __restrict__ out, long n4) {
+    long i = (long)blockIdx.x * blockDim.x + threadIdx.x;
+    float acc = 0.f;
+    long stride = (long)gridDim.x * blockDim.x;
+    for (; i < n4; i += stride) {
+        float4 v = x[i];
+        acc += v.x + v.y + v.z + v.w;
+    }
+    if (acc == 1234.5678f) out[0] = acc;  // never true; keeps the load alive
+}
+
+void launch_empty() {
+    empty_kernel<<<1, 32>>>();
+}
+
+void launch_read(torch::Tensor x, torch::Tensor out, int blocks, int threads) {
+    long n4 = x.numel() / 4;
+    read_kernel<<<blocks, threads>>>(
+        reinterpret_cast<const float4*>(x.data_ptr<float>()), out.data_ptr<float>(), n4);
+}
+"""
+
+mod = load_inline(
+    name="floor_probe",
+    cpp_sources="void launch_empty(); void launch_read(torch::Tensor, torch::Tensor, int, int);",
+    cuda_sources=src,
+    functions=["launch_empty", "launch_read"],
+    extra_cuda_cflags=["-O3", "--use_fast_math", "-gencode=arch=compute_120,code=sm_120"],
+    verbose=False,
+)
+
+_L2 = torch.empty(128 * 1024 * 1024 // 4, dtype=torch.float32, device="cuda")
+
+
+def time_fn(fn, iters=50, warmup=10):
+    for _ in range(warmup):
+        fn()
+    torch.cuda.synchronize()
+    times = []
+    for _ in range(iters):
+        _L2.zero_()
+        torch.cuda.synchronize()
+        s = torch.cuda.Event(enable_timing=True)
+        e = torch.cuda.Event(enable_timing=True)
+        s.record()
+        fn()
+        e.record()
+        torch.cuda.synchronize()
+        times.append(s.elapsed_time(e))
+    return statistics.median(times)
+
+
+out = torch.zeros(8, device="cuda")
+print(f"empty kernel: {time_fn(mod.launch_empty)*1000:.2f} us")
+
+for nbytes_mb, label in [(0.5, "0.5MB"), (2.0, "2MB"), (8.0, "8MB"), (64.0, "64MB")]:
+    n = int(nbytes_mb * 1024 * 1024 / 4)
+    x = torch.randn(n, device="cuda")
+    for blocks in [148, 188, 376, 752, 1504]:
+        ms = time_fn(lambda: mod.launch_read(x, out, blocks, 256))
+        gbps = n * 4 / (ms * 1e-3) / 1e9
+        print(f"read {label} blocks={blocks}: {ms*1000:7.2f} us  {gbps:7.1f} GB/s")
+
+# Also measure: python-side null op (event pair only)
+print(f"event pair only: {time_fn(lambda: None)*1000:.2f} us")
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/scratch/floor.py",
  "content": "<2479 chars \u2014 see diff>"
}
in 2out 39cache_r 52413cache_w 141
tool
stdout (148 chars)
File created successfully at: /workspace/problems/05_topk_bitonic/scratch/floor.py (file state is current in your context — no need to Read it back)
assistant
ToolSearch
args
{
  "query": "select:TaskCreate,TaskUpdate",
  "max_results": 2
}
in 2out 67cache_r 52554cache_w 1597
tool
stdout (0 chars)
assistant
TaskCreate
args
{
  "subject": "Measure timing floor (empty/read kernels)",
  "description": "Run scratch/floor.py to establish launch-overhead floor and achievable read bandwidth under harness timing methodology.",
  "activeForm": "Measuring timing floor"
}
in 2out 51cache_r 18087cache_w 38678
tool
stdout (71 chars)
Task #1 created successfully: Measure timing floor (empty/read kernels)
assistant
TaskCreate
args
{
  "subject": "Implement single-kernel top-k CUDA solution",
  "description": "Write solution.py with a fused one-launch top-k kernel (per-warp register selection + block merge; multi-block + last-block-reduce for batch=1). Preallocate outputs in Model.__init__.",
  "activeForm": "Implementing top-k kernel"
}
in 2out 51cache_r 18087cache_w 38678
tool
stdout (73 chars)
Task #2 created successfully: Implement single-kernel top-k CUDA solution
assistant
TaskCreate
args
{
  "subject": "Pass check.py and optimize benchmark",
  "description": "Iterate: python check.py must print PASS; then push peak_fraction in benchmark.py via ncu/profiling.",
  "activeForm": "Verifying and optimizing"
}
in 2out 51cache_r 18087cache_w 38678
tool
stdout (66 chars)
Task #3 created successfully: Pass check.py and optimize benchmark
assistant
TaskUpdate
args
{
  "taskId": "1",
  "status": "in_progress"
}
in 2out 73cache_r 56765cache_w 660
tool
stdout (22 chars)
Updated task #1 status
assistant
Bash
args
{
  "command": "uv run python scratch/floor.py 2>&1 | tail -30",
  "description": "Run timing floor measurement",
  "timeout": 600000
}
in 2out 73cache_r 56765cache_w 660
system — task_started
↳ subagent started
tool
stdout (985 chars)
empty kernel: 4.67 us
read 0.5MB blocks=148:    5.60 us     93.6 GB/s
read 0.5MB blocks=188:    5.73 us     91.5 GB/s
read 0.5MB blocks=376:    5.57 us     94.2 GB/s
read 0.5MB blocks=752:    5.39 us     97.2 GB/s
read 0.5MB blocks=1504:    5.62 us     93.4 GB/s
read 2MB blocks=148:    5.71 us    367.1 GB/s
read 2MB blocks=188:    5.60 us    374.5 GB/s
read 2MB blocks=376:    5.42 us    386.6 GB/s
read 2MB blocks=752:    5.60 us    374.5 GB/s
read 2MB blocks=1504:    5.76 us    364.1 GB/s
read 8MB blocks=148:    7.86 us   1067.8 GB/s
read 8MB blocks=188:    8.37 us   1002.5 GB/s
read 8MB blocks=376:    7.92 us   1059.2 GB/s
read 8MB blocks=752:    7.58 us   1106.1 GB/s
read 8MB blocks=1504:    7.82 us   1072.2 GB/s
read 64MB blocks=148:   47.90 us   1400.9 GB/s
read 64MB blocks=188:   47.49 us   1413.2 GB/s
read 64MB blocks=376:   46.94 us   1429.6 GB/s
read 64MB blocks=752:   46.74 us   1435.9 GB/s
read 64MB blocks=1504:   46.90 us   1431.0 GB/s
event pair only: 2.29 us
assistant
in 2out 68cache_r 57425cache_w 1147
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in 2out 68cache_r 57425cache_w 1147
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TaskUpdate
args
{
  "taskId": "1",
  "status": "completed"
}
in 2out 68cache_r 57425cache_w 1147
tool
stdout (22 chars)
Updated task #1 status
assistant
TaskUpdate
args
{
  "taskId": "2",
  "status": "in_progress"
}
in 2out 68cache_r 57425cache_w 1147
tool
stdout (22 chars)
Updated task #2 status
assistant
in 2out 40cache_r 58572cache_w 30499
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in 2out 40cache_r 58572cache_w 30499
assistant
Write /workspace/problems/05_topk_bitonic/solution.py
diff (500 lines — TRUNCATED)
--- /dev/null
+++ b//workspace/problems/05_topk_bitonic/solution.py
@@ -0,0 +1,497 @@
+"""Single-kernel top-k for SM120 (RTX PRO 6000).
+
+Strategy: one fused CUDA kernel per forward. Each row is split across one or
+more blocks; each warp streams its span keeping a register-resident sorted
+top-K (Faiss WarpSelect-style threshold + per-lane candidate queue, bitonic
+networks via warp shuffles). Warps merge through shared memory. Multi-split
+rows publish packed (key|idx) candidates to a scratch buffer; the last block
+per row (device-scope acq-rel counter) merges them and writes the output.
+
+Values travel as a monotonic fp32->u32 key packed with the source index into
+a u64, so all comparisons are single integer compares and the exact fp32 bits
+round-trip on output.
+"""
+import os
+
+import torch
+from torch.utils.cpp_extension import load_inline
+
+_CPP_SRC = r"""
+#include <cstdint>
+int64_t topk_configure(int64_t batch, int64_t n, int64_t k, int64_t splits,
+                       int64_t threads, int64_t vals_ptr, int64_t idx_ptr);
+void topk_run(int64_t handle, int64_t x_ptr);
+void topk_run_cached(int64_t handle);
+"""
+
+_CUDA_SRC = r"""
+#include <cuda_runtime.h>
+#include <cuda/atomic>
+#include <c10/cuda/CUDAStream.h>
+#include <c10/cuda/CUDAGuard.h>
+#include <ATen/cuda/CUDAContext.h>
+#include <torch/extension.h>
+#include <vector>
+
+using u32 = unsigned int;
+using u64 = unsigned long long;
+
+#define FULL_MASK 0xffffffffu
+
+// Monotonic transform: descending float order == descending u32 key order.
+__device__ __forceinline__ u32 fkey(u32 bits) {
+    return bits ^ (u32(int(bits) >> 31) | 0x80000000u);
+}
+__device__ __forceinline__ float unkey(u32 key) {
+    u32 b = key ^ ((key & 0x80000000u) ? 0x80000000u : 0xFFFFFFFFu);
+    return __uint_as_float(b);
+}
+__device__ __forceinline__ u64 umax(u64 a, u64 b) { return a > b ? a : b; }
+__device__ __forceinline__ u64 umin(u64 a, u64 b) { return a < b ? a : b; }
+
+// Descending bitonic merge of 32 elements held one-per-lane.
+__device__ __forceinline__ void bmerge32(u64 &v, int lane) {
+    #pragma unroll
+    for (int d = 16; d >= 1; d >>= 1) {
+        u64 o = __shfl_xor_sync(FULL_MASK, v, d);
+        v = ((lane & d) == 0) ? umax(v, o) : umin(v, o);
+    }
+}
+
+// Descending bitonic merge of 64 elements: element e = j*32+lane in regs a0,a1.
+__device__ __forceinline__ void bmerge64(u64 &a0, u64 &a1, int lane) {
+    u64 lo = umin(a0, a1);
+    a0 = umax(a0, a1);
+    a1 = lo;
+    bmerge32(a0, lane);
+    bmerge32(a1, lane);
+}
+
+// Full descending sort of 32 elements one-per-lane.
+__device__ __forceinline__ void sort32(u64 &v, int lane) {
+    #pragma unroll
+    for (int s = 2; s <= 32; s <<= 1) {
+        #pragma unroll
+        for (int d = s >> 1; d >= 1; d >>= 1) {
+            u64 o = __shfl_xor_sync(FULL_MASK, v, d);
+            bool i_low = (lane & d) == 0;
+            bool asc = (lane & s) != 0;   // gives overall descending
+            bool take_max = i_low ^ asc;
+            v = take_max ? umax(v, o) : umin(v, o);
+        }
+    }
+}
+
+// ---------- Warp-resident top-K buffer -------------------------------------
+// R registers per lane; element e = j*32 + lane; sorted descending by e.
+
+template <int R> struct WarpBuf;
+
+template <> struct WarpBuf<1> {
+    u64 b0;
+    __device__ __forceinline__ void init() { b0 = 0; }
+    // Merge a descending-sorted 32-vector (one per lane) into the buffer.
+    __device__ __forceinline__ void merge_sorted32(u64 v, int lane) {
+        u64 r = __shfl_xor_sync(FULL_MASK, v, 31);  // reversed
+        b0 = umax(b0, r);
+        bmerge32(b0, lane);
+    }
+    __device__ __forceinline__ u32 kth_key(int k, int lane) {
+        u64 e = __shfl_sync(FULL_MASK, b0, (k - 1) & 31);
+        return (u32)(e >> 32);
+    }
+    __device__ __forceinline__ void store(u64 *dst, int lane) { dst[lane] = b0; }
+    __device__ __forceinline__ void load(const u64 *src, int lane) { b0 = src[lane]; }
+    // Merge another descending list of 32 (in shared, reversed addressing).
+    __device__ __forceinline__ void merge_list(const u64 *src, int lane) {
+        b0 = umax(b0, src[31 - lane]);
+        bmerge32(b0, lane);
+    }
+};
+
+template <> struct WarpBuf<2> {
+    u64 b0, b1;
+    __device__ __forceinline__ void init() { b0 = 0; b1 = 0; }
+    __device__ __forceinline__ void merge_sorted32(u64 v, int lane) {
+        // positions 32..63 paired with reversed v
+        u64 r = __shfl_xor_sync(FULL_MASK, v, 31);
+        b1 = umax(b1, r);
+        bmerge64(b0, b1, lane);
+    }
+    __device__ __forceinline__ u32 kth_key(int k, int lane) {
+        u64 e = (k <= 32) ? __shfl_sync(FULL_MASK, b0, (k - 1) & 31)
+                          : __shfl_sync(FULL_MASK, b1, (k - 1) & 31);
+        return (u32)(e >> 32);
+    }
+    __device__ __forceinline__ void store(u64 *dst, int lane) {
+        dst[lane] = b0; dst[32 + lane] = b1;
+    }
+    __device__ __forceinline__ void load(const u64 *src, int lane) {
+        b0 = src[lane]; b1 = src[32 + lane];
+    }
+    __device__ __forceinline__ void merge_list(const u64 *src, int lane) {
+        b0 = umax(b0, src[63 - lane]);
+        b1 = umax(b1, src[31 - lane]);
+        bmerge64(b0, b1, lane);
+    }
+};
+
+// ---------- Streaming select: queue + flush ---------------------------------
+
+template <int R, int T> struct WarpSelect {
+    WarpBuf<R> buf;
+    u64 q[T];
+    int cnt;
+    u32 thresh;
+    int k;
+    int lane;
+
+    __device__ __forceinline__ void init(int k_, int lane_) {
+        buf.init();
+        cnt = 0;
+        thresh = 0;
+        k = k_;
+        lane = lane_;
+    }
+
+    __device__ __forceinline__ void flush() {
+        #pragma unroll
+        for (int j = 0; j < T; ++j) {
+            // skip slots empty across the whole warp
+            if (!__ballot_sync(FULL_MASK, cnt > j)) break;
+            u64 v = (j < cnt) ? q[j] : 0ULL;
+            sort32(v, lane);
+            buf.merge_sorted32(v, lane)

... (11037 more chars)
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/solution.py",
  "content": "<16454 chars \u2014 see diff>"
}
in 2out 40cache_r 58572cache_w 30499
tool
stdout (143 chars)
File created successfully at: /workspace/problems/05_topk_bitonic/solution.py (file state is current in your context — no need to Read it back)
assistant
in 2out 34cache_r 89071cache_w 8068
assistant
in 2out 34cache_r 89071cache_w 8068
assistant
Edit /workspace/problems/05_topk_bitonic/solution.py
diff (20 lines)
--- a//workspace/problems/05_topk_bitonic/solution.py
+++ b//workspace/problems/05_topk_bitonic/solution.py
@@ -231,9 +231,14 @@
                 sel.push4(fkey(__float_as_uint(v.x)), fkey(__float_as_uint(v.y)),
                           fkey(__float_as_uint(v.z)), fkey(__float_as_uint(v.w)), i0);
             }
-            for (int i = wbeg + (nfull << 7) + lane; i < wend; i += 32) {
-                u32 key = fkey(__float_as_uint(__ldg(xr + i)));
-                if (__ballot_sync(FULL_MASK, key > sel.thresh)) sel.push(key, (u32)i);
+            for (int ib = wbeg + (nfull << 7); ib < wend; ib += 32) {
+                const int i = ib + lane;
+                const bool act = i < wend;
+                u32 key = act ? fkey(__float_as_uint(__ldg(xr + i))) : 0u;
+                if (__ballot_sync(FULL_MASK, act && key > sel.thresh)) {
+                    if (act && key > sel.thresh) sel.q[sel.cnt++] = ((u64)key << 32) | (u64)(u32)i;
+                    if (__ballot_sync(FULL_MASK, sel.cnt == T)) sel.flush();
+                }
             }
         }
         sel.finish();
args
{
  "replace_all": false,
  "file_path": "/workspace/problems/05_topk_bitonic/solution.py",
  "old_string": "<270 chars \u2014 see diff>",
  "new_string": "<542 chars \u2014 see diff>"
}
in 2out 34cache_r 89071cache_w 8068
tool
stdout (153 chars)
The file /workspace/problems/05_topk_bitonic/solution.py has been updated successfully. (file state is current in your context — no need to Read it back)
assistant
Edit /workspace/problems/05_topk_bitonic/solution.py
diff (43 lines)
--- a//workspace/problems/05_topk_bitonic/solution.py
+++ b//workspace/problems/05_topk_bitonic/solution.py
@@ -254,27 +254,13 @@
 
     if (splits == 1) {
         if (w == 0) {
-            #pragma unroll
-            for (int j = 0; j < R; ++j) {
-                int e = j * 32 + lane;
-                if (e < k) {
-                    u64 p = (j == 0) ? sel.buf.b0 : sel.buf.kth_key(0, 0), q;
-                }
-            }
-            // (specialized below; see store_out)
-        }
-    }
-
-    // Unified output path helper is below via macro-free explicit code:
-    if (splits == 1) {
-        if (w == 0) {
             u64 e0 = sel.buf.b0;
             if (lane < k) {
                 out_vals[(size_t)row * k + lane] = unkey((u32)(e0 >> 32));
                 out_idx[(size_t)row * k + lane] = (long)(u32)e0;
             }
-            if (R == 2) {
-                u64 e1 = ((WarpBuf<2> *)&sel.buf)->b1;
+            if constexpr (R == 2) {
+                u64 e1 = sel.buf.b1;
                 int e = 32 + lane;
                 if (e < k) {
                     out_vals[(size_t)row * k + e] = unkey((u32)(e1 >> 32));
@@ -290,8 +276,8 @@
     if (w == 0) {
         u64 e0 = sel.buf.b0;
         if (lane < k) srow[(size_t)split * k + lane] = e0;
-        if (R == 2) {
-            u64 e1 = ((WarpBuf<2> *)&sel.buf)->b1;
+        if constexpr (R == 2) {
+            u64 e1 = sel.buf.b1;
             int e = 32 + lane;
             if (e < k) srow[(size_t)split * k + e] = e1;
         }
args
{
  "replace_all": false,
  "file_path": "/workspace/problems/05_topk_bitonic/solution.py",
  "old_string": "<1459 chars \u2014 see diff>",
  "new_string": "<1011 chars \u2014 see diff>"
}
in 2out 34cache_r 89071cache_w 8068
tool
stdout (153 chars)
The file /workspace/problems/05_topk_bitonic/solution.py has been updated successfully. (file state is current in your context — no need to Read it back)
assistant
in 2out 56cache_r 97139cache_w 9603
assistant
Edit /workspace/problems/05_topk_bitonic/solution.py
diff (13 lines)
--- a//workspace/problems/05_topk_bitonic/solution.py
+++ b//workspace/problems/05_topk_bitonic/solution.py
@@ -321,8 +321,8 @@
                 out_vals[(size_t)row * k + lane] = unkey((u32)(e0 >> 32));
                 out_idx[(size_t)row * k + lane] = (long)(u32)e0;
             }
-            if (R == 2) {
-                u64 e1 = ((WarpBuf<2> *)&sel.buf)->b1;
+            if constexpr (R == 2) {
+                u64 e1 = sel.buf.b1;
                 int e = 32 + lane;
                 if (e < k) {
                     out_vals[(size_t)row * k + e] = unkey((u32)(e1 >> 32));
args
{
  "replace_all": false,
  "file_path": "/workspace/problems/05_topk_bitonic/solution.py",
  "old_string": "<318 chars \u2014 see diff>",
  "new_string": "<310 chars \u2014 see diff>"
}
in 2out 56cache_r 97139cache_w 9603
tool
stdout (153 chars)
The file /workspace/problems/05_topk_bitonic/solution.py has been updated successfully. (file state is current in your context — no need to Read it back)
assistant
in 2out 62cache_r 106742cache_w 706
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Now a quick scratch correctness test against torch.topk (allowed in scratch files, not in solution.py).
in 2out 62cache_r 106742cache_w 706
assistant
Write /workspace/problems/05_topk_bitonic/scratch/test_sol.py
diff (50 lines)
--- /dev/null
+++ b//workspace/problems/05_topk_bitonic/scratch/test_sol.py
@@ -0,0 +1,47 @@
+import sys
+import torch
+
+sys.path.insert(0, "/workspace/problems/05_topk_bitonic")
+import solution
+
+SHAPES = [
+    (1, 131072, 64),
+    (64, 8192, 8),
+    (32, 16384, 32),
+    (16, 12000, 16),
+    (128, 4096, 1),
+    # extra edge shapes
+    (3, 700, 5),
+    (2, 64, 64),
+    (1, 65, 64),
+    (5, 4097, 33),
+    (7, 12345, 7),
+]
+
+dev = torch.device("cuda")
+fails = 0
+for (b, n, k) in SHAPES:
+    m = solution.Model(b, n, k).to(dev).eval()
+    for seed in (0, 1, 2):
+        torch.manual_seed(seed)
+        for scale in (1.0, 1e-4, 1e3):
+            x = torch.randn(b, n, device=dev) * scale
+            rv, ri = torch.topk(x, k=k, dim=-1, largest=True, sorted=True)
+            sv, si = m(x)
+            torch.cuda.synchronize()
+            ok_v = torch.allclose(rv, sv, atol=1e-4 * max(scale, 1), rtol=1e-4)
+            g = torch.gather(x, -1, si)
+            ok_i = torch.allclose(rv, g, atol=1e-4 * max(scale, 1), rtol=1e-4)
+            in_range = (si.min() >= 0) and (si.max() < n)
+            if not (ok_v and ok_i and in_range):
+                fails += 1
+                bad = (rv - sv).abs().max().item()
+                print(f"FAIL b={b} n={n} k={k} seed={seed} scale={scale} "
+                      f"ok_v={ok_v} ok_i={ok_i} in_range={in_range} maxdiff={bad}")
+                if fails < 3:
+                    row = (rv - sv).abs().amax(-1).argmax().item()
+                    print("  ref:", rv[row][:10].tolist())
+                    print("  sol:", sv[row][:10].tolist())
+    print(f"done b={b} n={n} k={k}")
+
+print("ALL OK" if fails == 0 else f"{fails} FAILURES")
args
{
  "file_path": "/workspace/problems/05_topk_bitonic/scratch/test_sol.py",
  "content": "<1579 chars \u2014 see diff>"
}
in 2out 62cache_r 106742cache_w 706
tool
stdout (151 chars)
File created successfully at: /workspace/problems/05_topk_bitonic/scratch/test_sol.py (file state is current in your context — no need to Read it back)
assistant
Bash
args
{
  "command": "uv run python scratch/test_sol.py 2>&1 | tail -25",
  "description": "Build and test solution against torch.topk",
  "timeout": 600000
}
in 2out 66cache_r 107448cache_w 1198
subagent · 0 events · 0 tools
tool
stdout (217 chars)
done b=1 n=131072 k=64
done b=64 n=8192 k=8
done b=32 n=16384 k=32
done b=16 n=12000 k=16
done b=128 n=4096 k=1
done b=3 n=700 k=5
done b=2 n=64 k=64
done b=1 n=65 k=64
done b=5 n=4097 k=33
done b=7 n=12345 k=7
ALL OK
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in 2out 35cache_r 108646cache_w 274
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in 2out 35cache_r 108646cache_w 274
assistant
Edit /workspace/problems/05_topk_bitonic/solution.py
diff (11 lines)
--- a//workspace/problems/05_topk_bitonic/solution.py
+++ b//workspace/problems/05_topk_bitonic/solution.py
@@ -199,7 +199,7 @@
     long *__restrict__ out_idx,
     u64 *__restrict__ scratch,   // batch * splits * k
     int *__restrict__ counters,  // batch
-    int n, int k, int splits, int chunk, int per_warp)
+    int n, int k, int splits, int chunk, int per_warp, int vec_ok)
 {
     constexpr int K32 = 32 * R;
     __shared__ u64 smem[W * K32];
args
{
  "replace_all": false,
  "file_path": "/workspace/problems/05_topk_bitonic/solution.py",
  "old_string": "    int n, int k, int splits, int chunk, int per_warp)",
  "new_string": "    int n, int k, int splits, int chunk, int per_warp, int vec_ok)"
}
in 2out 35cache_r 108646cache_w 274
tool
stdout (153 chars)
The file /workspace/problems/05_topk_bitonic/solution.py has been updated successfully. (file state is current in your context — no need to Read it back)
assistant
Edit /workspace/problems/05_topk_bitonic/solution.py
diff (11 lines)
--- a//workspace/problems/05_topk_bitonic/solution.py
+++ b//workspace/problems/05_topk_bitonic/solution.py
@@ -223,7 +223,7 @@
         const int wend = min(wbeg + per_warp, cend);
         if (wbeg < wend) {
             const int span = wend - wbeg;
-            const int nfull = span >> 7;  // full 128-element warp steps
+            const int nfull = vec_ok ? (span >> 7) : 0;  // full 128-elem warp steps
             const float4 *base = reinterpret_cast<const float4 *>(xr + wbeg);
             for (int s = 0; s < nfull; ++s) {
                 float4 v = __ldcs(base + s * 32 + lane);
args
{
  "replace_all": false,
  "file_path": "/workspace/problems/05_topk_bitonic/solution.py",
  "old_string": "<114 chars \u2014 see diff>",
  "new_string": "<126 chars \u2014 see diff>"
}
in 2out 35cache_r 108646cache_w 274
tool
stdout (153 chars)
The file /workspace/problems/05_topk_bitonic/solution.py has been updated successfully. (file state is current in your context — no need to Read it back)
assistant
Edit /workspace/problems/05_topk_bitonic/solution.py
diff (13 lines)
--- a//workspace/problems/05_topk_bitonic/solution.py
+++ b//workspace/problems/05_topk_bitonic/solution.py
@@ -352,8 +352,9 @@
     dim3 grid(c.splits, c.batch);
     dim3 block(c.threads);
     const int W = c.threads / 32;
+    const int vec_ok = (c.n % 4 == 0) ? 1 : 0;
     #define LAUNCH(RR, WW) topk_kernel<RR, 4, WW><<<grid, block, 0, st>>>( \
-        c.x, c.vals, c.idx, c.scratch, c.counters, c.n, c.k, c.splits, c.chunk, c.per_warp)
+        c.x, c.vals, c.idx, c.scratch, c.counters, c.n, c.k, c.splits, c.chunk, c.per_warp, vec_ok)
     if (c.R == 1) {
         switch (W) {
             case 4: LAUNCH(1, 4); break;
args
{
  "replace_all": false,
  "file_path": "/workspace/problems/05_topk_bitonic/solution.py",
  "old_string": "<168 chars \u2014 see diff>",
  "new_string": "<223 chars \u2014 see diff>"
}
in 2out 35cache_r 108646cache_w 274
tool
stdout (153 chars)
The file /workspace/problems/05_topk_bitonic/solution.py has been updated successfully. (file state is current in your context — no need to Read it back)