./kernelbenchhardv3runsopencode · ?
opencode / ? session: ses_2302ca6f5ffeqajx98zUlssk00 cwd: ?
harness
opencode
model
?
turns
47
tools called
24
events
70
input toks
28,625
output toks
6,207
cache hit
630,528
solution.py
final answer
check.log
result.json
"""Top-k solution: CUDA C++ bitonic sort + merge via load_inline.

Strategy:
  - For k == 1: block-wide argmax reduction (simple and fast).
  - For k > 1: tile-based bitonic sort in shared memory with a running top-k
    merge buffer. Each block processes one row; the row is processed in tiles
    of size TILE_SIZE (power of 2, up to 8192). Invalid positions beyond n
    are padded with -FLT_MAX so they don't pollute the top-k.
"""
import torch
import torch.nn as nn
from torch.utils.cpp_extension import load_inline
from pathlib import Path

# ---------------------------------------------------------------------------
# CUDA source
# ---------------------------------------------------------------------------
CUDA_SRC = r"""
#include <cuda_runtime.h>
#include <cstdint>
#include <cfloat>
#include <climits>

// ---------------------------------------------------------------------------
// Constants / helpers
// ---------------------------------------------------------------------------
#define TILE_SIZE 8192
#define BLOCK_SIZE 256
#define ELEMS_PER_THREAD (TILE_SIZE / BLOCK_SIZE)  // 32

// ---------------------------------------------------------------------------
// Argmax kernel (k == 1)
// ---------------------------------------------------------------------------
__global__ void argmax_kernel(
    const float* __restrict__ x,
    float* __restrict__ out_vals,
    int64_t* __restrict__ out_idxs,
    int batch, int n
) {
    // Shared memory for block reduction
    __shared__ float s_vals[BLOCK_SIZE];
    __shared__ int s_idxs[BLOCK_SIZE];

    int row = blockIdx.x;
    if (row >= batch) return;

    const float* row_x = x + row * n;
    int tid = threadIdx.x;

    float local_max = -FLT_MAX;
    int local_idx = -1;

    // Each thread scans its elements
    for (int i = tid; i < n; i += BLOCK_SIZE) {
        float v = row_x[i];
        if (v > local_max) {
            local_max = v;
            local_idx = i;
        }
    }

    s_vals[tid] = local_max;
    s_idxs[tid] = local_idx;
    __syncthreads();

    // Tree reduction (warp-level then block-level)
    for (int s = BLOCK_SIZE / 2; s > 0; s >>= 1) {
        if (tid < s) {
            if (s_vals[tid + s] > s_vals[tid]) {
                s_vals[tid] = s_vals[tid + s];
                s_idxs[tid] = s_idxs[tid + s];
            }
        }
        __syncthreads();
    }

    if (tid == 0) {
        out_vals[row] = s_vals[0];
        out_idxs[row] = (int64_t)s_idxs[0];
    }
}

// ---------------------------------------------------------------------------
// Top-k helper: merge a sorted pair list of length k into the running top-k
// ---------------------------------------------------------------------------
__device__ void merge_topk(
    float* running_vals, int* running_idxs, int k,
    const float* tile_vals, const int* tile_idxs
) {
    // Two sorted lists (descending): running and tile. Merge top-k into running.
    float tmp_vals[64];
    int tmp_idxs[64];
    int ri = 0, ti = 0, oi = 0;
    while (oi < k) {
        if (ti >= k || (ri < k && running_vals[ri] >= tile_vals[ti])) {
            tmp_vals[oi] = running_vals[ri];
            tmp_idxs[oi] = running_idxs[ri];
            ri++;
        } else {
            tmp_vals[oi] = tile_vals[ti];
            tmp_idxs[oi] = tile_idxs[ti];
            ti++;
        }
        oi++;
    }
    // Write back
    for (int i = 0; i < k; i++) {
        running_vals[i] = tmp_vals[i];
        running_idxs[i] = tmp_idxs[i];
    }
}

// ---------------------------------------------------------------------------
// Top-k kernel via bitonic sort in shared memory
// ---------------------------------------------------------------------------
template <int K>
__global__ void topk_kernel(
    const float* __restrict__ x,
    float* __restrict__ out_vals,
    int64_t* __restrict__ out_idxs,
    int batch, int n
) {
    // Dynamic shared memory: tile_vals[TILE_SIZE] + tile_idxs[TILE_SIZE]
    // We use the first K slots for the running top-k between tiles
    // (reuse the same memory to save space).
    extern __shared__ char smem[];
    float* tile_vals = (float*)smem;
    int* tile_idxs = (int*)(smem + TILE_SIZE * sizeof(float));

    // Running top-k occupies the same shared memory but we copy it out
    // before starting a new tile (conceptually it lives separately).
    float running_vals[64];
    int running_idxs[64];

    int row = blockIdx.x;
    if (row >= batch) return;

    // Initialize running top-k with -FLT_MAX
    #pragma unroll
    for (int i = 0; i < K; i++) {
        running_vals[i] = -FLT_MAX;
        running_idxs[i] = -1;
    }

    const float* row_x = x + row * n;
    int tid = threadIdx.x;  // 0..BLOCK_SIZE-1

    // Process tiles
    for (int tile_base = 0; tile_base < n; tile_base += TILE_SIZE) {
        int tile_end = min(tile_base + TILE_SIZE, n);
        int tile_actual = tile_end - tile_base;

        // ---- Load tile into shared memory (coalesced) ----
        #pragma unroll
        for (int i = 0; i < ELEMS_PER_THREAD; i++) {
            int pos = tile_base + i * BLOCK_SIZE + tid;
            int smem_pos = i * BLOCK_SIZE + tid;
            if (pos < n) {
                tile_vals[smem_pos] = row_x[pos];
                tile_idxs[smem_pos] = pos;
            } else {
                // Pad with -inf
                tile_vals[smem_pos] = -FLT_MAX;
                tile_idxs[smem_pos] = -1;
            }
        }
        __syncthreads();

        // ---- Bitonic sort (full TILE_SIZE in shared memory) ----
        int actual_tile_pow2 = 1;
        while (actual_tile_pow2 < tile_actual) actual_tile_pow2 <<= 1;
        // Use exactly TILE_SIZE (which is >= actual_tile_pow2) for the sort
        // since the padded -inf values don't affect top-K.

        for (int size = 2; size <= TILE_SIZE; size <<= 1) {
            for (int stride = size >> 1; stride > 0; stride >>= 1) {
                #pragma unroll
                for (int i = 0; i < ELEMS_PER_THREAD; i++) {
                    int pos = tid * ELEMS_PER_THREAD + i;
                    int partner = pos ^ stride;
                    if (partner > pos && partner < TILE_SIZE) {
                        float a = tile_vals[pos];
                        float b = tile_vals[partner];
                        bool asc = ((pos & size) == 0);
                        if (asc ? (a < b) : (a > b)) {
                            tile_vals[pos] = b;
                            tile_vals[partner] = a;
                            int tmp = tile_idxs[pos];
                            tile_idxs[pos] = tile_idxs[partner];
                            tile_idxs[partner] = tmp;
                        }
                    }
                }
                __syncthreads();
            }
        }

        // ---- Merge tile top-k into running top-k ----
        // Tile is sorted descending; top-K elements are at indices [0, K)
        if (K <= 64) {
            merge_topk(running_vals, running_idxs, K, &tile_vals[0], &tile_idxs[0]);
        }
    }

    // ---- Write final output ----
    if (tid < K) {
        out_vals[row * K + tid] = running_vals[tid];
        out_idxs[row * K + tid] = (int64_t)running_idxs[tid];
    }
}

// ---------------------------------------------------------------------------
// Host launcher
// ---------------------------------------------------------------------------
void launch_topk(
    const float* x, float* out_vals, int64_t* out_idxs,
    int batch, int n, int k
) {
    dim3 grid(batch);
    dim3 block(BLOCK_SIZE);

    if (k == 1) {
        argmax_kernel<<<grid, block>>>(x, out_vals, out_idxs, batch, n);
    } else {
        size_t smem_bytes = TILE_SIZE * (sizeof(float) + sizeof(int));
        // Choose template based on k
        switch (k) {
            case 8:   topk_kernel<8><<<grid, block, smem_bytes>>>(x, out_vals, out_idxs, batch, n); break;
            case 16:  topk_kernel<16><<<grid, block, smem_bytes>>>(x, out_vals, out_idxs, batch, n); break;
            case 32:  topk_kernel<32><<<grid, block, smem_bytes>>>(x, out_vals, out_idxs, batch, n); break;
            case 64:  topk_kernel<64><<<grid, block, smem_bytes>>>(x, out_vals, out_idxs, batch, n); break;
            default:  topk_kernel<8><<<grid, block, smem_bytes>>>(x, out_vals, out_idxs, batch, n); break;
        }
    }
    CUDA_CHECK(cudaGetLastError());
}
"""

CPP_SRC = r"""
void launch_topk(
    const float* x, float* out_vals, int64_t* out_idxs,
    int batch, int n, int k
);
"""

# Load inline
try:
    _ext = load_inline(
        name="topk_ext_v2",
        cpp_sources=CPP_SRC,
        cuda_sources=CUDA_SRC,
        functions=["launch_topk"],
        extra_cuda_cflags=[
            "-std=c++17",
            "-O3",
            "--use_fast_math",
            "-arch=sm_90",
            "-U__CUDA_NO_HALF_OPERATORS__",
            "-U__CUDA_NO_HALF_CONVERSIONS__",
        ],
        verbose=False,
    )
except Exception as e:
    print(f"[load_inline error] {e}")
    raise


class Model(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))

    def forward(self, x: torch.Tensor) -> tuple[torch.Tensor, torch.Tensor]:
        assert x.is_cuda and x.dtype == torch.float32
        batch, n = x.shape
        k = self.k
        out_vals = torch.empty(batch, k, dtype=torch.float32, device=x.device)
        out_idxs = torch.empty(batch, k, dtype=torch.int64, device=x.device)
        _ext.launch_topk(x.data_ptr(), out_vals.data_ptr(), out_idxs.data_ptr(),
                         batch, n, k)
        return out_vals, out_idxs


# 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]
Let me write a scratch implementation first to test the approach, then iterate:
[load_inline error] Error building extension 'topk_ext_v2': [1/3] /usr/local/cuda-13/bin/nvcc -MD -MF cuda.cuda.o.d -DTORCH_EXTENSION_NAME=topk_ext_v2 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda-13/include -isystem /home/infatoshi/.local/share/uv/python/cpython-3.11.15-linux-x86_64-gnu/include/python3.11 -D__CUDA_NO_HALF_OPERATORS__ -D__CUDA_NO_HALF_CONVERSIONS__ -D__CUDA_NO_BFLOAT16_CONVERSIONS__ -D__CUDA_NO_HALF2_OPERATORS__ --expt-relaxed-constexpr --compiler-options '-fPIC' -std=c++17 -O3 --use_fast_math -arch=sm_90 -U__CUDA_NO_HALF_OPERATORS__ -U__CUDA_NO_HALF_CONVERSIONS__ -c /home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu -o cuda.cuda.o 
FAILED: [code=2] cuda.cuda.o 
/usr/local/cuda-13/bin/nvcc -MD -MF cuda.cuda.o.d -DTORCH_EXTENSION_NAME=topk_ext_v2 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda-13/include -isystem /home/infatoshi/.local/share/uv/python/cpython-3.11.15-linux-x86_64-gnu/include/python3.11 -D__CUDA_NO_HALF_OPERATORS__ -D__CUDA_NO_HALF_CONVERSIONS__ -D__CUDA_NO_BFLOAT16_CONVERSIONS__ -D__CUDA_NO_HALF2_OPERATORS__ --expt-relaxed-constexpr --compiler-options '-fPIC' -std=c++17 -O3 --use_fast_math -arch=sm_90 -U__CUDA_NO_HALF_OPERATORS__ -U__CUDA_NO_HALF_CONVERSIONS__ -c /home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu -o cuda.cuda.o 
/home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu(221): error: identifier "CUDA_CHECK" is undefined
      CUDA_CHECK(cudaGetLastError());
      ^

1 error detected in the compilation of "/home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu".
[2/3] c++ -MMD -MF main.o.d -DTORCH_EXTENSION_NAME=topk_ext_v2 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda-13/include -isystem /home/infatoshi/.local/share/uv/python/cpython-3.11.15-linux-x86_64-gnu/include/python3.11 -fPIC -std=c++17 -c /home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/main.cpp -o main.o 
ninja: build stopped: subcommand failed.

FAIL: import error: Error building extension 'topk_ext_v2': [1/3] /usr/local/cuda-13/bin/nvcc -MD -MF cuda.cuda.o.d -DTORCH_EXTENSION_NAME=topk_ext_v2 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda-13/include -isystem /home/infatoshi/.local/share/uv/python/cpython-3.11.15-linux-x86_64-gnu/include/python3.11 -D__CUDA_NO_HALF_OPERATORS__ -D__CUDA_NO_HALF_CONVERSIONS__ -D__CUDA_NO_BFLOAT16_CONVERSIONS__ -D__CUDA_NO_HALF2_OPERATORS__ --expt-relaxed-constexpr --compiler-options '-fPIC' -std=c++17 -O3 --use_fast_math -arch=sm_90 -U__CUDA_NO_HALF_OPERATORS__ -U__CUDA_NO_HALF_CONVERSIONS__ -c /home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu -o cuda.cuda.o 
FAILED: [code=2] cuda.cuda.o 
/usr/local/cuda-13/bin/nvcc -MD -MF cuda.cuda.o.d -DTORCH_EXTENSION_NAME=topk_ext_v2 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda-13/include -isystem /home/infatoshi/.local/share/uv/python/cpython-3.11.15-linux-x86_64-gnu/include/python3.11 -D__CUDA_NO_HALF_OPERATORS__ -D__CUDA_NO_HALF_CONVERSIONS__ -D__CUDA_NO_BFLOAT16_CONVERSIONS__ -D__CUDA_NO_HALF2_OPERATORS__ --expt-relaxed-constexpr --compiler-options '-fPIC' -std=c++17 -O3 --use_fast_math -arch=sm_90 -U__CUDA_NO_HALF_OPERATORS__ -U__CUDA_NO_HALF_CONVERSIONS__ -c /home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu -o cuda.cuda.o 
/home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu(221): error: identifier "CUDA_CHECK" is undefined
      CUDA_CHECK(cudaGetLastError());
      ^

1 error detected in the compilation of "/home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/cuda.cu".
[2/3] c++ -MMD -MF main.o.d -DTORCH_EXTENSION_NAME=topk_ext_v2 -DTORCH_API_INCLUDE_EXTENSION_H -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include -isystem /home/infatoshi/cuda/KernelBench-Hard/.venv/lib/python3.11/site-packages/torch/include/torch/csrc/api/include -isystem /usr/local/cuda-13/include -isystem /home/infatoshi/.local/share/uv/python/cpython-3.11.15-linux-x86_64-gnu/include/python3.11 -fPIC -std=c++17 -c /home/infatoshi/.cache/torch_extensions/py311_cu130/topk_ext_v2/main.cpp -o main.o 
ninja: build stopped: subcommand failed.

{
    "problem": "05_topk_bitonic",
    "harness": "opencode",
    "model": "deepseek/deepseek-v4-flash",
    "reasoning_effort": "",
    "has_solution": true,
    "correct": false,
    "peak_fraction": null,
    "elapsed_seconds": 510,
    "harness_exit_code": 0,
    "session_complete": true,
    "usage": {"input_tokens": 28625, "output_tokens": 6207, "cache_read_tokens": 630528, "cache_creation_tokens": 0, "reasoning_tokens": 32410, "total_cost_usd": null}
}

timeline (70 events)

assistant
todowrite
args
{
  "todos": [
    {
      "content": "Read reference.py, solution.py, check.py, benchmark.py, and problem.yaml to understand requirements",
      "status": "in_progress",
      "priority": "high"
    },
    {
      "content": "Check GPU availability and capabilities (sm_120 Blackwell)",
      "status": "pending",
      "priority": "high"
    },
    {
      "content": "Design and implement top-k kernel in solution.py",
      "status": "pending",
      "priority": "high"
    },
    {
      "content": "Run check.py to verify correctness",
      "status": "pending",
      "priority": "high"
    }

... (255 more chars)
tool
stdout (601 chars)
content: 'Read reference.py, solution.py, check.py, benchmark.py, and problem.yaml to understand requirements'
status: 'in_progress'
priority: 'high'
content: 'Check GPU availability and capabilities (sm_120 Blackwell)'
status: 'pending'
priority: 'high'
content: 'Design and implement top-k kernel in solution.py'
status: 'pending'
priority: 'high'
content: 'Run check.py to verify correctness'
status: 'pending'
priority: 'high'
content: 'Profile and iterate for performance'
status: 'pending'
priority: 'medium'
content: 'Final correctness check and submission'
status: 'pending'
priority: 'medium'
assistant
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assistant
read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic"
}
tool
stdout (209 chars)
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic</path>
<type>directory</type>
<entries>
benchmark.py
check.py
problem.yaml
PROMPT.txt
reference.py
shapes.py
sota.py

(7 entries)
</entries>
assistant
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read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/reference.py
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/reference.py"
}
tool
stdout (1919 chars) — TRUNCATED
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/reference.py</path>
<type>file</type>
<content>
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 b

... (419 more chars)
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read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/check.py
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/check.py"
}
tool
stdout (6402 chars) — TRUNCATED
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/check.py</path>
<type>file</type>
<content>
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: 
27: 
28: def main():
29:     try:
30:         import reference
31:         import shapes
32:         import solution
33:     except Exception as e:
34:         print(f"FAIL: import error: {e}")
35:         sys.exit(1)
36: 
37:     problem_yaml = Path("problem.yaml")
38:     meta = yaml.safe_load(problem_yaml.read_text()) if problem_yaml.exists() else {}
39: 
40:     # --- Forbidden-op check --------------------------------

... (4902 more chars)
assistant
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read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/shapes.py
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/shapes.py"
}
tool
stdout (1148 chars)
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/shapes.py</path>
<type>file</type>
<content>
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: ]

(End of file - total 19 lines)
</content>
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assistant
read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/problem.yaml
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/problem.yaml"
}
tool
stdout (2571 chars) — TRUNCATED
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/problem.yaml</path>
<type>file</type>
<content>
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 corre

... (1071 more chars)
assistant
in 444out 65cache_r 19328cache_w 0
assistant
read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/benchmark.py
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/benchmark.py"
}
tool
stdout (4750 chars) — TRUNCATED
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/benchmark.py</path>
<type>file</type>
<content>
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 time_fn  # 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

... (3250 more chars)
assistant
in 938out 67cache_r 19712cache_w 0
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read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/sota.py
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/sota.py"
}
tool
stdout (1188 chars)
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/sota.py</path>
<type>file</type>
<content>
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

(End of file - total 25 lines)
</content>
assistant
bash
args
{
  "command": "nvidia-smi --query-gpu=name,compute_cap,memory.total,memory.bandwidth --format=csv,noheader",
  "description": "Check GPU capabilities"
}
tool
stdout (57 chars)
Field "memory.bandwidth" is not a valid field to query.

assistant
read /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/PROMPT.txt
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/PROMPT.txt"
}
tool
stdout (2249 chars) — TRUNCATED
<path>/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/PROMPT.txt</path>
<type>file</type>
<content>
1: I need you to optimize a top-k kernel for the RTX PRO 6000 (SM120 Blackwell, GDDR7, 1.8 TB/s). The reference implementation is in reference.py and your kernel goes in solution.py. You can make whatever mess you want in this directory — scratch files, intermediate kernels, build artifacts, profiling traces — but the final answer has to be in solution.py with the same Model, get_inputs, and get_init_inputs interface as reference.py.
2: 
3: The input is a 2D fp32 tensor and you return the top-k values and their int64 indices along the last dim, sorted descending, same contract as torch.topk(largest=True, sorted=True). Correctness tolerance is 1e-4 abs/rel on the values; index ties are handled leniently — what matters is the returned values match the reference to tolerance, not that the index sets are bitwise identical. The shapes you have to handle are batch=1 n=131072 k=64 (decoder vocab top-k over a Llama-size vocabulary), batch=64 n=8192 k=8 (prefill / attention top-k), batch=32 n=16384 k=32 (mid-size batched), batch=16 n=12000 k=16 (non-power-of-two n, which bitonic networks don't naturally want), and batch=128 n=4096 k=1 (batched argmax).
4: 
5: This needs to be a real custom kernel — CUDA C++ via torch.utils.cpp_extension.load_inline, Triton, inline PTX, or CUTLASS, whatever you think fits. Don't reach for torch.topk, torch.kthvalue, torch.sort, or torch.ar

... (749 more chars)
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assistant
bash
args
{
  "command": "nvidia-smi --query-gpu=name,compute_cap --format=csv,noheader",
  "description": "Check GPU name and compute capability"
}
tool
stdout (56 chars)
NVIDIA RTX PRO 6000 Blackwell Workstation Edition, 12.0
assistant
bash
args
{
  "command": "ls /workspace/ 2>/dev/null || echo \"no /workspace\"; ls /home/infatoshi/cuda/projects/ 2>/dev/null || echo \"no cuda projects dir\"",
  "description": "Check workspace and CUDA projects"
}
tool
stdout (35 chars)
no /workspace
no cuda projects dir
assistant
in 1023out 177cache_r 22400cache_w 0
assistant
bash
args
{
  "command": "python -c \"import triton; print(triton.__version__)\" 2>&1; python -c \"import torch; print('torch', torch.__version__)\" 2>&1; nvcc --version 2>&1",
  "description": "Check Triton, Torch, and CUDA versions"
}
tool
stdout (236 chars)
3.6.0
torch 2.11.0+cu130
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2026 NVIDIA Corporation
Built on Mon_Mar_02_09:52:23_PM_PST_2026
Cuda compilation tools, release 13.2, V13.2.51
Build cuda_13.2.r13.2/compiler.37434383_0
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assistant
bash
args
{
  "command": "<600 chars \u2014 see below>",
  "description": "Check GPU device properties"
}
command (600 chars)
python -c "
import torch
props = torch.cuda.get_device_properties(0)
print(f'Name: {props.name}')
print(f'SM: {props.major}.{props.minor}')
print(f'Mem: {props.total_memory / 1e9:.1f} GB')
print(f'Multi procs: {props.multi_processor_count}')
print(f'Max threads per block: {props.max_threads_per_block}')
print(f'Max shared mem per block: {props.shared_mem_per_block / 1024:.1f} KB')
print(f'Max shared mem per SM: {props.shared_mem_per_multiprocessor / 1024:.1f} KB}')
print(f'Warp size: {props.warp_size}')
# Check compute capability
print(f'Compute Capability: {props.major}.{props.minor}')
" 2>&1
tool
stdout (252 chars)
File "<string>", line 10
    print(f'Max shared mem per SM: {props.shared_mem_per_multiprocessor / 1024:.1f} KB}')
                                                                                      ^
SyntaxError: f-string: single '}' is not allowed
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in 196out 250cache_r 29440cache_w 0
assistant
bash
args
{
  "command": "<522 chars \u2014 see below>",
  "description": "Check GPU device properties"
}
command (522 chars)
python -c "
import torch
props = torch.cuda.get_device_properties(0)
print(f'Name: {props.name}')
print(f'SM: {props.major}.{props.minor}')
print(f'Mem: {props.total_memory / 1e9:.1f} GB')
print(f'Multi procs: {props.multi_processor_count}')
print(f'Max threads per block: {props.max_threads_per_block}')
print(f'Max shared mem per block: {props.shared_mem_per_block / 1024:.1f} KB')
print(f'Warp size: {props.warp_size}')
pl = props.shared_mem_per_multiprocessor
print(f'Max shared mem per SM: {pl / 1024:.1f} KB')
" 2>&1
tool
stdout (336 chars)
Traceback (most recent call last):
  File "<string>", line 9, in <module>
AttributeError: 'torch._C._CudaDeviceProperties' object has no attribute 'shared_mem_per_block'. Did you mean: 'shared_memory_per_block'?
Name: NVIDIA RTX PRO 6000 Blackwell Workstation Edition
SM: 12.0
Mem: 101.9 GB
Multi procs: 188
Max threads per block: 1024
assistant
in 81out 232cache_r 29952cache_w 0
assistant
bash
args
{
  "command": "<245 chars \u2014 see below>",
  "description": "Find GPU shared memory attribute"
}
command (245 chars)
python -c "
import torch
props = torch.cuda.get_device_properties(0)
# Try to find the right attribute name
for attr in dir(props):
    if 'shared' in attr.lower() or 'mem' in attr.lower():
        print(f'{attr}: {getattr(props, attr)}')
" 2>&1
tool
stdout (187 chars)
memory_bus_width: 512
memory_clock_rate: 14001000
shared_memory_per_block: 49152
shared_memory_per_block_optin: 101376
shared_memory_per_multiprocessor: 102400
total_memory: 101949898752
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assistant
Now let me understand the full setup and check that SM120 (Blackwell) is supported by Triton:
assistant
bash
args
{
  "command": "<801 chars \u2014 see below>",
  "description": "Detailed GPU properties"
}
command (801 chars)
python -c "
import torch
print('CUDA available:', torch.cuda.is_available())
print('Device count:', torch.cuda.device_count())
print('CUDA version:', torch.version.cuda)
print('Torch version:', torch.__version__)
props = torch.cuda.get_device_properties(0)
print(f'SM: {props.major}.{props.minor}')
print(f'Multiprocessors: {props.multi_processor_count}')
print(f'Max threads per block: {props.max_threads_per_block}')
print(f'Shared mem/block: {props.shared_memory_per_block}')
print(f'Shared mem/block optin: {props.shared_memory_per_block_optin}')
print(f'Shared mem/SM: {props.shared_memory_per_multiprocessor}')
print(f'Memory clock: {props.memory_clock_rate / 1e6:.0f} MHz')
print(f'Memory bus: {props.memory_bus_width}-bit')
print(f'L2 cache: {getattr(props, \"l2_cache_size\", \"?\")}')
" 2>&1
tool
stdout (272 chars)
CUDA available: True
Device count: 1
CUDA version: 13.0
Torch version: 2.11.0+cu130
SM: 12.0
Multiprocessors: 188
Max threads per block: 1024
Shared mem/block: 49152
Shared mem/block optin: 101376
Shared mem/SM: 102400
Memory clock: 14 MHz
Memory bus: 512-bit
L2 cache: ?
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in 125out 317cache_r 30464cache_w 0
assistant
bash
args
{
  "command": "<465 chars \u2014 see below>",
  "description": "Check Triton SM120 support"
}
command (465 chars)
python -c "
import triton
print('Triton version:', triton.__version__)
try:
    supported = triton.runtime.driver.active.get_compute_capability()
    print('Active driver compute capability:', '.'.join(str(x) for x in supported))
except:
    pass
try:
    support = triton.backends.nvidia.compiler.is_cuda_compute_capability_supported(12, 0)
    print(f'Triton supports SM 12.0: {support}')
except Exception as e:
    print(f'Error checking SM support: {e}')
" 2>&1
tool
stdout (146 chars)
Triton version: 3.6.0
Error checking SM support: module 'triton.backends.nvidia.compiler' has no attribute 'is_cuda_compute_capability_supported'
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in 157out 194cache_r 38912cache_w 0
assistant
bash
args
{
  "command": "<465 chars \u2014 see below>",
  "description": "Verify Triton works on SM120"
}
command (465 chars)
python -c "
import torch
import triton
import triton.language as tl

@triton.jit
def test_kernel(x_ptr, y_ptr, n: tl.constexpr):
    pid = tl.program_id(0)
    offsets = pid * 128 + tl.arange(0, 128)
    x = tl.load(x_ptr + offsets)
    tl.store(y_ptr + offsets, x * 2.0)

x = torch.randn(128, device='cuda')
y = torch.zeros(128, device='cuda')
test_kernel[(1,)](x, y, n=128)
print('Triton works on this GPU!')
print(torch.max(torch.abs(y - x * 2.0)).item())
" 2>&1
tool
stdout (1410 chars)
Traceback (most recent call last):
  File "/home/infatoshi/.local/lib/python3.12/site-packages/triton/runtime/jit.py", line 461, in __init__
    self.raw_src, self.starting_line_number = inspect.getsourcelines(fn)
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/inspect.py", line 1260, in getsourcelines
    lines, lnum = findsource(object)
                  ^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/inspect.py", line 1089, in findsource
    raise OSError('could not get source code')
OSError: could not get source code

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<string>", line 6, in <module>
  File "/home/infatoshi/.local/lib/python3.12/site-packages/triton/runtime/jit.py", line 935, in jit
    return decorator(fn)
           ^^^^^^^^^^^^^
  File "/home/infatoshi/.local/lib/python3.12/site-packages/triton/runtime/jit.py", line 923, in decorator
    return JITFunction(
           ^^^^^^^^^^^^
  File "/home/infatoshi/.local/lib/python3.12/site-packages/triton/runtime/jit.py", line 756, in __init__
    super().__init__(fn)
  File "/home/infatoshi/.local/lib/python3.12/site-packages/triton/runtime/jit.py", line 463, in __init__
    raise ValueError("@jit functions should be defined in a Python file") from e
ValueError: @jit functions should be defined in a Python file
assistant
in 84out 231cache_r 39424cache_w 0
assistant
bash
args
{
  "command": "<517 chars \u2014 see below>",
  "description": "Verify Triton works on SM120"
}
command (517 chars)
cat > /tmp/test_triton.py << 'EOF'
import torch
import triton
import triton.language as tl

@triton.jit
def test_kernel(x_ptr, y_ptr, n: tl.constexpr):
    pid = tl.program_id(0)
    offsets = pid * 128 + tl.arange(0, 128)
    x = tl.load(x_ptr + offsets)
    tl.store(y_ptr + offsets, x * 2.0)

x = torch.randn(128, device='cuda')
y = torch.zeros(128, device='cuda')
test_kernel[(1,)](x, y, n=128)
print('Triton works on this GPU!')
print(torch.max(torch.abs(y - x * 2.0)).item())
EOF
python /tmp/test_triton.py 2>&1
tool
stdout (30 chars)
Triton works on this GPU!
0.0
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assistant
todowrite
args
{
  "todos": [
    {
      "priority": "high",
      "content": "Read reference.py, solution.py, check.py, benchmark.py, and problem.yaml to understand requirements",
      "status": "completed"
    },
    {
      "priority": "high",
      "content": "Check GPU availability and capabilities (sm_120 Blackwell)",
      "status": "completed"
    },
    {
      "priority": "high",
      "content": "Design and implement top-k kernel in solution.py",
      "status": "in_progress"
    },
    {
      "priority": "high",
      "content": "Run check.py to verify correctness",
      "status": "pending"
 

... (259 more chars)
tool
stdout (605 chars)
content: 'Read reference.py, solution.py, check.py, benchmark.py, and problem.yaml to understand requirements'
status: 'completed'
priority: 'high'
content: 'Check GPU availability and capabilities (sm_120 Blackwell)'
status: 'completed'
priority: 'high'
content: 'Design and implement top-k kernel in solution.py'
status: 'in_progress'
priority: 'high'
content: 'Run check.py to verify correctness'
status: 'pending'
priority: 'high'
content: 'Profile and iterate for performance'
status: 'pending'
priority: 'medium'
content: 'Final correctness check and submission'
status: 'pending'
priority: 'medium'
assistant
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assistant
write /home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/solution.py
diff (300 lines — TRUNCATED)
--- /dev/null
+++ b//home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/solution.py
@@ -0,0 +1,297 @@
+"""Top-k solution: CUDA C++ bitonic sort + merge via load_inline.
+
+Strategy:
+  - For k == 1: block-wide argmax reduction (simple and fast).
+  - For k > 1: tile-based bitonic sort in shared memory with a running top-k
+    merge buffer. Each block processes one row; the row is processed in tiles
+    of size TILE_SIZE (power of 2, up to 8192). Invalid positions beyond n
+    are padded with -FLT_MAX so they don't pollute the top-k.
+"""
+import torch
+import torch.nn as nn
+from torch.utils.cpp_extension import load_inline
+from pathlib import Path
+
+# ---------------------------------------------------------------------------
+# CUDA source
+# ---------------------------------------------------------------------------
+CUDA_SRC = r"""
+#include <cuda_runtime.h>
+#include <cstdint>
+#include <cfloat>
+#include <climits>
+
+// ---------------------------------------------------------------------------
+// Constants / helpers
+// ---------------------------------------------------------------------------
+#define TILE_SIZE 8192
+#define BLOCK_SIZE 256
+#define ELEMS_PER_THREAD (TILE_SIZE / BLOCK_SIZE)  // 32
+
+// ---------------------------------------------------------------------------
+// Argmax kernel (k == 1)
+// ---------------------------------------------------------------------------
+__global__ void argmax_kernel(
+    const float* __restrict__ x,
+    float* __restrict__ out_vals,
+    int64_t* __restrict__ out_idxs,
+    int batch, int n
+) {
+    // Shared memory for block reduction
+    __shared__ float s_vals[BLOCK_SIZE];
+    __shared__ int s_idxs[BLOCK_SIZE];
+
+    int row = blockIdx.x;
+    if (row >= batch) return;
+
+    const float* row_x = x + row * n;
+    int tid = threadIdx.x;
+
+    float local_max = -FLT_MAX;
+    int local_idx = -1;
+
+    // Each thread scans its elements
+    for (int i = tid; i < n; i += BLOCK_SIZE) {
+        float v = row_x[i];
+        if (v > local_max) {
+            local_max = v;
+            local_idx = i;
+        }
+    }
+
+    s_vals[tid] = local_max;
+    s_idxs[tid] = local_idx;
+    __syncthreads();
+
+    // Tree reduction (warp-level then block-level)
+    for (int s = BLOCK_SIZE / 2; s > 0; s >>= 1) {
+        if (tid < s) {
+            if (s_vals[tid + s] > s_vals[tid]) {
+                s_vals[tid] = s_vals[tid + s];
+                s_idxs[tid] = s_idxs[tid + s];
+            }
+        }
+        __syncthreads();
+    }
+
+    if (tid == 0) {
+        out_vals[row] = s_vals[0];
+        out_idxs[row] = (int64_t)s_idxs[0];
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Top-k helper: merge a sorted pair list of length k into the running top-k
+// ---------------------------------------------------------------------------
+__device__ void merge_topk(
+    float* running_vals, int* running_idxs, int k,
+    const float* tile_vals, const int* tile_idxs
+) {
+    // Two sorted lists (descending): running and tile. Merge top-k into running.
+    float tmp_vals[64];
+    int tmp_idxs[64];
+    int ri = 0, ti = 0, oi = 0;
+    while (oi < k) {
+        if (ti >= k || (ri < k && running_vals[ri] >= tile_vals[ti])) {
+            tmp_vals[oi] = running_vals[ri];
+            tmp_idxs[oi] = running_idxs[ri];
+            ri++;
+        } else {
+            tmp_vals[oi] = tile_vals[ti];
+            tmp_idxs[oi] = tile_idxs[ti];
+            ti++;
+        }
+        oi++;
+    }
+    // Write back
+    for (int i = 0; i < k; i++) {
+        running_vals[i] = tmp_vals[i];
+        running_idxs[i] = tmp_idxs[i];
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Top-k kernel via bitonic sort in shared memory
+// ---------------------------------------------------------------------------
+template <int K>
+__global__ void topk_kernel(
+    const float* __restrict__ x,
+    float* __restrict__ out_vals,
+    int64_t* __restrict__ out_idxs,
+    int batch, int n
+) {
+    // Dynamic shared memory: tile_vals[TILE_SIZE] + tile_idxs[TILE_SIZE]
+    // We use the first K slots for the running top-k between tiles
+    // (reuse the same memory to save space).
+    extern __shared__ char smem[];
+    float* tile_vals = (float*)smem;
+    int* tile_idxs = (int*)(smem + TILE_SIZE * sizeof(float));
+
+    // Running top-k occupies the same shared memory but we copy it out
+    // before starting a new tile (conceptually it lives separately).
+    float running_vals[64];
+    int running_idxs[64];
+
+    int row = blockIdx.x;
+    if (row >= batch) return;
+
+    // Initialize running top-k with -FLT_MAX
+    #pragma unroll
+    for (int i = 0; i < K; i++) {
+        running_vals[i] = -FLT_MAX;
+        running_idxs[i] = -1;
+    }
+
+    const float* row_x = x + row * n;
+    int tid = threadIdx.x;  // 0..BLOCK_SIZE-1
+
+    // Process tiles
+    for (int tile_base = 0; tile_base < n; tile_base += TILE_SIZE) {
+        int tile_end = min(tile_base + TILE_SIZE, n);
+        int tile_actual = tile_end - tile_base;
+
+        // ---- Load tile into shared memory (coalesced) ----
+        #pragma unroll
+        for (int i = 0; i < ELEMS_PER_THREAD; i++) {
+            int pos = tile_base + i * BLOCK_SIZE + tid;
+            int smem_pos = i * BLOCK_SIZE + tid;
+            if (pos < n) {
+                tile_vals[smem_pos] = row_x[pos];
+                tile_idxs[smem_pos] = pos;
+            } else {
+                // Pad with -inf
+                tile_vals[smem_pos] = -FLT_MAX;
+                tile_idxs[smem_pos] = -1;
+            }
+        }
+        __syncthreads();
+
+        // ---- Bitonic sort (full TILE_SIZE in shared memory) ----
+        int actual_tile_pow2 = 1;
+        while (actual_tile_pow2 < tile_actual) actual_tile_pow2 <<= 1;
+        // Use exactly TILE_SIZE (which is >= actual_tile_pow2) for the sort
+       

... (4330 more chars)
args
{
  "filePath": "/home/infatoshi/cuda/KernelBench-Hard/problems/05_topk_bitonic/solution.py",
  "content": "<9920 chars \u2014 see diff>"
}
tool
stdout (24 chars)
Wrote file successfully.
assistant
Let me write a scratch implementation first to test the approach, then iterate:
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bash
args
{
  "command": "<604 chars \u2014 see below>",
  "description": "Test CUDA load_inline"
}
command (604 chars)
python -c "
import torch
print('CUDA arch list:', torch.cuda.get_arch_list() if hasattr(torch.cuda, 'get_arch_list') else 'n/a')
# Test if we can compile CUDA inline
from torch.utils.cpp_extension import load_inline
src = 'extern \"C\" __global__ void dummy(float* x) { *x = 1.0f; }'
cpp = 'void dummy_launch(float* x) { dummy<<<1,1>>>(x); cudaDeviceSynchronize(); }'
ext = load_inline(name='test_compile', cpp_sources=cpp, cuda_sources=src, functions=['dummy_launch'], verbose=False)
x = torch.zeros(1, device='cuda')
ext.dummy_launch(x.data_ptr())
print(x.item())
print('CUDA compilation works')
" 2>&1
tool
stdout (6378 chars) — TRUNCATED
CUDA arch list: ['sm_75', 'sm_80', 'sm_86', 'sm_90', 'sm_100', 'sm_120']
Traceback (most recent call last):
  File "/home/infatoshi/.local/lib/python3.12/site-packages/torch/utils/cpp_extension.py", line 2774, in _run_ninja_build
    subprocess.run(
  File "/usr/lib/python3.12/subprocess.py", line 571, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['ninja', '-v']' returned non-zero exit status 1.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<string>", line 8, in <module>
  File "/home/infatoshi/.local/lib/python3.12/site-packages/torch/utils/cpp_extension.py", line 2174, in load_inline
    return _jit_compile(
           ^^^^^^^^^^^^^
  File "/home/infatoshi/.local/lib/python3.12/site-packages/torch/utils/cpp_extension.py", line 2268, in _jit_compile
    _write_ninja_file_and_build_library(
  File "/home/infatoshi/.local/lib/python3.12/site-packages/torch/utils/cpp_extension.py", line 2429, in _write_ninja_file_and_build_library
    _run_ninja_build(
  File "/home/infatoshi/.local/lib/python3.12/site-packages/torch/utils/cpp_extension.py", line 2791, in _run_ninja_build
    raise RuntimeError(message) from e
RuntimeError: Error building extension 'test_compile': [1/3] c++ -MMD -MF main.o.d -DTORCH_EXTENSION_NAME=test_compile -DTORCH_API_INCLUDE_EXTENSION_H -isystem /home/infatoshi/.local/lib/python3.12/site-packages/torch/include -isystem /home/infatoshi/.

... (4878 more chars)
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write /tmp/test_compile2.py
diff (26 lines)
--- /dev/null
+++ b//tmp/test_compile2.py
@@ -0,0 +1,23 @@
+import torch
+from torch.utils.cpp_extension import load_inline
+
+cuda_src = """
+extern "C" __global__ void dummy_kernel(float* x) {
+    *x = 1.0f;
+}
+
+extern "C" void launch_dummy(float* x) {
+    dummy_kernel<<<1, 1>>>(x);
+}
+"""
+
+cpp_src = """
+void launch_dummy(float* x);
+"""
+
+ext = load_inline(name='test_compile2', cpp_sources=cpp_src, cuda_sources=cuda_src, functions=['launch_dummy'], verbose=False)
+x = torch.zeros(1, device='cuda')
+ext.launch_dummy(x.data_ptr())
+torch.cuda.synchronize()
+print(x.item())
+print('CUDA compilation works!')
args
{
  "filePath": "/tmp/test_compile2.py",
  "content": "<542 chars \u2014 see diff>"
}
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