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Exploring Global Reduce Optimization: Could Reducing Memory Roundtrips Improve Performance? #39

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Exploring Global Reduce Optimization: Could Reducing Memory Roundtrips Improve Performance? #39

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14 changes: 5 additions & 9 deletions marlin/marlin_cuda_kernel.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -527,18 +527,14 @@ __global__ void Marlin(
int row = (threadIdx.x % 32) / 4;

if (!first) {
// Interestingly, doing direct global accesses here really seems to mess up the compiler and lead to slowdowns,
// hence we also use async-copies even though these fetches are not actually asynchronous.
#pragma unroll
for (int i = 0; i < thread_m_blocks * 4; i++) {
cp_async4_pred(
&sh[c_sh_wr + c_sh_wr_delta * i],
&C[c_gl_wr + c_gl_wr_delta_o * (i / 2) + c_gl_wr_delta_i * (i % 2)],
i < (thread_m_blocks - 1) * 4 || 8 * (i / 2) + row < prob_m
);
if (i < (thread_m_blocks - 1) * 4 || 8 * (i / 2) + row < prob_m) {
int4 c_val = C[c_gl_wr + c_gl_wr_delta_o * (i / 2) + c_gl_wr_delta_i * (i % 2)];
sh[c_sh_wr + c_sh_wr_delta * i] = c_val;
}
}
cp_async_fence();
cp_async_wait<0>();
__syncthreads();
}

#pragma unroll
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