135 lines
2.7 KiB
Plaintext
135 lines
2.7 KiB
Plaintext
#include "../common/error.cuh"
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#include "../common/floats.hpp"
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#include "../common/clock.cuh"
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__global__ void reduce(real *x, real *y, const int N)
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{
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int tid = threadIdx.x;
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int ind = tid + blockIdx.x * blockDim.x;
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extern __shared__ real curr_x[];
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curr_x[tid] = (ind < N) ? x[ind] : 0.0;
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for (int offset = blockDim.x/2 ; offset > 0 ; offset /= 2)
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{
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if (tid < offset)
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{
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curr_x[tid] += curr_x[tid + offset];
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}
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__syncthreads();
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}
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if (tid == 0)
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{
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y[blockIdx.x] = curr_x[0];
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}
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}
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__global__ void reduce2(real *x, real *y, const int N)
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{
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int tid = threadIdx.x;
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int ind = tid + blockIdx.x * blockDim.x;
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extern __shared__ real curr_x[];
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curr_x[tid] = (ind < N) ? x[ind] : 0.0;
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for (int offset = blockDim.x/2 ; offset > 0 ; offset /= 2)
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{
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if (tid < offset)
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{
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curr_x[tid] += curr_x[tid + offset];
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}
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__syncthreads();
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}
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if (tid == 0)
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{
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// 原子函数 atomicAdd(*address, val).
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atomicAdd(y, curr_x[0]);
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}
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}
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int main()
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{
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int N = 1e8;
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int M = N * sizeof(real);
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int bSize = 32;
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int gSize = (N + bSize - 1)/bSize;
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cout << FLOAT_PREC << endl;
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real *h_x, *h_y;
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h_x = new real[N];
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h_y = new real[gSize];
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for (int i = 0; i < N; ++i)
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{
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h_x[i] = 1.23;
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}
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cudaClockStart
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real *d_x, *d_y;
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CHECK(cudaMalloc(&d_x, M));
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CHECK(cudaMalloc(&d_y, gSize*sizeof(real)));
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CHECK(cudaMemcpy(d_x, h_x, M, cudaMemcpyDefault));
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cudaClockCurr
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reduce<<<gSize, bSize, (bSize+1)*sizeof(real)>>>(d_x, d_y, N);
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CHECK(cudaMemcpy(h_y, d_y, gSize*sizeof(real), cudaMemcpyDefault));
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real res = 0;
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for(int i = 0; i < gSize; ++i)
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{
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res += h_y[i];
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}
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cout << "reduce result: " << res << endl;
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cudaClockCurr
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reduce<<<gSize, bSize, (bSize)*sizeof(real)>>>(d_x, d_y, N);
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CHECK(cudaMemcpy(h_y, d_y, gSize*sizeof(real), cudaMemcpyDefault));
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res = 0.0;
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for(int i = 0; i < gSize; ++i)
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{
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res += h_y[i];
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}
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cout << "reduce result: " << res << endl;
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cudaClockCurr
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real *d_y2, *h_y2;
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h_y2 = new real(0.0);
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CHECK(cudaMalloc(&d_y2, sizeof(real)));
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// 采用原子函数、共享内存的核函数归约，
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// 由于减少了主机和设备间的数据传输，效率得以提高。
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reduce2<<<gSize, bSize, (bSize)*sizeof(real)>>>(d_x, d_y2, N);
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CHECK(cudaMemcpy(h_y2, d_y2, sizeof(real), cudaMemcpyDefault));
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cout << "reduce2 result: " << *h_y2 << endl;
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cudaClockCurr
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delete[] h_x;
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delete[] h_y;
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delete h_y2;
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CHECK(cudaFree(d_x));
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CHECK(cudaFree(d_y));
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CHECK(cudaFree(d_y2));
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return 0;
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}
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