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// SPDX-License-Identifier: BSD-3-Clause
/*
* streams2.cu - two non-default streams, concurrent kernels, event ordering.
*
* Two independent vectorAdds run concurrently on two non-default streams.
* A cross-stream dependency is then imposed with events: stream 2's in-place
* scale waits on stream 1's add via cudaEventRecord/cudaStreamWaitEvent, and
* stream 1's copy-back waits on stream 2's scale the same way. Both streams
* are joined with cudaStreamSynchronize before the host verifies:
*
* c1 == a1 + b1
* c2 == (a2 + b2) * 2
*
* Output lines are stable and greppable:
*
* DEVICE <name> cc=<major>.<minor> sm=<count> mem=<bytes>
* STREAMS n=<count> bad=<mismatches>
* TIMING ms=<elapsed>
* STATUS OK|FAIL
*
* Build with a static CUDA runtime (--cudart=static) so the guest only needs
* the driver's libcuda.so, not a CUDA toolkit installation:
*
* nvcc -O2 --cudart=static -o streams2 streams2.cu
*
* Then, from the guest: /tmp/streams2
*/
#include <cstdio>
#include <cstdlib>
#include <cstdint>
#include <cuda_runtime.h>
#define CHECK(x) \
do { \
cudaError_t e_ = (x); \
if (e_ != cudaSuccess) { \
printf("CUDA_ERROR %s at line %d\n", \
cudaGetErrorString(e_), __LINE__); \
printf("STATUS FAIL\n"); \
return 1; \
} \
} while (0)
__global__ void vadd(const float *a, const float *b, float *c, int n)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
if (i < n)
c[i] = a[i] + b[i];
}
__global__ void scale(float *c, float s, int n)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
if (i < n)
c[i] = c[i] * s;
}
int main(void)
{
cudaDeviceProp prop;
const int n = 1 << 15;
const float s2 = 2.0f;
size_t bytes = (size_t)n * sizeof(float);
float *h_a1, *h_b1, *h_c1, *h_a2, *h_b2, *h_c2;
float *d_a1, *d_b1, *d_c1, *d_a2, *d_b2, *d_c2;
cudaStream_t s1, s2s;
cudaEvent_t ev_add1, ev_scale2, t0, t1;
float ms = 0.0f;
int bad = 0, i;
const int grid = (n + 255) / 256;
setvbuf(stdout, NULL, _IONBF, 0);
CHECK(cudaGetDeviceProperties(&prop, 0));
printf("DEVICE %s cc=%d.%d sm=%d mem=%llu\n", prop.name,
prop.major, prop.minor, prop.multiProcessorCount,
(unsigned long long)prop.totalGlobalMem);
h_a1 = (float *)malloc(bytes);
h_b1 = (float *)malloc(bytes);
h_c1 = (float *)malloc(bytes);
h_a2 = (float *)malloc(bytes);
h_b2 = (float *)malloc(bytes);
h_c2 = (float *)malloc(bytes);
if (!h_a1 || !h_b1 || !h_c1 || !h_a2 || !h_b2 || !h_c2)
return 1;
for (i = 0; i < n; i++) {
h_a1[i] = (float)(i % 1000) * 0.5f;
h_b1[i] = (float)(i % 997) * 0.25f;
h_a2[i] = (float)(i % 991) * 0.125f;
h_b2[i] = (float)(i % 983) * 0.0625f;
}
CHECK(cudaMalloc(&d_a1, bytes));
CHECK(cudaMalloc(&d_b1, bytes));
CHECK(cudaMalloc(&d_c1, bytes));
CHECK(cudaMalloc(&d_a2, bytes));
CHECK(cudaMalloc(&d_b2, bytes));
CHECK(cudaMalloc(&d_c2, bytes));
CHECK(cudaStreamCreate(&s1));
CHECK(cudaStreamCreate(&s2s));
CHECK(cudaEventCreate(&ev_add1));
CHECK(cudaEventCreate(&ev_scale2));
CHECK(cudaEventCreate(&t0));
CHECK(cudaEventCreate(&t1));
CHECK(cudaEventRecord(t0));
/* Both input copies and both add kernels run concurrently. */
CHECK(cudaMemcpyAsync(d_a1, h_a1, bytes, cudaMemcpyHostToDevice, s1));
CHECK(cudaMemcpyAsync(d_b1, h_b1, bytes, cudaMemcpyHostToDevice, s1));
CHECK(cudaMemcpyAsync(d_a2, h_a2, bytes, cudaMemcpyHostToDevice, s2s));
CHECK(cudaMemcpyAsync(d_b2, h_b2, bytes, cudaMemcpyHostToDevice, s2s));
vadd<<<grid, 256, 0, s1>>>(d_a1, d_b1, d_c1, n);
vadd<<<grid, 256, 0, s2s>>>(d_a2, d_b2, d_c2, n);
CHECK(cudaGetLastError());
/* stream 2's scale waits for stream 1's add... */
CHECK(cudaEventRecord(ev_add1, s1));
CHECK(cudaStreamWaitEvent(s2s, ev_add1, 0));
scale<<<grid, 256, 0, s2s>>>(d_c2, s2, n);
CHECK(cudaGetLastError());
/* ...and stream 1's copy-back waits for stream 2's scale. */
CHECK(cudaEventRecord(ev_scale2, s2s));
CHECK(cudaStreamWaitEvent(s1, ev_scale2, 0));
CHECK(cudaMemcpyAsync(h_c1, d_c1, bytes, cudaMemcpyDeviceToHost, s1));
CHECK(cudaMemcpyAsync(h_c2, d_c2, bytes, cudaMemcpyDeviceToHost, s2s));
CHECK(cudaEventRecord(t1, s1));
CHECK(cudaStreamSynchronize(s1));
CHECK(cudaStreamSynchronize(s2s));
CHECK(cudaEventElapsedTime(&ms, t0, t1));
for (i = 0; i < n; i++) {
if (h_c1[i] != h_a1[i] + h_b1[i])
bad++;
if (h_c2[i] != (h_a2[i] + h_b2[i]) * s2)
bad++;
}
printf("STREAMS n=%d bad=%d\n", n, bad);
printf("TIMING ms=%.3f\n", ms);
if (bad != 0) {
printf("STATUS FAIL\n");
return 1;
}
printf("STATUS OK\n");
CHECK(cudaStreamDestroy(s1));
CHECK(cudaStreamDestroy(s2s));
CHECK(cudaEventDestroy(ev_add1));
CHECK(cudaEventDestroy(ev_scale2));
CHECK(cudaEventDestroy(t0));
CHECK(cudaEventDestroy(t1));
CHECK(cudaFree(d_a1));
CHECK(cudaFree(d_b1));
CHECK(cudaFree(d_c1));
CHECK(cudaFree(d_a2));
CHECK(cudaFree(d_b2));
CHECK(cudaFree(d_c2));
free(h_a1);
free(h_b1);
free(h_c1);
free(h_a2);
free(h_b2);
free(h_c2);
return 0;
}
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