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// SPDX-License-Identifier: BSD-3-Clause
/*
* inplace_scale.cu - minimal in-place scale repro for the streams2
* "scale wrote 1 page" class.
*
* One H2D, one in-place scale launch (c[i] *= 2 over 128 KB = 32 pages),
* one D2H, per-page diff. Run it repeatedly: if the launch writes only
* part of the buffer the per-page report names how many 4 KB blocks
* changed and the host log carries the launch's retire wait.
*
* Build: nvcc -O2 --cudart=static -o inplace_scale inplace_scale.cu
*/
#include <cstdio>
#include <cstdlib>
#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 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)
{
const int n = 1 << 15;
size_t bytes = (size_t)n * sizeof(float);
float *h, *d;
int i, bad = 0, first = -1, last = -1;
int nb = (n + 1023) / 1024, blk_bad = 0;
setvbuf(stdout, NULL, _IONBF, 0);
h = (float *)malloc(bytes);
if (!h)
return 1;
for (i = 0; i < n; i++)
h[i] = (float)(i % 1000) * 0.5f;
CHECK(cudaMalloc(&d, bytes));
CHECK(cudaMemcpy(d, h, bytes, cudaMemcpyHostToDevice));
printf("PTR d=%p\n", (void *)d);
scale<<<(n + 255) / 256, 256>>>(d, 2.0f, n);
CHECK(cudaGetLastError());
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(h, d, bytes, cudaMemcpyDeviceToHost));
for (i = 0; i < n; i++) {
float exp = (float)(i % 1000) * 0.5f * 2.0f;
if (h[i] != exp) {
bad++;
if (first < 0)
first = i;
last = i;
}
}
for (i = 0; i < nb; i++) {
int j, hit = 0;
for (j = i * 1024; j < (i + 1) * 1024 && j < n; j++)
if (h[j] != (float)(j % 1000) * 0.5f * 2.0f) {
hit = 1;
break;
}
if (hit)
blk_bad++;
}
printf("SCALE n=%d bad=%d first=%d last=%d blocks=%d/%d\n",
n, bad, first, last, blk_bad, nb);
printf("STATUS %s\n", bad ? "FAIL" : "OK");
return bad ? 1 : 0;
}
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