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// SPDX-License-Identifier: BSD-3-Clause
/*
* ip_probe2.cu - why do in-place c stores vanish while prog stores land?
*
* After a vadd that fills c, three variants run on the SAME c:
* 1. scale_if : if (i<n) c[i] *= s; (control, like ip_probe)
* 2. scale_u : c[i] *= s; (unconditional, grid exact)
* 3. fill_c : c[i] = 7.0f; (store only, no load)
* 4. add_c : c[i] = c[i] + 1.0f; (load + store)
* Each stage reads c back and compares against the expected value at that
* stage. A separate prog buffer marks CTA execution.
*
* Build: nvcc -O2 --cudart=static -o ip_probe2 ip_probe2.cu
*/
#include <cstdio>
#include <cstdlib>
#include <cstring>
#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_if(float *c, float s, int n, unsigned *prog)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
if (i < n)
c[i] = c[i] * s;
if (threadIdx.x == 0)
prog[blockIdx.x] = 0xCAFEBABEu;
}
__global__ void scale_u(float *c, float s, unsigned *prog)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
c[i] = c[i] * s;
if (threadIdx.x == 0)
prog[blockIdx.x] = 0xDEADBEEFu;
}
__global__ void fill_c(float *c, unsigned *prog)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
c[i] = 7.0f;
if (threadIdx.x == 0)
prog[blockIdx.x] = 0xFEEDFACu;
}
__global__ void add_c(float *c, unsigned *prog)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
c[i] = c[i] + 1.0f;
if (threadIdx.x == 0)
prog[blockIdx.x] = 0x0DDF00Du;
}
int main(int argc, char **argv)
{
cudaDeviceProp prop;
const int n = 1 << 15;
const int grid = (n + 255) / 256;
size_t bytes = (size_t)n * sizeof(float);
float k = argc > 1 ? atof(argv[1]) : 0.0f;
float *ha, *hb, *hc;
float *da, *db, *dc;
unsigned *d_prog, h_prog[128];
int i, stage;
float mult;
setvbuf(stdout, NULL, _IONBF, 0);
CHECK(cudaGetDeviceProperties(&prop, 0));
printf("DEVICE %s seed=%g\n", prop.name, (double)k);
ha = (float *)malloc(bytes);
hb = (float *)malloc(bytes);
hc = (float *)malloc(bytes);
for (i = 0; i < n; i++) {
ha[i] = (float)(i % 1000) * 0.5f + k;
hb[i] = (float)(i % 997) * 0.25f + 2.0f * k;
}
memset(hc, 0xCD, bytes);
CHECK(cudaMalloc(&da, bytes));
CHECK(cudaMalloc(&db, bytes));
CHECK(cudaMalloc(&dc, bytes));
CHECK(cudaMalloc(&d_prog, 128 * sizeof(unsigned)));
printf("DPTRS da=%p db=%p dc=%p prog=%p\n", (void *)da, (void *)db,
(void *)dc, (void *)d_prog);
CHECK(cudaMemcpy(da, ha, bytes, cudaMemcpyHostToDevice));
CHECK(cudaMemcpy(db, hb, bytes, cudaMemcpyHostToDevice));
vadd<<<grid, 256>>>(da, db, dc, n);
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(hc, dc, bytes, cudaMemcpyDeviceToHost));
{
int b = 0;
for (i = 0; i < n; i++)
if (hc[i] != ha[i] + hb[i])
b++;
printf("VADD readback bad=%d/%d\n", b, n);
}
mult = 2.0f;
for (stage = 0; stage < 4; stage++) {
unsigned mark = 0;
CHECK(cudaMemset(d_prog, 0xEE, 128 * sizeof(unsigned)));
switch (stage) {
case 0:
scale_if<<<grid, 256>>>(dc, 2.0f, n, d_prog);
mult = 2.0f;
mark = 0xCAFEBABEu;
break;
case 1:
scale_u<<<grid, 256>>>(dc, 2.0f, d_prog);
mult = 4.0f;
mark = 0xDEADBEEFu;
break;
case 2:
fill_c<<<grid, 256>>>(dc, d_prog);
mark = 0xFEEDFACu;
break;
default:
add_c<<<grid, 256>>>(dc, d_prog);
mult = -1.0f;
mark = 0x0DDF00Du;
break;
}
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(h_prog, d_prog, 128 * sizeof(unsigned),
cudaMemcpyDeviceToHost));
{
int marked = 0;
for (i = 0; i < grid; i++)
if (h_prog[i] == mark)
marked++;
printf("S%d CTA-MARK marked=%d/%d\n", stage + 1,
marked, grid);
}
CHECK(cudaMemcpy(hc, dc, bytes, cudaMemcpyDeviceToHost));
if (stage < 2) {
int b = 0, first = -1;
for (i = 0; i < n; i++)
if (hc[i] != (ha[i] + hb[i]) * mult) {
b++;
if (first < 0)
first = i;
}
printf("S%d readback bad=%d/%d first=%d\n",
stage + 1, b, n, first);
} else if (stage == 2) {
int b = 0, first = -1;
for (i = 0; i < n; i++)
if (hc[i] != 7.0f) {
b++;
if (first < 0)
first = i;
}
printf("S3 readback bad=%d/%d first=%d (fill 7.0)\n",
b, n, first);
} else {
int b = 0, first = -1;
for (i = 0; i < n; i++)
if (hc[i] != 8.0f) {
b++;
if (first < 0)
first = i;
}
printf("S4 readback bad=%d/%d first=%d (add 1.0 to fill)\n",
b, n, first);
}
}
printf("STATUS DONE\n");
return 0;
}
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