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// SPDX-License-Identifier: BSD-3-Clause
/*
* scale_probe.cu - localize the deterministic "in-place scale writes only the
* first 4 KB page" failure.
*
* Modes (argv[1]):
* V : vadd(a,b->c); sync; D2H+verify; vadd again; D2H+verify
* I : vadd(a,b->c); sync; D2H+verify; scale(c,*2 in place); sync;
* D2H+verify (with page map); scale again; sync; D2H+verify; D2H again
* O : vadd(a,b->c); sync; D2H+verify; scale_out(c->d,*2); sync;
* D2H+verify (with page map)
*
* Every stage also runs a GPU-side verify kernel that counts matching
* elements reading the device buffers (engine's own view) and writes the
* counts to a small buffer, D2H'd afterwards: separates "device pages never
* written" (GPU count low) from "D2H readback stale" (GPU count high, host
* count low).
*
* Build: nvcc -O2 --cudart=static -o scale_probe scale_probe.cu
*/
#include <cstdio>
#include <cstdlib>
#include <cstdint>
#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(float *c, float s, int n)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
if (i < n)
c[i] = c[i] * s;
}
__global__ void scale_out(const float *c, float *d, float s, int n)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
if (i < n)
d[i] = c[i] * s;
}
/* verify kernel: out[0]=count(c==a+b), out[1]=count(c==2*(a+b)) */
__global__ void vdigest(const float *a, const float *b, const float *c, int n,
unsigned long long *out)
{
int i = blockIdx.x * blockDim.x + threadIdx.x;
if (i >= n)
return;
if (c[i] == a[i] + b[i])
atomicAdd(&out[0], 1ull);
if (c[i] == (a[i] + b[i]) * 2.0f)
atomicAdd(&out[1], 1ull);
}
int main(int argc, char **argv)
{
const char *mode = argc > 1 ? argv[1] : "V";
cudaDeviceProp prop;
const int n = 1 << 15;
const int grid = (n + 255) / 256;
size_t bytes = (size_t)n * sizeof(float);
float *ha, *hb, *hc, *hd;
float *da, *db, *dc, *dd;
unsigned long long *d_out, h_out[2];
int i;
float k = argc > 2 ? atof(argv[2]) : 0.0f;
setvbuf(stdout, NULL, _IONBF, 0);
CHECK(cudaGetDeviceProperties(&prop, 0));
{
FILE *f = fopen("/proc/uptime", "r");
double up = -1.0;
if (f) { if (fscanf(f, "%lf", &up) != 1) up = -1.0; fclose(f); }
printf("UPTIME %.3f\n", up);
}
printf("DEVICE %s mode=%s seed=%g\n", prop.name, mode, (double)k);
ha = (float *)malloc(bytes);
hb = (float *)malloc(bytes);
hc = (float *)malloc(bytes);
hd = (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);
memset(hd, 0xCD, bytes);
CHECK(cudaMalloc(&da, bytes));
CHECK(cudaMalloc(&db, bytes));
CHECK(cudaMalloc(&dc, bytes));
CHECK(cudaMalloc(&dd, bytes));
CHECK(cudaMalloc(&d_out, 2 * sizeof(unsigned long long)));
printf("DPTRS da=%p db=%p dc=%p dd=%p\n", (void *)da, (void *)db,
(void *)dc, (void *)dd);
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("S1 vadd readback bad=%d/%d\n", b, n);
CHECK(cudaMemset(d_out, 0, 2 * sizeof(unsigned long long)));
vdigest<<<grid, 256>>>(da, db, dc, n, d_out);
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(h_out, d_out,
2 * sizeof(unsigned long long),
cudaMemcpyDeviceToHost));
printf("S1 GPU-DIGEST c_eq_ab=%llu c_eq_2ab=%llu\n", h_out[0],
h_out[1]);
}
if (!strcmp(mode, "V")) {
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("S2 vadd-again readback bad=%d/%d\n", b, n);
}
printf("STATUS DONE\n");
return 0;
}
if (!strcmp(mode, "I")) {
int stage;
for (stage = 0; stage < 2; stage++) {
float mult = stage == 0 ? 2.0f : 4.0f;
scale<<<grid, 256>>>(dc, 2.0f, n);
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(hc, dc, bytes, cudaMemcpyDeviceToHost));
{
int b = 0, page;
for (i = 0; i < n; i++)
if (hc[i] != (ha[i] + hb[i]) * mult)
b++;
printf("S%d inplace-scale readback bad=%d/%d (mult=%g)\n",
2 + stage, b, n, mult);
if (stage == 0)
for (page = 0; page < 32; page++) {
int pb = 0, k;
for (k = 0; k < 256; k++)
if (hc[page * 256 + k] !=
(ha[page * 256 + k] +
hb[page * 256 + k]) * mult)
pb++;
if (pb)
printf("S%d PAGE %d bad=%d/256 first=%g want=%g\n",
2 + stage, page,
pb, hc[page * 256],
(ha[page * 256] +
hb[page * 256]) * mult);
}
}
if (stage == 0) {
CHECK(cudaMemset(d_out, 0,
2 * sizeof(unsigned long long)));
vdigest<<<grid, 256>>>(da, db, dc, n, d_out);
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(h_out, d_out,
2 * sizeof(unsigned long long),
cudaMemcpyDeviceToHost));
printf("S2 GPU-DIGEST c_eq_ab=%llu c_eq_2ab=%llu\n",
h_out[0], h_out[1]);
}
}
printf("STATUS DONE\n");
return 0;
}
if (!strcmp(mode, "O")) {
scale_out<<<grid, 256>>>(dc, dd, 2.0f, n);
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(hd, dd, bytes, cudaMemcpyDeviceToHost));
{
int b = 0, page;
for (i = 0; i < n; i++)
if (hd[i] != (ha[i] + hb[i]) * 2.0f)
b++;
printf("S2 outofplace-scale readback bad=%d/%d\n", b, n);
for (page = 0; page < 32; page++) {
int pb = 0, k;
for (k = 0; k < 256; k++)
if (hd[page * 256 + k] !=
(ha[page * 256 + k] +
hb[page * 256 + k]) * 2.0f)
pb++;
if (pb)
printf("S2 PAGE %d bad=%d/256\n", page,
pb);
}
}
CHECK(cudaMemset(d_out, 0, 2 * sizeof(unsigned long long)));
vdigest<<<grid, 256>>>(da, db, dd, n, d_out);
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(h_out, d_out, 2 * sizeof(unsigned long long),
cudaMemcpyDeviceToHost));
printf("S2 GPU-DIGEST d_eq_ab=%llu d_eq_2ab=%llu\n", h_out[0],
h_out[1]);
printf("STATUS DONE\n");
return 0;
}
return 1;
}
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