cuda-samples/Samples/jacobiCudaGraphs/main.cpp

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// This sample demonstrates Instantiated CUDA Graph Update
// with Jacobi Iterative Method in 3 different methods:
// 1 - JacobiMethodGpuCudaGraphExecKernelSetParams() - CUDA Graph with
// cudaGraphExecKernelNodeSetParams() 2 - JacobiMethodGpuCudaGraphExecUpdate() -
// CUDA Graph with cudaGraphExecUpdate() 3 - JacobiMethodGpu() - Non CUDA Graph
// method

// Jacobi method on a linear system A*x = b,
// where A is diagonally dominant and the exact solution consists
// of all ones.
// The dimension N_ROWS is included in jacobi.h

#include <cuda_runtime.h>
#include <helper_cuda.h>
#include <helper_timer.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "jacobi.h"

// Run the Jacobi method for A*x = b on GPU with CUDA Graph -
// cudaGraphExecKernelNodeSetParams().
extern double JacobiMethodGpuCudaGraphExecKernelSetParams(
    const float *A, const double *b, const float conv_threshold,
    const int max_iter, double *x, double *x_new, cudaStream_t stream);

// Run the Jacobi method for A*x = b on GPU with Instantiated CUDA Graph Update
// API - cudaGraphExecUpdate().
extern double JacobiMethodGpuCudaGraphExecUpdate(
    const float *A, const double *b, const float conv_threshold,
    const int max_iter, double *x, double *x_new, cudaStream_t stream);

// Run the Jacobi method for A*x = b on GPU without CUDA Graph.
extern double JacobiMethodGpu(const float *A, const double *b,
                              const float conv_threshold, const int max_iter,
                              double *x, double *x_new, cudaStream_t stream);

// creates N_ROWS x N_ROWS matrix A with N_ROWS+1 on the diagonal and 1
// elsewhere. The elements of the right hand side b all equal 2*n, hence the
// exact solution x to A*x = b is a vector of ones.
void createLinearSystem(float *A, double *b);

// Run the Jacobi method for A*x = b on CPU.
void JacobiMethodCPU(float *A, double *b, float conv_threshold, int max_iter,
                     int *numit, double *x);

int main(int argc, char **argv) {
  if (checkCmdLineFlag(argc, (const char **)argv, "help")) {
    printf("Command line: jacobiCudaGraphs [-option]\n");
    printf("Valid options:\n");
    printf(
        "-gpumethod=<0,1 or 2>  : 0 - [Default] "
        "JacobiMethodGpuCudaGraphExecKernelSetParams\n");
    printf("                       : 1 - JacobiMethodGpuCudaGraphExecUpdate\n");
    printf("                       : 2 - JacobiMethodGpu - Non CUDA Graph\n");
    printf("-device=device_num     : cuda device id");
    printf("-help         : Output a help message\n");
    exit(EXIT_SUCCESS);
  }

  int gpumethod = 0;
  if (checkCmdLineFlag(argc, (const char **)argv, "gpumethod")) {
    gpumethod = getCmdLineArgumentInt(argc, (const char **)argv, "gpumethod");

    if (gpumethod < 0 || gpumethod > 2) {
      printf("Error: gpumethod must be 0 or 1 or 2, gpumethod=%d is invalid\n",
             gpumethod);
      exit(EXIT_SUCCESS);
    }
  }

  int dev = findCudaDevice(argc, (const char **)argv);

  double *b = NULL;
  float *A = NULL;
  b = (double *)calloc(N_ROWS, sizeof(double));
  A = (float *)calloc(N_ROWS * N_ROWS, sizeof(float));

  createLinearSystem(A, b);
  double *x = NULL;
  // start with array of all zeroes
  x = (double *)calloc(N_ROWS, sizeof(double));

  float conv_threshold = 1.0e-2;
  int max_iter = 4 * N_ROWS * N_ROWS;
  int cnt = 0;

  // create timer
  StopWatchInterface *timerCPU = NULL, *timerGpu = NULL;
  sdkCreateTimer(&timerCPU);

  sdkStartTimer(&timerCPU);
  JacobiMethodCPU(A, b, conv_threshold, max_iter, &cnt, x);

  double sum = 0.0;
  // Compute error
  for (int i = 0; i < N_ROWS; i++) {
    double d = x[i] - 1.0;
    sum += fabs(d);
  }
  sdkStopTimer(&timerCPU);
  printf("CPU iterations : %d\n", cnt);
  printf("CPU error : %.3e\n", sum);
  printf("CPU Processing time: %f (ms)\n", sdkGetTimerValue(&timerCPU));

  float *d_A;
  double *d_b, *d_x, *d_x_new;
  cudaStream_t stream1;
  checkCudaErrors(cudaStreamCreateWithFlags(&stream1, cudaStreamNonBlocking));
  checkCudaErrors(cudaMalloc(&d_b, sizeof(double) * N_ROWS));
  checkCudaErrors(cudaMalloc(&d_A, sizeof(float) * N_ROWS * N_ROWS));
  checkCudaErrors(cudaMalloc(&d_x, sizeof(double) * N_ROWS));
  checkCudaErrors(cudaMalloc(&d_x_new, sizeof(double) * N_ROWS));

  checkCudaErrors(cudaMemsetAsync(d_x, 0, sizeof(double) * N_ROWS, stream1));
  checkCudaErrors(
      cudaMemsetAsync(d_x_new, 0, sizeof(double) * N_ROWS, stream1));
  checkCudaErrors(cudaMemcpyAsync(d_A, A, sizeof(float) * N_ROWS * N_ROWS,
                                  cudaMemcpyHostToDevice, stream1));
  checkCudaErrors(cudaMemcpyAsync(d_b, b, sizeof(double) * N_ROWS,
                                  cudaMemcpyHostToDevice, stream1));

  sdkCreateTimer(&timerGpu);
  sdkStartTimer(&timerGpu);

  double sumGPU = 0.0;
  if (gpumethod == 0) {
    sumGPU = JacobiMethodGpuCudaGraphExecKernelSetParams(
        d_A, d_b, conv_threshold, max_iter, d_x, d_x_new, stream1);
  } else if (gpumethod == 1) {
    sumGPU = JacobiMethodGpuCudaGraphExecUpdate(
        d_A, d_b, conv_threshold, max_iter, d_x, d_x_new, stream1);
  } else if (gpumethod == 2) {
    sumGPU = JacobiMethodGpu(d_A, d_b, conv_threshold, max_iter, d_x, d_x_new,
                             stream1);
  }

  sdkStopTimer(&timerGpu);
  printf("GPU Processing time: %f (ms)\n", sdkGetTimerValue(&timerGpu));

  checkCudaErrors(cudaFree(d_b));
  checkCudaErrors(cudaFree(d_A));
  checkCudaErrors(cudaFree(d_x));
  checkCudaErrors(cudaFree(d_x_new));

  printf("&&&& jacobiCudaGraphs %s\n",
         (fabs(sum - sumGPU) < conv_threshold) ? "PASSED" : "FAILED");

  return (fabs(sum - sumGPU) < conv_threshold) ? EXIT_SUCCESS : EXIT_FAILURE;
}

void createLinearSystem(float *A, double *b) {
  int i, j;
  for (i = 0; i < N_ROWS; i++) {
    b[i] = 2.0 * N_ROWS;
    for (j = 0; j < N_ROWS; j++) A[i * N_ROWS + j] = 1.0;
    A[i * N_ROWS + i] = N_ROWS + 1.0;
  }
}

void JacobiMethodCPU(float *A, double *b, float conv_threshold, int max_iter,
                     int *num_iter, double *x) {
  double *x_new;
  x_new = (double *)calloc(N_ROWS, sizeof(double));
  int k;

  for (k = 0; k < max_iter; k++) {
    double sum = 0.0;
    for (int i = 0; i < N_ROWS; i++) {
      double temp_dx = b[i];
      for (int j = 0; j < N_ROWS; j++) temp_dx -= A[i * N_ROWS + j] * x[j];
      temp_dx /= A[i * N_ROWS + i];
      x_new[i] += temp_dx;
      sum += fabs(temp_dx);
    }

    for (int i = 0; i < N_ROWS; i++) x[i] = x_new[i];

    if (sum <= conv_threshold) break;
  }
  *num_iter = k + 1;
  free(x_new);
}