project_6/cccl_upstream/cub/examples/device/example_device_scan.cu

// SPDX-FileCopyrightText: Copyright (c) 2011, Duane Merrill. All rights reserved.
// SPDX-FileCopyrightText: Copyright (c) 2011-2018, NVIDIA CORPORATION. All rights reserved.
// SPDX-License-Identifier: BSD-3

/******************************************************************************
 * Simple example of DeviceScan::ExclusiveSum().
 *
 * Computes an exclusive sum of int keys.
 *
 * To compile using the command line:
 *   nvcc -arch=sm_XX example_device_scan.cu -I../.. -lcudart -O3
 *
 ******************************************************************************/

// Ensure printing of CUDA runtime errors to console
#define CUB_STDERR

#include <cub/device/device_scan.cuh>
#include <cub/util_allocator.cuh>

#include <cstdio>

#include "../../test/test_util.h"

using namespace cub;

//---------------------------------------------------------------------
// Globals, constants and aliases
//---------------------------------------------------------------------

bool g_verbose = false; // Whether to display input/output to console
CachingDeviceAllocator g_allocator(true); // Caching allocator for device memory

//---------------------------------------------------------------------
// Test generation
//---------------------------------------------------------------------

/**
 * Initialize problem
 */
void Initialize(int* h_in, int num_items)
{
  for (int i = 0; i < num_items; ++i)
  {
    h_in[i] = i;
  }

  if (g_verbose)
  {
    printf("Input:\n");
    DisplayResults(h_in, num_items);
    printf("\n\n");
  }
}

/**
 * Solve exclusive-scan problem
 */
int Solve(int* h_in, int* h_reference, int num_items)
{
  int inclusive = 0;
  int aggregate = 0;

  for (int i = 0; i < num_items; ++i)
  {
    h_reference[i] = inclusive;
    inclusive += h_in[i];
    aggregate += h_in[i];
  }

  return aggregate;
}

//---------------------------------------------------------------------
// Main
//---------------------------------------------------------------------

/**
 * Main
 */
int main(int argc, char** argv)
{
  int num_items = 150;

  // Initialize command line
  CommandLineArgs args(argc, argv);
  g_verbose = args.CheckCmdLineFlag("v");
  args.GetCmdLineArgument("n", num_items);

  // Print usage
  if (args.CheckCmdLineFlag("help"))
  {
    printf("%s "
           "[--n=<input items> "
           "[--device=<device-id>] "
           "[--v] "
           "\n",
           argv[0]);
    exit(0);
  }

  // Initialize device
  CubDebugExit(args.DeviceInit());

  printf("cub::DeviceScan::ExclusiveSum %d items (%d-byte elements)\n", num_items, (int) sizeof(int));
  fflush(stdout);

  // Allocate host arrays
  int* h_in        = new int[num_items];
  int* h_reference = new int[num_items];

  // Initialize problem and solution
  Initialize(h_in, num_items);
  Solve(h_in, h_reference, num_items);

  // Allocate problem device arrays
  int* d_in = nullptr;
  CubDebugExit(g_allocator.DeviceAllocate((void**) &d_in, sizeof(int) * num_items));

  // Initialize device input
  CubDebugExit(cudaMemcpy(d_in, h_in, sizeof(int) * num_items, cudaMemcpyHostToDevice));

  // Allocate device output array
  int* d_out = nullptr;
  CubDebugExit(g_allocator.DeviceAllocate((void**) &d_out, sizeof(int) * num_items));

  // Allocate temporary storage
  void* d_temp_storage      = nullptr;
  size_t temp_storage_bytes = 0;
  CubDebugExit(DeviceScan::ExclusiveSum(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items));
  CubDebugExit(g_allocator.DeviceAllocate(&d_temp_storage, temp_storage_bytes));

  // Run
  CubDebugExit(DeviceScan::ExclusiveSum(d_temp_storage, temp_storage_bytes, d_in, d_out, num_items));

  // Check for correctness (and display results, if specified)
  int compare = CompareDeviceResults(h_reference, d_out, num_items, true, g_verbose);
  printf("\t%s", compare ? "FAIL" : "PASS");
  AssertEquals(0, compare);

  // Cleanup
  if (h_in)
  {
    delete[] h_in;
  }
  if (h_reference)
  {
    delete[] h_reference;
  }
  if (d_in)
  {
    CubDebugExit(g_allocator.DeviceFree(d_in));
  }
  if (d_out)
  {
    CubDebugExit(g_allocator.DeviceFree(d_out));
  }
  if (d_temp_storage)
  {
    CubDebugExit(g_allocator.DeviceFree(d_temp_storage));
  }

  printf("\n\n");

  return 0;
}