example_device_scan.cu

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 * Copyright (c) 2011, Duane Merrill.  All rights reserved.
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/******************************************************************************
 * 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 <stdio.h>

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

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

using namespace cub;


//---------------------------------------------------------------------
// Globals, constants and typedefs
//---------------------------------------------------------------------

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


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


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");
    }
}

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
//---------------------------------------------------------------------

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 = NULL;
    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 = NULL;
    CubDebugExit(g_allocator.DeviceAllocate((void**)&d_out, sizeof(int) * num_items));

    // Allocate temporary storage
    void            *d_temp_storage = NULL;
    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;
}