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example_device_select_if.cu
/******************************************************************************
* Copyright (c) 2011, Duane Merrill. All rights reserved.
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/******************************************************************************
* Simple example of DeviceSelect::If().
*
* Selects items from from a sequence of int keys using a
* section functor (greater-than)
*
* To compile using the command line:
* nvcc -arch=sm_XX example_device_select_if.cu -I../.. -lcudart -O3
*
******************************************************************************/
// Ensure printing of CUDA runtime errors to console
#define CUB_STDERR
#include <stdio.h>
#include <cub/util_allocator.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
struct GreaterThan
{
int compare;
__host__ __device__ __forceinline__
GreaterThan(int compare) : compare(compare) {}
__host__ __device__ __forceinline__
bool operator()(const int &a) const {
return (a > compare);
}
};
//---------------------------------------------------------------------
// Test generation
//---------------------------------------------------------------------
void Initialize(
int *h_in,
int num_items,
int max_segment)
{
int key = 0;
int i = 0;
while (i < num_items)
{
// Randomly select number of repeating occurrences uniformly from [1..max_segment]
unsigned short max_short = (unsigned short) -1;
unsigned short repeat;
RandomBits(repeat);
repeat = (unsigned short) ((float(repeat) * (float(max_segment) / float(max_short))));
repeat = CUB_MAX(1, repeat);
int j = i;
while (j < CUB_MIN(i + repeat, num_items))
{
h_in[j] = key;
j++;
}
i = j;
key++;
}
if (g_verbose)
{
printf("Input:\n");
DisplayResults(h_in, num_items);
printf("\n\n");
}
}
template <typename SelectOp>
int Solve(
int *h_in,
SelectOp select_op,
int *h_reference,
int num_items)
{
int num_selected = 0;
for (int i = 0; i < num_items; ++i)
{
if (select_op(h_in[i]))
{
h_reference[num_selected] = h_in[i];
num_selected++;
}
else
{
h_reference[num_items - (i - num_selected) - 1] = h_in[i];
}
}
return num_selected;
}
//---------------------------------------------------------------------
// Main
//---------------------------------------------------------------------
int main(int argc, char** argv)
{
int num_items = 150;
int max_segment = 40; // Maximum segment length
// Initialize command line
CommandLineArgs args(argc, argv);
g_verbose = args.CheckCmdLineFlag("v");
args.GetCmdLineArgument("n", num_items);
args.GetCmdLineArgument("maxseg", max_segment);
// Print usage
if (args.CheckCmdLineFlag("help"))
{
printf("%s "
"[--n=<input items> "
"[--device=<device-id>] "
"[--maxseg=<max segment length>]"
"[--v] "
"\n", argv[0]);
exit(0);
}
// Initialize device
CubDebugExit(args.DeviceInit());
// Allocate host arrays
int *h_in = new int[num_items];
int *h_reference = new int[num_items];
// Select a pivot index
unsigned int pivot_index;
unsigned int max_int = (unsigned int) -1;
RandomBits(pivot_index);
pivot_index = (unsigned int) ((float(pivot_index) * (float(num_items - 1) / float(max_int))));
printf("Pivot idx: %d\n", pivot_index); fflush(stdout);
// Initialize problem and solution
Initialize(h_in, num_items, max_segment);
GreaterThan select_op(h_in[pivot_index]);
int num_selected = Solve(h_in, select_op, h_reference, num_items);
printf("cub::DeviceSelect::If %d items, %d selected (avg run length %d), %d-byte elements\n",
num_items, num_selected, (num_selected > 0) ? num_items / num_selected : 0, (int) sizeof(int));
fflush(stdout);
// 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 and num selected
int *d_out = NULL;
int *d_num_selected_out = NULL;
CubDebugExit(g_allocator.DeviceAllocate((void**)&d_out, sizeof(int) * num_items));
CubDebugExit(g_allocator.DeviceAllocate((void**)&d_num_selected_out, sizeof(int)));
// Allocate temporary storage
void *d_temp_storage = NULL;
size_t temp_storage_bytes = 0;
CubDebugExit(DeviceSelect::If(d_temp_storage, temp_storage_bytes, d_in, d_out, d_num_selected_out, num_items, select_op));
CubDebugExit(g_allocator.DeviceAllocate(&d_temp_storage, temp_storage_bytes));
// Run
CubDebugExit(DeviceSelect::If(d_temp_storage, temp_storage_bytes, d_in, d_out, d_num_selected_out, num_items, select_op));
// Check for correctness (and display results, if specified)
int compare = CompareDeviceResults(h_reference, d_out, num_selected, true, g_verbose);
printf("\t Data %s ", compare ? "FAIL" : "PASS");
compare = compare | CompareDeviceResults(&num_selected, d_num_selected_out, 1, true, g_verbose);
printf("\t Count %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_num_selected_out) CubDebugExit(g_allocator.DeviceFree(d_num_selected_out));
if (d_temp_storage) CubDebugExit(g_allocator.DeviceFree(d_temp_storage));
printf("\n\n");
return 0;
}