error in using cuda mapped memory a test program for mapped memory

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi, guys,

I wrote a test program for the use of mapped memory. However, the it failed and I don’t know why.

Here is the source code:

#include "cuda_runtime.h"

#include <stdlib.h>

#include <stdio.h>

int main(void) {

	unsigned int *h_array, *d_array, *h_array_test;

	int cudaError;

	int num = 5;

	int size = num * sizeof(unsigned int);

	cudaSetDevice(0);

	// set device flag

	cudaSetDeviceFlags( cudaDeviceMapHost );

	// allocate pinned memory

	cudaError=cudaHostAlloc( (void**) &(h_array), size, cudaHostAllocMapped );

	if (cudaError) 

		printf ("Failed to allocate pinned memory \n");

	// get device ptr

	cudaError=cudaHostGetDevicePointer( (void**) &(d_array), h_array, 0 );

	if (cudaError) 

		printf ("Failed to get device pointer \n");

	// initialize test data

	for (int i = 0; i < num; i ++)

	{

		h_array[i] = i;

	}

	// output array in host memory

	printf("array in host memory:\n");

	for (int i = 0; i < num; i ++)

	{

		printf("%d: %d\n", i, h_array[i]);

	}

	printf("\n");

	

	// output array in device memory

	//cudaMemcpy(d_array, h_array, size, cudaMemcpyHostToDevice);

	h_array_test = (unsigned int*)malloc(size);

	cudaError=cudaMemcpy( h_array_test, d_array, size, cudaMemcpyDeviceToHost );

	if (cudaError) 

		printf ("Failed to copy device memory \n");

	printf("array in device memory:\n");

	for (int i = 0; i < num; i ++)

	{

		printf("%d: %d\n", i, h_array_test[i]);

	}

	printf("\n");

}

And the result is as follows:

array in host memory:

0: 0

1: 1

2: 2

3: 3

4: 4

Failed to copy device memory

array in device memory:

0: -1163005939

1: -1163005939

2: -1163005939

3: -1163005939

4: -1163005939

Apparently, the mapping was not sucessful. Anyone can help me out? Lots of thanks!

BTW: my GPU is Quadro FX3800 and the compute capability is 1.3, which supports page-locked memory mapping