topic Yes, it work! Thanks a lot! in Software Archive

Return pointer from MIC malloc

Guangming_T_ — Tue, 24 Dec 2013 03:28:50 GMT

In my project, I need to pass pointer among different offload functions. However, I do not want to use global variables. For example.

I want to allocate an array on accelerator in new_array function, and hope that it would return an address on accelerator side so that I could pass the address to the next function exe_array. But, the following codes do not work.

Any solution to this case? Say again, I do not want to use global variables. Thanks!

#include <stdio.h>
#include <stdlib.h>

void* new_array();
void exe_array(int *);
int main()
{
int i;
int * p;
p = new_array();
exe_array(p);
for(i=0;i<32;i++)
printf("p=%p: %d\n",&p, p);

#pragma offload target(mic) nocopy(p)
free(p);
}

void* new_array()
{
int i;
int *p;
#pragma offload target(mic) nocopy(p)
{
p=(int *) malloc(32*sizeof(int));
for(i=0; i<32; i++)
p=i;
}
return p;
}

void exe_array(int *p)
{
int i;
#pragma offload target(mic) nocopy(p)
{
for(i=0; i<32;i++)
p=-1;
}
}

Maybe you want something like

Gregg_S_Intel — Tue, 24 Dec 2013 13:53:10 GMT

Maybe you want something like this.

#include <stdio.h>
#include <stdlib.h>

void* new_array();
void exe_array(void *);
int main()
{
   int i;
   void * p;
   p = new_array();
   exe_array(p);

#pragma offload target(mic)
free(p);
}

void* new_array()
{
   void *p;
#pragma offload target(mic)
   {
   p=malloc(32*sizeof(int));
   int i;
   int* q=(int*)p;
   for(i=0; i<32; i++)
     q=i;
   }
   return p;
}

void exe_array(void *p)
{
   #pragma offload target(mic)
   {
     int i;
     int* q=(int*)p;
     for(i=0; i<32;i++)
       printf("%d ",q);
     printf("\n");
   }
}

Yes, it work! Thanks a lot!

Guangming_T_ — Tue, 24 Dec 2013 14:10:00 GMT

Yes, it work! Thanks a lot!

Greg,

jimdempseyatthecove — Tue, 24 Dec 2013 15:35:35 GMT

Greg,

Is there a requirement that the copy of the pointer on the host be void*?

I would imagine that it is not, however, use of void* will hinder your using the pointer unintentionally and would be good programming practice.

Jim Dempsey

Jim,

Gregg_S_Intel — Tue, 24 Dec 2013 19:52:50 GMT

Jim,

I think we do have to use a void type to get a pointer from the coprocessor.

Gregg Skinner