openacc create data while running inside a kernels - openacc

Question

I'm having a task that is to be accelerated by OpenACC. I need to do dynamic memory allocation within a kernel computation. I've built a simpler demo for it as following.
#include <iostream>
using namespace std;
#pragma acc routine seq
int *routine(int init) {
int *ptr;
#pragma acc data create(ptr[:10])
for (int i = 0; i < 10; ++i) {
ptr[i] = init + i;
}
return ptr;
}
void print_array(int *arr) {
for (int i = 0; i < 10; ++i) {
cout << arr[i] << " ";
}
cout << endl;
}
int main(void) {
int *arrs[5];
#pragma acc kernels
for (int i = 0; i < 5; ++i) {
arrs[i] = routine(i);
}
for (int i = 0; i < 5; ++i) {
print_array(arrs[i]);
}
return 0;
}
In this demo, I'm trying to call the routine while running inside a kernel construct. The routine procedure wants to create some data within the GPU and put some values into it.
While I can compile the code, but it reports runtime problems as following.
lisanhu#lisanhu-XPS-15-9550:create_and_copyout$ pgc++ -o test main.cc -acc -Minfo=accel
routine(int):
6, Generating acc routine seq
main:
23, Generating implicit copyout(arrs[:])
26, Accelerator restriction: size of the GPU copy of arrs is unknown
Loop is parallelizable
Generating implicit copy(arrs[:][:])
Accelerator kernel generated
Generating Tesla code
26, #pragma acc loop gang, vector(32) /* blockIdx.x threadIdx.x */
lisanhu#lisanhu-XPS-15-9550:create_and_copyout$ ./test
call to cuStreamSynchronize returned error 715: Illegal instruction
I'm wondering what I should do to accomplish this task (dynamically allocating memory within processing of a kernel construct). Really appreciate it if you could help.

Answer 1

This is untested, and probably very slow, but this might do what you need it to.
int main() {
const int num = 20;
int a[x] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
int* sizes = (int *)malloc(num * sizeof(int));
int *ptrs[num];
int* temp, *temp2;
int sum;
int* finished = (int *)malloc(num * sizeof(int));
for (int x = 0; x < num; ++x){
finished[x] = 0;
}
#pragma acc kernels copyin(a[0:10]) copyout(ptrs[:num][:1]) async(num*2+1)
{
#pragma acc loop private(temp)
for (int i = 0; i < num; ++i){
#pragma acc loop seq async(i)
for (int j = 0; j < 1; ++j){
temp = ptrs[x];
sizes[i] = ...
}
while (ptrs[x] != x);
ptrs[x] = routine(a, sizes[i]);
}
}
while (true){
sum = 0;
for (int x = 0; x < num; ++x){
sum += finished[x];
}
if (sum == num){
break;
}
for (int x = 0; x < num; ++x){
if (acc_async_test(x) != 0 && finished[x] == 0){
finished[x] = 1;
#pragma acc update host(sizes[x:1])
temp = (int *)malloc(size[x] * sizeof(int));
#pragma acc enter data copyin(temp[0:x])
temp2 = acc_deviceptr(temp);
ptrs[x] = temp2;
#pragma acc update device(ptrs[x:1][0:1])
}
}
}
}