OpenACC is getting a lot of attention recently and especially in the application to scientific computing. The main reason I believe is that these are compiler directives and hence reasonably fast to learn as long as you have pieces of code that are parallelisable. I wanted to see what compilers are publicly available for OpenACC.
Compiler support
The following compilers support the OpenACC directives (as of today)
OpenUH and accULL are open source and are available for download now. On a linux platform you can get these to build and check sone cool features of OpenACC.
/*
* Simple test
* allocates two vectors, fills the vectors, does axpy a couple of times,
* compares the results for correctness.
* This is the same as version s1.cpp with 'int' instead of 'double'
*/
#include <iostream>
#include <cstdio>
#include <openacc.h>
/* Depending on the GCC version you have installed, this cause warnings */
extern "C" int atoi(const char*);
static void
axpy( int* y, int* x, int a, int n ){
#pragma acc parallel loop present(x[0:n],y[0:n])
for( int i = 0; i < n; ++i )
y[i] += a*x[i];
}
static void
test( int* a, int* b, int n ){
#pragma acc data copy(a[0:n]) copyin(b[0:n])
{
axpy( a, b, 2, n );
for( int i = 0; i < n; ++i ) b[i] = 2;
#pragma acc update device(b[0:n])
axpy( a, b, 1.0, n );
}
}
int main( int argc, char* argv[] ){
int n = 1000;
if( argc > 1 ) n = atoi(argv[1]);
int* a, *b;
a = new int[n];
b = new int[n];
for( int i = 0; i < n; ++i ) a[i] = i;
for( int i = 0; i < n; ++i ) b[i] = n-i;
test( a, b, n );
int sum = 0;
for( int i = 0; i < n; ++i ) sum += a[i];
int exp = 0;
for( int i = 0; i < n; ++i ) exp += (int)i + 2*(int)(n-i) + 2;
std::cout << "Checksum is " << sum << std::endl;
if( exp != sum )
std::cout << "Difference is " << exp - sum << std::endl;
else
std::cout << "PASSED" << std::endl;
return 0;
}The most difficult bit is to get a compiler installed. The rest is very exciting!