code example
POSIX threads
Brook+ ATI GPU stream computing

#include <pthread.h>

float *x, *y;
#define PROC (8)
float e_vec[PROC];
int n_thread0, n_thread1;

// kernel
kernel void sub1(float x[], float y[],
  out float xout<>, out float eout<>)
{
  // do computation
  float i = 1 + indexof(xout).x;
  xout = x[i] + (y[i+1] + y[i-1])*.5f;
  eout = y[i] * y[i];
}

reduce void sub2(float y<>, reduce float e<>)
{
  e += y;
}

void *thread1(void *arg) {
  int p = (int)arg;
  int n0 = n_thread0 + (p * (n_thread1-n_thread0)) / PROC;
  int n1 = n_thread0 + ((p+1) * (n_thread1-n_thread0)) / PROC;
  #define BLOCK (8190)
  float xStream<BLOCK>;
  float xoutStream<BLOCK>;
  float yStream<BLOCK+2>;
  float einStream<BLOCK+2>;
  float eStream<1>;
  float e = 0;
  float ee = 0;
  for (int i=n0; i<n1; i+=BLOCK) {
   streamRead(xStream, x+i);
   streamRead(yStream, y+i-1);
   sub1(xStream, yStream, xoutStream, einStream);
   streamWrite(xoutStream, x+i);
   sub2(einStream, eStream);
   float e_local;
   streamWrite(eStream, &e_local);
   ee += e_local;
  }
  e += ee;
  e_vec[p] = e;
  return (void*) 0;
}

int main(int argc, char *argv[]) {
  int n = ...;
  float *x, *y;
  x = new float[n+1];
  y = new float[n+1];

  ... // fill x, y

  pthread_t threads[PROC];
  pthread_attr_t attr;
  pthread_attr_init(&attr);
  n_thread0 = 1;
  n_thread1 = n;
  float e = 0;
  // start threads and wait for termination
  for (int p=0; p<PROC; ++p)
   pthread_create(&threads[p], &attr, thread1, (void *)p);
  for (int p=0; p<PROC; ++p) {
   pthread_join(threads[p], NULL);
   e += e_vec[p];
  }

  ... // output x, e

  delete[] x, y;
  return 0;
}

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