Using  "#pragma omp flush" in emulator

Yes Ted, I am using pragma in the middle of the code. A simple test code is attached. You will see that a variable called 'size'

in core B is incremented by core A, but sometimes it is not visible by core A in its future access. Test the code with 4 cores.

Omid

Any ideas? Plus is there anything wrong with using 'pragma' in the middle of executing code?

Omid

Thanks for the modified code. Executing the above code on emulator leads to 3 possible results:

(1) it works as we expect (each code copy its id to its right hand nieghbor in a round robin manner)

(2) Sometimes just one core copy its ID to the nieghbor core and then Assert statement will be false. (this behaviour is not expected)

(3) Sometimes it crashes in the middle of execution. (this is also unexpected)

Could anyone test the above code on SCC platform, since we haven't got the platform yet? I want to understand whether the emulator is guilty or RCCE library (or maybe the code itself !).

Thanks,

Omid

This is exactly my code which runs on emulator:

#include <stdio.h>
#include <stdlib.h>
#include "../../include/RCCE_lib.h"
#include "../../include/RCCE.h"
#include<assert.h>

int RCCE_APP(int argc, char** argv) {
char *p;
int ID, next, prev;
RCCE_init(&argc, &argv);
ID = RCCE_ue();
next = (ID + 1) % RCCE_num_ues();
prev = (ID - 1 >= 0) ? ID - 1 : RCCE_num_ues() - 1;
p = (char *)RCCE_malloc(32);
*(int *)p = 0;
RCCE_barrier(&RCCE_COMM_WORLD);
RCCE_acquire_lock(0);
printf("Core %d writes ' %d ' to the MPB of core %d\n", ID, ID, next);
*(int *)(p - (char *)RCCE_comm_buffer[ID] + (char *)RCCE_comm_buffer[next]) = ID;
RCCE_release_lock(0);
RCCE_barrier(&RCCE_COMM_WORLD);
assert(*(int *)p == prev);
RCCE_finalize();
}

And RCCE version is : "1.0.13.x" and I am using the trunc revision.

I still have the same strange behaviour. Are you sure no "#pragma omp flush " is needed (befroe reads or after writes) in order to make changes made by one thread to shared variables be visible to others threads too?

Omid

Strange. I also build emulator with gcc.

App behaves in this way:

Sometimes it crashes -> Here I suspect the RCCE_barrier on emulator.

Sometimes Assert statement is false -> Here I am not sure how it can be explained. Maybe some coherence issues between omp threads.

And sometimes it works as it should.

Could you please send me the code that you already run on actual hardware?

Thanks,

Omid