Hello,

I have a problem while reading a couple of positions in a double array from different threads.

I enqueue the execution with :

nelements = nx*ny;

err = clEnqueueNDRangeKernel(queue,kernelTvl2of,1,NULL,&nelements,NULL,0,NULL,NULL);

kernelTvl2of has (among other) the code

size_t k = get_global_id(0);

(…)

u1_[k] = (float)u1[k];

(…)

barrier(CLK_GLOBAL_MEM_FENCE);

forwardgradient(u1_,u1x,u1y,k,nx,ny);

barrier(CLK_GLOBAL_MEM_FENCE);

and forwardgradient has the code:

void forwardgradient(global double *f, global double fx, global double fy, int ker,int nx, int ny){
unsigned int rowsnotlast = ((nx)(ny-1));
if(ker<rowsnotlast){
fx[ker] = f[ker+1] - f[ker];
fy[ker] = f[ker+nx] - f[ker];
}
if(ker<nxny){
fx[ker] = f[ker+1] - f[ker];
if(ker==4607){
fx[0] = f[4607];
fx[1] = f[4608];
fx[2] = f[4608] - f[4607];
fx[3] = f[ker];
fx[4] = f[ker+1];
fx[5] = f[ker+1] - f[ker];
}
}
if(ker==(nx*ny)-1){

fx[ker] = 0;

fy[ker] = 0;

}

if(ker%nx == nx-1){

fx[ker]=0;

}

fx[6] = f[4608];

}

When I get the contents of the first positions of fx, they are:

-6 0 6 -6 0 6 -6

And here’s my problem: when I query fx[ker+1] or fx[4608] on thread with id 4607 I get a ‘0’ (positions second and fifth of the output array), but from other threads I get a ‘-6’ last position of the output array)

Anyone has a clue on what I’m doing wrong, or where I could look to?

Thanks a lot,

Anton