OpenCL device memory read/write issue

问题

I am using TI's Keystone II which has ARM as host and 8 accelerator DSP cores. These DSP cores don't talk to each other as they do not have any shared memory with them.

I am getting this strange issue that I am unable to rewrite into this 'cum' array in which I am computing the cumulative frequency. I am only able to read whatever I wrote to it the first time. The writes after that are not registered. Any solutions to this issue?

The device has a Unified Memory architecture. Also 'cum' and 'frequency' are of 'CL_MEM_READ_WRITE' type.

This code snippet runs on the DSP cores

...             
        //upscan
        for(i=0; i < 32; i++)
        {   
            if(pid<4)
            {
            localvar1 = frequency[(i*8)+(2*pid)];
            localvar2 = frequency[(i*8)+(2*pid)+1];
            cum[(i*8)+(2*pid)+1] = localvar1 + localvar2;
            }
        }
        for(i=0; i < 32; i++)
        {
            if(pid<2)
            {
            localvar1 = cum[(i*8)+(4*pid)+3];
            localvar2 = cum[(i*8)+(4*pid)+1];
            cum[(i*8)+(4*pid)+3] = localvar1 + localvar2;
            }           
        }
        for(i=0; i < 32; i++)
        {
            if(pid<1)
            {
            localvar1 = cum[(i*8)+(pid)+7];
            localvar2 = cum[(i*8)+(pid)+3];
            cum[(i*8)+(pid)+7] = localvar1 + localvar2;
            }
        }
...

回答1:

use a barrier or mem_fence between your for-loops, the exact flags choice depends on the type of memory you're using (global, local) and device specific details but a barrier should solve your problem.

来源：https://stackoverflow.com/questions/29887169/opencl-device-memory-read-write-issue