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Question on Sample OpenMP configuration file post

RIZUAN
Expert 1285 points


Hi everyone,

This post is actually about another post by a member of TI, Sample OpenMP configuration file. I don't want to mess that page. My question is, by using that configuration file and the platform.xdc, does it mean that

   1. SharedRegion is in APP_HEAPOMP,

   2. HeapOMP.sharedRegionId is in DDR3_DATA, and

   3. OpenMP.stackRegionId is in DDR3_DATA as well?

In the configuration file, all three above is set to 2. From other pages, I understand that when set the OpenMP.stackRegionID to -1, this will map the region to L2SRAM, and 2 for DDR3. Since in the platform.xdc, the DDR3 now has 3 section; DDR3 for codeMemory, DDR3_DATA for dataMemory and APP_HEAPOMP for (I believe) for the SharedRegion, setting those values to 2 made me confuse. 

I'm a beginner in OpenMP in this embedded system (C6678L). Hope the answer later can improve my understanding. Thanks also to the TI member that wrote the page.

Many thanks,

Rizuan

  • 0
    TI__Expert 3350 points

    Rizuan,

    APP_HEAPOMP, DDR3_DATA and DDR3 are names of regions in memory as defined in the sample Platform file. The sample configuration file uses DDR3 for code and DDR3_DATA for data.

    The SharedRegion definition in the configuration file creates a shared region in APP_HEAPOMP and assigns it an id of 2.

    • Setting HeapOMP.sharedRegionId to 2 specifies that all mallocs in the application are satisfied out of the heap created in SharedRegion #2
    • Setting OpenMP.stackRegionId to 2 specifies that OpenMP thread stacks are allocated out of the same heap in SharedRegion #2

    Typically, OpenMP.stackRegionId is set to a SharedRegion Id - the only exception is -1 which is used to indicate L2SRAM.

    Note: The OpenMP runtime internally creates SharedRegion 0 (in OpenMP.xs).

    Ajay

  • 0 in reply to Ajay Jayaraj
    Expert 1285 points

    Hi Ajay,

    Thanks. Your explanation makes me understand better now.

    Let said if I assign the SharedRegion with Id = 2 and I set all the HeapOMP.sharedRegionId, OpenMP.stackRegionId to 2 in my project, and I have created several variables like input, A, B, and C using Memory_alloc, by utilizing a heap in my DDR3 but the initialization is at the beginning of my program i.e. outside the parallel region. Then in my code I have:

    #pragma omp parallel shared(input) private(A, B, C)

    {

    .......

    From your explanation in your previous post before, I understand that the memory section that have the heap above should be my SharedRegion. Am I right?

    This question is related to my problem and discussing about the same project that you have replied here.

    Many thanks, Ajay.

    Kind regards,

    Rizuan

  • 0 in reply to RIZUAN
    TI__Expert 3350 points

    Rizuan,

    A malloc() will allocate out of the heap in Shared Region 2. The behavior of Memory_alloc will depend on the first argument - if it's NULL, the allocation will occur out of heap in Shared Region 2.

    Ajay