[Starpu-devel] data_unregister_submit() does not flush data from GPU to CPU

[Aleksandr Mikhalev <aleksandr.mikhalev@kaust.edu.sa>]

Dear StarPU developers,

My name is Aleksandr, I am a post-doctoral fellow in KAUST. I work on STARS-H 
project, a low-rank and hierarchical matrix market. I am about to submit 
StarPU issue, related with data synchronisation between CPU and GPU. Attached 
is a minimal working example, that I tested against several versions of 
StarPU. Problem is StarPU does not copy output data from GPU to CPU if 
corresponding handle is destroyed by starpu_data_unregister_submit(). The 
same holds true for starpu_invalidate_data_submit(). If I understood 
correctly, idea of “submit” functions is to hint StarPU to flush data from 
GPU to CPU, but instead it simply purges data on GPU without update in the 
main RAM. I could not find this problem in a bug tracker of StarPU, so I put 
it in the mailing list.

If I miss any critical info about setup and execution of the example, just 
let me now. This is how I did it:

1. I tested official release and 3 branches of git repository:
    release 1.2.4
    master branch (commit 5a69695aaeb434553ec193d184620c93311a4dc7)
    starpu-1.2 branch (commit 02085cfbf9605106467f4bde52cf0abc7e7db0d3)
    starpu-1.3 branch (commit 62cb08e2e2aa71e21847cad6cd02e0edb2d49c3a)

2. How I installed each StarPU from git repo:
    ./autogen.sh
    ./configure --disable-opencl --disable-build-examples --disable-starpu-top
        --disable-build-doc --disable-build-tests --disable-starpufft
        --disable-fortran --prefix=/starpu/path
    make -j
    make install

3. Test with "dmda" scheduler, result was the same for all tested versions:
    data_unregister: OK
    data_unregister_submit: WRONG
    data_unregister_submit: WRONG


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Regards,
Aleksandr.

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