[Starpu-devel] Question about sequential transfers in Starpu/SimGrid

[Lionel Eyraud-Dubois <lionel.eyraud-dubois@inria.fr>]

Hello,

   I was reading core/simgrid.c to understand the way StarPU models GPU 
transfers, which ones are sequential. And I found the following lines of 
code (simgrid.c:643) :

    /* GPU-GPU transfers are sequential with any RAM->GPU transfer */
    if (new_is_gpu_gpu
            && old_transfer->dst_node == new_transfer->src_node
            && old_transfer->dst_node == new_transfer->dst_node)
        return 1;
    if (old_is_gpu_gpu
            && new_transfer->dst_node == old_transfer->src_node
            && new_transfer->dst_node == old_transfer->dst_node)
        return 1;

And this confuses me because this can only be true if 
new_transfer->src_node == new_transfer->dst_node (resp. for old_transfer 
in the second case), which I believe is not supposed to happen. Am I 
missing anything ?

Best,

Lionel.