Re: upc_all_gather algorithm ...

From: Paul H. Hargrove (PHHargrove_at_lbl_dot_gov)
Date: Tue Dec 19 2006 - 10:52:30 PST

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    Konstantin Kleisouris wrote:
    >Hi everyone, 
    >   Does anyone know what algorithm is used for the implementation of
    >Thank you,
      The current gather algorithm is a "flat tree" topology with all data 
    being sent by the source threads to the destination thread.  Depending 
    on the SYNC flags and size of the data, a few different mechanisms may 
    be used to move the data (message-send, RDMA-put, Rendezous-RDMA-put).  
    If you want or need more detail, let me know.
      The current implementations of the UPC collectives in the Berkeley UPC 
    compiler were written to be correct, but little effort was given to 
    making them the most efficient or most scalable.  Work is in progress 
    right now to rewrite the collectives for efficiency and scalability.  We 
    hope to offer much improved UPC collectives performance in a future release.
    Paul H. Hargrove                          PHHargrove_at_lbl_dot_gov
    Future Technologies Group                 
    HPC Research Department                   Tel: +1-510-495-2352
    Lawrence Berkeley National Laboratory     Fax: +1-510-486-6900

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