Re: CCL:EWALD PME problem

Hi, Rick,
 The transpose in CHARMM is a problem mainly because of the limitations
 in CHARMM's communication library. WIth full freedom to use
 simple MPI asynchronous send and receives, we could resolve a
 lot of the trouble. That remark is to justify the work I
 did to try to fix an abominable communication time during
 the FFT transpose (for the same basic algorithm CHARMM took
 3-4 times as long as AMBER). Of the several methods I
 came up with, what appeared best was a binary-tree type idea
 which required a power-of-two number of PEs.
 THere is another method I worked out which only requires
 even number of PEs so there are always pairs communicating between
 each other.
 Anyway the bottom line is that the 2**N restriction will work the
 best, though an asychronous method is much better.
 You should try MPIFFT in your pref.dat and see if that gets you
 more of what you want. Yikes, I forgot all about these restrictions
 and making sure they got documented.
 Physical mail:   Dr. Michael F. Crowley
                  Department of Molecular Biology, TPC6
                  The Scripps Research Institute
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