Hi Graham, here are the all-to-all test results with the modification to the decision routine you suggested yesterday. Now the routine behaves nicely for 128 and 256 float messages on 128 CPUs! For the other sizes one probably wants to keep the original algorithm, since it is faster there. However I have the feeling that for messages >= 4096 floats there still exists the old problem since the execution times are so variable there (note that the standard deviation rises by more than a factor of 10 when going from 2048 to 4096 floats.) If you need additional test results to tune the decision functions please let me know.
Carsten OMPI tuned all-to-all with modification: ======================================== mesg size time in seconds #CPUs floats average std.dev. min. max. 128 1 0.001253 0.000074 0.001141 0.001470 128 2 0.023507 0.000563 0.022562 0.024761 128 4 0.023435 0.000426 0.022582 0.024166 128 8 0.023438 0.000359 0.022904 0.024104 128 16 0.023664 0.000438 0.022844 0.024670 128 32 0.024136 0.000463 0.023297 0.025117 128 64 0.024704 0.000535 0.023727 0.026030 128 128 0.025750 0.000525 0.024592 0.026799 * 128 256 0.028862 0.000683 0.027389 0.030168 * 128 512 0.035869 0.001214 0.034067 0.038655 128 1024 0.046528 0.001722 0.043549 0.050432 128 2048 0.072388 0.007032 0.066708 0.104358 128 4096 0.217678 0.097312 0.135113 0.409431 128 8192 0.378586 0.090267 0.297878 0.577771 128 16384 0.567473 0.105083 0.483573 0.735509 128 32768 1.151343 0.146547 0.937150 1.404478 128 65536 2.298998 0.169669 1.983286 2.572027 128 131072 4.070989 0.159958 3.691039 4.373587 > > OMPI tuned all-to-all: > > ====================== > > mesg size time in seconds > > #CPUs floats average std.dev. min. max. > > 128 1 0.001288 0.000102 0.001077 0.001512 > > 128 2 0.008391 0.000400 0.007861 0.009958 > > 128 4 0.008403 0.000237 0.008095 0.009018 > > 128 8 0.008228 0.000942 0.003801 0.008810 > > 128 16 0.008503 0.000191 0.008233 0.008839 > > 128 32 0.008656 0.000271 0.008084 0.009177 > > 128 64 0.009085 0.000209 0.008757 0.009603 > > 128 128 0.251414 0.073069 0.011547 0.506703 ! > > 128 256 0.385515 0.127661 0.251431 0.578955 ! > > 128 512 0.035111 0.000872 0.033358 0.036262 > > 128 1024 0.046028 0.002116 0.043381 0.052602 > > 128 2048 0.073392 0.007745 0.066432 0.104531 > > 128 4096 0.165052 0.072889 0.124589 0.404213 > > 128 8192 0.341377 0.041815 0.309457 0.530409 > > 128 16384 0.507200 0.050872 0.492307 0.750956 > > 128 32768 1.050291 0.132867 0.954496 1.344978 > > 128 65536 2.213977 0.154987 1.962907 2.492560 > > 128 131072 4.026107 0.147103 3.800191 4.336205 > > > > alternative all-to-all: > > ====================== > > 128 1 0.012584 0.000724 0.011073 0.015331 > > 128 2 0.012506 0.000444 0.011707 0.013461 > > 128 4 0.012412 0.000511 0.011157 0.013413 > > 128 8 0.012488 0.000455 0.011767 0.013746 > > 128 16 0.012664 0.000416 0.011745 0.013362 > > 128 32 0.012878 0.000410 0.012157 0.013609 > > 128 64 0.013138 0.000417 0.012452 0.013826 > > 128 128 0.014016 0.000505 0.013195 0.014942 + > > 128 256 0.015843 0.000521 0.015107 0.016725 + > > 128 512 0.052240 0.079323 0.027019 0.320653 ! > > 128 1024 0.123884 0.121560 0.038062 0.308929 ! > > 128 2048 0.176877 0.125229 0.074457 0.387276 ! > > 128 4096 0.305030 0.121716 0.176640 0.496375 ! > > 128 8192 0.546405 0.108007 0.415272 0.899858 ! > > 128 16384 0.604844 0.056576 0.558657 0.843943 ! > > 128 32768 1.235298 0.097969 1.094720 1.451241 ! > > 128 65536 2.926902 0.312733 2.458742 3.895563 ! > > 128 131072 6.208087 0.472115 5.354304 7.317153 ! --------------------------------------------------- Dr. Carsten Kutzner Max Planck Institute for Biophysical Chemistry Theoretical and Computational Biophysics Department Am Fassberg 11 37077 Goettingen, Germany Tel. +49-551-2012313, Fax: +49-551-2012302 eMail ckut...@gwdg.de http://www.gwdg.de/~ckutzne