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

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