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→‎timings for processing sweep "e" as a function of MAXIMUM_NUMBER_OF_PROCESSORS and MAXIMUM_NUMBER_OF_JOBS
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== timings for processing sweep "e" as a function of MAXIMUM_NUMBER_OF_PROCESSORS and MAXIMUM_NUMBER_OF_JOBS ==
The following is going to be rather technical! If you are only interested in crystallography, skip this.
Using
MAXIMUM_NUMBER_OF_PROCESSORS=2
MAXIMUM_NUMBER_OF_JOBS=8
we observe for the INTEGRATE step:
total cpu time used              2063.6 sec
total elapsed wall-clock time      296.1 sec
Using
MAXIMUM_NUMBER_OF_PROCESSORS=1
MAXIMUM_NUMBER_OF_JOBS=16
the times are
total cpu time used              2077.1 sec
total elapsed wall-clock time      408.2 sec
Using
MAXIMUM_NUMBER_OF_PROCESSORS=4
MAXIMUM_NUMBER_OF_JOBS=4
the times are
total cpu time used              2102.8 sec
total elapsed wall-clock time      315.6 sec
Using
MAXIMUM_NUMBER_OF_PROCESSORS=16 ! the default for xds_par on a 16-core machine
MAXIMUM_NUMBER_OF_JOBS=1 ! the default
the times are
total cpu time used              2833.4 sec
total elapsed wall-clock time      566.5 sec
but please note that this actually only uses 10 processors, since the default DELPHI=5
and the OSCILLATION_RANGE is 0.5°.
Using
MAXIMUM_NUMBER_OF_PROCESSORS=4
MAXIMUM_NUMBER_OF_JOBS=8
(thus overcommitting the available cores by a factor of 2) the times are
total cpu time used              2263.5 sec
total elapsed wall-clock time      320.8 sec
Using
MAXIMUM_NUMBER_OF_PROCESSORS=4
MAXIMUM_NUMBER_OF_JOBS=6
(thus overcommitting the available cores, but less severely) the times are
total cpu time used              2367.6 sec
total elapsed wall-clock time      267.2 sec
Thus,
MAXIMUM_NUMBER_OF_PROCESSORS=4
MAXIMUM_NUMBER_OF_JOBS=6
performs best for a 2-Xeon X5570 (HT enabled, thus 16 cores) machine with 24GB of memory and a RAID1 consisting of 2 1TB SATA disks. It should be noted that the dataset has 27GB, and in 296 seconds this means 92 MB/s continuous reading. The processing time is thus limited by the disk access, not by the CPU. And no, the data are not simply read from RAM (tested by "echo 3 > /proc/sys/vm/drop_caches" before the XDS run).
Kay
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