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--- hpc:bghep:benchmarks [2014/02/17 16:48]
asc
+++ hpc:bghep:benchmarks [2014/05/27 16:33]
edmay
@@ Line 42: / Line 42: @@
 {{:hpc:bghep:alcf-vesta-pythia6-promc-mpi-c.png?400|}}
+This plot shows the efficiency (R_1c / Nc / R_Nc) v. Nc, where
+<code>
+R == sec/event  =       job_run_time/total_number_of_events
+Nc == number of cores used in job
+</code>
+For a perfect speed-up this would always be 1. My experience with clusters of
+smaller size is that 80% is usually achievable while 20% is quite low and the
+usual interpretation is the code has high fraction of serialization. For this
+case it would be more efficient to run 8 jobs of 512 cores than 1 job of 4096.
+This of course is speculation on my part as I have not identified to cause of
+the inefficiency!
 ===== Fig 4 =====
@@ Line 47: / Line 61: @@
 {{:hpc:bghep:alcf-vesta-pythia6-promc-mpi-d.png?400|}}
+The ALCF experts suggested the I/O model of 1 directory and many files in that 1 directory would preform badly due to lock contention
+on the directory! Thus the example code was modified to use a model
+of 1 output promc data file per directory. Running the modified code
+produced the following figures:
+http://www.hep.anl.gov/may/ALCF/new.vesta.4up.pdf Vesta Plots
+Focusing on the 'Efficiency' plots there appears to be some (small)
+improvements both at low core numbers and a high core numbers
+As part of the bootcamp for MIRA the code was moved to the
+BG/Q Mira and a subset up the benchmarks were run in the new
+IO model. The results are shown in
+http://www.hep.anl.gov/may/ALCF/new.mira.4up.pdf Mira figures
 [[hpc:bghep:| << back]]
- --- //[[[email protected]|Ed May]] 2014/02/04 10:42//
+ --- //[[[email protected]|Ed May]] 2014/02/04 //
+ --- //[[[email protected]|Ed May]] 2014/05/27 //
  --- //[[[email protected]|Sergei Chekanov]] 2014/02/04 10:42//

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