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Dr. K. H. Coats

 

Unparalleled Example

Unfortunately, and amazingly after all these years of research, there are no reproducible examples in the literature with absolute timings substantiating the performance of any vendor's parallel model.  Typically, only virtually meaningless figures of 'parallel speedup' over their own undisclosed serial run times are given.  So, we can only present a hypothetical example, using commonly observed Sensor serial speedups.

Scenario 1

Sensitivity of simulation results to 10 variables is examined.  A base run is the best guess.  Each variable will be assigned low, best guess, and high values.  So 21 runs need to be made.  This or something similar might be done for history matching, optimization, or uncertainty quantification, possibly for training of a proxy model or in computing gradients, or in generation of probabilistic reserves estimates.

One user has a 16-node cluster and a parallel simulator.  He's getting parallel speedup of about 10, let's say from a 20 hour serial job to a 2 hour parallel job.  All runs are complete in 42 hours.

Another user has Sensor and 11 pc's (or that same 16-node cluster).  Let's say this is a black oil case, and Sensor is only 3 times faster than the first model, in serial.  Sensor completes all runs in 13.33 hours.  If it was a compositional case and Sensor was 8 times faster, Sensor would complete all runs in 5 hours.  If the Sensor user had the first user's cluster, he could look at sensitivities to 15 variables instead of 10, in the same time (this would take 62 hours for the parallel user).

Scenario 2

The same 21 runs are to be made.  The parallel user has five 16-node clusters.   So each cluster must run 4 jobs, and one cluster must run another one.  All runs are complete in 10 hours.

The Sensor user has 21 pc's, representing only about a quarter of the total computing power of the parallel user.  For the black oil case, Sensor completes all runs in 6.67 hours.  For the compositional case, in which Sensor has a greater serial speed advantage, all runs are complete in 2.5 hours.  If the Sensor user had those five clusters, he could look at sensitivities to 39 variables instead of 10 in the same time (this would take the parallel user 32 hours).

Scenario 3

Let's say that instead of 21 runs, 99 runs are needed (for 49 variables).

The parallel user needs to make 20 sets of runs on his five clusters.  All runs are complete in 40 hours.

The Sensor user has 50 pc's.  For the black oil case, all runs are complete in 13.33 hours.  For the compositional case, Sensor completes all runs in 5 hours.  The Sensor user could look at sensitivities to 79 variables instead of 49 in the same time, if he had the five clusters (this would take 64 hours for the parallel user).

Please check our numbers by comparing model performance on individual runs.


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