The user may also set the KMP Offset, which is the core offset for the current run. The KMP Offset relates to the number of cores already being used by the system, and is therefore usually set to zero. The KMP Offset should only be adjusted if the user wishes to run more than one model on the same machine. In order to run second model the KMP Offset should be set to the number of cores being used in the already running model. For example, assume a system comprising a Xeon Processer with 6 cores (12 threads), is already running a model on 2 cores (where KMP Offset had been set to 0). If the user wishes to run a second model, they then should set the KMP Offset to 2 and the OMP threads to 4. if you are using a machine with 16 cores, 32 threads, then
Run 1: # Threads = 8, KMP Offset = 0
Run 2: # Threads = 8, KMP Offset = 8
This will lock each thread to a unique core. Run 1 will be using 8 cores and Run 2 the other 8 cores. The total CPU usage will only show 50% because those calculations are based on the total number of threads, i.e. 32.
A typical Intel I7 computer had from has 4 to 6 cores. The way these cores are handled in the EFDC code is with the KMP_AFFINITY variable, defined as:
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Note that a "0_RunEFDC" file is created in the model folder each time the EFDC_DSI model is run. This file tells EE whether the model ran to completion or not as it is deleted on successful model completion.. If the user opens that file then they can see these parameters.
Figure 1 2381147 illustrates the binding of OpenMP thread to hardware thread contexts when specifying "KMP_AFFINITY=granularity=fine,compact".
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