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The activated modes of ePHASORSIM’s parallel feature are determined using the following license keys:

EPHASOR_PARALLELIZE_GENUNITS

ePHASORSIM parallelizes the computation of generator units (GenUnits)

EPHASOR_PARTITION_POWERSYSTEM

ePHASORSIM also parallelizes the nodal equations

Note: If neither of the above license keys is enabled, no parallelization occurs.

The parallelization is controlled using:

  • the EPHASOR_THREADS environment variable

  • Two parameters in the Simulation settings tab of the Simulink mask: Number of partitions and Optimize number of threads (Windows only)

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It is not recommended to use the EPHASOR_THREADS variable so that the algorithm can find the best setting. Defining EPHASOR_THREADS on Windows restricts the range of number of thread-pool sizes the algorithm will test.

Note: If MATLAB is started in standalone mode (i.e. not through RT-LAB), the EPHASOR_THREADS variable potentially defined in the RT-LAB project will not be active, unless this variable is defined explicitly as an environment variable of the machine.

On Linux, by default, ePHASORSIM uses the 3rd core (core No. 2 with zero indexing) unless the EPHASOR_THREADS environment variable is defined. If the performance is not optimal (e.g. if there are overruns) parallelism can be controlled by defining EPHASOR_THREADS to change the number of threads, or to control core assignment to avoid conflicts with other RT-LAB features such as ARTEMiS or some drivers.

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The following abbreviations are used throughout this guide:

NP

Number of partitions parameter, set in the mask.

ONT

Optimize number of threads (Windows only) algorithm, set in the mask.

NC

Number of available physical cores of simulator.


  • on Windows: NC = number of exiting CPU cores.

  • on Linux: NC = min(number of existing CPU cores, value of EPHASOR_NUM_CORES in the license)

maxNTH

maximum number of threads that can be used for parallelization.


  • if EPHASOR_THREADS is defined: maxNTH = number of cores specified in EPHASOR_THREADS, with an upper limit of NC - 2

  • if EPHASOR_THREADS is not defined: maxNTH = 1

NTH

actual number of threads used by ePHASORSIM to parallelize GenUnits (and nodal equations if NP > 1)


  • if ONT is disabled: NTH = min(maxNTH, NC - 2)

  • if ONT is enabled (Windows only): During the first few steps of the simulation, the optimization algorithm finds the optimal value for NTH within the following range: 1<= NTH <= min(maxNTH, NC - 2)

The first and second table below summarizes calculations of NTH and also parallelization modes for Windows and Linux targets respectively.

Summary of Parallelization Modes for a Windows Target

ONT

Enabled

Disabled

NP

=1

>1

=1

>1

NTH is

:

calculated

Calculated

optimally in

this

the range

:

[1,min(maxNTH, NC-2)]

min(maxNTH, NC-2)

Parallelization

Mode

mode is

:

applied to

GenUnits only

Entire Network

GenUnits only

Entire Network

Summary of Parallelization Modes for a Linux Target

NP

=1

>1

NTH is

:

calculated

min(maxNTH, NC-2)

Parallelization

Mode

mode is

:

applied to

GenUnits only

Entire Network

EPHASOR_THREADS Syntax

The syntax for EPHASOR_THREADS is EPHASOR_THREADS=<core<core_list>list>, where the <core<core_list> list> grammar is given in the following table.

...

<core_id> :=

Syntax Table for Grammar of the EPHASOR_THREADS Variable

...

<core_list> :=

...

<elem> | <elem>,<core_list>

...

<elem> :=

...

<core_id> | <range>

...

<range> :=

...

<core_id>-<core_id>

variable

Code Block
<core_list> := <elem> | <elem>,<core_list>
<elem>      := <core_id> | <range>
<range>     := <core_id>-<core_id>
<core_id>   := <positive_integer>

Its meaning is the same on Windows and Linux, with the exception that:

  • On Linux, it is used to define which cores specifically will be used in the simulation (sets the affinity).

  • On Windows, it is used only to deduce the number of cores that the simulation will run on, but cannot assign specific cores.

For example, EPHASOR_THREADS=3 and EPHASOR_THREADS=5 mean that we want the simulation to run on only one core. On Linux, it also defines which core should be used (core 3 in the first case, core 5 in the second case).

The following examples are all valid values:

EPHASOR_THREADS=2,3,5

in this case, we want to use 3 cores (on Linux, cores 2, 3, and 5)

EPHASOR_THREADS=3-6

this is equivalent to EPHASOR_THREADS=3,4,5,6 meaning we want to use 4 cores (on Linux, cores 3, 4, 5, and 6)

EPHASOR_THREADS=2,4-6

this is equivalent to EPHASOR_THREADS=2,4,5,6

If EPHASOR_THREADS is not defined, the default value is 2 - (NC - 2)

Definition of EPHASOR_THREADS

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The EPHASOR_THREADS variable may be defined as a user environment variable.

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When using MATLAB directly, set EPHASOR_THREADS as a system environment variable prior to launching MATLAB. This can be done in System Properties, as in the figure below.

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Notes on Linux Targets and EPHASOR_THREADS

  • Care must be taken to avoid conflicts in core assignment. For example, if in the model there is a driver that uses core 4, this core should not be used in the value of EPHASOR_THREADS.
    Otherwise, unknown behavior could occur.

  • The core IDs are 0 indexed.

  • Cores 0 and 1 are reserved for RT-LAB. Only cores indexed 2 and greater are recommended for use with the EPHASOR_THREADS variable.

  • Please refer to, Migration Notes, to see changes regarding EPHASOR_THREADS in different versions.