How to run a compiled .rex model from command line for fast repeated cost-function evaluation

stepan.ozana

Hi,
I have the following use case.

My REXYGEN model contains blocks with tunable parameters. One of the model outputs represents the value of interest, for example a cost function.

I would like to run the compiled model (*.rex) from the command line as fast as possible, ideally offline rather than in real time. For each run, I need to:

provide a specific set of parameter values,
execute one full evaluation of the model,
obtain the resulting value of the selected output.

More specifically, I want to call the model repeatedly from an external environment such as Python or Julia in order to tune the parameters and minimize the cost function.

Could you please advise what is the recommended workflow for this in REXYGEN?

In particular, I would like to know:

whether this can be done with the compiled .rex model directly,
how to pass parameter values from an external program,
how to read back the value of a selected output,
and whether Local Simulation mode is the right approach for this kind of fast offline repeated evaluation, for example with a fixed number of simulation steps or counter ticks.
Is this workflow supported, and if so, what is the simplest way to implement it?
Thanks Stepan

cechurat

@stepan-ozana Hi Stepan,

Thank you for your advanced question.

The proposed solution can look like the following:

Run RexCore from the command line with specific simulation parameters:
RexCore -z simulation.enabled=1

Simulation-related parameters (other parameters can be found at /rex/rexcore/rexcore.cfg.help):

simulation.enabled=1 // turns on simulation mode
simulation.tickmin=0 // minimum tick time in milliseconds (if calculations finish earlier, sleep is done; default 0, so no sleep is done)
simulation.steps // number of ticks after start, then the run stops
simulation.start // date and time before the start of the simulation; default 0, i.e. Rex epoch 1.1.2000 00:00:00

Load set of input parameters - use SILO/SILOS function block or STATELOAD/STATESAVE function block.
At the end of the simulation, you can store the results using the same FB as mentioned in 2. It is also possible to read the result values via the REST API. The RexCore will continue running after the specified tick count, but the blocks will no longer be executed.

If you have any additional questions, just let me know.

Regards,
Tomas

stepan.ozana

@cechurat Hi Tomas,

Thank you for your valuable comments.

I tried running:

"c:\Program Files\REX Controls\REXYGEN 3.0.5.17331\Bin\RexCore.exe" -z exec.file=myproject_exec.rex -z simulation.enabled=1 -z simulation.tickmin=0 -z simulation.steps=20000 -z simulation.start=0

I do not think it was successful, because it did not do anything. At the very least, it was supposed to create f.txt via the SILO block.

I believe there may be something wrong with this REXYGEN project, because whenever I try Local Simulation within REXYGEN Studio, it reports a RexCore crash; please see the screenshot in the bottom-right corner. As a consequence, the application freezes and I have to kill the RexCore process manually.

In Real Time mode, it seems to run normally: it shows trends and creates f.txt via the SILO block. There is also a minor issue with overtime in diagnostics, probably related to the PYTHON blocks. I am not sure whether this issue is critical enough to cause RexCore to crash in Local Simulation mode.

However, I believe this is a separate issue and is not directly related to the original topic of running Local Simulation mode in general.

Below you will find the project version needed to reproduce the issue.

Best regards,
Stepan

Project:
FC_Compact_Rezerovar_REXYGEN_V2.zip