New cplex options file for HPC runs, including documentation update

base/documentation/gh-pages/running_on_hpc/submitting_a_job.md

@@ -10,7 +10,12 @@ Remember to study the log report after your job finishes, so you can be more acc
 
 After having transferred our Balmorel model through WinSCP (see [previous page](access.md)), we need to submit a job. This means creating a job script that asks for the right amount of memory usage and time before completion. This is done through a job script, illustrated in the code snippet below. We refer to [this general guide](https://www.hpc.dtu.dk/?page_id=1416) by DTU Computing Center for the exact explanations of the different elements. Note that the paths in the `export` commands are specific to our setup at DTU's clusters. 
 
-The bottom commands assumes that the job script is submitted from inside your Balmorel folder, and that your Balmorel project contains a "scenario1" scenario - see [how to create new scenarios](../get_started/scenario_setup.md). The `--threads=$LSB_DJOB_NUMPROC` command makes sure that Balmorel does not use more cores than defined  in your job script (four in this case, due to `#BSUB -n 4`)
+The bottom commands assumes that the job script is submitted from inside your Balmorel folder, and that your Balmorel project contains a "scenario1" scenario - see [how to create new scenarios](../get_started/scenario_setup.md). The `threads=$LSB_DJOB_NUMPROC` command makes sure that Balmorel does not use more cores than defined  in your job script (four in this case, due to `#BSUB -n 4`)
+
+:::{warning}
+Please make sure to switch to the solver options file `cplex.op2`, by going into the `balgams.opt` file and setting `$Setglobal USEOPTIONFILE 2`. Otherwise CPLEX will overwrite the number of chosen threads and will ue more resources than requested.
+:::
+
 ```bash
 #!/bin/sh 
 ### General options 
@@ -48,7 +53,7 @@ export LD_LIBRARY_PATH=/appl/gams/47.6.0:$LD_LIBRARY_PATH
 # Go to model folder of your scenario - this assumes that the job script is at the same level of the Balmorel folder
 cd scenario1/model 
 # Run Balmorel
-gams Balmorel --threads=$LSB_DJOB_NUMPROC
+gams Balmorel threads=$LSB_DJOB_NUMPROC
 ```
 
 ## Submitting the Job from PuTTY

base/model/balgams.opt

@@ -152,6 +152,7 @@ option intVarUp = 0
 $Setglobal USEOPTIONFILE 4
 *!option 0   No option file is used. Note that not setting anything will generate an error.
 *!option 1   Use option file SolverName.opt.
+*!option 2   Predefined, don't change. Used with CPLEX it opens cplex.op2 and sets 'LPmethod 4' to run barrior method. Also does not set any Threads option to allow running on HPC.
 *!option 4   Predefined, don't change. Used with CPLEX it opens cplex.op4 and sets 'LPmethod 4' to run barrior method.
 *!option 6   Predefined, don't change. Used with CPLEX it opens cplex.op6 and sets 'LPmethod 6' to run multiple methods in parallel.
 

base/model/cplex.op2

@@ -0,0 +1,11 @@
+* Option file 2 for CPLEX solver for HPC runs. For possible options, see the GAMS Solver Manual.
+* To use with CPLEX,  set  '$Setglobal USEOPTIONFILE 2' in balgams.opt.
+* Do not change this file, it is predefined.
+* To use other options with CPLEX, make and/or use some other file, see USEOPTIONFILE in balgams.opt.
+* "LPmethod  4": Barrier method
+* If memory tight, set the Threads parameter to 1.
+* advind is set to 0 by default since for large problems a better performance has been experienced. If 0, the optimization will not use the previous solution to try to find the next run faster.
+
+LPmethod  4
+advind 0
+predual -1