Parametrize a filename

GAMS
1

Let me preface this question by noting that I’m pretty new to GAMS.

I have a GAMS file which makes multiple calls to load and unload data from GDX files and I’d like to have a single line somewhere in the GAMS code to change the filenames referenced.

In particular, I want to include a specified parameter in a filename.

So for example I specify a parameter ‘scenario’ as ‘low’ somehow and then in all subsequent references the filename reflects this.

Something like:

execute_unload “C:\File directory\outputs_%scenario%.gdx”

To get :

“C:\File directory\outputs_low.gdx”

Is there a way to do this?

Cheers

Josh

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2

Hi Josh



You could use the following at the beginning of your gams file:

$if not set scenario $setglobal scenario low





Now you can run your model either:

  •      Without setting the scenario. In this case it will take the scenario “low”. If you want to change this scenario, you change it to “high”.

  •      with a batch file in the command window with the following text in your batch file (for example run.bat)

o gams mymodel – scenario=low

o gams mymodel --scenario=high

  •      in a dos window either as:

o gams mymodel (takes the default value for the scenario, e.g. low)

o gams mymode –scenario=high (for another scenario)

  •       or in the ide by putting –scenario=high in the parameters field (left of the dos command button). Without setting the parameter, it will run the default scenario.

Hope this helps

Renger


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From: gamsworld@googlegroups.com [mailto:gamsworld@googlegroups.com] On Behalf Of Josh Craig
Sent: Monday, November 10, 2014 04:47
To: gamsworld@googlegroups.com
Subject: Parametrize a filename





Let me preface this question by noting that I’m pretty new to GAMS.



I have a GAMS file which makes multiple calls to load and unload data from GDX files and I’d like to have a single line somewhere in the GAMS code to change the filenames referenced.



In particular, I want to include a specified parameter in a filename.



So for example I specify a parameter ‘scenario’ as ‘low’ somehow and then in all subsequent references the filename reflects this.



Something like:



execute_unload “C:\File directory\outputs_%scenario%.gdx”



To get :



“C:\File directory\outputs_low.gdx”



Is there a way to do this?



Cheers



Josh

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3

Josh,

you can use put commands for this, you can loop over the elements of a
set for the scenarios. This example below would actually write the
code, so you would have to run the resulting file. I suggest you to
use this after having ready all the previous elements of the model,
until its declaration. Then at the end you move the output into a new
file in each loop. With the details you have sent, an example could
be:

SET scenario /low, high, morescenarios/;
FILE josh /josh.gms/; PUT josh; josh.LW=0; josh.NW=0;
$onput
$onecho > exercise1.gms
$include CURRENT.gms
$include YOUR_MODEL_UNTIL_DECLARATION.gms
solve modelname using SOLVER maximizing OBJVAR;
execute_unload ‘output.gdx’ var1.L var2.L;
$offecho
$offput
LOOP(scenario,
PUT “$echo “,'”',“SET CURRENT(scenario) /”,scenario.TL,”/;“, '” >
CURRENT.gms’ /;
PUT “$call gams exercise1.gms " /;
PUT “$call mv output.gdx > output_”,scenario.TL,”.gdx" / /;
);

After running it, look for “josh.gms”

This initially seems complicated, but it is very useful, there is a
lot of documentation about using put commands.

I shall give credit to Uwe Schneider, who helped me to solve a similar
problem a few months ago (any mistake in the code above is only my
responsability)

Good luck,

Best,
Roger

\

4

Thanks Renger. $setglobal is just what I was looking for!

On Monday, November 10, 2014 6:56:35 PM UTC+11, Renger van Nieuwkoop wrote:

Hi Josh



You could use the following at the beginning of your gams file:

$if not set scenario $setglobal scenario low





Now you can run your model either:

  •      Without setting the scenario. In this case it will take the scenario “low”. If you want to change this scenario, you change it to “high”.

  •      with a batch file in the command window with the following text in your batch file (for example run.bat)

o gams mymodel – scenario=low

o gams mymodel --scenario=high

  •      in a dos window either as:

o gams mymodel (takes the default value for the scenario, e.g. low)

o gams mymode –scenario=high (for another scenario)

  •       or in the ide by putting –scenario=high in the parameters field (left of the dos command button). Without setting the parameter, it will run the default scenario.

Hope this helps

Renger


\

Modelworks

Gewerbestrasse 15

3600 Thun – Switzerland

+41 79 818 53 73

In…@modelworks.ch

blog.modelworks.ch







From: gams...@googlegroups.com [mailto:gams...@googlegroups.com] On Behalf Of Josh Craig
Sent: Monday, November 10, 2014 04:47
To: gams...@googlegroups.com
Subject: Parametrize a filename





Let me preface this question by noting that I’m pretty new to GAMS.



I have a GAMS file which makes multiple calls to load and unload data from GDX files and I’d like to have a single line somewhere in the GAMS code to change the filenames referenced.



In particular, I want to include a specified parameter in a filename.



So for example I specify a parameter ‘scenario’ as ‘low’ somehow and then in all subsequent references the filename reflects this.



Something like:



execute_unload “C:\File directory\outputs_%scenario%.gdx”



To get :



“C:\File directory\outputs_low.gdx”



Is there a way to do this?



Cheers



Josh

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5

Thanks Roger. I like the idea of being able to loop through scenarios.

On Monday, November 10, 2014 8:54:57 PM UTC+11, Roger Cremades wrote:

Josh,

you can use put commands for this, you can loop over the elements of a
set for the scenarios. This example below would actually write the
code, so you would have to run the resulting file. I suggest you to
use this after having ready all the previous elements of the model,
until its declaration. Then at the end you move the output into a new
file in each loop. With the details you have sent, an example could
be:

SET scenario /low, high, morescenarios/;
FILE josh /josh.gms/; PUT josh; josh.LW=0; josh.NW=0;
$onput
$onecho > exercise1.gms
$include CURRENT.gms
$include YOUR_MODEL_UNTIL_DECLARATION.gms
solve modelname using SOLVER maximizing OBJVAR;
execute_unload ‘output.gdx’ var1.L var2.L;
$offecho
$offput
LOOP(scenario,
PUT “$echo “,'”',“SET CURRENT(scenario) /”,scenario.TL,”/;“, '” >
CURRENT.gms’ /;
PUT “$call gams exercise1.gms " /;
PUT “$call mv output.gdx > output_”,scenario.TL,”.gdx" / /;
);

After running it, look for “josh.gms”

This initially seems complicated, but it is very useful, there is a
lot of documentation about using put commands.

I shall give credit to Uwe Schneider, who helped me to solve a similar
problem a few months ago (any mistake in the code above is only my
responsability)

Good luck,

Best,
Roger

–
To unsubscribe from this group and stop receiving emails from it, send an email to gamsworld+unsubscribe@googlegroups.com.
To post to this group, send email to gamsworld@googlegroups.com.
Visit this group at http://groups.google.com/group/gamsworld.
For more options, visit https://groups.google.com/d/optout.