7_advanced_changeCode.md

Advanced: Change MAgPIE GAMS Code

Florian Humpenöder ([email protected]) 13 October, 2019

1 Learning objectives

MAgPIE has a modular concept. Each module (e.g. cropland) can have several realization (e.g. dynamic and static). This tutorial shows how to add new realizations and how to modify existing realizations.

2 Adding a new realization (cropland)

We want to add a new realization to the cropland module. In the MAgPIE 4.1 release the cropland module (30_crop) has only one realization called “endo_jun13”. In this realization irrigation of bioenergy crops is prohibited. We will add a new realization, based on “endo_jun13”, which allows for irrigation of bioenergy crops. We will call the new realization “endo_sep19”.

Create a new realization by copying an existing one

We first copy-paste the folder “endo_jun13” and the file “endo_jun13.gms” (both located in “modules/30_crop”), and rename them to “endo_sep19” and “endo_sep19.gms” respectivly.

Include it properly via lucode::update_modules_embedding()

To include the new realization “endo_sep19” properly into the GAMS code we run a specific R command in the main folder. First navigate in your command line to the MAgPIE main folder, then open a new R session (type “R” followed by ENTER), and then copy-paste the following R command: lucode::update_modules_embedding()

Do a simple modification in the new realization

The prohibition of irrigated bioenergy is specified in the file “presolve.gms” within the “endo_sep19” realization. We just have to remove (or comment out) lines 8-9 from this file to allow for irrigation of bioenergy crops.

*vm_area.fx(j,"begr","irrigated")=0;

*vm_area.fx(j,"betr","irrigated")=0;

Finally, we run lucode::update_fulldataOutput() to update the automatic GAMS code declarations and output definitions.

Note: This command is not needed for this exercise. But if you change, add or delete variables/parameters this command is of high importance to avoid GAMS compilation errors.

Set the new realization in cfg and test the model

For a quick test, we simply set the new realization in the file main.gms in line 179 (replace endo_jun13 by endo_sep19). We can then check if the model compiles correctly with gams main.gms action=C

For starting a model run, we would have to make a change in the config file config/default.cfg in line 219 (replace endo_jun13 by endo_sep19). We could then start a model run with Rscript start.R -> 1: default -> 1: Direct execution.

3 Changing an existing realization (cropland)

We now extend the new cropland realization endo_sep19 by two switches related to bioenergy, which increases the flexibility of the realization. We add one switch for the type of bioenergy feedstock (begr/betr), and another switch for rainfed/irrigated bioenergy production. For this we work with dynamic sets, which are filled depending on choices in the config file.

Define the switch in input.gms

We add the following lines of code to input.gms:

$setglobal c30_bioen_type  all
* options: begr, betr, all

$setglobal c30_bioen_water  rainfed
* options: rainfed, irrigated, all

Define the dynamic sets in sets.gms

We add the following lines of code to sets.gms:

   kbe30(kcr) bio energy activities
        / betr, begr /

   bioen_type_30(kbe30) dynamic set bioen type
   bioen_water_30(w) dynamic set bioen water

Fill and use the dynmic sets in presolve.gms

In presolve.gms we replace lines 8-9 with the following:

$ifthen "%c30_bioen_type%" == "all" bioen_type_30(kbe30) = yes;
$else bioen_type_30("%c30_bioen_type%") = yes;
$endif

$ifthen "%c30_bioen_water%" == "all" bioen_water_30(w) = yes;
$else bioen_water_30("%c30_bioen_water%") = yes;
$endif

*' @code
*' First, all 2nd generation bioenergy area is fixed to zero, irrespective of type and 
*' rainfed/irrigation.
vm_area.fx(j,kbe30,w)=0;
*' Second, the bounds for 2nd generation bioenergy area are released depending on 
*' the dynamic sets bioen_type_30 and bioen_water_30.
vm_area.up(j,bioen_type_30,bioen_water_30)=Inf;
*' @stop

Add to config

We can then add c30_bioen_type and c30_bioen_water to the config file config/default.cfg, after line 219.

# * (c30_bioen_type): switch for type of bioenergy crops; options: begr, betr, all
cfg$gms$c30_bioen_type <- "all"               # def = "all"
# * (c30_bioen_water): switch for irrigation of bioenergy crops; options: rainfed, irrigated, all
cfg$gms$c30_bioen_water <- "rainfed"               # def = "rainfed"

Quick test

We can then check if the model compiles correctly with gams main.gms action=C.