I located a bug in the Python-api. When iterating through all symbols in the database, the last symbol from the database is missing.
The database reads a gdx file, exported using execute_unload.
When I iterate over the symbols in the database, the first symbol is the universal set, but the last symbol in the database is missing. Looking up the symbol name works fine.
db = gams.GamsWorkspace().add_database_from_gdx(gdx_file_unloaded_with_execute_unload)
symbol_names = [x.name for x in db]
last_symbol_name in symbol_names # False
db[last_symbol_name] # Returns a GamsVariable
I believe the bug was introduced somewhere since GAMS 46.
(Updated: the bug happens regardless of using execute_unload or execute_unloaddi)
Best,
Martin
This seems not a general problem, but related to your GDX file. If I take trnsport.gms (from the GAMS Model Library) (and even move the declarations around so I have variable z that is the last symbol) and run gams trnsport gdx=t.gdx and then use the following Control API script:
from gams.control import *
ws = GamsWorkspace(working_directory='.')
db = ws.add_database_from_gdx('t.gdx')
symbol_names = [x.name for x in db]
print(symbol_names)
I get ['i', 'j', 'a', 'b', 'd', 'f', 'c', 'cost', 'supply', 'demand', 'x', 'z'] which is the same as is in the GDX file:
$ gdxdump t.gdx nodata | grep loadDC
$loadDC i
$loadDC j
$loadDC a
$loadDC b
$loadDC d
$loadDC f
$loadDC c
$loadDC cost
$loadDC supply
$loadDC demand
$loadDC x
$loadDC z
Perhaps, you can share your GDX file and tell us what symbols you expect last.
-Michael
Sure, I have attached a minimum example here with just two sets, a and t.
[x.name for x in db] returns [‘*’, ‘a’] instead of [‘a’, ‘t’]
apibug.gdx (2.2 KB)
I just noticed the warning
— Warning: The GAMS version (49.3.0) differs from the API version (46.5.0).
This seems to be the cause of the bug. Upgrading the api to match the GAMS version fixes the issue. Sorry for the somewhat false alarm.
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