Merge branch 'master' into gentle-optimization-status

Author: FabianHofmann

doc/release_notes.rst

@@ -11,6 +11,7 @@ Version 0.4.4
 
 * **IMPORTANT BUGFIX**: The last slice of constraints was not correctly written to LP files in case the constraint size was not a multiple of the slice size. This is fixed now.
 * Solution files that following a different naming scheme of variables and constraints using more than on initial letter in the prefix (e.g. `col123`, `row456`) are now supported.
+* GLPK solver is always called with the `--freemps` option instead of the `--mps` when using the Solver API to solve an external MPS file. `--mps` is for the older fixed-column MPS format that is rarely used nowadays. Almost all fixed MPS files can be parsed by the free MPS format.
 
 Version 0.4.3
 --------------

linopy/solvers.py

@@ -556,7 +556,8 @@ def solve_problem_from_file(
         Path(solution_fn).parent.mkdir(exist_ok=True)
 
         # TODO use --nopresol argument for non-optimal solution output
-        command = f"glpsol --{io_api} {problem_fn} --output {solution_fn} "
+        io_api_arg = "freemps" if io_api == "mps" else io_api
+        command = f"glpsol --{io_api_arg} {problem_fn} --output {solution_fn} "
         if log_fn is not None:
             command += f"--log {log_fn} "
         if warmstart_fn:

test/test_solvers.py

@@ -9,7 +9,7 @@
 
 from linopy import solvers
 
-free_mps_problem = """NAME          sample_mip
+free_mps_problem = """NAME               sample_mip
 ROWS
  N  obj
  G  c1