Add --gurobi-make-mps flag

Author: staadecker

switch_model/solve.py

@@ -597,7 +597,7 @@ def define_arguments(argparser):
     # whether that does the same thing as --solver-options-string so we don't reuse the same name.
     argparser.add_argument(
         "--solver-options-string",
-        default=None,
+        default="",
         help="A quoted string of options to pass to the model solver. Each option must be of the form option=value. "
         "(e.g., --solver-options-string \"mipgap=0.001 primalopt='' advance=2 threads=1\")",
     )
@@ -764,6 +764,14 @@ def define_arguments(argparser):
         help="Path to folder of directory to use for warm start",
     )
 
+    argparser.add_argument(
+        "--gurobi-make-mps",
+        default=False,
+        action="store_true",
+        help="Instead of solving just output a Gurobi .mps file that can be used for debugging numerical properties."
+        " See https://github.com/staadecker/lp-analyzer/ for details.",
+    )
+
 
 def add_recommended_args(argparser):
     """
@@ -933,27 +941,25 @@ def solve(model):
         # Note previously solver was saved in model however this is very memory inefficient.
         solver = SolverFactory(model.options.solver, solver_io=model.options.solver_io)
 
-        # If this option is enabled, gurobi will output an IIS to outputs\iis.ilp.
-        if model.options.gurobi_find_iis:
-            # Enable symbolic labels since otherwise we can't debug the .ilp file.
-            model.options.symbolic_solver_labels = True
+        if model.options.gurobi_find_iis and model.options.gurobi_make_mps:
+            raise Exception("Can't use --gurobi-find-iis with --gurobi-make-mps.")
 
-            # If no string is passed make the string empty so we can add to it
-            if model.options.solver_options_string is None:
-                model.options.solver_options_string = ""
+        if model.options.gurobi_find_iis or model.options.gurobi_make_mps:
+            # If we are outputting a file we want to enable symbolic labels to help debugging
+            model.options.symbolic_solver_labels = True
 
+        # If this option is enabled, gurobi will output an IIS to outputs\iis.ilp.
+        if model.options.gurobi_find_iis:
             # Add to the solver options 'ResultFile=iis.ilp'
             # https://stackoverflow.com/a/51994135/5864903
-            iis_file_path = os.path.join(model.options.outputs_dir, "iis.ilp")
-            model.options.solver_options_string += " ResultFile={}".format(
-                iis_file_path
+            model.options.solver_options_string += " ResultFile=iis.ilp"
+        if model.options.gurobi_make_mps:
+            # Output the input file and set time limit to zero to ensure it doesn't actually solve
+            model.options.solver_options_string += (
+                f" ResultFile=problem.mps TimeLimit=0"
             )
 
         if model.options.threads:
-            # If no string is passed make the string empty so we can add to it
-            if model.options.solver_options_string is None:
-                model.options.solver_options_string = ""
-
             model.options.solver_options_string += f" Threads={model.options.threads}"
 
         solver_manager = SolverManagerFactory(model.options.solver_manager)