Modified _parse_gdx_results in GAMS.py to replace _parse_special_value and Updated Import Statement

pyomo/solvers/plugins/solvers/GAMS.py

@@ -40,8 +40,27 @@
 )
 
 from pyomo.common.dependencies import attempt_import
+import struct
 
-gdxcc, gdxcc_available = attempt_import('gdxcc')
+
+def _gams_importer():
+    try:
+        import gams.core.gdx as gdx
+
+        return gdx
+    except ImportError:
+        try:
+            # fall back to the pre-GAMS-45.0 API
+            import gdxcc
+
+            return gdxcc
+        except:
+            # suppress the error from the old API and reraise the current API import error
+            pass
+        raise
+
+
+gdxcc, gdxcc_available = attempt_import('gdxcc', importer=_gams_importer)
 
 logger = logging.getLogger('pyomo.solvers')
 
@@ -728,18 +747,6 @@ def _get_version(self):
             )
             return _extract_version(results.stdout)
 
-    @staticmethod
-    def _parse_special_values(value):
-        if value == 1.0e300 or value == 2.0e300:
-            return float('nan')
-        if value == 3.0e300:
-            return float('inf')
-        if value == 4.0e300:
-            return -float('inf')
-        if value == 5.0e300:
-            return sys.float_info.epsilon
-        return value
-
     def _rewrite_path_win8p3(self, path):
         """
         Return the 8.3 short path on Windows; unchanged elsewhere.
@@ -1278,6 +1285,18 @@ def _parse_gdx_results(self, results_filename, statresults_filename):
             if not ret[0]:
                 raise RuntimeError("GAMS GDX failure (gdxOpenRead): %d." % ret[1])
 
+            specVals = gdxcc.doubleArray(gdxcc.GMS_SVIDX_MAX)
+            rc = gdxcc.gdxGetSpecialValues(pgdx, specVals)
+
+            specVals[gdxcc.GMS_SVIDX_EPS] = sys.float_info.min
+            specVals[gdxcc.GMS_SVIDX_UNDEF] = float("nan")
+            specVals[gdxcc.GMS_SVIDX_PINF] = float("inf")
+            specVals[gdxcc.GMS_SVIDX_MINF] = float("-inf")
+            specVals[gdxcc.GMS_SVIDX_NA] = struct.unpack(
+                ">d", bytes.fromhex("fffffffffffffffe")
+            )[0]
+            gdxcc.gdxSetSpecialValues(pgdx, specVals)
+
             i = 0
             while True:
                 i += 1
@@ -1299,7 +1318,7 @@ def _parse_gdx_results(self, results_filename, statresults_filename):
                     raise RuntimeError("GAMS GDX failure (gdxDataReadRaw).")
 
                 if stat in ('OBJEST', 'OBJVAL', 'ETSOLVE'):
-                    stat_vars[stat] = self._parse_special_values(ret[2][0])
+                    stat_vars[stat] = ret[2][0]
                 else:
                     stat_vars[stat] = int(ret[2][0])
 
@@ -1311,6 +1330,18 @@ def _parse_gdx_results(self, results_filename, statresults_filename):
             if not ret[0]:
                 raise RuntimeError("GAMS GDX failure (gdxOpenRead): %d." % ret[1])
 
+            specVals = gdxcc.doubleArray(gdxcc.GMS_SVIDX_MAX)
+            rc = gdxcc.gdxGetSpecialValues(pgdx, specVals)
+
+            specVals[gdxcc.GMS_SVIDX_EPS] = sys.float_info.min
+            specVals[gdxcc.GMS_SVIDX_UNDEF] = float("nan")
+            specVals[gdxcc.GMS_SVIDX_PINF] = float("inf")
+            specVals[gdxcc.GMS_SVIDX_MINF] = float("-inf")
+            specVals[gdxcc.GMS_SVIDX_NA] = struct.unpack(
+                ">d", bytes.fromhex("fffffffffffffffe")
+            )[0]
+            gdxcc.gdxSetSpecialValues(pgdx, specVals)
+
             i = 0
             while True:
                 i += 1
@@ -1321,8 +1352,8 @@ def _parse_gdx_results(self, results_filename, statresults_filename):
                 ret = gdxcc.gdxDataReadRaw(pgdx)
                 if not ret[0] or len(ret[2]) < 2:
                     raise RuntimeError("GAMS GDX failure (gdxDataReadRaw).")
-                level = self._parse_special_values(ret[2][0])
-                dual = self._parse_special_values(ret[2][1])
+                level = ret[2][0]
+                dual = ret[2][1]
 
                 ret = gdxcc.gdxSymbolInfo(pgdx, i)
                 if not ret[0]:
@@ -1335,6 +1366,7 @@ def _parse_gdx_results(self, results_filename, statresults_filename):
             gdxcc.gdxClose(pgdx)
 
         gdxcc.gdxFree(pgdx)
+        gdxcc.gdxLibraryUnload()
         return model_soln, stat_vars
 
     def _parse_dat_results(self, results_filename, statresults_filename):