add warning when AD encounters monomial

convexengineering · Jun 29, 2021 · 041c504 · 041c504
1 parent 2a41a97
commit 041c504
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Showing 2 changed files with 12 additions and 8 deletions.
diff --git a/gpkit/constraints/prog_factories.py b/gpkit/constraints/prog_factories.py
@@ -43,8 +43,7 @@ def evaluate_linked(constants, linked):
                     "Linked function for %s did not return a united value."
                     "Modifying it to do so (e.g. by using `()` instead of `[]`"
                     " to access variables) will reduce errors." % v)
-            if hasattr(out, "__len__"):
-                out = out.item()  # break out of 0-dimensional arrays
+            out = maybe_flatten(out)
             if not hasattr(out, "x"):
                 constants[v] = out
                 continue  # a new fixed variable, not a calculated one
@@ -57,14 +56,19 @@ def evaluate_linked(constants, linked):
             from .. import settings
             if settings.get("ad_errors_raise", None):
                 raise
-            print("Warning: skipped auto-differentiation of linked variable"
-                  " %s because %s was raised. Set `gpkit.settings"
-                  "[\"ad_errors_raise\"] = True` to raise such Exceptions"
-                  " directly.\n" % (v, repr(exception)))
             if kdc_plain is None:
                 kdc_plain = KeyDict(constants)
             constants[v] = f(kdc_plain)
             v.descr.pop("gradients", None)
+            print("Warning: skipped auto-differentiation of linked variable"
+                  " %s because %s was raised. Set `gpkit.settings"
+                  "[\"ad_errors_raise\"] = True` to raise such Exceptions"
+                  " directly.\n" % (v, repr(exception)))
+            if ("Automatic differentiation not yet supported for <class "
+                    "'gpkit.nomials.math.Monomial'> objects") in str(exception):
+                print("This particular warning may have come from using"
+                      " gpkit.units.* in the function for %s; try using"
+                      " gpkit.ureg.* or gpkit.units.*.units instead." % v)
 
 
 def progify(program, return_attr=None):

diff --git a/gpkit/small_scripts.py b/gpkit/small_scripts.py
@@ -40,8 +40,8 @@ def isnan(element):
 
 def maybe_flatten(value):
     "Extract values from 0-d numpy arrays, if necessary"
-    if hasattr(value, "shape") and not value.shape:
-        return value.flatten()[0]  # 0-d numpy arrays
+    if hasattr(value, "size") and value.size == 1:
+        return value.item()
     return value