adding protection against div-by-zero in BadOptimization `__str__

theano/compile/debugmode.py

@@ -279,7 +279,7 @@ class BadOptimization(DebugModeError):
             print >> ssio, "  Mean Abs Diff: ", numpy.mean(numpy.absolute(nv-ov))
             print >> ssio, "  Median Abs Diff: ", numpy.median(numpy.absolute(nv-ov))
             print >> ssio, "  Std Abs Diff: ", numpy.std(numpy.absolute(nv-ov))
-            reldiff = numpy.absolute(nv-ov) / (numpy.absolute(nv)+numpy.absolute(ov))
+            reldiff = numpy.absolute(nv-ov) / (numpy.absolute(nv)+numpy.absolute(ov)+1e-8)
             print >> ssio, "  Max Rel Diff: ", numpy.max(reldiff)
             print >> ssio, "  Mean Rel Diff: ", numpy.mean(reldiff)
             print >> ssio, "  Median Rel Diff: ", numpy.median(reldiff)