id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
2924	Extending a model fails	Adam Dershowitz <dersh@…>	Adrian Pop	"I have a model (unfortunately, proprietary, so i can't put it here) that I have been working with that is now causing me some difficulties.  The base model is working fine.  I then extended that model, with some additions, and it is also working fine. 
The strange difficulty that I am running into, is that if I extend that model, I run into errors.  And, the occur, even if I do nothing but this:
model Model3
extends Model2;
end Model3;

If I check Model2, I see that it is balanced with 894 equations and 894 variables. And it runs just fine.  
If I check Model3 (created with nothing but extends, as above, and no actual additions or changes) it shows 1264 equations and 1571 variables (!?!?).  If I try to run this model, I see a bunch of ""Model is structurally singular, error found sorting equations"", ""Internal error pre-optimization model clockPartioning failed"", ""Too many equations, over-determined system.  The model has 1264 equations and 894 variables""

I don't see how extending a model, with no changes, or even just a minor addition, can cause the addi4tion of hundreds of equations and variables.  "	defect	accepted	high	Future	Frontend	trunk