id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
6408	Wrong start values for NLS with homotopy	trabuzin@…	Andreas Heuermann	"Hi, 

I have noticed that with some of my power system models the nonlinear solver gets wrong start values for the iteration variables. I think the culprit is the inclusion of homotopy in the model. 

I attached a package with two network models in the examples package. In one of them, there is no homotopy and in the other I included homotopy just to demonstrate the issue (even though it is not needed). Homotopy is introduced in line 280 of CompositeLoadWithDummyHomotopy. 

The parameter of interest that becomes an iteration variable for the nonlinear solver is w_0. The start value of this parameter is assigned through another parameter omega_0 which is explicitly defined to be 1.

I also attached the two screenshot which show the difference in the start values of w_0. In the case with homotopy, the start value of w_0 is zero, while without homotopy it is correctly set to 1. 

I tried this out on OM 1.17-beta3 and the nightly build from yesterday."	defect	assigned	high	NeedsInput	*unknown*	1.18.0-dev			Francesco Casella