Initial addition of angle constraints

[rsdefever]

@adowling2 can you have a look at my attempted implementation of angle constraints. I'm getting the following error, even for a very simple test case. Any ideas?

EXIT: Converged to a point of local infeasibility. Problem may be infeasible.                                                                                                                                                                                                                             

[adowling2]

@rsdefever This is on my todo list. I might not get to it for a week.

[rsdefever]

The angle constraints now seem to be working in a simple case (an important simple case!) of a water molecule (so two bond constraints with one angle constraint). A more difficult test case of a dimethyl ether molecule still reports the same error on the solver. When I check the geometry, all the bonds meet the bond-length constraints. However, there are several angles that do not meet the angle constraints. I am unsure if it is feasible for all the angles to be satisfied, although the total number of constraints is 21 and the number of variables is 27.

Here is the molecule:

[rsdefever]

/azp run

[azure-pipelines]

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.

[rsdefever]

Also of note is that the molecule changes configuration a fair bit more than in the case of the bond constraints alone. Blue = start; color based on atom type = end; cyan = C, red = O, white = H.