allow eps_rel = 0?

[mlubin]

OSQP currently enforces that eps_rel be positive:
https://github.com/oxfordcontrol/osqp/blob/515ceba7c72c47ea73f01b136cb729d62ae27dc0/src/auxil.c#L887-L890

Is there a reason to not allow eps_abs positive and eps_rel zero? Many other QP solvers allow you to enforce an absolute tolerance on constraints, so setting eps_rel to zero would help when comparing OSQP to these solvers. Of course, it's possible to set it to an extremely tiny value, but you shouldn't need to do this.

[bstellato]

You are right, there is not an explicit reason. I have updated it here b53d590

[mlubin]

Thanks! You may want to add a check that at least one of eps_abs and eps_rel is positive.

[bstellato]

Thanks for the tip. It should be added in the develop branch now.