tried to get threshold of m=8 cylinder mode for n = 2.0 + 0.01i cylinder. D = 0.066 achieved, but the calculation was super slow; about 5 second per iteration. I suspected the part in SaltSolve where I SNESSetFunction and Jacobian every iteration for Nm = 1, but I commented that out and it is still slow.

It might be the line search in the beginning. Perhaps turn off the line search?