Fix NaN and over/underflow in the HMM functions for long sequences and large log densities (#2677) - #3440

Fix NaN and over/underflow in the HMM functions for long sequences and large log densities (#2677)#3440

atarutin wants to merge 5 commits into

stan-dev:developstan-dev/math:developfrom

atarutin:bugfix/issue-2677-hmm-hidden-state-prob-underflowatarutin/math:bugfix/issue-2677-hmm-hidden-state-prob-underflowCopy head branch name to clipboard