logsumexp-softmax

logsumexp and softmax evaluate the log-sum-exp function $lse(x) = \log \sum_{i=1}^n e^{x_i}$ and the softmax function $g(x)$ with $g_j(x) = \frac{e^{x_j}}{\sum_{i=1}^n e^{x_i}$, where x is a vector.