Module math 

Log-space arithmetic helpers.

Salmon performs nearly all of its probability accumulation in log space to avoid underflow. These helpers mirror the conventions in the C++ code where LOG_0 is negative infinity and LOG_1 is zero.

Constants

LOG_0

log(0) = -inf

LOG_1

log(1) = 0

LOG_EPSILON

A very small log-space epsilon used as an effective “zero” mass in places where strict -inf would propagate NaNs.

Functions

log_add

Numerically stable log(exp(x) + exp(y)).

log_sub

Numerically stable log(exp(x) - exp(y)), requires x >= y.

log_sum

Log-sum-exp over an iterator of log-space values.