Improved memory efficiency in phyltr-dp with dated species trees
Improved memory efficiency in phyltr-dp with dated species trees

The backtrack_dated() function now uses vector's swap() method to return
the vector of scenarios thereby halving the memory requirement of the
scenarios. Previously an assignment between vectors was used resulting
in the computed scenarios existing in two separate vectors.

atofigh/phyltr,atofigh/phyltr,atofigh/phyltr