[dagw]

I don't know. Having "rewrote X kloc of scientific Fortran to modern idiomatic C++" on your CV should get you to the head of the line in many places when looking for a job.

[roel_v]

Only if you go after run of the mill coding jobs after your phd, in which case why bother at all. When applying for a postdoc, you'll very much want to bury that part of your work.

[cocoablazing]

Plenty of high-paying quantitative jobs requires such a degree and experience. The majority of phd’s don’t go on to support their family with a tenure-track academic salary.

[dagw]

Or you could be applying for a HPC research job in one of the countless non-university setting that also does that sort of thing. Then having both a relevant PhD and some relevant hands on experience will be extremely helpful.

[0xbear]

Why would you rewrite something that works well instead of just linking to it?

[quadruplebond]

Because you need to modify or extend it in some nontrivial way.