It's really odd for him to keep harping on Mathematica when the LIGO computations were clearly done in a Python ecosystem as shown in:

http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.0611...

https://dcc.ligo.org/public/0122/P1500217/014/LIGO-P1500217_...

https://software.intel.com/en-us/blogs/2016/02/14/python-bri...