To install the Mathmap filter follow these directions PRECISELY!
Or it will not work.

The MMInstsall folder has 3 folders inside
1 bin-folder place files in bin folder 
2 mathmap-folder place entire folder in .gimp-2.8 folder
3 plugins-folder place entire mathmap folder inside in your .gimp-2.8 plugins folder
  Next you must create a new path in preferances-Folders-Plugins for your .gimp-2.8/plugins/mathmap folder
-------------------Now restart and you should have mathmap------------------
---------------------Thats it.That is all there is to it.-------------------
You will find Mathmap under Filters > Generic > Mathmap