With vector machines, Fortran yielded (much) faster code because (a) there was a whole lot of work on preprocessors for "dusty deck" code and (b) the lack of pointers and their overlap let the compilers do their stuff. C code needed a lot of #pragma's to let it know that some pointers didn't overlap and so could be optimized.

We found it best to to the front-end and I/O of the code in C and the compute in Fortran. Fastest calculations especially with those tailored libraries.