Splines, contours and SVD subroutines

Portability of Fortran code is a major concern these days, since hardware and commercial software change faster than the codes themselves. Hence, using public domain, portable, mathematical subroutines is imperative. Here we present a collection of subroutines we have used in the past, and found to be particularly useful. They are: 2-dimensional splines, contour tracing of flux surface (based on 2-D spline), and singular Value Matrix Decomposition (for Chi-square minimization)