Port Fidimag to C++

Large commit - port Fidimag to build everything as C++ rather than C.
Why? Because this is Stage 1 of our complex plan to make Fidimag faster
and more readable, and part of this involves using Classes at the C++
level rather than at the Python level for energy terms in order to
reduce the amount of slow Python code.

Co-Authored-By: David Ignacio Cortee <[email protected]>

Author: rpep

fidimag/atomistic/hexagonal_mesh.py

@@ -1,5 +1,4 @@
-
-"""
+r"""
 Represent hexagonal 2D mesh.
 
 The hexagons are pointy topped (as against flat topped). We use axial
@@ -38,6 +37,7 @@
 Coordinates a
 
 """
+
 import numpy as np
 from math import sqrt
 

fidimag/atomistic/lib/anis.c renamed to fidimag/atomistic/lib/anis.cpp

@@ -1,10 +1,10 @@
 #include "clib.h"
 
 
-void compute_anis(double *restrict spin, double *restrict field,
-                  double *restrict mu_s_inv,
-                  double *restrict energy,
-	              double *restrict Ku, double *restrict axis, int n) {
+void compute_anis(double * spin, double * field,
+                  double * mu_s_inv,
+                  double * energy,
+	              double * Ku, double * axis, int n) {
 
     /* Remember that the magnetisation order is
      *      mx1, my1, mz1, mx2, my2, mz2, mx3,...
@@ -40,10 +40,10 @@ void compute_anis(double *restrict spin, double *restrict field,
 }
 
 
-void compute_anis_cubic(double *restrict spin, double *restrict field,
-                        double *restrict mu_s_inv,
-                        double *restrict energy,
-                        double *restrict Kc, int n) {
+void compute_anis_cubic(double * spin, double * field,
+                        double * mu_s_inv,
+                        double * energy,
+                        double * Kc, int n) {
 
     /* Remember that the magnetisation order is
      *      mx1, my1, mz1, mx2, my2, mz2, mx3,...