dot-and-cross.h

#include <arrayfire.h>

// Computes the element-wise dot product of 2 arrays
// The default of dim = -1 computes the dot for the first non-empty dimension
// otherwise, it is the dimension that the vectors are located in
array elem_dot(const array& a, const array& b, const int dim = -1) {
  return sum(a * b, dim);
}

// computes the cross product of an array of vectors
// dim is the dimension that the vectors live in
// ***WARNING***
// I havn't tried this with vectors of size different from 3,
// so be careful! it may not work
array elem_cross(const array& a, const array& b, const int dim = 0) {
  array sh_a;
  array sh_b;
  switch (dim) {
    case 0:
      sh_a = shift(a, 1);
      sh_b = shift(b, 1);
      break;
    case 1:
      sh_a = shift(a, 0, 1);
      sh_b = shift(b, 0, 1);
      break;
    case 2:
      sh_a = shift(a, 0, 0, 1);
      sh_b = shift(b, 0, 0, 1);
      break;
    case 3:
      sh_a = shift(a, 0, 0, 0, 1);
      sh_b = shift(b, 0, 0, 0, 1);
      break;
  }

  array res = (b * sh_a) - (a * sh_b);

  switch (dim) {
    case 0:
      res = shift(res, 1);
      break;
    case 1:
      res = shift(res, 0, 1);
      break;
    case 2:
      res = shift(res, 0, 0, 1);
      break;
    case 3:
      res = shift(res, 0, 0, 0, 1);
      break;
  }

  return res;
}