tensorProd.cpp

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#include "tensorProd.h"
#include <cassert>

// This implementation only applies to SU(3) group and Nd=4 case.
#define NC      3
#define NC2     6
#define NDF     18
#define ND      4
#define NCD     12
#define NCD2    24

void tensorProd_Field_F(Field_G& u, const Field_F& v1, const Field_F& v2)
{
  int Nvol = u.nvol();

  assert(Nvol == v1.nvol());
  assert(Nvol == v2.nvol());
  assert(u.nex() == 1);
  assert(v1.nex() == 1);
  assert(v2.nex() == 1);

  double *w1;
  double *w2;
  double *g;
  w1 = const_cast<Field_F *>(&v1)->ptr(0);
  w2 = const_cast<Field_F *>(&v2)->ptr(0);
  g  = (&u)->ptr(0);

  for (int site = 0; site < Nvol; ++site) {
    int iw = NCD2 * site;
    int ig = NDF * site;
    for (int c1 = 0; c1 < NC; ++c1) {
      for (int c2 = 0; c2 < NC; ++c2) {
        int ig2 = c2 * 2 + c1 * NC2 + ig;
        g[ig2]     = 0.0;
        g[ig2 + 1] = 0.0;
        for (int s = 0; s < ND; ++s) {
          g[ig2] +=
            w1[2 * c2 + s * NC2 + iw] * w2[2 * c1 + s * NC2 + iw]
            + w1[2 * c2 + 1 + s * NC2 + iw] * w2[2 * c1 + 1 + s * NC2 + iw];
          g[ig2 + 1] +=
            w1[2 * c2 + s * NC2 + iw] * w2[2 * c1 + 1 + s * NC2 + iw]
            - w1[2 * c2 + 1 + s * NC2 + iw] * w2[2 * c1 + s * NC2 + iw];
        }
      }
    }
  }
}