fix factor in adjoint gradient from symmetry

python/meep.i

@@ -1523,10 +1523,6 @@ void _get_gradient(PyObject *grad, PyObject *fields_a, PyObject *fields_f, PyObj
     memcpy(PyArray_DATA((PyArrayObject*) $result), &$1[0], vec_len * sizeof(double) * 2);
 }
 
-std::vector<struct meep::sourcedata> meep::dft_near2far::near_sourcedata(const meep::vec &x_0, double* farpt_list, size_t nfar_pts, std::complex<double>* dJ);
-
-void meep::fields::add_srcdata(struct meep::sourcedata cur_data, meep::src_time *src, size_t n, std::complex<double>* amp_arr);
-
 struct vector3 {
     double x;
     double y;

src/meep/vec.hpp

@@ -1079,6 +1079,7 @@ class symmetry {
   int transform(int, int n) const;
   std::complex<double> phase_shift(int, int n) const;
   int multiplicity() const;
+  int multiplicity(vec &) const;
   bool is_primitive(const ivec &) const;
 
   volume_list *reduce(const volume_list *gl) const;

src/near2far.cpp

@@ -692,7 +692,8 @@ std::vector<struct sourcedata> dft_near2far::near_sourcedata(const vec &x_0, dou
         idx_dft++;
         if (is_electric(temp_struct.near_fd_comp))
           EH0 *= -1;
-        temp_struct.amp_arr.push_back(EH0);
+        EH0 /= f->S.multiplicity(x0);
+        temp_struct.amp_arr.push_back(EH0 / f->S.multiplicity(x0));
       }
     }
     temp.push_back(temp_struct);

src/vec.cpp

@@ -1217,6 +1217,15 @@ int symmetry::multiplicity() const {
     return g;
 }
 
+int symmetry::multiplicity(vec &x) const {
+  int m = multiplicity();
+  for (int n=1; n<m; ++n){
+    if (transform(x,n) == x)
+      return n;
+  }
+  return m;
+}
+
 symmetry symmetry::operator+(const symmetry &b) const {
   // The following optimization ignores identity when adding symmetries
   // together.  This is important because identity has an undefined