Modify FLV coupling view handling, given sometimes the size is zero

Author: Qubitol

madgraph/iolibs/template_files/madmatrix/cpp_hel_amps_h.inc

@@ -49,19 +49,36 @@ namespace mg5amcCpu
 
   struct FLV_COUPLING_VIEW {
 
-      const int* partner1;
-      const int* partner2;
-      const fptype* value;
+      const int* const partner1;
+      const int* const partner2;
+      const fptype* const value;
 
-      __host__ __device__ FLV_COUPLING_VIEW() = default;
       __host__ __device__
-      FLV_COUPLING_VIEW(const int* partner1_base,
-                        const int* partner2_base,
-                        const fptype* value_base,
-                        const int n)
-      : partner1(partner1_base + n),
-        partner2(partner2_base + n),
-        value(value_base + 2*n) {}
+      FLV_COUPLING_VIEW(const int* p1, const int* p2, const fptype* v)
+      : partner1(p1), partner2(p2), value(v) {}
   };
 
+  template<int SIZE, int STRIDE>
+  class FLV_COUPLING_ARRAY {
+
+      static_assert(SIZE >= 0, "flvCOUPs SIZE must be non-negative");
+      static_assert(STRIDE > 0, "flvCOUPs STRIDE must be positive");
+      const int* const partner1;
+      const int* const partner2;
+      const fptype* const value;
+
+    public:
+      __host__ __device__
+      FLV_COUPLING_ARRAY(const int* p1, const int* p2, const fptype* v)
+      : partner1(p1), partner2(p2), value(v) {}
+
+      __host__ __device__
+      FLV_COUPLING_VIEW operator[](const int i) const {
+        return FLV_COUPLING_VIEW{
+          partner1 + i*STRIDE,
+          partner2 + i*STRIDE,
+          value + i*2*STRIDE
+        };
+      }
+  };
 %(function_declarations)s

madmatrix/model_handling.py

@@ -2304,9 +2304,7 @@ def super_get_matrix_element_calls(self, matrix_element, color_amplitudes, multi
       fptype* denominators = DEN_ACCESS::ieventAccessRecord( allDenominators, ievt0 );
 #endif
       // Create an array of views over the Flavor Couplings
-      FLV_COUPLING_VIEW flvCOUPs[nIPF];
-      for ( int idflv = 0; idflv < nIPF; idflv++ )
-        flvCOUPs[idflv] = FLV_COUPLING_VIEW{ cIPF_partner1, cIPF_partner2, cIPF_value, idflv * nMF };
+      FLV_COUPLING_ARRAY<nIPF, nMF> flvCOUPs{ cIPF_partner1, cIPF_partner2, cIPF_value };
 
       // Reset color flows (reset jamp_sv) at the beginning of a new event or event page
       for( int i = 0; i < ncolor; i++ ) { jamp_sv[i] = cxzero_sv(); }