increase readibility and move from map to array

epochX/cudacpp/CODEGEN/PLUGIN/CUDACPP_SA_OUTPUT/madgraph/iolibs/template_files/gpu/coloramps.h

@@ -10,10 +10,27 @@
 
 namespace mgOnGpu
 {
+  // Summary of numbering and indexing conventions for the relevant concepts (see issue #826 and PR #852)
+  // - Diagram number (no variable) in [1, N_diagrams]: all values are allowed (N_diagrams distinct values)
+  //   => this number is displayed for information before each block of code in CPPProcess.cc
+  // - Channel number ("channelId" in C, CHANNEL_ID in F) in [1, N_diagrams]: not all values are allowed (N_config <= N_diagrams distinct values)
+  //   0 is allowed to fallback to no multi-channel mode.
+  //   => this number (with indexing like ps/pdf output) is passed around as an API argument between cudacpp functions
+  // - Channel number in C indexing: "channelIdC" = channelIdC_to_iconfig[channelId]
+  //   => this number (with C indexing) is used as the index of the channelIdC_to_iconfig array below
+  //   This correspond to iconfig on the fortran side (with iconfig = channelIdC + 1)
+  //NOTE: All those ordering are event by event specific (with the intent to have those fix within a vector size/wrap   
+
+  // Map channelId to channelIdC
+  // This array has N_diagrams+1 elements, but only N_config <= N_diagrams valid (non-zero) values
+  // The 0 entry is a fall back to still write events even if no multi-channel is setup (wrong color selected in that mode) 
+    __device__ constexpr int channelId_to_channelIdC[%(nb_diag_plus_one)i] = {
+     0, // channelId=0: This value means not multi-channel, color will be wrong anyway -> pick the first
+%(diag_to_channel)s
+  };
 
-    __device__ std::map<int,int> diag_to_channel = {
-        %(diag_to_channel)s
-  };          
+  // Map iconfigC (in C indexing, i.e. iconfig-1) to the set of allowed colors
+  // This array has N_config <= N_diagrams elements    
     __device__ constexpr bool icolamp[%(nb_channel)s][%(nb_color)s] = {
 %(is_LC)s
   };

epochX/cudacpp/CODEGEN/PLUGIN/CUDACPP_SA_OUTPUT/madgraph/iolibs/template_files/gpu/process_sigmaKin_function.inc

@@ -72,7 +72,7 @@
     // Event-by-event random choice of color #402
     if( channelId != 0 ) // no event-by-event choice of color if channelId == 0 (fix FPE #783)
     {
-      const unsigned int channelIdC = mgOnGpu::diag_to_channel[channelId]; // coloramps.h uses a channel ordering not the diagram id 
+      const unsigned int channelIdC = mgOnGpu::channelId_to_channelIdC[channelId]; // coloramps.h uses a channel ordering not the diagram id 
       fptype targetamp[ncolor] = { 0 };
       for( int icolC = 0; icolC < ncolor; icolC++ )
       {
@@ -115,7 +115,7 @@
     // - firstprivate: give each thread its own copy, and initialise with value from outside
 #define _OMPLIST0 allcouplings, allMEs, allmomenta, allrndcol, allrndhel, allselcol, allselhel, cGoodHel, cNGoodHel, npagV2
 #ifdef MGONGPU_SUPPORTS_MULTICHANNEL
-#define _OMPLIST1 , allDenominators, allNumerators, channelId, mgOnGpu::icolamp,mgOnGpu::diag_to_channel
+#define _OMPLIST1 , allDenominators, allNumerators, channelId, mgOnGpu::icolamp,mgOnGpu::channelId_to_channelIdC
 #else
 #define _OMPLIST1
 #endif
@@ -187,7 +187,7 @@
       // Event-by-event random choice of color #402
       if( channelId != 0 ) // no event-by-event choice of color if channelId == 0 (fix FPE #783)
       {
-        const unsigned int channelIdC = mgOnGpu::diag_to_channel[channelId]; // coloramps.h uses a channel ordering not the diagram id 
+        const unsigned int channelIdC = mgOnGpu::channelId_to_channelIdC[channelId]; // coloramps.h uses a channel ordering not the diagram id 
         fptype_sv targetamp[ncolor] = { 0 };
         for( int icolC = 0; icolC < ncolor; icolC++ )
         {

epochX/cudacpp/CODEGEN/PLUGIN/CUDACPP_SA_OUTPUT/model_handling.py

@@ -1531,30 +1531,65 @@ def edit_coloramps(self, config_subproc_map):
         # The following five lines from OneProcessExporterCPP.get_sigmaKin_lines (using OneProcessExporterCPP.get_icolamp_lines)
         replace_dict={}
 
-        lines = []
-        # Output only configs that have some corresponding diagrams
-        iconfig = 0
+
+        iconfig_to_diag = {}
+        diag_to_iconfig = {}
+        iconfig = 0 
         for config in config_subproc_map:
             if set(config) == set([0]):
                 continue
-            lines.append("     {%i, %i}," % (config[0], iconfig))
             iconfig += 1
+            iconfig_to_diag[iconfig] = config[0] 
+            diag_to_iconfig[config[0]] = iconfig
+
+        misc.sprint(iconfig_to_diag)
+        misc.sprint(diag_to_iconfig)
+
+        # Note that if the last diagram is/are not mapped to a channel nb_diag 
+        # will be smaller than the true number of diagram. This is fine for color
+        # but maybe not for something else.
+        nb_diag = max(config[0] for config in config_subproc_map)
+        # Output which diagrams correspond ot a channel to get information for valid color
+        lines = []
+        # Note: line for index 0 (no multi-channel is hardcoded in the template, so here we fill the array from index 1)
+        for diag in range(1, nb_diag+1):
+            if diag in diag_to_iconfig:
+                iconfig = diag_to_iconfig[diag]
+                channel = iconfig -1 # C convention 
+                text = "     %(channel)i, // channelId=%(diag)i (diagram=%(diag)i) i.e. channelIdC=%(channel)i --> iconfig=%(iconfig)i   " 
+            else:
+                iconfig = -1
+                channel = -1 
+                text = "     -1, // channelId=%(diag)i (diagram=%(diag)i): Not consider as a channel of integration (presence of 4 point interaction?)" 
+            lines.append(text % {'diag': diag, 'channel': channel, 'iconfig':  iconfig})  
+
         replace_dict['diag_to_channel'] = '\n'.join(lines)
-        misc.sprint(replace_dict)
 
         if self.include_multi_channel: # NB unnecessary as edit_coloramps is not called otherwise...
             multi_channel = self.get_multi_channel_dictionary(self.matrix_elements[0].get('diagrams'), self.include_multi_channel)
             replace_dict['is_LC'] = self.get_icolamp_lines(multi_channel, self.matrix_elements[0], 1)
             replace_dict['nb_channel'] = len(multi_channel)
+            replace_dict['nb_diag_plus_one'] = max(config[0] for config in config_subproc_map)+1
             replace_dict['nb_color'] = max(1,len(self.matrix_elements[0].get('color_basis')))
 
             misc.sprint(multi_channel)
             misc.sprint(self.path, os.getcwd())
             #raise Exception
 
             # AV extra formatting (e.g. gg_tt was "{{true,true};,{true,false};,{false,true};};")
-            replace_dict['is_LC'] = replace_dict['is_LC'].replace(',',', ').replace('{{','    { ').replace('};, {',' },\n    { ').replace('};};',' }')
-        ff.write(template % replace_dict)
+            split = replace_dict['is_LC'].split(';,') 
+            misc.sprint(replace_dict['is_LC'])
+            for i in range(len(split)): 
+                misc.sprint(split[i])
+                split[i] = '    ' + split[i].replace(',',', ').replace('{{', '{')
+                misc.sprint(split[i])
+                if '};};' in split[i]:
+                   split[i] = split[i][:-4] + '}, // channelIdC=%i' % i 
+                elif 'false' in split[i] or 'true' in split[i]:
+                    split[i] += ', // channelIdC=%i' % i
+                misc.sprint(split[i])
+            replace_dict['is_LC'] = '\n'.join(split)
+            ff.write(template % replace_dict)
         ff.close()
 
     # AV - new method