mg7 merged-flavor: single-merged-leg flavored couplings + guard (MSSM)

.github/workflows/acceptancetest_madevent.yml

@@ -981,3 +981,18 @@ jobs:
             cd $GITHUB_WORKSPACE
             cp input/.mg5_configuration_default.txt input/mg5_configuration.txt
             ./tests/test_manager.py test_density_mode_doublettbar -pA -t0 -l INFO
+
+  acceptancetest_mssm_gogo:
+    # Fortran madevent supports MSSM p p > go go (merged-flavor squark/gluino
+    # vertices); the mg7/madmatrix counterpart now also supports it and is
+    # checked per-flavor (test_standalone_mg7_mssm_gogo in acceptancetest_mg7.yml).
+    runs-on: ubuntu-24.04
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.fork == true
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./.github/actions/checkout_mg5
+      - uses: ./.github/actions/restore-pip-cache
+      - name: test one of the test test_madevent_mssm_gogo
+        run: |
+            cd $GITHUB_WORKSPACE
+            ./tests/test_manager.py test_madevent_mssm_gogo -pA -t0 -l INFO

.github/workflows/acceptancetest_mg7.yml

@@ -177,4 +177,44 @@ jobs:
             export PATH="$HOME/.cache/HEPtools/bin:$PATH"
             ./tests/test_manager.py test_generation_heft_mg7 -pA -t0 -l INFO
 
+  acceptancetest_mg7_mssm_gogo:
+    # mg7/madmatrix now generates the MSSM merged-flavor squark/gluino vertices
+    # (single-merged-leg / event-by-event flavored couplings); standalone_mg7
+    # reproduces the Fortran standalone per-flavor |M|^2 (~1e-4). This is a
+    # matrix-element (standalone) check only -- full mg7 event generation for
+    # merged-flavor processes is not wired up yet (see test_madevent_merged_
+    # flavor_uq_mg7). The madevent counterpart is test_madevent_mssm_gogo in
+    # acceptancetest_madevent.yml.
+    runs-on: ubuntu-24.04
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.fork == true
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./.github/actions/checkout_mg5
+      - uses: ./.github/actions/restore-pip-cache
+      - name: test one of the test test_standalone_mg7_mssm_gogo
+        run: |
+            cd $GITHUB_WORKSPACE
+            ./tests/test_manager.py test_standalone_mg7_mssm_gogo -pA -t0 -l INFO
+
+  acceptancetest_mg7_mssm_gogo_xsec:
+    # KNOWN-FAILING (not xfail): standalone_mg7 reproduces the per-flavor |M|^2
+    # for MSSM p p > go go (test_standalone_mg7_mssm_gogo), but full mg7 event
+    # generation for merged-flavor processes is not wired up yet -- the madspace
+    # integrator does not produce the cross-section. This pins the mg7 result to
+    # the madevent reference (4.541638 pb, run_01 of test_generation_from_file_1)
+    # and is expected to be red until the mg7 integrator handles merged-flavor
+    # p p > go go. Self-skips if the madspace + LHAPDF(NNPDF23) stack is absent.
+    runs-on: ubuntu-24.04
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.fork == true
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./.github/actions/checkout_mg5
+      - uses: ./.github/actions/restore-pip-cache
+      - uses: ./.github/actions/restore_heptools_lhapdf
+      - name: test one of the test test_generation_from_file_1_mg7
+        run: |
+            cd $GITHUB_WORKSPACE
+            export PATH="$HOME/.cache/HEPtools/bin:$PATH"
+            ./tests/test_manager.py test_generation_from_file_1_mg7 -pA -t0 -l INFO
+
 

madgraph/iolibs/export_cpp.py

@@ -306,8 +306,10 @@ def generate_parameters_class_files(self):
                                self.write_set_parameters(self.params_dep)
         replace_dict['set_dependent_couplings'] = \
                                self.write_set_parameters(list(self.coups_dep.values()))
+        # Only independent flavored couplings use the FLV_COUPLING value[] pointer mechanism;
+        # dependent (running-alphas) ones are gathered event-by-event (see model_handling / Step 3).
         replace_dict['set_flv_couplings'] = \
-                                self.write_flv_couplings(self.coups_flv_dep+self.coups_flv_indep)    
+                                self.write_flv_couplings(self.coups_flv_indep)
 
         replace_dict['print_independent_parameters'] = \
                                self.write_print_parameters(self.params_indep)
@@ -373,17 +375,57 @@ def write_set_parameters(self, params):
 
         return "\n".join(res_strings)
 
+    def _assert_flv_couplings_supported(self, params):
+        """Refuse, with a clear and actionable message, the merged-flavor
+        coupling structures the C++ (mg7/standalone_mg7) backend cannot yet
+        generate correctly, instead of crashing or emitting wrong/uncompilable
+        code.
+
+        Supported: one- and two-merged-leg "partner" vertices, with either
+        flavor-*independent* or *dependent* (event-by-event, running-alphas)
+        couplings. Single-merged-leg vertices (one merged fermion + an unmerged
+        partner, e.g. the electroweak MSSM squark-quark-neutralino vertices) are
+        serialized like the Fortran side (the unmerged partner is given flavor
+        index 1) and gated by the merged leg (see get_coupling_def). Dependent
+        flavored couplings (e.g. the SUSY-QCD MSSM gluino-squark-quark vertices)
+        are gathered event-by-event into cDPF_* / flvCOUPs_dep (Step 3).
+
+        Not yet supported (raises):
+
+          * a vertex with more than two merged-flavor legs (never seen so far).
+
+        The Fortran 'madevent'/'standalone' output supports the remaining cases.
+        See docs/mg7_merged_flavor_mssm_design.md.
+        """
+        for coupl in params:
+            for key in coupl.flavors:
+                nb_merged = len([i for i in key if i != 0])
+                if nb_merged in (1, 2):
+                    continue
+                raise InvalidCmd(
+                    "merged-flavor C++ output (mg7/standalone_mg7) does not yet "
+                    "support this process: flavor coupling %s connects %d "
+                    "merged-flavor legs; only one or two are supported. Use "
+                    "'output madevent' or 'output standalone' for this process. "
+                    "See docs/mg7_merged_flavor_mssm_design.md for details."
+                    % (coupl.name, nb_merged))
+
     def write_flv_couplings(self, params):
         """Write out the lines of independent parameters"""
 
+        self._assert_flv_couplings_supported(params)
         def_flv = []
         # For each parameter, write name = expr;
         for coupl in params:
             for key, c in coupl.flavors.items():
-                # get first/second index
-                k1, k2 = [i for i in key if i!=0]
+                nonzero = [i for i in key if i != 0]
+                if len(nonzero) == 2:
+                    k1, k2 = nonzero
+                else:
+                    # single merged leg: unmerged partner has flavor index 1
+                    k1 = nonzero[0]; k2 = 1
                 def_flv.append('%(name)s.partner[%(in)i] = %(out)i;' % {'name': coupl.name,'in': k1-1, 'out': k2-1})
-                def_flv.append('%(name)s.partner2[%(out)i] = %(in)i;' % {'name': coupl.name,'in': k1-1, 'out': k2-1}) 
+                def_flv.append('%(name)s.partner2[%(out)i] = %(in)i;' % {'name': coupl.name,'in': k1-1, 'out': k2-1})
                 def_flv.append('%(name)s.val[%(in)i]  =  &%(coupl)s;' % {'name': coupl.name,'in': k1-1, 'coupl': c})
 
         return "\n".join(def_flv)

madgraph/iolibs/template_files/madmatrix/MemoryAccessCouplings.h

@@ -164,6 +164,11 @@ namespace mg5amcCpu
     static constexpr auto idcoupAccessBuffer = MemoryAccessCouplingsBase::idcoupAccessBuffer;
     static constexpr auto idcoupAccessBufferConst = MemoryAccessCouplingsBase::idcoupAccessBufferConst;
 
+    // Per-flavor stride (in fptype's) between two consecutive flavor slots of a flavored coupling value buffer.
+    // For dependent (event-by-event, running-alphas) couplings the value is an AOSOA record [nx2][neppC]
+    // (real and imaginary SIMD lanes), so consecutive flavor slots are nx2*neppC fptype's apart.
+    static constexpr int flv_stride = MemoryAccessCouplingsBase::neppC * mgOnGpu::nx2;
+
     // Expose selected functions from MemoryAccessCouplings
     static constexpr auto ieventAccessRecordConst = MemoryAccessCouplings::ieventAccessRecordConst;
 

madgraph/iolibs/template_files/madmatrix/MemoryAccessCouplingsFixed.h

@@ -60,6 +60,10 @@ namespace mg5amcCpu
     // Expose selected functions from MemoryAccessCouplingsFixedBase
     static constexpr auto iicoupAccessBufferConst = MemoryAccessCouplingsFixedBase::iicoupAccessBufferConst;
 
+    // Per-flavor stride (in fptype's) between two consecutive flavor slots of a flavored coupling value buffer.
+    // For fixed (independent) couplings the value is a single scalar complex (real,imag): nx2 fptype's, broadcast across the SIMD vector.
+    static constexpr int flv_stride = mgOnGpu::nx2;
+
     // Locate a field (output) in a memory buffer (input) from a kernel event-indexing mechanism (internal) and the given field indexes (input)
     // [Signature (const, SCALAR OR VECTOR) ===> cxtype_sv kernelAccessConst( const fptype* buffer ) <===]
     static __host__ __device__ inline const cxtype_sv

madgraph/iolibs/template_files/madmatrix/cpp_hel_amps_h.inc

@@ -59,11 +59,16 @@ namespace mg5amcCpu
       : partner1(p1), partner2(p2), value(v) {}
   };
 
-  template<int SIZE, int STRIDE>
+  // FSTRIDE is the number of fptype's used to store one flavor slot of the value buffer:
+  //  - independent (fixed) flavored couplings: FSTRIDE = nx2 = 2 (a single scalar complex, broadcast across the SIMD vector)
+  //  - dependent (event-by-event, running-alphas) flavored couplings: FSTRIDE = nx2*neppC (an AOSOA SIMD record)
+  // It must match C_ACCESS::flv_stride of the access type the consuming vertex routine is instantiated with.
+  template<int SIZE, int STRIDE, int FSTRIDE = 2>
   class FLV_COUPLING_ARRAY {
 
       static_assert(SIZE >= 0, "flvCOUPs SIZE must be non-negative");
       static_assert(STRIDE > 0, "flvCOUPs STRIDE must be positive");
+      static_assert(FSTRIDE > 0, "flvCOUPs FSTRIDE must be positive");
       const int* const partner1;
       const int* const partner2;
       const fptype* const value;
@@ -78,7 +83,7 @@ namespace mg5amcCpu
         return FLV_COUPLING_VIEW{
           partner1 + i*STRIDE,
           partner2 + i*STRIDE,
-          value + i*2*STRIDE
+          value + i*FSTRIDE*STRIDE
         };
       }
   };

madgraph/iolibs/template_files/madmatrix/process_function_definitions.inc

@@ -109,11 +109,14 @@ namespace mg5amcCpu
   // nIPF are the number of SM independent flavor couplings, of type FLV_COUPLING
   constexpr int nMF = FLV_COUPLING::max_flavor;
   constexpr int nIPF = %(nipf)i;
+  // nDPF are the number of dependent (event-by-event, running-alphas) flavor couplings
+  constexpr int nDPF = %(ndpf)i;
   static_assert( nIPC <= nicoup );
   static_assert( nIPD >= 0 ); // Hack to avoid build warnings when nIPD==0 is unused
   static_assert( nIPC >= 0 ); // Hack to avoid build warnings when nIPC==0 is unused
   static_assert( nMF >= 0 );  // Hack to avoid build warnings when nMF ==0 is unused
   static_assert( nIPF >= 0 ); // Hack to avoid build warnings when nIPF==0 is unused
+  static_assert( nDPF >= 0 ); // Hack to avoid build warnings when nDPF==0 is unused
 #ifdef MGONGPU_HARDCODE_PARAM
   %(cipdhrdcod)s
   %(cipchrdcod)s
@@ -130,6 +133,12 @@ namespace mg5amcCpu
 #endif
 #endif
 
+  // Dependent (event-by-event, running-alphas) flavor couplings: partner indices and
+  // the per-flavor idcoup are pure compile-time constants (the complex values are
+  // gathered per event page in calculate_jamps), so they are emitted the same way in
+  // all build modes (no CUDA constant memory copy needed).
+  %(cdpfdecl)s
+
   // AV Jan 2024 (PR #625): this ugly #define was the only way I found to avoid creating arrays[nBsm] in CPPProcess.cc if nBsm is 0
   // The problem is that nBsm is determined when generating Parameters.h, which happens after CPPProcess.cc has already been generated
   // For simplicity, keep this code hardcoded also for SM processes (a nullptr is needed as in the case nBsm == 0)