From 1f72ffce79413c617840f9a4ca1a33e4f81d974e Mon Sep 17 00:00:00 2001
From: aletempiac <alessandro.tempia@gmail.com>
Date: Mon, 25 Mar 2024 14:23:43 +0100
Subject: [PATCH] Improving ACD performance with bail-out conditions

---
 src/map/if/acd/ac_decomposition.hpp | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/map/if/acd/ac_decomposition.hpp b/src/map/if/acd/ac_decomposition.hpp
index 0ad1e34c2..a384cc2e1 100644
--- a/src/map/if/acd/ac_decomposition.hpp
+++ b/src/map/if/acd/ac_decomposition.hpp
@@ -232,7 +232,7 @@ private:
         best_cost = multiplicity + additional_cost;
         best_free_set = i;
 
-        if ( !ps.use_first )
+        if ( !ps.use_first && multiplicity > 2 )
         {
           continue;
         }
@@ -270,7 +270,7 @@ private:
           best_cost = multiplicity + additional_cost;
           best_free_set = i;
 
-          if ( !ps.use_first )
+          if ( !ps.use_first && multiplicity > 2 )
           {
             continue;
           }
@@ -478,6 +478,13 @@ private:
       pComb[i] = pInvPerm[i] = i;
     }
 
+    /* early bail-out conditions */
+    uint32_t bail_multiplicity = 2;
+    if ( best_multiplicity < UINT32_MAX )
+    {
+      bail_multiplicity = ( best_multiplicity >> 1 ) + ( best_multiplicity & 1 );
+    }
+
     /* enumerate combinations */
     do
     {
@@ -490,6 +497,11 @@ private:
         {
           bestPerm[i] = pComb[i];
         }
+
+        if ( best_cost <= bail_multiplicity )
+        {
+          break;
+        }
       }
     } while ( combinations_offset_next( free_set_size, offset, pComb, pInvPerm, tt ) );