A combo of parameters tweaks

This patch is a combinaison of two recent parameters tweaks which had
failed narrowly (yellow) at long time control:

• improvement in move ordering during search by softening the distinction
  between bad captures and good captures during move generation, leading
  to improved awareness of Stockfish of potential piece sacrifices (idea
  by Rahul Dsilva)
• increase in the weight of pawns in the "initiative" part of the evaluation
  function. With this change Stockfish should have more incentive to exchange
  pawns when losing, and to keep pawns when winning.

STC:
LLR: 2.93 (-2.94,2.94) {-0.50,1.50}
Total: 10704 W: 2178 L: 1974 D: 6552
Ptnml(0-2): 168, 1185, 2464, 1345, 190
https://tests.stockfishchess.org/tests/view/5ec5553b377121ac09e1023d

LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 60592 W: 7835 L: 7494 D: 45263
Ptnml(0-2): 430, 5514, 18086, 5817, 449
https://tests.stockfishchess.org/tests/view/5ec55ca2377121ac09e10249

Closes https://github.com/official-stockfish/Stockfish/pull/2691

Bench: 4519117

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index d04d724ae5bb8b185c8b2a230ef242cb3b602a2d..449cf6d7463f4ed3f716daf7af0bc91e34c50165 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -730,7 +730,7 @@ namespace {
 
     // Compute the initiative bonus for the attacking side
     int complexity =   9 * pe->passed_count()
 
     // Compute the initiative bonus for the attacking side
     int complexity =   9 * pe->passed_count()

-                    + 11 * pos.count<PAWN>()
+                    + 12 * pos.count<PAWN>()

                     +  9 * outflanking
                     + 21 * pawnsOnBothFlanks
                     + 24 * infiltration
                     +  9 * outflanking
                     + 21 * pawnsOnBothFlanks
                     + 24 * infiltration

diff --git a/src/movepick.cpp b/src/movepick.cpp
index b1e10587cf4a1496d9cb68ed6fc8e10b1e4190c3..e26f42ef98cdef9ba5dba7b1bfbe8682356bcd41 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -169,7 +169,7 @@ top:
 
   case GOOD_CAPTURE:
       if (select<Best>([&](){
 
   case GOOD_CAPTURE:
       if (select<Best>([&](){

-                       return pos.see_ge(*cur, Value(-55 * cur->value / 1024)) ?
+                       return pos.see_ge(*cur, Value(-69 * cur->value / 1024)) ?

                               // Move losing capture to endBadCaptures to be tried later
                               true : (*endBadCaptures++ = *cur, false); }))
           return *(cur - 1);
                               // Move losing capture to endBadCaptures to be tried later
                               true : (*endBadCaptures++ = *cur, false); }))
           return *(cur - 1);