From: cj5716 <125858804+cj5716@users.noreply.github.com>
Date: Tue, 31 Oct 2023 00:25:06 +0000 (+0800)
Subject: Prefetch TT entries in probcut
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=e277dda7166992536124891e212d6d6a866f8a12

Prefetch TT entries in probcut

Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 101344 W: 25893 L: 25491 D: 49960
Ptnml(0-2): 303, 11350, 26991, 11698, 330
https://tests.stockfishchess.org/tests/view/6540daa6cc309ae83956669b

slight speedup:
```
Result of 100 runs
==================
base (./stockfish.master       ) =    1170705  +/- 3133
test (./stockfish.patch        ) =    1174545  +/- 2895
diff                             =      +3841  +/- 3196

speedup        = +0.0033
P(speedup > 0) =  0.9907
```

closes https://github.com/official-stockfish/Stockfish/pull/4856

No functional change
---

diff --git a/src/search.cpp b/src/search.cpp
index daab1eb1..6e719be8 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -869,6 +869,9 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
             {
                 assert(pos.capture_stage(move));
 
+                // Prefetch the TT entry for the resulting position
+                prefetch(TT.first_entry(pos.key_after(move)));
+
                 ss->currentMove = move;
                 ss->continuationHistory =
                   &thisThread