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Decrease NullMoveMargin and adjust razoring

Browse source 
Also retire razoring margins vector and use
a simpler formula instead.

Now that we use a more accurate static evaluation
try to avoid useless null searches when we are well
below beta. And for teh same reason increase a bit
the razoring.

After 972 games at 1+0
Mod vs Orig +224 =558 -190 +12 ELO

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2010-01-10 01:12:15 +01:00
parent 638f3d31cc
commit e817a55bc6
1 changed files with 4 additions and 11 deletions
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15
src/search.cpp
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@ -172,9 +172,9 @@ namespace {
// best move from the previous iteration, Problem is set back to false.
const Value NoProblemMargin = Value(0x14);
// Null move margin. A null move search will not be done if the approximate
// Null move margin. A null move search will not be done if the static
// evaluation of the position is more than NullMoveMargin below beta.
const Value NullMoveMargin = Value(0x300);
const Value NullMoveMargin = Value(0x200);
// If the TT move is at least SingleReplyMargin better then the
// remaining ones we will extend it.
@ -190,13 +190,6 @@ namespace {
// Depth limit for razoring
const Depth RazorDepth = 4 * OnePly;
// Remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
const Value RazorMargins[6] = { Value(0x180), Value(0x300), Value(0x300), Value(0x3C0), Value(0x3C0), Value(0x3C0) };
// Remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
const Value RazorApprMargins[6] = { Value(0x520), Value(0x300), Value(0x300), Value(0x300), Value(0x300), Value(0x300) };
/// Variables initialized by UCI options
// Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV nodes
@ -1453,12 +1446,12 @@ namespace {
// Null move search not allowed, try razoring
else if ( !value_is_mate(beta)
&& depth < RazorDepth
&& staticValue < beta - RazorApprMargins[int(depth) - 2]
&& staticValue < beta - (depth > OnePly ? NullMoveMargin + 16 * depth : 2*NullMoveMargin)
&& ss[ply - 1].currentMove != MOVE_NULL
&& ttMove == MOVE_NONE
&& !pos.has_pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - RazorMargins[int(depth) - 2];
Value rbeta = beta - (NullMoveMargin + 16 * depth);
Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
if (v < rbeta)
return v;