Hi, I am just posting a link to the message in the main forum
about my humble evaluation project, as Marco suggested : http://www.talkchess.com/forum/viewtopi ... 12&t=44074
Best regards,
Ludmil
A link to a message in the main forum
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Re: A link to a message in the main forum
This is pawn evaluation in SF (it is a very standard one and very common across engines). It is a loop across each pawn, it means each pawn is individually evaluated to get a score and the score summed to the total value.Lyudmil Tsvetkov wrote:Hi, I am just posting a link to the message in the main forum
about my humble evaluation project, as Marco suggested : http://www.talkchess.com/forum/viewtopi ... 12&t=44074
Best regards,
Ludmil
Even if you are not a programmer perhaps you reconize somthing similar to your ideas. Remember that the lines starting with '//' are so called comments. They are free text written in natural language by the programmer as a kind of note. They are not instructions and are discarded by the computer that ignores them.
Code: Select all
const Square* pl = pos.piece_list(Us, PAWN);
// Loop through all pawns of the current color and score each pawn
while ((s = *pl++) != SQ_NONE)
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
f = file_of(s);
r = rank_of(s);
// This file cannot be half open
e->halfOpenFiles[Us] &= ~(1 << f);
// Our rank plus previous one. Used for chain detection
b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
// Flag the pawn as passed, isolated, doubled or member of a pawn
// chain (but not the backward one).
chain = ourPawns & adjacent_files_bb(f) & b;
isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & forward_bb(Us, s);
opposed = theirPawns & forward_bb(Us, s);
passed = !(theirPawns & passed_pawn_mask(Us, s));
// Test for backward pawn
backward = false;
// If the pawn is passed, isolated, or member of a pawn chain it cannot
// be backward. If there are friendly pawns behind on adjacent files
// or if can capture an enemy pawn it cannot be backward either.
if ( !(passed | isolated | chain)
&& !(ourPawns & attack_span_mask(Them, s))
&& !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
{
// We now know that there are no friendly pawns beside or behind this
// pawn on adjacent files. We now check whether the pawn is
// backward by looking in the forward direction on the adjacent
// files, and seeing whether we meet a friendly or an enemy pawn first.
b = pos.attacks_from<PAWN>(s, Us);
// Note that we are sure to find something because pawn is not passed
// nor isolated, so loop is potentially infinite, but it isn't.
while (!(b & (ourPawns | theirPawns)))
Us == WHITE ? b <<= 8 : b >>= 8;
// The friendly pawn needs to be at least two ranks closer than the
// enemy pawn in order to help the potentially backward pawn advance.
backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
}
assert(opposed | passed | (attack_span_mask(Us, s) & theirPawns));
// A not passed pawn is a candidate to become passed if it is free to
// advance and if the number of friendly pawns beside or behind this
// pawn on adjacent files is higher or equal than the number of
// enemy pawns in the forward direction on the adjacent files.
candidate = !(opposed | passed | backward | isolated)
&& (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0
&& popcount<Max15>(b) >= popcount<Max15>(attack_span_mask(Us, s) & theirPawns);
// Passed pawns will be properly scored in evaluation because we need
// full attack info to evaluate passed pawns. Only the frontmost passed
// pawn on each file is considered a true passed pawn.
if (passed && !doubled)
e->passedPawns[Us] |= s;
// Score this pawn
if (isolated)
value -= IsolatedPawnPenalty[opposed][f];
if (doubled)
value -= DoubledPawnPenalty[opposed][f];
if (backward)
value -= BackwardPawnPenalty[opposed][f];
if (chain)
value += ChainBonus[f];
if (candidate)
value += CandidateBonus[relative_rank(Us, s)];
}
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// Doubled pawn penalty by opposed flag and file
const Score DoubledPawnPenalty[2][8] = {
{ S(13, 43), S(20, 48), S(23, 48), S(23, 48),
S(23, 48), S(23, 48), S(20, 48), S(13, 43) },
{ S(13, 43), S(20, 48), S(23, 48), S(23, 48),
S(23, 48), S(23, 48), S(20, 48), S(13, 43) }};
// Isolated pawn penalty by opposed flag and file
const Score IsolatedPawnPenalty[2][8] = {
{ S(37, 45), S(54, 52), S(60, 52), S(60, 52),
S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
{ S(25, 30), S(36, 35), S(40, 35), S(40, 35),
S(40, 35), S(40, 35), S(36, 35), S(25, 30) }};
// Backward pawn penalty by opposed flag and file
const Score BackwardPawnPenalty[2][8] = {
{ S(30, 42), S(43, 46), S(49, 46), S(49, 46),
S(49, 46), S(49, 46), S(43, 46), S(30, 42) },
{ S(20, 28), S(29, 31), S(33, 31), S(33, 31),
S(33, 31), S(33, 31), S(29, 31), S(20, 28) }};
// Pawn chain membership bonus by file
const Score ChainBonus[8] = {
S(11,-1), S(13,-1), S(13,-1), S(14,-1),
S(14,-1), S(13,-1), S(13,-1), S(11,-1)
};
// Candidate passed pawn bonus by rank
const Score CandidateBonus[8] = {
S( 0, 0), S( 6, 13), S(6,13), S(14,29),
S(34,68), S(83,166), S(0, 0), S( 0, 0)
};
Code: Select all
S(83,166)
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Re: A link to a message in the main forum
Have you done any testing ?Lyudmil Tsvetkov wrote:Hi, I am just posting a link to the message in the main forum
about my humble evaluation project, as Marco suggested : http://www.talkchess.com/forum/viewtopi ... 12&t=44074
Best regards,
Ludmil