Better condition in is_pseudo_legal()

Simplify occupied destination condition.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Use arrow operator instead of * and .

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Tune pawn PSQT values

Reduces the influence of PSQT for entries such as
the extended center and the h-file.

Passed both short TC test:
LLR: 2.95 (-2.94,2.94)
Total: 23919 W: 5207 L: 5029 D: 13683

And long TC one:
LLR: 2.96 (-2.94,2.94)
Total: 5762 W: 1108 L: 974 D: 3680

Bench: 4617880

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Revert "Halve king eval margin"

This reverts commit 4b3a0fdab03a7529ede42891963d3036712a0bd5.

As Gary says: " It failed when I tried it at long TC previously, and only
barely passed this time.  Some anecdotal evidence is that it hurts vs other
engines as well (the Lightspeed rating list showed a 16 elo drop from previous
best version - still +- 5 error bars on both, but that's still significant)"

I also agree that if we have some doubts (like in this case) it is better to
be safe than sorry.

bench: 4615572
Simplify captures ordering

A big simplification and removing of useless code.

Finished at 50% both at short TC (with SPRT) than
at long TC at fixed number of games:
ELO: -0.14 +-3.4 (95%) LOS: 46.8%
Total: 15206 W: 2836 L: 2842 D: 9528

bench: 5059948
Use #ifndef instead of #if !defined

And #ifdef instead of #if defined

This is more standard form (see for example iostream file).

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Fix a typo in bitboard.h

Introduced by previous patch.

Spotted by Joerg Oster

No functional change.
Rewrite pawn shield and storm code

Passes quickly both short TC:
LLR: 2.95 (-2.94,2.94)
Total: 5755 W: 1349 L: 1222 D: 3184

And long TC:
LLR: 2.95 (-2.94,2.94)
Total: 2744 W: 628 L: 505 D: 1611

bench: 4727133
Fix an assert in KBK endgame

The endgame king + minor vs king is erroneusly
detected as king + minor vs king + minor

Here the fix is to detect king + minor earlier,
in particular to add these trivial cases to
endgame evaluation functions.

Spotted by Reuven Peleg

bench: 4727133
Annotate an unlikely condition

No functional change.
Increase pruning if evaluation is not improving

Add an additional set of margins to movecount pruning
to be used when static evaluation is getting worse
than previous move.

Here are the margins table with changing
depth (fm0 not improving, fm1 improving):

    d: 0, fm0: 3, fm1: 3
    d: 1, fm0: 4, fm1: 4
    d: 2, fm0: 6, fm1: 6
    d: 3, fm0: 7, fm1: 10
    d: 4, fm0: 11, fm1: 15
    d: 5, fm0: 15, fm1: 21
    d: 6, fm0: 21, fm1: 29
    d: 7, fm0: 27, fm1: 37
    d: 8, fm0: 35, fm1: 47
    d: 9, fm0: 42, fm1: 57
    d: 10, fm0: 51, fm1: 68
    d: 11, fm0: 60, fm1: 81
    d: 12, fm0: 70, fm1: 94
    d: 13, fm0: 81, fm1: 108
    d: 14, fm0: 92, fm1: 123
    d: 15, fm0: 104, fm1: 139

Good at both short TC

LLR: 2.97 (-2.94,2.94)
Total: 11502 W: 2503 L: 2361 D: 6638

And long TC

LLR: 2.98 (-2.94,2.94)
Total: 7189 W: 1421 L: 1277 D: 4491

bench: 4364793
Speed up move generation

Pass the color as template parameter
to generate_all()

Speedup of 1,3% in perft and 2,5% in bench !

No functional change.
Small renaming

No functional change.
Tidy up Position::pretty

No functional change.
Fix a race at thread creation

At thread creation start_routine() is called
and from there the virtual function idle_loop()
because we do this inside Thread c'tor, where the
virtual mechanism is disabled, it could happen that
the base class idle_loop() is called instead.

The issue happens with TimerThread and MainThread
where, at launch, start_routine calls
Thread::idle_loop instead of the derived ones.

Normally this bug is hidden because c'tor finishes
before start_routine() is actually called in the
just created execution thread, but on some platforms
and in some cases this is not guaranteed and the
engine hangs.

Reported by Ted Wong on talkchess

No functional change.
Rework Thread hierarchy

Introduce ThreadBase struct that is search
agnostic and just handles low level stuff,
and derive all the other specialized classes
form here.

In particular TimerThread does not hinerits
anymore all the search related stuff from Thread.

Also some renaming while there.

Suggested by Steven Edwards

No functional change.
Factor out pieceList updating code

The new Position methods add_piece, move_piece, and remove_piece
now manage the member variables pieceList, pieceCount, and index,
and 9 blocks of code in Position that used to manipulate those
data structures by hand now call the new methods.

There is a slightly slowdown (< 1%) on Clang and on perft,
but the cleanup compensates the little speed loss.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Further factor out position update code

Along the lines of previous patch.

No functional change
Retire cpu_count()

Set threads number always to 1 at startup and let the
user explicitly to chose the number of threads.

Also preserve the useful behavior of automatically set
"Min Split Depth" according to the requested threads,
indeed this parameter is too technical for a casual user,
so, when left to zero, we set it on a sensible value.

No functional change
Manuale merge from 'master'

bench: 4364793