If you are at a root node, and you retrieve an UPPER bound from the TT, and if you find that
"UPPER BOUND FROM TABLE <= alpha", you can safely return alpha. But, like I said, if you are at the root node,
can you safely use the move stored in the TT, since that corresponded to the upper bound in ...

Miyagi403 wrote: if (entry.depthleft <= depthleft) { ... }

That should be:
if (entry.depthleft >= depthleft) { ... }

...could you explain what your addition, below, to evaluation.h and .c does?

This is standard bitboard pin-detection adapted to positional scoring for pins or discovered attack (wR -> bQ). With the proviso that I haven't seen the full source (i.e. based only on the code snippets):
On entry ...

[...] im currently developing using gcc and the assembler there is just a bitch [...]
These built-ins work nicely with gcc and clang. No assembler; no look-up tables; just plain function calls.

static inline int GetLowestBit( BitBoard b ) { return __builtin_ctzll( b ); }

static inline int ...

I have got the concept of knight moves in bitboard. I need an array knight[64] in which all possible knight moves will be stored.
But how can I get the position of my knights in bitboard without looping through the bits of knight ??
i.e. How can I know , where my knights are placed in chessboard ...

The easiest bitboard slider-attacks code to write is the standard or classical method:
http://chessprogramming.wikispaces.com/Classical+Approach

Here's an implementation of RookAttacks().
extern BitBoard gRayN[64], gRayE[64], gRayS[64], gRayW[64];

BitBoard RookAttacks( int fromSquare, BitBoard ...

Until now, my Board struct has contained an 'attack board'
BitBoard attacksFrom[64];
as a distant legacy from Slate & Atkin's Chess 4.5.
Caching attacks in this way not only inflates Board size, it requires elaborate code for incremental updating in MakeMove().

Stimulated by this thread, I ...

My engine uses CopyBoard() because of laziness. In a new engine it's much easier to copy (essentially one line of code) than to write a complex and bug-prone Unmake().
Careful profiling shows that time is spent:
15.7% MakeMove
5.5% CopyBoard
77.9% MoveGen, Evaluate, Search,...

I doubt that I am ...