who understands my code

[flok]

Hi,

I was looking at my quiescence code and found this:

Code: Select all

  if (score > bestVal)
  {
          bestVal = score;
          // remember move for sibling-node-best-move
          selMove = *newCause.causingMove;
  
          if (score > alpha)
          {
                  alpha = score;
  
                  // remember PV
                  newPv.assign(tempPv, false);
  
                  if (score >= beta)
                          break;
          }
  }

I wonder why is there a if (score > bestval) and also a if (score > alpha)?
Because if > bestval then always also > alpha. I think I can just remove that if > alpha and maybe even rewrite things and get rid of bestVal (using alpha instead).

Any opinions on this?

(probably code I copied from somewhere)[/code]

[stegemma]

It would have sense only if you can start with a bestval < alpha (-infinite, for sample) and your search can returns something less than alpha but greater than actual bestval.

[Henk]

Always simplify even it is wrong.

[For code usually only gets more and more complicated. ]

[hgm]

I wonder why is there a if (score > bestval) and also a if (score > alpha)?
Because if > bestval then always also > alpha.

Not if you use fail-soft. Then bestVal starts at -INFINITY even if alpha is much larger. At the end you return bestScore, and in case of a fail low this can still be smaller than alpha (which would then still be the original alpha). With fail-hard one usually does not keep a bestValue at all, as one would return alpha.

[bob]

Normally that is written differently:

if (score > alpha) {
if (score >= beta)
return beta
alpha = score;
}

Seems more rational that way. If score is <= alpha, ignore it. Else if it is > beta, return instantly (beta cutoff) otherwise remember it as best since we now know it is > alpha and < beta...

[Robert]

Code: Select all

  if (score > bestVal)
  {
          bestVal = score;
          // remember move for sibling-node-best-move
          selMove = *newCause.causingMove;
  
          if (score > alpha)
          {
                  alpha = score;
  
                  // remember PV
                  newPv.assign(tempPv, false);
  
                  if (score >= beta)
                          break;              <= I don't understand This!!!
          }
  }

[flok]

Code: Select all

  if (score > bestVal)
  {
          bestVal = score;
          // remember move for sibling-node-best-move
          selMove = *newCause.causingMove;
  
          if (score > alpha)
          {
                  alpha = score;
  
                  // remember PV
                  newPv.assign(tempPv, false);
  
                  if (score >= beta)
                          break;              <= I don't understand This!!!
          }
  }

beta cut-off; stop the loop and return the best bestval.

[kbhearn]

then why'd you write it? ;)

the break in this case does something outside the scope of the quoted code - it removes you from the innermost loop you're currently in perhaps to the final 'return bestVal;' line (which you now have scored as the current score > beta). It may avoid some code duplication if the TT update is similar enough for the fail high and fail low cases to write it in this manner.

[lauriet]

I'm with Kevin......how is it that you have written code and you don't know what it does ??? How did you write it to start with ???

[flok]

copy/paste from somewhere