Author: Bernd Nürnberger
Date: 05:32:40 05/06/04
Go up one level in this thread
On May 06, 2004 at 07:58:12, Renze Steenhuisen wrote:
>On May 06, 2004 at 07:07:57, Bernd Nürnberger wrote:
>
>>Hello,
>>
>>I have a really strange bug in my move generator, but in the meantime,
>>after thourough debugging, I am more and more convinced, that it is not
>>a bug in my programming but a bug in Java itself or in the OS/Hardware
>>(but I am still hoping, I made a mistake somewhere ...).
>>
>>I have a iBook 300, Mac OS 9.x, and the latest Java for Mac OS 9.x (I think
>>its MRJ SDK 2.2.4 or so).
>>
>>HERE COMES THE PROBLEM:
>>
>>Some 64 bit long values behave really strange: the upper part (the 32 MSBs)
>>are trashed from time to time (lower 32 bits are OK, upper 32 bits seem
>>more or less random). I looked through the code again and again, so that
>>all literals have a "L" appended, and all literals seems ok now.
>>
>>Could it be, that some operators in Java on long values are not properly
>>implemented and make errors on certain circumstances? Maybe a set upper
>>bit (64th bit, sign bit) causes problems in some cases?
>>
>>I would be really glad to hear your thoughts are even solutions to this
>>kind of problem.
>>
>>Many many thanks in advance for your answers!
>>
>>Best wishes,
>>
>>Bernd
>
>
>Hi Bernd,
>
>could you give me some code to work with that causes the problem already?
>
>Cheers!
>
> Renze
An example:
The variables are declared int/long as appropriate; it's straight forward
implementation as in many other bitboard based programs; hope just a
snippet helps, because the whole relevant code maybe would be some
thousand lines %-/
--- snip ---
...
blackLegalMoves = board.whitePieces; // captures
...
// k -- black king
/////////////////////
// o normal moves and captures
from = board.blackKing;
// (*)
mvboard = KING_MOVES[from] & blackLegalMoves;
halfply = from | Move.BPC_KING;
while (mvboard != 0L) {
to = Bitboard.last(mvboard);
mvboard &= Bitboard.CLEAR_MASK[to];
moves[mvidx++] = halfply | to << Move.TO | piece[to] << Move.CAPTY;
}
--- snap ---
if I insert System.out.println(blackLegalMoves); at point (*) and similiar
points in the code, the error is not present -- even more strange!?!
what can here go wrong with longs? code for other piece types is
similiar...
Greetings,
Bernd
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