Author: Dieter Buerssner
Date: 23:30:53 02/10/02
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On February 10, 2002 at 23:37:54, Robert Hyatt wrote: >On February 10, 2002 at 18:55:59, Angrim wrote: > >>On February 09, 2002 at 22:35:54, Robert Hyatt wrote: >> >>>1. 6 piece files are going to require some large mate-in-N scores. IE they >>>will need 16 bits at least, which doubles the size compared to a current 5 >>>piece file where all scores are 8 bits max. >> >>This doubles the size of the file before compression, but has little >>effect on the size of the compressed file. At least as long as the >>majority of the positions in the file are relatively short mates or >>draws. Only the positions which are long mates will take extra >>space after compression. Compression could be further improved by >>switching to building DTC tables. >> > >Think about that a moment, and you will see it is a flawed statement. IF >the file is 2x larger _before_ compression it will most likely be 2x larger >_after_ compression. Otherwise you are saying that larger files compress >more than smaller files which is a simply flaw in reasoning. I think, Angrim is correct. The file of the double size file has much less randomness, and so can compress better. For example a file of random bytes (values 0-255) cannot be compressed. Storing the value as 16-bit words makes this compressable to half size. Of course, in the case of TBs not all second bytes will be the same, but they should still be predictable with good probability (for example it can be known in advance, that there is no mate > 300 in a specific TB, which makes most available values in the 16 bit range not occuring at all). To the other point you mentioned - the efficiency of storing (say) 9-bit values instead of 16-bit values. As you point out, this needs more CPU resources - sure. But it will need much less memory/disk bandwidth, and I think it is not unlikely at all, that it will be faster in the end. Anyway, I think after compression it won't make a difference anymore. Regards, Dieter
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