Author: Miguel A. Ballicora
Date: 09:41:29 12/18/01
Go up one level in this thread
On December 18, 2001 at 02:15:31, Rafael Andrist wrote: >On December 17, 2001 at 15:06:09, Dann Corbit wrote: > >>On December 17, 2001 at 14:53:12, Rafael Andrist wrote: >> >>>In the PGN/EPD specification I couldn't find any human friendly way to indicate >>>the distance to the mate if it is the side the move which will be mated. I know >>>it would be possible with the "ce" opcode but this is a little bit more >>>difficult to read. Is there any way to indicate it in an easy way like the "dm" >>>it does if the side to move mates the opponent? Should I use e.g. "dm -3" or is >>>this a bad idea? Any suggestions? >> >>From the PGN Standard, we have this: >>------------------------------------------------------------------------------- >>16.2.5.7: Opcode "dm": direct mate fullmove count >> >>The "dm" opcode is used to indicate the number of fullmoves until checkmate is >>to be delivered by the active color for the indicated position. It always >>takes a single operand which is a positive integer giving the fullmove count. >>For example, a position known to be a "mate in three" would have an operation >>of "dm 3;" to indicate this. >> >>This opcode is intended for use with problem sets composed of positions >>requiring direct mate answers as solutions. >>------------------------------------------------------------------------------- >>Because of the statement "by the active color" I think negative numbers are out. >> >>Unfortunately, *most* implementers of PGN ignore the correct use of the ce >>opcode (though I think 32767 should be allowed for 'this is a checkmate' rather >>than used for indication of error). At any rate, you cannot count on 32767-n >>being ply distance to mate. All sorts of values are used, and that is why >>distance to mate is unclear. Because people ignore the standard. > >32767-n is wrong too... Please have a look at the standard again. >Most ce-programs are using a 16 bit integer for the score. The range of a signed >integer is [-32768;32767] I guess it might depend on the language, but in C the portable range for a signed integer is -32767 to 32767. >in the "ce" opcode -32767 is used for illegal position and the effective "ce" >range for legal positions goes from -32766 to 32766, and -32768/32767 can >internally used for -/+ infinity. I will check the EPD standard again but I do not think they contemplate the possibility of using -32768. Otherwise, it is broken. Regards, Miguel > > >>My suggestion is: >>c0 "Mate in three for the opposing side." > >This may be a solution for a single position, but not for a list of 1000 or more >positions. This would also nearly double the needed disk space. > >I think i will use a new opcode "om x" (= opponent mates in x) and then add a >"ce" opcode to make it clear for other programs. > >Rafael B. Andrist
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