Comment: Re:How can you be sure it's identical? (Score 1) 315
As posted previous -- here is the PDF of the report: http://www.chessvibes.com/plaatjes/rybkaevidence/Rybka_Investigation_report.pdf
Specifically see section 2. Investigation:
2.1 Executable file analysis
Quote “Rybka 1.0 Beta and Fruit 2.1 have exactly the same evaluation features“. Disassembly of the root search analysis indicates nearly identical code and variables, even including the ordering of the variables. Appendix B on the evaluation of Rybka 2.3.2a shows “the evaluation function in Rybka 2.3.2a is substantially the same as in Rybka 1.0 Beta”. Watkins compares evaluation function features between Rybka, Fruit and four other open source programs (Phalanx, Pepito, Crafty and Faile). In section D.2.3 he shows an overlap of 18.8 out of 24 evaluation terms for Rybka-Fruit (73% overlap), with much lower overlaps than between the other programs. Crafty 19.0-Fruit eval overlap: 12.9/24 = 54%, Phalanx-Fruit overlap: 43%, Pepito-Fruit overlap 37%, Faile-Fruit Overlap 23%. This has been expanded with more statistical rigour in a separate 50+ page paper mentioned in 2.4 below.