Boolean Satisfiability Research Group at PrincetonNEW: zChaff 2007.3.12 is available both in 32 bit version and 64 bit version. It fixes the inefficiency bug in zverify_df. Thanks to Allen Van Gelder and Tjark Weber for reporting the bug and proving the fixes. zChaff 2004.11.15 is available here. It is a trimmed version of 2004.5.13. Many unused or dead codes are removed. Most codes are re-formatted for easy reading. You might get a little speed
