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[.Net only] - fast bit operations
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Zong Li



Joined: 12 May 2012
Posts: 13
PostPost subject: Re: [.Net only] - fast bit operations    Posted: Fri Jun 22, 2012 5:09 pm Reply to topic Reply with quote
I think you mean -bb or ~bb + 1. Smile It is indeed annoying that you can't just negate a UInt64 value. For the pop function I found that isolating the LSB first was a bit faster in practice (perft) even though it was slower when testing with random values in a loop:

Code:

public static Int32 pop_first_x64_sw(ref UInt64 b) {
     UInt64 bb = b & (0UL - b);
     b &= b - 1;
     return BitIndex[(bb * 0x218A392CD3D5DBFUL) >> 58];
}
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Subject Author Date/Time
[.Net only] - fast bit operations Balint Pfliegel Mon Jun 18, 2012 9:59 pm
      Re: [.Net only] - fast bit operations Balint Pfliegel Mon Jun 18, 2012 10:18 pm
            Re: [.Net only] - fast bit operations Balint Pfliegel Thu Jun 21, 2012 10:35 pm
                  Re: [.Net only] - fast bit operations Gerd Isenberg Fri Jun 22, 2012 6:40 am
                        Re: [.Net only] - fast bit operations Balint Pfliegel Fri Jun 22, 2012 6:47 am
                              Re: [.Net only] - fast bit operations Zong Li Fri Jun 22, 2012 5:09 pm
                                    Re: [.Net only] - fast bit operations Balint Pfliegel Fri Jun 22, 2012 5:49 pm
                                          Re: [.Net only] - fast bit operations Balint Pfliegel Fri Jun 22, 2012 7:20 pm
                                                Re: [.Net only] - fast bit operations Zong Li Sat Jun 23, 2012 4:47 pm
                                                      Re: [.Net only] - fast bit operations Balint Pfliegel Mon Jun 25, 2012 5:40 am
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