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Is there such a thing as branchless move generation?
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Gerd Isenberg



Joined: 08 Mar 2006
Posts: 1802
Location: Hattingen, Germany
PostPost subject: Re: Is there such a thing as branchless move generation?    Posted: Sat Jun 09, 2012 7:48 pm Reply to topic Reply with quote
johnhamlen wrote:
So I was very happy to get the following response from my old friend Gerd:
Gerd Isenberg wrote:
Direction-wise move generation can be done almost branchless without any lookups but pure SIMD register computation with fill algorithms aka Kogge-Stone for sliding piece attacks.


However, it's not immediately obvious to me how the Koggie-Stone methods work and how I can map them to branchless code.


First, thank you for your kind words on cpw, founded by Mark Lefler, where I happen to become addicted editor.

The point with fill-stuff is that it is SIMD-friendly and one may compute vectors of bitboards simultanously, i.e. a quad-bitboard within two SSE 128-bit xmm or one AVX 256-bit ymm register(s), for instance with white/black rooks/queens and kings for the four orthogonal directions, and white/black bishops/queens and kings for the diagonal directions, for all sliding and pseudo attacks to determine pinned pieces etc, to finally store legal (one condition per direction) move-targets for each direction as a kind of fixed-sized unsorted move-list. May be better look on dumb7fill first, which is not much worse than its parallel prefix Kogge-Stone approach.

Of course, picking the moves from this move-lists requires an appropriate state machine (big jump-table on state) and conditional branches, bitscan target, determining source, and you don't want to sac exponential speedup due to worse move-ordering by linear one from almost branchless and parallel generation. I use such a thing within a quad-bitboard color-flipper, white to move only, boosting probe-hash prefetch.

Cheers,
Gerd
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Subject Author Date/Time
Is there such a thing as branchless move generation? John Hamlen Thu Jun 07, 2012 7:50 pm
      Re: Is there such a thing as branchless move generation? Gerd Isenberg Thu Jun 07, 2012 8:44 pm
            Re: Is there such a thing as branchless move generation? John Hamlen Thu Jun 07, 2012 10:18 pm
      Re: Is there such a thing as branchless move generation? Edmund Moshammer Thu Jun 07, 2012 10:57 pm
            Re: Is there such a thing as branchless move generation? John Hamlen Fri Jun 08, 2012 8:21 am
                  Re: Is there such a thing as branchless move generation? Sven Schüle Fri Jun 08, 2012 9:21 am
                        Re: Is there such a thing as branchless move generation? John Hamlen Fri Jun 08, 2012 10:31 am
                              Re: Is there such a thing as branchless move generation? Edmund Moshammer Fri Jun 08, 2012 10:41 am
                                    Re: Is there such a thing as branchless move generation? John Hamlen Sat Jun 09, 2012 1:17 pm
                              Re: Is there such a thing as branchless move generation? Daniel Shawul Fri Jun 08, 2012 11:12 am
                                    Re: Is there such a thing as branchless move generation? Edmund Moshammer Fri Jun 08, 2012 11:18 am
                                          Re: Is there such a thing as branchless move generation? Daniel Shawul Fri Jun 08, 2012 3:39 pm
                                                Re: Is there such a thing as branchless move generation? Vincent Diepeveen Sat Jun 16, 2012 9:07 am
                                                      Re: Is there such a thing as branchless move generation? Daniel Shawul Sat Jun 16, 2012 11:27 am
                                                            Re: Is there such a thing as branchless move generation? Vincent Diepeveen Sat Jun 16, 2012 11:35 am
                                    Re: Is there such a thing as branchless move generation? John Hamlen Sat Jun 09, 2012 2:43 pm
                                          Re: Is there such a thing as branchless move generation? Daniel Shawul Sat Jun 09, 2012 6:02 pm
                                                Re: Is there such a thing as branchless move generation? John Hamlen Sun Jun 10, 2012 2:21 pm
                                                      Re: Is there such a thing as branchless move generation? Daniel Shawul Sun Jun 10, 2012 6:33 pm
                                                            Re: Is there such a thing as branchless move generation? Daniel Shawul Sun Jun 10, 2012 7:16 pm
                                                                  Re: Is there such a thing as branchless move generation? Edmund Moshammer Sun Jun 10, 2012 9:24 pm
                                                                        Re: Is there such a thing as branchless move generation? Daniel Shawul Sun Jun 10, 2012 9:54 pm
                                                                  Re: Is there such a thing as branchless move generation? John Hamlen Sun Jun 10, 2012 10:14 pm
                                                                        Re: Is there such a thing as branchless move generation? Daniel Shawul Mon Jun 11, 2012 12:49 am
                                                                              Re: Is there such a thing as branchless move generation? John Hamlen Mon Jun 11, 2012 12:43 pm
                                                                                    Re: Is there such a thing as branchless move generation? Daniel Shawul Mon Jun 11, 2012 2:41 pm
                                                                                          Re: Is there such a thing as branchless move generation? John Hamlen Mon Jun 11, 2012 10:12 pm
                                                                                          Re: Is there such a thing as branchless move generation? Daniel Shawul Mon Jun 11, 2012 11:12 pm
                                                                                          Re: Is there such a thing as branchless move generation? John Hamlen Mon Jun 11, 2012 11:41 pm
                                                                        Re: Is there such a thing as branchless move generation? Vincent Diepeveen Sat Jun 16, 2012 9:56 am
                                                            Re: Is there such a thing as branchless move generation? John Hamlen Sun Jun 10, 2012 10:58 pm
                                          Re: Is there such a thing as branchless move generation? Gerd Isenberg Sat Jun 09, 2012 7:48 pm
                                                Re: Is there such a thing as branchless move generation? John Hamlen Sun Jun 10, 2012 5:28 pm
            Re: Is there such a thing as branchless move generation? Edmund Moshammer Fri Jun 08, 2012 10:32 am
                  Re: Is there such a thing as branchless move generation? John Hamlen Sat Jun 09, 2012 2:57 pm
                  Re: Is there such a thing as branchless move generation? Vincent Diepeveen Sat Jun 16, 2012 8:57 am
      Re: Zeta CL uses Magic Bitboards Srdja Matovic Mon Jun 11, 2012 2:53 pm
            Re: Zeta CL uses Magic Bitboards Gerd Isenberg Mon Jun 11, 2012 8:55 pm
                  Re: Zeta CL uses Magic Bitboards Srdja Matovic Mon Jun 11, 2012 9:35 pm
                        Re: Zeta CL uses Magic Bitboards Daniel Shawul Mon Jun 11, 2012 11:26 pm
                              Re: Zeta CL uses Magic Bitboards Srdja Matovic Tue Jun 12, 2012 1:16 am
                              Re: Zeta CL uses Magic Bitboards Gerd Isenberg Tue Jun 12, 2012 6:58 am
                                    Re: Zeta CL uses Magic Bitboards Daniel Shawul Tue Jun 12, 2012 1:46 pm
                                          Re: Zeta CL uses Magic Bitboards Srdja Matovic Tue Jun 12, 2012 2:35 pm
                                                Re: Zeta CL uses Magic Bitboards Daniel Shawul Tue Jun 12, 2012 4:37 pm
                                                      Re: Zeta CL uses Magic Bitboards Vincent Diepeveen Sat Jun 16, 2012 8:46 am
                                                            Re: Zeta CL uses Magic Bitboards Daniel Shawul Sat Jun 16, 2012 11:17 am
                                                                  Re: Zeta CL uses Magic Bitboards Vincent Diepeveen Sat Jun 16, 2012 11:30 am
                                                                        Re: Zeta CL uses Magic Bitboards Daniel Shawul Sat Jun 16, 2012 1:56 pm
                                                                              Re: Zeta CL uses Magic Bitboards Vincent Diepeveen Sat Jun 16, 2012 2:51 pm
                  Re: Zeta CL uses Magic Bitboards vs Kogge-Stone Srdja Matovic Tue Jun 12, 2012 1:05 am
                        Re: Zeta CL uses Magic Bitboards vs Kogge-Stone Gerd Isenberg Tue Jun 12, 2012 6:31 am
            Re: Zeta CL uses Magic Bitboards John Hamlen Mon Jun 11, 2012 10:35 pm
                  Re: Zeta CL uses Magic Bitboards Daniel Shawul Mon Jun 11, 2012 11:00 pm
      Re: Is there such a thing as branchless move generation? Vincent Diepeveen Sat Jun 16, 2012 8:40 am
      Re: Is there such a thing as branchless move generation? Vincent Diepeveen Sat Jun 16, 2012 9:23 am
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