From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-5.7 required=3.0 tests=AWL,BAYES_00, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 38AF12023C for ; Tue, 5 Jul 2016 11:43:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754822AbcGELnT (ORCPT ); Tue, 5 Jul 2016 07:43:19 -0400 Received: from mout.gmx.net ([212.227.15.18]:60419 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754779AbcGELnS (ORCPT ); Tue, 5 Jul 2016 07:43:18 -0400 Received: from virtualbox ([37.24.141.253]) by mail.gmx.com (mrgmx001) with ESMTPSA (Nemesis) id 0M2L2a-1bd1ZD3rXA-00s2tf; Tue, 05 Jul 2016 13:43:04 +0200 Date: Tue, 5 Jul 2016 13:43:01 +0200 (CEST) From: Johannes Schindelin X-X-Sender: virtualbox@virtualbox To: Jeff King cc: Junio C Hamano , =?UTF-8?Q?Jakub_Nar=C4=99bski?= , Stefan Beller , Linus Torvalds , Marc Strapetz , Git Mailing List Subject: Re: topological index field for commit objects In-Reply-To: <20160629223007.GA4726@sigill.intra.peff.net> Message-ID: References: <20160629205647.GA25987@sigill.intra.peff.net> <5774426F.3090000@gmail.com> <20160629220049.GA4416@sigill.intra.peff.net> <20160629223007.GA4726@sigill.intra.peff.net> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Provags-ID: V03:K0:zDCwenbvbjfuKnwO2obJtgMLc9m3xN/5lOoIsHBxQTVONnEj5WS edpN2TVzc2gLcgUnS4dFQl30XSpkyai3cp2Z/1yidzJ2FC+RJ3k+35BeY+zybLZkm5/UWuw u/ezV7mI6h9LjwaHLd4eKek4d+FtsHGecadFGF8aS1viVfI40P/RaZ5oOKFAogEs0H7sK4a V4tb9PV0Heg4843fnuETQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:ApsJu5hx5nk=:tKNknOlYBuoFh/XJojg2gO MjADH7hUz+tUSomBa4OGEjkHQbTlq7GxvvttxhvagaB5A0TGormgvIMS8lT37FdCzY4HhF2ys 1ad6j9RklukxWCm9vtEq6mTPyWSrhEahvs684e9SPFUomLGzhHCEBaoq/IKnB2rGxDEPBoStA NUBHRz+4bPMmmf8lKUULwyZs85Mh2HX8tEsbUNu+RvfxENnSEGBI4fvsHsoZdmxGi6075oVWd ph0IzfzN5zDU+9qPyW9ixtGg0uDrC82DUEMqOhfDQYmcf2LoJaxtikAJOaVIoiRKTG0DxzHea YuKNEyrVQbIHdhCfv8Vf+3h5yYjfXH0NsLGJbj2ZZHjUXFRXuuv9s47bIUMjuqr8vrRJjeiIs z6pBBwVTg7o9YLw/ypn7JxSr0ToTrgcmn8/870uMl3/Yj67B0TGTDnUf52w7AC2JDKXn1MyYl EAR0nvcY3NHKtNwKO4ldUHnDB2fXhGsJrOBuwckip447M1k5niZvMO1CGvn606X2j3996fMJx cvf8wnp6d/Qa3+dQRCa7c5c71cvOmuxsJFW4ZNhxFFib+Mq9OfTL/0B9J5EhxVve6qd1X6MBr W3Nrr400d4KwdQ+Z3XTxaszDYRZ+ndgrkG29W9HSw1D1sM8wY1sjqSYbet+isUxOrRg+QWelY FbCmJGf8vCWmTQ/4S1qT+nrMpx5hLmtdKn5cYQavvb89opn3+LJ+9h81wlN3rVTGCjTK2o8X4 SCOioCJRLZC8pac84EYLZRq93F2BUSCXMPlLgkGZ6rOLR60rUmQmGZ/dDY1ftPpK7xRMkziix dd87CTA Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Hi Peff, On Wed, 29 Jun 2016, Jeff King wrote: > I haven't thought hard specifically about merge bases computation, so > perhaps that is a case that isn't helped at all. I guess it is not helped by generation numbers. But then, we often ask: "is commit A an ancestor of commit B" e.g. to check whether we can fast-forward. The way we do it now is to compute the merge base (singular: if there are more than one, we stop at the first one we found) and then look whether commit A is identical to the merge base. If we had generation numbers available, then we would have to change those computations in order to benefit from them when determining ancestry. But then, reachability would accelerate that even more than generation numbers. Ciao, Dscho