From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.8 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_NONE shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id D99391F461 for ; Tue, 25 Jun 2019 10:54:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732155AbfFYKyd (ORCPT ); Tue, 25 Jun 2019 06:54:33 -0400 Received: from mail-yw1-f66.google.com ([209.85.161.66]:42166 "EHLO mail-yw1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728078AbfFYKyd (ORCPT ); Tue, 25 Jun 2019 06:54:33 -0400 Received: by mail-yw1-f66.google.com with SMTP id s5so7294708ywd.9 for ; Tue, 25 Jun 2019 03:54:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=26o+FyRKzJnl3Rw9K5Qfp2lxztX2OqCgVbfmtZN2t58=; b=tpvgzzGMSFqLnBxOz+e1y9siJ9qf1YyLZpQydCYmUH4NprCzNtL+M5h98dfbgFxtis xgaQS/tNmpWSFzMjLPl61GVQ0tmnNnE1NKRyOwcHkgbKTLX+m4VdgKw66grKvTkLVj8o +n+Pm2pw3QzSue/pUUfo8cQmwwCoEdENFKNHkojgic1mr//KzQQjhP/xNOC7040HUGwL hx02jZcB3PxWuqDIxoEg42v5GCcfwrDbuduSS8VNCoreRlboINxd57XiUEM0p0onOkfx aGwNRkgKFMOlw63xthm7VofWQL2hgBkFP6xo0DyH6vDTs0/FWuoGblGbrCNZwP0B38+X sT3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=26o+FyRKzJnl3Rw9K5Qfp2lxztX2OqCgVbfmtZN2t58=; b=QNXlPoAxKl0MOnOz/4Ph5S/sbvEQ15QSkcjrGBVH9m7/Vr41Ys3KaGRcftsgyd0VDO UUyYS03caulZk9ztFNA5DEoz753Oy7Fll6Oy4rRH8OtLSvYaqwhCHYx/6AHMl/J6+Y8m 2GCTDAZU74QYTP3lv3SkCwXeh68V6odgLfSzFwPCHSi1ZaDQzBwdHQO7wpZXfvAS0u3M xLrl6WypHicKSvYOPmLwmi9Cc19zPh9TRPz9QDovguwJJPx7QM/o1IcmAaim+Y2JtJT7 zKKmUqNQ+UDsR5bzzZHMSoeqX854Md9lcAr6bnyHLNVYsvxJSO6p61RRu0Im5zj3jl3K VWoA== X-Gm-Message-State: APjAAAV35iDebf5mOgwIbZ6agrKtjV3rZXNLFNQdM+I1ucrLT4oGOphg ThePCRX1cIxmziEXlF6wDTJv1Str X-Google-Smtp-Source: APXvYqztxaF/UpsI9rsGYBPlYMqoB416bYtcNesghzRu0HqbqDyDlfAn5yzaMPxg8nB4d+KbDGAd4Q== X-Received: by 2002:a81:25d1:: with SMTP id l200mr55141243ywl.11.1561460072145; Tue, 25 Jun 2019 03:54:32 -0700 (PDT) Received: from [192.168.1.16] ([98.122.173.75]) by smtp.gmail.com with ESMTPSA id a82sm3575612ywh.42.2019.06.25.03.54.31 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Tue, 25 Jun 2019 03:54:31 -0700 (PDT) Subject: Re: Revision walking, commit dates, slop To: Jakub Narebski Cc: Mike Hommey , =?UTF-8?Q?SZEDER_G=c3=a1bor?= , git@vger.kernel.org References: <20190518005412.n45pj5p2rrtm2bfj@glandium.org> <20190518015005.GA951@szeder.dev> <20190518035828.pjaqfrkkvldhri6v@glandium.org> <20190518041706.ct6ie5trvxgdhjar@glandium.org> <86mujhpewj.fsf@gmail.com> <86ftp9p7i8.fsf@gmail.com> <86mui63xwr.fsf@gmail.com> From: Derrick Stolee Message-ID: <55fad895-2c18-5a91-79b9-7b958fe280c6@gmail.com> Date: Tue, 25 Jun 2019 06:54:29 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.0 MIME-Version: 1.0 In-Reply-To: <86mui63xwr.fsf@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 6/25/2019 3:51 AM, Jakub Narebski wrote: > Jakub Narebski writes: >> Derrick Stolee writes: >>> On 5/20/2019 7:02 AM, Jakub Narebski wrote: >>>> >>>> Are there any blockers that prevent the switch to this >>>> "generation number v2"? >>>> >>>> - Is it a problem with insufficient data to choose the correct numbering >>>> as "generation number v2' (there can be only one)? >>>> - Is it a problem with selected "generation number v2" being >>>> incompatibile with gen v2, and Git failing when new version of >>>> commit-graph is used instead of softly just not using commit-graph? >>>> - Or is it something else? > [...] > >>> Using the generation number column for the corrected >>> commit-date offsets (assuming we also guarantee the offset is strictly >>> increasing from parent to child), these new values will be backwards- >>> compatible _except_ for 'git commit-graph verify'. >> >> O.K., so the "generation number v2 (legacy)" would be incremental and >> backward-compatibile in use (though not in generation and validation). >> >> Do I understand it correctly how it is calculated: >> >> corrected_date(C) = max(committer_date(C), >> max_{P ∈ parents(C)}(corrected_date(P)) + 1) >> offset(C) = corrected_date(C) - committer_date(C) >> gen_v2(C) = max(offset(C), max_{P ∈ parents(C)}(gen_v2(P)) + 1) > > Do you remember who first came up with this idea for backward > compatibile corrected commit date offsets (monotonically offset > corrected date)? I remember saying that the "corrected commit date" that I had suggested was weak because it was not backwards-compatible with generation numbers if you are only looking at the offsets. I don't remember who suggested simply increasing the offset so they do become backwards-compatible. >> Do you have benchmark for this "monotonically offset corrected commit >> date" generation number in https://github.com/derrickstolee/git/commits/reach-perf >> and https://github.com/derrickstolee/gen-test ? > > I guess this will have to wait... I have not had time to revisit this topic and re-run performance numbers, sorry. -Stolee