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=-4.0 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 F289B1F462 for ; Tue, 21 May 2019 01:20:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727508AbfEUBUs (ORCPT ); Mon, 20 May 2019 21:20:48 -0400 Received: from mail-qt1-f176.google.com ([209.85.160.176]:46178 "EHLO mail-qt1-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726677AbfEUBUs (ORCPT ); Mon, 20 May 2019 21:20:48 -0400 Received: by mail-qt1-f176.google.com with SMTP id z19so18558328qtz.13 for ; Mon, 20 May 2019 18:20:47 -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=M5u4aA4Iphs6DqlAdQLY7i/HTcsB7tBGk1i++syX/vs=; b=nnJRSrQuNtLA87dPfp7OhrJ6VjUB9ZJrkfNlDa25ln+yTBMYm0RCaM9C3RqJm/wbDZ 0DsENNN7HPr28aLi7+aMw+jsl1+MrF4ORc2QTW2DyceWHzp5eLLUHIJ+1rlXW3hIDfRH ScNC2txOz5o3k5R48VqHFQUfXjvEIluGPrXfZ9K9QVE8l0qYm0Ltr/ZE5HkfSnRuqUQv ebqLBgmtWZCkm1bRuekIuNvfTZ5BjQZLm1Tfg1jNqZXrpCJM7QxbmLYzmLbtR9r7ZT8s Nw6kKpfdRHQL8Xn1can2z5wgzXGi/oWcdzNYz06cvcVlREuILscA2Gmgp5S0V0ZPflkM ONFA== 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=M5u4aA4Iphs6DqlAdQLY7i/HTcsB7tBGk1i++syX/vs=; b=CQuD29gf11EMY+B5tZmITUsn25401Ue9RosAXg2zfz3OscgH7L6YfEpMId2YCjvCOW r9x7Lp+4dwRPKyz9sDBrqryWvSrnX/IXKL4AnCTY1y+Ni7TuSMjaeeO6n24ChsGliAce /+6EsCYKg7kh24XOX96tN4UasQRriWhbCm921n93o4IBUlIsYa4Dhc8Fx2jUoJq8eKGG FwjMRc8EKoVd8+Ukf0/1Rp/XUBFLrdMK+Slb4IbRdKRIAnIqfjRalPK0UrJRWuNVk8WY YwrYyHSA57aeU4BIWUBz9ljmHRon8CMrquCMcSl5dhco68XxZ+zW77Vd/fNgh9wdwPq+ kfVw== X-Gm-Message-State: APjAAAXblKbX/LmpojO95lsxb74pYUAaebBZUHaFcNFV3lBhsIpcwzHX KxA9XxS3QNVsmz27AqoB3pV85oO5c/0= X-Google-Smtp-Source: APXvYqzO559yPrnyIr/ZfuP2F1OkkiGpqAl6l2Ao7JacVSYqt4ka8xYUUwIwDdjNEMWv2MsSvGyH8Q== X-Received: by 2002:a0c:fca6:: with SMTP id h6mr4711334qvq.41.1558401646700; Mon, 20 May 2019 18:20:46 -0700 (PDT) Received: from [10.0.1.7] ([98.122.173.75]) by smtp.gmail.com with ESMTPSA id t47sm10126156qtb.43.2019.05.20.18.20.45 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 20 May 2019 18:20:46 -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> <864l5opuz1.fsf@gmail.com> From: Derrick Stolee Message-ID: <88662e18-db51-cb48-3307-0ea2a91c4ebe@gmail.com> Date: Mon, 20 May 2019 21:20:45 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:67.0) Gecko/20100101 Thunderbird/67.0 MIME-Version: 1.0 In-Reply-To: <864l5opuz1.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 5/20/2019 7:27 PM, 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"? > [...] > >>> 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) > > This should probably read > > offset_date(P) = committer_date(P) + gen_v2(P) > corrected_date(C) = max(committer_date(C), > max_{P ∈ parents(C)}(offset_date(P)) + 1) The final definition needs two conditions on the offset of a commit C for every parent P: 1. committer_date(C) + offset(C) > committer_date(P) + offset(P) 2. offset(C) > offset(P) Condition (1) will give us the performance benefits related to the committer-date heuristic. Condition (2) will give us backwards-compatibility with generation numbers. Thanks, -Stolee