From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E15EC433E0 for ; Wed, 20 May 2020 16:38:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 758DB2065F for ; Wed, 20 May 2020 16:38:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GDG9+mfp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726959AbgETQiy (ORCPT ); Wed, 20 May 2020 12:38:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726545AbgETQiy (ORCPT ); Wed, 20 May 2020 12:38:54 -0400 Received: from mail-pj1-x1044.google.com (mail-pj1-x1044.google.com [IPv6:2607:f8b0:4864:20::1044]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F096AC061A0E for ; Wed, 20 May 2020 09:38:53 -0700 (PDT) Received: by mail-pj1-x1044.google.com with SMTP id k7so1546873pjs.5 for ; Wed, 20 May 2020 09:38:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mime-version:content-disposition; bh=dbmyRaX0B3lETX0AuaZ50PFMd4qRE35Pjb62ZYcNrZc=; b=GDG9+mfpcZCd5NBp64DAenjucsRu3KY90gQp8WM+0uWmDO7ow41MCiPjh5czNwPfVW lwV1ibzdhMVdkmqNkMEXwMf4MtB6VoFjYUse7cUIxzq6p1tyfNxLcS1JRLKqFUGGd1lA cIWhVLdlHgPL8DyFCA8zc9LQSrfXDnUXZJXnYkPMoYS/4jKTOlbU/SmVZx/sgeXBn644 rgJbk+dCD/Ao9wn9WIjEci2h8TMOky1yisqA6wiaL8aMlH0W8qCgnLzPisI6+d98ZxDu AwfY7WlUtWjRRRbH3Cd5QLMwCmlYno7RsMzRvBVPCWRWLj661WXsHg5HHUyBLm+roG6s hEVQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition; bh=dbmyRaX0B3lETX0AuaZ50PFMd4qRE35Pjb62ZYcNrZc=; b=Obbf5icKENsSlEWH/YaDHjH+TqnGOuCV50toSyaA9RrPfvtu38L+5ucP7I9F+B45Bs cx7oLfPIkVf4b2YbGTRAK4pZton8Rxqz9BZi+Cpul6Km1oWyVx8Ir/JdgHjjrcssVAo+ zfx16gWXhY1foUv4/rtXYXYhM9E5XZ7hVC9/+ucj0DqTYPFvct8ljES4MtE3Z36XOSqw F9xxvT8k+L8VWmKfgfyt0XKnNLtiTCZcebB4USWPU+uOsM2LhbezuOdzlJPx6kYjQkHI 4MvfOsQ/RjVxorIAnZPC+8mgq2A4cwCEeOa1/PHM8slpzf990WHmoOxxmwVG6d3xLtzb 1vDA== X-Gm-Message-State: AOAM531iwADg4a5wgoMwFJkoCMHC3y/R9LAFErypbeC2AimrjcnPqNeU +5Yt8MnPQQZJWFKTVeO5unn2l4JvR/8= X-Google-Smtp-Source: ABdhPJxiKERqS/ZWgHks4Z97B7mJtpTQXuBemh+xI6wpDMSCDfntVTtNnCQAVCAL9owD3PfaSc9WUQ== X-Received: by 2002:a17:90b:1288:: with SMTP id fw8mr6304373pjb.160.1589992732938; Wed, 20 May 2020 09:38:52 -0700 (PDT) Received: from Abhishek-Arch ([2409:4064:316:d87b:8116:b1b3:f6a2:1f84]) by smtp.gmail.com with ESMTPSA id m7sm2788660pfk.36.2020.05.20.09.38.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2020 09:38:51 -0700 (PDT) Date: Wed, 20 May 2020 22:07:22 +0530 From: Abhishek Kumar To: git@vger.kernel.org Cc: stolee@gmail.com, jnareb@gmail.com Subject: [GSoC] Blog post on reachability queries Message-ID: <20200520163653.GA76552@Abhishek-Arch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Greetings everyone! I am working on implementing Generation Number v2. I have written an article about reachability queries, which I feel is necessary background for understanding the project. Here's the summary of article: > Reachability refers to the ability to get from one vertex to another > within a graph. > > Reachability queries are an interesting problem, improving performance > for many graph operations. Better and more sophisticated solutions are > being created as the size of working graphs keeps increasing. > > Reachability for the undirected graph can be found in linear > preprocessing and constant query time with disjoint set unions. The > answer isn't as evident for a directed graph because of differing > performance on positive and negative queries, nature and size of graph > and other factors. Topological Levels, Post Order DFS Intervals and > Contraction Hierachies are some of the building blocks for such > algorithms. In a later article, I will talk about the specifics of generation number for Git. In particular, how Git uses reachability queries, the need for Generation Number v2 i.e., _Correted Commit Date With Strictly Monotonic Offset_ and other interesting tidbits I come across. You can find the article here: https://abhishekkumar2718.github.io/programming/2020/05/20/reachability-queries.html I appreciate any suggestions or feedback. Thanks Abhishek