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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2AE1C43334 for ; Fri, 15 Jul 2022 18:48:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230045AbiGOSse (ORCPT ); Fri, 15 Jul 2022 14:48:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229619AbiGOSsd (ORCPT ); Fri, 15 Jul 2022 14:48:33 -0400 Received: from mail-ej1-x630.google.com (mail-ej1-x630.google.com [IPv6:2a00:1450:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 00BEC3CBDA for ; Fri, 15 Jul 2022 11:48:31 -0700 (PDT) Received: by mail-ej1-x630.google.com with SMTP id j22so10504761ejs.2 for ; Fri, 15 Jul 2022 11:48:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jyYlA609E4/BoCrb3J0r/ZxsHDS2aV2PjfqW5oSX5E0=; b=RtHPS08NsNXuVyoGIenalbZFNfE+5zodrzT3f/eYC/ruuRgbKbozoOMQ9aY5Ksw9Jt s98OwFFZfn8ISfNv+bobvLelb4HsSz8q6Hs7/CRC0sPMHfCZs0zoJuaq7Gl0vUqY85sT wQ7IktnRw6LHdZv3JUDzFZEorPaff7jqkmR6OHhfRhxOVn+rnt/C6ChXZi+BMAZOG2YR WcR1OwF8HyEmAKe0DdqcC73B0XD4vNA5f6rrxZo1AYtT62KWINKIoWMOFEk1oPQzQm16 M/Et/DgVML1IajGT6yW/nMH2BIVxfNr2ahNOW65t9nvj0IdifaSG1cpqrk+Mhcv++99O jBmg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=jyYlA609E4/BoCrb3J0r/ZxsHDS2aV2PjfqW5oSX5E0=; b=kn6y0YwxLwcNul7FJwHBtP+hZk3reLYo+S8YtPhjpSSysOuf7kpVeZwQ1+3cZ0zxXB WawDmMT3T00iZXT8itOVcT6v0gdQX02/8sJWGfGdRxfp1rz5GouBZYz1GeYukrjicS9W uEq9vEOar5ENQlFZ+mtPw/rWq5wPWvHIB4mxKJnyWtXtb95CWpIxJgkWwWgz5ek2GvSP 8601viviMfEdUPZQpD677SIFDIQVqtonMX+rvib8ZN2pp22qpl0Vk8LFBm4iDT1HFV9D rEge6EKygtGbXMrcVw21PLSvo4h2aIfcfEkdd6rrIAsal/xRvVgeOqwMciA8IE8m43/O JgSA== X-Gm-Message-State: AJIora/3FuERpaoh1x8dfGQYpPlLoj13JeuQMG3k/re0aT6J+J0XD1vt DtptXSxCD+/Ley4A8iwZ37hjGZqvv1fobKHwqXc= X-Google-Smtp-Source: AGRyM1tB0bLwRceCjg+cfD9WQ0J+Q1KZ4oshhc2nm759hYs77PIDLOH+jLfqh/QDji9YsQv5cyvX0B9lmrQl4XjhsCY= X-Received: by 2002:a17:907:6890:b0:72e:e404:46d2 with SMTP id qy16-20020a170907689000b0072ee40446d2mr7678407ejc.578.1657910910526; Fri, 15 Jul 2022 11:48:30 -0700 (PDT) MIME-Version: 1.0 References: <20220709075310.83848-1-chakrabortyabhradeep79@gmail.com> In-Reply-To: From: Abhradeep Chakraborty Date: Sat, 16 Jul 2022 00:18:19 +0530 Message-ID: Subject: Re: [PATCH v3 1/6] Documentation/technical: describe bitmap lookup table extension To: Philip Oakley Cc: Git , Kaartic Sivaraam , Taylor Blau , Derrick Stolee , Junio C Hamano Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Sun, Jul 10, 2022 at 8:31 PM Philip Oakley wrote: > > On 09/07/2022 08:53, Abhradeep Chakraborty wrote: > > Hello Philip, > > > > Philip Oakley wrote: > > > >> Not sure if this is new in this extension, but should there be a link or > >> two to the basics of XOR compression and some of the bitmap look up > >> techniques? > >> > >> It's not always obvious if these techniques are 'heuristic' and only > >> have partial commit data, or they have all the commits listed, Nor > >> how/why they work. My point is more about giving new readers a hand-up > >> in their understanding, rather than simple implementation details for > >> those who already know what is going on. For example, are there any > >> external articles that you found helpful in getting started that could > >> be referenced somewhere in the docs? > > As this series is only about adding a lookup-table extension (and not > > about bitmap itself), I am not sure whether it's good to include those > > things in this series. > > Thanks for the clarification. I must have slight misread some of the > discussions and falsely thought it was the XOR compression (which is a > technique I wasn't really aware of), that was being provided by the > extension - Where would it be best for me to look up the background to > your "extension" project? Sorry that I missed this message. I got the information related to this project from the gsoc project ideas[1] page, additionally you can see the comments[2]. [1] https://git.github.io/SoC-2022-Ideas/ [2] https://lore.kernel.org/git/YNovuzAsaEb2uIaa@nand.local/ > > (As the name > > suggests, this file should only contain format details of bitmaps). > > That file would provide the answers of "Why bitmaps", "how they are > > stored", "How they are fetched", "how they work with pack-objects, > > git-fetch, midx etc.", "Detailed explanation of each bitmap extension" > > , and lastly "what are the future works" (if any). > > One thing I've realised on reflection is that I'm unclear how the > 'reachability bitmaps' and the 'commit-graph file' techniques relate to > each other (and to the ODB DAG), and what features they pick out within > their heuristic, explained at just enough level to allow folks to > appreciate what the options that select them will do for their use case. I am not familiar with 'commit-graph file', so I can't tell you about that. But for bitmaps, you can look at the introductory patches[3]. After that, if you wish, you can also inspect the code related to bitmaps. [3] https://github.com/gitster/git/commit/e127310 > > What do you think? > > I'd be happy to collate contributions, suggestions and thoughts. > > Trying to create these good introductory descriptions can be really > difficult, as you can only step into the same river once (the 'reading > for the first time problem' of not being able to un-hear the > explanations of others when reading a 2nd draft...) I agree ;-) Thanks :)