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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 DAB21C433E6 for ; Thu, 4 Mar 2021 00:23:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD7D164F02 for ; Thu, 4 Mar 2021 00:23:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355319AbhCDAXT (ORCPT ); Wed, 3 Mar 2021 19:23:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47340 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234831AbhCCP2a (ORCPT ); Wed, 3 Mar 2021 10:28:30 -0500 Received: from mail-qk1-x72d.google.com (mail-qk1-x72d.google.com [IPv6:2607:f8b0:4864:20::72d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3DC3C061760 for ; Wed, 3 Mar 2021 07:27:22 -0800 (PST) Received: by mail-qk1-x72d.google.com with SMTP id q85so24305955qke.8 for ; Wed, 03 Mar 2021 07:27:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ttaylorr-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Bmz7bo1UdYH+cuLhX7XtgLV8nuzBCUyj+ldZh/QrXsA=; b=jf/0ZgPuMbihyIdrVT3rzWiK8tIwl68p60ssrh/aL4il5lcHM5W8N16fAwzd2OdDkV fMQqlkjQ1NJgxjDHj/kBF02WFzWvw5N/kIaVgP7FheTIbro95QnIGhbwiH1K6TfpvAZn 5R0/fjklt2AECkoIvRSEzLGfYnv/CJNncT4T34q0iepKGMpNDdx0JZfR7M4epcMxCEAS had0i3x8LijBDXWQo3ZLGWmBeWtvyr81nWuIFAT16T6gKao4xR8WdOZ4VwEcvxShG69k N/I0j30635dDGo09DNcG0IVEpi4NuaiyWAKda5c39xztfLgJwgjL5k0VWaYtnYuTMYMb n16g== 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:references :mime-version:content-disposition:in-reply-to; bh=Bmz7bo1UdYH+cuLhX7XtgLV8nuzBCUyj+ldZh/QrXsA=; b=BFGPdUcHpY4FxaKWdi4Jy8naGlg79CReN1N9k0i0E7BHtRNVW39CYoGFyLreNyZQyV wZmOWoAl6MSgbqeIkUmTALKK4xmZDcWomYl6eOZm0R6TRKDp6WAx83OJDykPtj92dncR dE/LoD5PitKkVFAdYt0gCUJaTrCdqWPNuAXgEUFikZaULoC0hdPSNWstamKSr2UFi5p5 JfCNmz78tMvAmvIObrhj1IYzlcfypwmTpCvjsyxjHXruBly9Rcp9RQ6syGPhdfagtD29 eutGiZzOsvZcAzvA4KKKftfWXwgSEGddIlAh67vDgvw8RSsDU1I9FD8SCqN+WuqKmtu9 5yQg== X-Gm-Message-State: AOAM533ussaedqrlws4ZnAOuweePuuqvdPrGC9R/50lU3xauj10FYHYM 5mQaXeHYjJRfjVD1aX5W5N+Vdw== X-Google-Smtp-Source: ABdhPJx3R2/g965ThQRr9K3VBREtZvHD+LsmVrLqfwYj72Gfv/19BdyCBpW3scf0eRW9LBNuMYOwZw== X-Received: by 2002:a05:620a:2013:: with SMTP id c19mr24014039qka.403.1614785242018; Wed, 03 Mar 2021 07:27:22 -0800 (PST) Received: from localhost ([2605:9480:22e:ff10:7fe2:f960:a24a:8111]) by smtp.gmail.com with ESMTPSA id z65sm15567520qtd.15.2021.03.03.07.27.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Mar 2021 07:27:21 -0800 (PST) Date: Wed, 3 Mar 2021 10:27:18 -0500 From: Taylor Blau To: Jonathan Tan Cc: git@vger.kernel.org, peff@peff.net, dstolee@microsoft.com, avarab@gmail.com, gitster@pobox.com Subject: Re: [PATCH v2 13/15] pack-revindex: read multi-pack reverse indexes Message-ID: References: <20210302183620.11040-1-jonathantanmy@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210302183620.11040-1-jonathantanmy@google.com> Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Tue, Mar 02, 2021 at 10:36:20AM -0800, Jonathan Tan wrote: > > midx_to_pack_pos() is the trickiest, since it needs to find an object's > > position in the psuedo-pack order, but that order can only be recovered > > in the .rev file itself. This mapping can be implemented with a binary > > search, but note that the thing we're binary searching over isn't an > > array, but rather a _permutation_. > > > > So, when comparing two items, it's helpful to keep in mind the > > difference. Instead of a traditional binary search, where you are > > comparing two things directly, here we're comparing a (pack, offset) > > tuple with an index into the multi-pack index. That index describes > > another (pack, offset) tuple, and it is _those_ two tuples that are > > compared. > > Well, the binary search is indeed over an array :-) :-). This might be more clearer as: ...isn't an array of values, but rather a permuted order of those values. > The patch itself looks good. Thanks. Taylor