From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.8 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 67F3B20193 for ; Thu, 4 Aug 2016 16:55:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965341AbcHDQzr (ORCPT ); Thu, 4 Aug 2016 12:55:47 -0400 Received: from mail-it0-f41.google.com ([209.85.214.41]:35471 "EHLO mail-it0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965122AbcHDQzp (ORCPT ); Thu, 4 Aug 2016 12:55:45 -0400 Received: by mail-it0-f41.google.com with SMTP id u186so805501ita.0 for ; Thu, 04 Aug 2016 09:55:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=S1+tMGl8Tz1pUQ7Vli9deOweDWRY1rxzGlDLU4UGCdA=; b=pYaKbjpQIC2+q7Y6moNhuM0OTxqh2sBJNBnYw0OItQ3QNvnWuBuOb99DNlDzKFUE6v xpiTEFEwO7R+phgZe4ARkrbN207IIporjGWrevvFhxSBC/wdyD1zmcVUrlY5ngMK+sMr 5Cj7S5dH1JC7iCY6VZXRp8cJ/4Ufk+aM9nWapXA/ClMcWtynAKxTexXR5Ms/NvEyPROr OIu+ZhQcau3stqTg9jMEK+EYeVGbaNPGYt/gp52b1/BtBRbOo2CLxp5vLDvTG88S7Lj/ r0zW7jtYFQc7pgXMhWwu6MtC9Z4iZrlFUNK34Q8VcNUGqgw2sspl/SElmfwEnyDU3sni ol/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=S1+tMGl8Tz1pUQ7Vli9deOweDWRY1rxzGlDLU4UGCdA=; b=aJnMp992Ou6ow9eCVtutPpEOIs7b5nDDsKKZRfcKD1cFptvfuNeTyuX7ilHqhNra0u ehHdjRumgWiU2x5u9mRmpz2RXUlLMYVMriiB0Bflbo4dai7USmiweMqumVgkgcPa9XRH XDKrEkbEcSrSvKEfG8wcIwlAfkBABfa5na/k6tdg3P/6D6NHCS9ozBc+uHpp7beSdHUe RqEJMVJJj5/qfDMrGfFG9y8gm9JrxwaPxmUFeniv0wKHGIoPe3Y7L+yx+ttAo2z3nQ03 eSX3cY2apP26eEKLqpc8lb9fKWiCXTzeGRNcLyrxzcWdN5t1HcaLFGew8NgpqzlXdZ42 KFyg== X-Gm-Message-State: AEkooutucRh55CtyI5LW4/BK6YkuHUN22loWYpigxlyqS0CKOUXllUmRwjZmTEDVcNZCqZxbtvKtfxBweI1BgnX0 X-Received: by 10.36.189.7 with SMTP id x7mr36967348ite.97.1470329739709; Thu, 04 Aug 2016 09:55:39 -0700 (PDT) MIME-Version: 1.0 Received: by 10.107.128.66 with HTTP; Thu, 4 Aug 2016 09:55:39 -0700 (PDT) In-Reply-To: <20160804075631.jakbi5dbsbxsqcpr@sigill.intra.peff.net> References: <7b0680ed7a10fc13acd8d7816a75ed05a5f9e28c.1470259583.git.mhagger@alum.mit.edu> <20160804075631.jakbi5dbsbxsqcpr@sigill.intra.peff.net> From: Stefan Beller Date: Thu, 4 Aug 2016 09:55:39 -0700 Message-ID: Subject: Re: [PATCH 8/8] diff: improve positioning of add/delete blocks in diffs To: Jeff King Cc: Michael Haggerty , "git@vger.kernel.org" , Junio C Hamano , =?UTF-8?Q?Jakub_Nar=C4=99bski?= , Jacob Keller Content-Type: text/plain; charset=UTF-8 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Thu, Aug 4, 2016 at 12:56 AM, Jeff King wrote: > On Thu, Aug 04, 2016 at 12:00:36AM +0200, Michael Haggerty wrote: > >> This table shows the number of diff slider groups that were positioned >> differently than the human-generated values, for various repositories. >> "default" is the default "git diff" algorithm. "compaction" is Git 2.9.0 >> with the `--compaction-heuristic` option "indent" is an earlier, > > s/option/&./ > >> static int diff_detect_rename_default; >> +static int diff_indent_heuristic; /* experimental */ >> static int diff_compaction_heuristic; /* experimental */ > > These two flags are mutually exclusive in the xdiff code, so we should > probably handle that here. > > TBH, I do not care that much what: > > [diff] > compactionHeuristic = true > indentHeuristic = true > > does. But right now: > > git config diff.compactionHeuristic true > git show --indent-heuristic > > still prefers the compaction heuristic, which I think is objectively > wrong. > > So perhaps we need a single variable: > > enum { > DIFF_HEURISTIC_COMPACTION, > DIFF_HEURISTIC_INDENT > } diff_heuristic; > > and set it in last-one-wins fashion (it would be nice if the config and > command line options were shaped the same way so it's clear to the user > that they are exclusive, but we may have to keep --compaction-heuristic > around for compatibility, as an alias for --diff-heuristic=compaction). > >> diff --git a/git-add--interactive.perl b/git-add--interactive.perl >> index 642cce1..ee3d812 100755 >> --- a/git-add--interactive.perl >> +++ b/git-add--interactive.perl >> @@ -45,6 +45,7 @@ my ($diff_new_color) = >> my $normal_color = $repo->get_color("", "reset"); >> >> my $diff_algorithm = $repo->config('diff.algorithm'); >> +my $diff_indent_heuristic = $repo->config_bool('diff.indentheuristic'); >> my $diff_compaction_heuristic = $repo->config_bool('diff.compactionheuristic'); > > Nice touch. > > Unfortunately the mutual-exclusivity handling will probably bleed over > to here, too. > >> +/* >> + * If a line is indented more than this, get_indent() just returns this value. >> + * This avoids having to do absurd amounts of work for data that are not >> + * human-readable text, and also ensures that the output of get_indent fits within >> + * an int. >> + */ >> +#define MAX_INDENT 200 > > Speaking of absurd amounts of work, I was curious if there was a > noticeable performance penalty for using this heuristic (just because > it's a lot more complicated than the others). I couldn't detect any > differences running "git log -p --no-merges -3000" on git.git with no > heuristic, compaction, and indent. There may be other repositories that > behave more pathologically (it looks like having 20 blank lines at the > end of each hunk?), but I'd guess in most cases this will always be > drowned out in the noise of doing the actual diff. > >> +#define START_OF_FILE_BONUS 9 >> +#define END_OF_FILE_BONUS 46 >> +#define TOTAL_BLANK_WEIGHT 4 >> +#define PRE_BLANK_WEIGHT 16 >> +#define RELATIVE_INDENT_BONUS -1 >> +#define RELATIVE_INDENT_HAS_BLANK_BONUS 15 >> +#define RELATIVE_OUTDENT_BONUS -19 >> +#define RELATIVE_OUTDENT_HAS_BLANK_BONUS 2 >> +#define RELATIVE_DEDENT_BONUS -63 >> +#define RELATIVE_DEDENT_HAS_BLANK_BONUS 50 > > I see there is a comment below here mentioning that these are empirical > voodoo, but it might be worth one at the top (or just moving these below > the comment) because the comment looks like it's just associated with > the function (and these are sufficiently bizarre that anybody reading is > going to double-take on them). > >> + return 10 * score - bonus; > > I don't mind this not "10" not being a #define constant, but after > reading the exchange between you and Stefan, I think it would be nice to > describe what it is in a comment. The rest of the function is commented > so nicely that this one left me thinking "huh?" upon seeing the "10". After a night of sleep I agree with Peffs statement here, it's not about the #define, it's about the comment. (which the #define would have given in a short cryptic way in angry capital letters). I have just reread the scoring function and I think you could pull out the `score=indent` assignment (it is always assigned except for indent <0) if (indent == -1) score = 0; else score = indent; ... lots of bonus computation below, which in its current implementation have lots of "score = indent;" lines as well. Thanks, Stefan