From dev-return-339232-archive-asf-public=cust-asf.ponee.io@lucene.apache.org Mon Nov 12 18:14:04 2018 Return-Path: X-Original-To: archive-asf-public@cust-asf.ponee.io Delivered-To: archive-asf-public@cust-asf.ponee.io Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by mx-eu-01.ponee.io (Postfix) with SMTP id 62D22180660 for ; Mon, 12 Nov 2018 18:14:04 +0100 (CET) Received: (qmail 30107 invoked by uid 500); 12 Nov 2018 17:14:03 -0000 Mailing-List: contact dev-help@lucene.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: dev@lucene.apache.org Delivered-To: mailing list dev@lucene.apache.org Received: (qmail 30097 invoked by uid 99); 12 Nov 2018 17:14:03 -0000 Received: from pnap-us-west-generic-nat.apache.org (HELO spamd1-us-west.apache.org) (209.188.14.142) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 12 Nov 2018 17:14:03 +0000 Received: from localhost (localhost [127.0.0.1]) by spamd1-us-west.apache.org (ASF Mail Server at spamd1-us-west.apache.org) with ESMTP id A7FE8C1A63 for ; Mon, 12 Nov 2018 17:14:02 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at spamd1-us-west.apache.org X-Spam-Flag: NO X-Spam-Score: -110.301 X-Spam-Level: X-Spam-Status: No, score=-110.301 tagged_above=-999 required=6.31 tests=[ENV_AND_HDR_SPF_MATCH=-0.5, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001, USER_IN_DEF_SPF_WL=-7.5, USER_IN_WHITELIST=-100] autolearn=disabled Received: from mx1-lw-us.apache.org ([10.40.0.8]) by localhost (spamd1-us-west.apache.org [10.40.0.7]) (amavisd-new, port 10024) with ESMTP id UBDAENxrmGAJ for ; Mon, 12 Nov 2018 17:14:01 +0000 (UTC) Received: from mailrelay1-us-west.apache.org (mailrelay1-us-west.apache.org [209.188.14.139]) by mx1-lw-us.apache.org (ASF Mail Server at mx1-lw-us.apache.org) with ESMTP id 6F13D5F332 for ; Mon, 12 Nov 2018 17:14:01 +0000 (UTC) Received: from jira-lw-us.apache.org (unknown [207.244.88.139]) by mailrelay1-us-west.apache.org (ASF Mail Server at mailrelay1-us-west.apache.org) with ESMTP id 1A953E0E87 for ; Mon, 12 Nov 2018 17:14:01 +0000 (UTC) Received: from jira-lw-us.apache.org (localhost [127.0.0.1]) by jira-lw-us.apache.org (ASF Mail Server at jira-lw-us.apache.org) with ESMTP id CFE69266FD for ; Mon, 12 Nov 2018 17:14:00 +0000 (UTC) Date: Mon, 12 Nov 2018 17:14:00 +0000 (UTC) From: "Adrien Grand (JIRA)" To: dev@lucene.apache.org Message-ID: In-Reply-To: References: Subject: [jira] [Commented] (LUCENE-8563) Remove k1+1 from the numerator of BM25Similarity MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-JIRA-FingerPrint: 30527f35849b9dde25b450d4833f0394 [ https://issues.apache.org/jira/browse/LUCENE-8563?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16684107#comment-16684107 ] Adrien Grand commented on LUCENE-8563: -------------------------------------- Agreed [~softwaredoug] I was assuming a single similarity. This would also change ordering if other fields use different similarities. > Remove k1+1 from the numerator of BM25Similarity > ------------------------------------------------- > > Key: LUCENE-8563 > URL: https://issues.apache.org/jira/browse/LUCENE-8563 > Project: Lucene - Core > Issue Type: Improvement > Reporter: Adrien Grand > Priority: Minor > > Our current implementation of BM25 does > {code:java} > boost * IDF * (k1+1) * tf / (tf + norm) > {code} > As (k1+1) is a constant, it is the same for every term and doesn't modify ordering. It is often omitted and I found out that the "The Probabilistic Relevance Framework: BM25 and Beyond" paper by Robertson (BM25's author) and Zaragova even describes adding (k1+1) to the numerator as a variant whose benefit is to be more comparable with Robertson/Sparck-Jones weighting, which we don't care about. > {quote}A common variant is to add a (k1 + 1) component to the > numerator of the saturation function. This is the same for all > terms, and therefore does not affect the ranking produced. > The reason for including it was to make the final formula > more compatible with the RSJ weight used on its own > {quote} > Should we remove it from BM25Similarity as well? > A side-effect that I'm interested in is that integrating other score contributions (eg. via oal.document.FeatureField) would be a bit easier to reason about. For instance a weight of 3 in FeatureField#newSaturationQuery would have a similar impact as a term whose IDF is 3 (and thus docFreq ~= 5%) rather than a term whose IDF is 3/(k1 + 1). -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org For additional commands, e-mail: dev-help@lucene.apache.org