From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail3-relais-sop.national.inria.fr (mail3-relais-sop.national.inria.fr [192.134.164.104]) by sourceware.org (Postfix) with ESMTPS id CEDB13858D20 for ; Fri, 11 Aug 2023 09:25:27 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org CEDB13858D20 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=inria.fr Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=inria.fr DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=inria.fr; s=dc; h=date:message-id:from:to:cc:in-reply-to:subject: references; bh=5lyENMeMCkgUP6nTme6XFgDkfXzIhtcBKLdQx7zZfw4=; b=ZKRDxXxzBG35AWSpLrTIXfIjqfm/tWAbe+vkSsKKqxxt+H/dM5m9QhbZ vDDbgMsZ8ovhKejS33uDvGYb9D0AcHs2HccmmFqmLbU1HDBN9odjZEFaJ US2MTWPSwsPmF5G8Es55KbrGUdN0GPR1UD9dRe9m2+9qmtt1M8u43xzFB Q=; Authentication-Results: mail3-relais-sop.national.inria.fr; dkim=none (message not signed) header.i=none; spf=SoftFail smtp.mailfrom=Paul.Zimmermann@inria.fr; spf=None smtp.helo=postmaster@coriandre Received-SPF: SoftFail (mail3-relais-sop.national.inria.fr: domain of Paul.Zimmermann@inria.fr is inclined to not designate 152.81.9.227 as permitted sender) identity=mailfrom; client-ip=152.81.9.227; receiver=mail3-relais-sop.national.inria.fr; envelope-from="Paul.Zimmermann@inria.fr"; x-sender="Paul.Zimmermann@inria.fr"; x-conformance=spf_only; x-record-type="v=spf1"; x-record-text="v=spf1 ip4:128.93.142.0/24 ip4:192.134.164.0/24 ip4:128.93.162.160 ip4:89.107.174.7 mx ~all" Received-SPF: None (mail3-relais-sop.national.inria.fr: no sender authenticity information available from domain of postmaster@coriandre) identity=helo; client-ip=152.81.9.227; receiver=mail3-relais-sop.national.inria.fr; envelope-from="Paul.Zimmermann@inria.fr"; x-sender="postmaster@coriandre"; x-conformance=spf_only X-IronPort-AV: E=Sophos;i="6.01,165,1684792800"; d="scan'208";a="63346527" Received: from coriandre.loria.fr (HELO coriandre) ([152.81.9.227]) by mail3-relais-sop.national.inria.fr with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Aug 2023 11:25:27 +0200 Date: Fri, 11 Aug 2023 11:25:25 +0200 Message-Id: From: Paul Zimmermann To: "H.J. Lu" Cc: libc-alpha@sourceware.org In-Reply-To: <20230810182430.6859-1-hjl.tools@gmail.com> (libc-alpha@sourceware.org) Subject: Re: [PATCH] x86_64: Add log2 with FMA References: <20230810182430.6859-1-hjl.tools@gmail.com> X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hi H.J., > On Skylake, it improves log2 bench performance by: > > Before After Improvement > max 208.779 63.827 69% > min 9.977 6.55 34% > mean 10.366 6.8191 34% for what concerns accuracy, after a limited search, I get a small improvement for the largest known error. It was 0.554114 ulp before (obtained for x=0x1.0b53197bd66c8p+0), and I find 0.547517 ulp now (obtained for x=0x1.140c8ac38f327p+0). Paul