From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x72c.google.com (mail-qk1-x72c.google.com [IPv6:2607:f8b0:4864:20::72c]) by sourceware.org (Postfix) with ESMTPS id 20C283951CBD for ; Mon, 25 Jan 2021 13:01:44 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 20C283951CBD Received: by mail-qk1-x72c.google.com with SMTP id v126so12255762qkd.11 for ; Mon, 25 Jan 2021 05:01:44 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=fZieyfwYo0y61lZq5avmQ9wfDHoauAWx3nuL4yHFu6I=; b=mvcXMkhtUY0tEp83V4y9Fpf+4BsGoDDmQBLVCL5AlmdLY6oI1CSIxRxPgE1eiIawl/ ONBiqOBVPbIx3L85IrRZ1H9eEfGnNZBvdoeXNdaLN+JSCS0OHtl9DSb1/bFDe1SDJxjs CybGe0NhZp1QJLfcz3YZjHHjU06DfrgEzfa/uIEhjbMnCpW+m0RfjOL8tfZtk1A3RxGh BJYhcb4fVVQWOGPNq7d5GAutjaeSxIogO1D/D4FKgUY9nzuSM2z933ZXijyIQVe0pH3t j6/vNbrhutRElcWMNFVuCYUyWP9JQmeIM1Xw6x6XzENv5ZNBD4AY2Gyzv4nKld8zAm7g SB4w== X-Gm-Message-State: AOAM532k89WCWx3nAweVknVOQ8VkiMnrQ91sfBivvFYQo36kXSS8FuHs mrTqsthCuLAvTozuzJcV8zYoPs55qdF+QA== X-Google-Smtp-Source: ABdhPJxXh76esY8wP3Yk0SXJDGPomASkJU6ow3O+qY9Z5bNfZ2wUry5QETE5KnLrsEg1jCte1ALCug== X-Received: by 2002:a37:528b:: with SMTP id g133mr529354qkb.149.1611579703505; Mon, 25 Jan 2021 05:01:43 -0800 (PST) Received: from [192.168.1.4] ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id q70sm11293399qka.107.2021.01.25.05.01.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 Jan 2021 05:01:42 -0800 (PST) To: Paul Zimmermann Cc: libc-alpha@sourceware.org, joseph@codesourcery.com References: <70d6243c-36a0-1cda-43ec-6984e65b113e@linaro.org> From: Adhemerval Zanella Autocrypt: addr=adhemerval.zanella@linaro.org; prefer-encrypt=mutual; keydata= mQINBFcVGkoBEADiQU2x/cBBmAVf5C2d1xgz6zCnlCefbqaflUBw4hB/bEME40QsrVzWZ5Nq 8kxkEczZzAOKkkvv4pRVLlLn/zDtFXhlcvQRJ3yFMGqzBjofucOrmdYkOGo0uCaoJKPT186L NWp53SACXguFJpnw4ODI64ziInzXQs/rUJqrFoVIlrPDmNv/LUv1OVPKz20ETjgfpg8MNwG6 iMizMefCl+RbtXbIEZ3TE/IaDT/jcOirjv96lBKrc/pAL0h/O71Kwbbp43fimW80GhjiaN2y WGByepnkAVP7FyNarhdDpJhoDmUk9yfwNuIuESaCQtfd3vgKKuo6grcKZ8bHy7IXX1XJj2X/ BgRVhVgMHAnDPFIkXtP+SiarkUaLjGzCz7XkUn4XAGDskBNfbizFqYUQCaL2FdbW3DeZqNIa nSzKAZK7Dm9+0VVSRZXP89w71Y7JUV56xL/PlOE+YKKFdEw+gQjQi0e+DZILAtFjJLoCrkEX w4LluMhYX/X8XP6/C3xW0yOZhvHYyn72sV4yJ1uyc/qz3OY32CRy+bwPzAMAkhdwcORA3JPb kPTlimhQqVgvca8m+MQ/JFZ6D+K7QPyvEv7bQ7M+IzFmTkOCwCJ3xqOD6GjX3aphk8Sr0dq3 4Awlf5xFDAG8dn8Uuutb7naGBd/fEv6t8dfkNyzj6yvc4jpVxwARAQABtElBZGhlbWVydmFs IFphbmVsbGEgTmV0dG8gKExpbmFybyBWUE4gS2V5KSA8YWRoZW1lcnZhbC56YW5lbGxhQGxp bmFyby5vcmc+iQI3BBMBCAAhBQJXFRpKAhsDBQsJCAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJ EKqx7BSnlIjv0e8P/1YOYoNkvJ+AJcNUaM5a2SA9oAKjSJ/M/EN4Id5Ow41ZJS4lUA0apSXW NjQg3VeVc2RiHab2LIB4MxdJhaWTuzfLkYnBeoy4u6njYcaoSwf3g9dSsvsl3mhtuzm6aXFH /Qsauav77enJh99tI4T+58rp0EuLhDsQbnBic/ukYNv7sQV8dy9KxA54yLnYUFqH6pfH8Lly sTVAMyi5Fg5O5/hVV+Z0Kpr+ZocC1YFJkTsNLAW5EIYSP9ftniqaVsim7MNmodv/zqK0IyDB GLLH1kjhvb5+6ySGlWbMTomt/or/uvMgulz0bRS+LUyOmlfXDdT+t38VPKBBVwFMarNuREU2 69M3a3jdTfScboDd2ck1u7l+QbaGoHZQ8ZNUrzgObltjohiIsazqkgYDQzXIMrD9H19E+8fw kCNUlXxjEgH/Kg8DlpoYJXSJCX0fjMWfXywL6ZXc2xyG/hbl5hvsLNmqDpLpc1CfKcA0BkK+ k8R57fr91mTCppSwwKJYO9T+8J+o4ho/CJnK/jBy1pWKMYJPvvrpdBCWq3MfzVpXYdahRKHI ypk8m4QlRlbOXWJ3TDd/SKNfSSrWgwRSg7XCjSlR7PNzNFXTULLB34sZhjrN6Q8NQZsZnMNs TX8nlGOVrKolnQPjKCLwCyu8PhllU8OwbSMKskcD1PSkG6h3r0AquQINBFcVGkoBEACgAdbR Ck+fsfOVwT8zowMiL3l9a2DP3Eeak23ifdZG+8Avb/SImpv0UMSbRfnw/N81IWwlbjkjbGTu oT37iZHLRwYUFmA8fZX0wNDNKQUUTjN6XalJmvhdz9l71H3WnE0wneEM5ahu5V1L1utUWTyh VUwzX1lwJeV3vyrNgI1kYOaeuNVvq7npNR6t6XxEpqPsNc6O77I12XELic2+36YibyqlTJIQ V1SZEbIy26AbC2zH9WqaKyGyQnr/IPbTJ2Lv0dM3RaXoVf+CeK7gB2B+w1hZummD21c1Laua +VIMPCUQ+EM8W9EtX+0iJXxI+wsztLT6vltQcm+5Q7tY+HFUucizJkAOAz98YFucwKefbkTp eKvCfCwiM1bGatZEFFKIlvJ2QNMQNiUrqJBlW9nZp/k7pbG3oStOjvawD9ZbP9e0fnlWJIsj 6c7pX354Yi7kxIk/6gREidHLLqEb/otuwt1aoMPg97iUgDV5mlNef77lWE8vxmlY0FBWIXuZ yv0XYxf1WF6dRizwFFbxvUZzIJp3spAao7jLsQj1DbD2s5+S1BW09A0mI/1DjB6EhNN+4bDB SJCOv/ReK3tFJXuj/HbyDrOdoMt8aIFbe7YFLEExHpSk+HgN05Lg5TyTro8oW7TSMTk+8a5M kzaH4UGXTTBDP/g5cfL3RFPl79ubXwARAQABiQIfBBgBCAAJBQJXFRpKAhsMAAoJEKqx7BSn lIjvI/8P/jg0jl4Tbvg3B5kT6PxJOXHYu9OoyaHLcay6Cd+ZrOd1VQQCbOcgLFbf4Yr+rE9l mYsY67AUgq2QKmVVbn9pjvGsEaz8UmfDnz5epUhDxC6yRRvY4hreMXZhPZ1pbMa6A0a/WOSt AgFj5V6Z4dXGTM/lNManr0HjXxbUYv2WfbNt3/07Db9T+GZkpUotC6iknsTA4rJi6u2ls0W9 1UIvW4o01vb4nZRCj4rni0g6eWoQCGoVDk/xFfy7ZliR5B+3Z3EWRJcQskip/QAHjbLa3pml xAZ484fVxgeESOoaeC9TiBIp0NfH8akWOI0HpBCiBD5xaCTvR7ujUWMvhsX2n881r/hNlR9g fcE6q00qHSPAEgGr1bnFv74/1vbKtjeXLCcRKk3Ulw0bY1OoDxWQr86T2fZGJ/HIZuVVBf3+ gaYJF92GXFynHnea14nFFuFgOni0Mi1zDxYH/8yGGBXvo14KWd8JOW0NJPaCDFJkdS5hu0VY 7vJwKcyHJGxsCLU+Et0mryX8qZwqibJIzu7kUJQdQDljbRPDFd/xmGUFCQiQAncSilYOcxNU EMVCXPAQTteqkvA+gNqSaK1NM9tY0eQ4iJpo+aoX8HAcn4sZzt2pfUB9vQMTBJ2d4+m/qO6+ cFTAceXmIoFsN8+gFN3i8Is3u12u8xGudcBPvpoy4OoG Subject: Re: [PATCH] Fix the inaccuracy of j0f (BZ 14469) and y0f (BZ 14471) [v2] Message-ID: <40700a2f-ee93-4b2f-2f62-a8d27e7a7d6b@linaro.org> Date: Mon, 25 Jan 2021 10:01:40 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-7.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 25 Jan 2021 13:01:45 -0000 On 25/01/2021 06:59, Paul Zimmermann wrote: > Dear Adhemerval, > >> So if I understand correctly, you patch increase the ulps for non-default >> rounding for this specific inputs? If it were the case, could be fix it >> as well? > > I guess the previous code already had an error > 9 ulps on this specific > input: > > Failure: Test: j0_downward (0x3.17bcfcp+4) > Result: > is: 1.1670220923447945e-04 0x1.e97c0b0296dc8p-14 > should be: 1.1670220923447976e-04 0x1.e97c0b0296ddfp-14 > difference: 3.1170812458958252e-19 0x1.7000000000000p-62 > ulp : 23.0000 > max.ulp : 2.0000 > > However on my machine I have an error of only 9 ulps for that input. > Maybe your machine doesn't have fma? Maybe I should develop my code > on a machine without fma, assuming the errors will be smaller with fma. > > Paul > My machine is not really the issue, although it does support FMA3 (it is i7-4790K haswell). The issue is we need to handle the all possible compiler options used, which is my case it is the default for the x86_64 compiler produces with build-many-glibcs.py. Using -march=native, the maximum error does improve although it is still large in some cases (below). For the FMA issue, newer implementation handles it by checking __FP_FAST_FMA and using __builtin_fma{f,l}. Check the double e_log2.c implementaion (3e08ff544b86834cd). $ cat math/test-float-j0.out testing float (without inline functions) Failure: Test: j0_towardzero (0x3.17bcfcp+4) Result: is: 1.16702285e-04 0x1.e97c20p-14 should be: 1.16702205e-04 0x1.e97c0ap-14 difference: 8.00355337e-11 0x1.600000p-34 ulp : 11.0000 max.ulp : 7.0000 Failure: Test: j0_upward (0x3.17bcfcp+4) Result: is: 1.16702315e-04 0x1.e97c28p-14 should be: 1.16702213e-04 0x1.e97c0cp-14 difference: 1.01863407e-10 0x1.c00000p-34 ulp : 14.0000 max.ulp : 5.0000 Test suite completed: 164 test cases plus 160 tests for exception flags and 160 tests for errno executed. 2 errors occurred. $ cat math/test-double-j0.out testing double (without inline functions) Failure: Test: j0 (0x3.17bcfcp+4) Result: is: 1.1670220923447967e-04 0x1.e97c0b0296dd8p-14 should be: 1.1670220923447977e-04 0x1.e97c0b0296ddfp-14 difference: 9.4867690092481638e-20 0x1.c000000000000p-64 ulp : 7.0000 max.ulp : 5.0000 Maximal error of `j0' is : 7 ulp accepted: 5 ulp Failure: Test: j0_downward (0x3.17bcfcp+4) Result: is: 1.1670220923447949e-04 0x1.e97c0b0296dcbp-14 should be: 1.1670220923447976e-04 0x1.e97c0b0296ddfp-14 difference: 2.7105054312137610e-19 0x1.4000000000000p-62 ulp : 20.0000 max.ulp : 2.0000 Test suite completed: 204 test cases plus 200 tests for exception flags and 200 tests for errno executed. 3 errors occurred.