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From: "liubov.dmitrieva at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Subject: [Bug math/14470] Inaccurate j1f function on x86_32 and x86_64
Date: Thu, 16 Aug 2012 08:12:00 -0000
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http://sourceware.org/bugzilla/show_bug.cgi?id=14470

--- Comment #2 from Liubov Dmitrieva <liubov.dmitrieva at gmail dot com> 2012-08-16 08:11:45 UTC ---
represent the test argument using a hex float value, test case update:

#include <stdio.h>
#include <math.h>
#include <fenv.h>

extern float j1f(float);
extern double j1(double);

int main() {
    float a,r1;
    double r2;

    a=0x1.458d14p3;    //argument

    fesetround(FE_TONEAREST);

    r1 = j1f(a);  //actual result
    r2 = j1(a);   //actual result 2

    printf("inputs: a = %.6a\n", a);
    printf("actual    = %.6a\n", r1);
    printf("expected  = %.6a\n", r2);
    printf("error     = %f ulp\n", fabs(r1 - r2) * exp2(23.0-logbf(r1)));
    return 0;
}

Result x86:
inputs: a = 0x1.458d14p+3
actual    = -0x1.bc9adap-21
expected  = -0x1.bc818dp-21
error     = 3238.561446 ulp

Result x86_64:
inputs: a = 0x1.458d14p+3
actual    = -0x1.bc55a6p-21
expected  = -0x1.bc818dp-21
error     = 5619.438563 ulp

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