[Bug math/14468] New: Inaccurate j0f function

[Bug math/14468] New: Inaccurate j0f function

[liubov.dmitrieva at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14468

             Bug #: 14468
           Summary: Inaccurate j0f function
           Product: glibc
           Version: 2.17
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: liubov.dmitrieva@gmail.com
    Classification: Unclassified


Test case:

// gcc main.c -std=c99 -lm
#include <stdio.h>
#include <fenv.h>
#include <stdlib.h>  // abs function for int argument

extern float j0f(float);
extern double j0(double);

#define i32(a)    (((int*)&(a))[0])

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

    i32(a)=0x413caa1f;    //argument

    fesetround(FE_TONEAREST);

    r1 = j0f(a);  //actual result
    r2 = j0(a);   //actual result 2

    printf("inputs: a = (0x%08x)\t%e\n", i32(a), a);
    printf("actual    = (0x%08x)\t%.13e\n", i32(r1), r1);
    printf("expected  = (0x%08x)\t%.13e\n", i32(r2), r2);
    printf("error     = %d ulp\n", abs(i32(r1) - i32(r2)));

    return 0;
}

Result:

inputs: a = (0x413caa1f)        1.179153e+01
actual    = (0xb471e828)        -2.2529331999976e-07
expected  = (0xb471d452)        -2.2522115727952e-07
error     = 5078 ulp

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[Bug math/14468] Inaccurate j0f function

[liubov.dmitrieva at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14468

Liubov Dmitrieva <liubov.dmitrieva at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE

--- Comment #1 from Liubov Dmitrieva <liubov.dmitrieva at gmail dot com> 2012-08-15 14:24:41 UTC ---
Duplicate, was filed twice due to network connection problems.

*** This bug has been marked as a duplicate of bug 14469 ***

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[Bug math/14468] Inaccurate j0f function

[joseph at codesourcery dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14468

--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2012-08-15 15:03:06 UTC ---
Could you please give versions of the tests, for all your recent bugs, 
that represent the test argument using a hex float value rather than by 
violating ISO C aliasing rules (type punning int and float)?  Hex float 
values are generally more convenient to deal with; you can put them 
directly in tests in libm-test.inc, or use them with MPFR to confirm the 
correct results.

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[Bug math/14468] Inaccurate j0f function

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14468

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com
              Flags|                            |security-

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