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Re: Fix e_logl (128ibm) spurious underflow
Ping.
On 11-03-2013 09:27, Adhemerval Zanella wrote:
> Ping.
>
>
> On 03/07/2013 02:33 PM, Adhemerval Zanella wrote:
>> Ping.
>>
>> On 02/28/2013 02:02 AM, Adhemerval Zanella wrote:
>>> On 02/27/2013 08:50 PM, Joseph S. Myers wrote:
>>>> On Wed, 27 Feb 2013, Adhemerval Zanella wrote:
>>>>
>>>>> 2013-02-27 Adhemerval Zanella <azanella@linux.vnet.ibm.com>
>>>>>
>>>>> * sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): Fix spurious
>>>>> underflow.
>>>>> * sysdeps/powerpc/fpu/libm-test-ulps: Update.
>>>> What is the bug report in Bugzilla for this issue, which presumably is
>>>> user-visible in a release so should have a bug report? If there isn't
>>>> one, please file one; in any case, include the [BZ #N] annotation in the
>>>> ChangeLog entry (and a commit of a fix should include updating NEWS).
>>>> (If the issue isn't user-visible in a release and so doesn't need a bug
>>>> report, please explain why not. But any bug being fixed that was
>>>> user-visible in a release should have a corresponding Bugzilla entry.)
>>>>
>>>> In my view you should add a testcase for this issue for log to
>>>> libm-test.inc, even if there are tests for other functions that show the
>>>> problem as well.
>>>>
>>> I create BZ #15214 to track this issue. I didn't add the specific testcase yet
>>> because it is showing some higher ULPs that I'd like to take a look (this is
>>> showing without my patch also).
>>>
>>> --
>>>
>>> 2013-02-28 Adhemerval Zanella <azanella@linux.vnet.ibm.com>
>>>
>>> [BZ #15214]
>>> * NEWS: Mention BZ #15214.
>>> * sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): Fix spurious
>>> underflow.
>>> * sysdeps/powerpc/fpu/libm-test-ulps: Update.
>>>
>>> diff --git a/NEWS b/NEWS
>>> index a4c5638..945aa9d 100644
>>> --- a/NEWS
>>> +++ b/NEWS
>>> @@ -11,7 +11,7 @@ Version 2.18
>>>
>>> 11561, 13951, 14142, 14200, 14317, 14327, 14496, 14920, 14964, 14981,
>>> 14982, 14985, 14994, 14996, 15003, 15006, 15020, 15023, 15036, 15054,
>>> - 15062, 15078, 15160.
>>> + 15062, 15078, 15160, 15214.
>>>
>>> * Add support for calling C++11 thread_local object destructors on thread
>>> and program exit. This needs compiler support for offloading C++11
>>> diff --git a/sysdeps/ieee754/ldbl-128ibm/e_logl.c b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
>>> index 14f47eb..15b5edf 100644
>>> --- a/sysdeps/ieee754/ldbl-128ibm/e_logl.c
>>> +++ b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
>>> @@ -182,6 +182,9 @@ static const long double
>>> ln2a = 6.93145751953125e-1L,
>>> ln2b = 1.4286068203094172321214581765680755001344E-6L;
>>>
>>> +static const long double
>>> + ldbl_epsilon = 0x1p-106L;
>>> +
>>> long double
>>> __ieee754_logl(long double x)
>>> {
>>> @@ -258,7 +261,12 @@ __ieee754_logl(long double x)
>>> }
>>> /* Series expansion of log(1+z). */
>>> w = z * z;
>>> - y = ((((((((((((l15 * z
>>> + /* Avoid spurious underflows. */
>>> + if (__glibc_unlikely(w <= ldbl_epsilon))
>>> + y = 0.0L;
>>> + else
>>> + {
>>> + y = ((((((((((((l15 * z
>>> + l14) * z
>>> + l13) * z
>>> + l12) * z
>>> @@ -271,7 +279,8 @@ __ieee754_logl(long double x)
>>> + l5) * z
>>> + l4) * z
>>> + l3) * z * w;
>>> - y -= 0.5 * w;
>>> + y -= 0.5 * w;
>>> + }
>>> y += e * ln2b; /* Base 2 exponent offset times ln(2). */
>>> y += z;
>>> y += logtbl[k-26]; /* log(t) - (t-1) */
>>> diff --git a/sysdeps/powerpc/fpu/libm-test-ulps b/sysdeps/powerpc/fpu/libm-test-ulps
>>> index 4221967..5072190 100644
>>> --- a/sysdeps/powerpc/fpu/libm-test-ulps
>>> +++ b/sysdeps/powerpc/fpu/libm-test-ulps
>>> @@ -243,9 +243,11 @@ idouble: 1
>>> Test "Real part of: cacos (-0.5 + +0 i) == 2.094395102393195492308428922186335256131 - 0 i":
>>> double: 1
>>> idouble: 1
>>> +ldouble: 1
>>> Test "Real part of: cacos (-0.5 - 0 i) == 2.094395102393195492308428922186335256131 + +0 i":
>>> double: 1
>>> idouble: 1
>>> +ldouble: 1
>>> Test "Imaginary part of: cacos (-1.5 + +0 i) == pi - 0.9624236501192068949955178268487368462704 i":
>>> double: 1
>>> float: 1
>>> @@ -265,6 +267,10 @@ double: 1
>>> float: 1
>>> idouble: 1
>>> ifloat: 1
>>> +Test "Imaginary part of: cacos (0x1.fp1023 + 0x1.fp1023 i) == 7.853981633974483096156608458198757210493e-1 - 7.107906849659093345062145442726115449315e2 i":
>>> +ldouble: 1
>>> +Test "Imaginary part of: cacos (0x1.fp127 + 0x1.fp127 i) == 7.853981633974483096156608458198757210493e-1 - 8.973081118419833726837456344608533993585e1 i":
>>> +ldouble: 1
>>>
>>> # cacosh
>>> Test "Real part of: cacosh (+0 + 0.5 i) == 0.4812118250596034474977589134243684231352 + pi/2 i":