* [PATCH 1/1] newlib: libm: fix complex atan for +/- 1 + 0i
@ 2023-09-26 11:07 Joseph Faulls
2023-10-09 10:47 ` Joseph Faulls
0 siblings, 1 reply; 3+ messages in thread
From: Joseph Faulls @ 2023-09-26 11:07 UTC (permalink / raw)
To: newlib
[-- Attachment #1: Type: text/plain, Size: 889 bytes --]
Delete check which ensured atan2 was not called with x=0. This is not
necessary as atan2 is defined for x=0 when y != 0. The check incorrectly
resulted in catan returning nan + inf i for when real part is +/- 1 and
imaginary part is 0.
The check could also have implications when called with imaginary number
x + yi where x^2 + y^2 == 1.0. Although this is unlikely due to floating
point precision.
---
newlib/libm/complex/catan.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/newlib/libm/complex/catan.c b/newlib/libm/complex/catan.c
index 77510ec2f..34d75b849 100644
--- a/newlib/libm/complex/catan.c
+++ b/newlib/libm/complex/catan.c
@@ -105,8 +105,6 @@ catan(double complex z)
x2 = x * x;
a = 1.0 - x2 - (y * y);
- if (a == 0.0)
- goto ovrf;
t = 0.5 * atan2(2.0 * x, a);
w = _redupi(t);
--
2.34.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: [PATCH 1/1] newlib: libm: fix complex atan for +/- 1 + 0i
2023-09-26 11:07 [PATCH 1/1] newlib: libm: fix complex atan for +/- 1 + 0i Joseph Faulls
@ 2023-10-09 10:47 ` Joseph Faulls
2023-10-10 19:26 ` Jeff Johnston
0 siblings, 1 reply; 3+ messages in thread
From: Joseph Faulls @ 2023-10-09 10:47 UTC (permalink / raw)
To: newlib; +Cc: jjohnstn
[-- Attachment #1: Type: text/plain, Size: 1059 bytes --]
Ping
From: Joseph Faulls
Sent: Tuesday, September 26, 2023 12:07 PM
To: newlib@sourceware.org
Subject: [PATCH 1/1] newlib: libm: fix complex atan for +/- 1 + 0i
Delete check which ensured atan2 was not called with x=0. This is not
necessary as atan2 is defined for x=0 when y != 0. The check incorrectly
resulted in catan returning nan + inf i for when real part is +/- 1 and
imaginary part is 0.
The check could also have implications when called with imaginary number
x + yi where x^2 + y^2 == 1.0. Although this is unlikely due to floating
point precision.
---
newlib/libm/complex/catan.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/newlib/libm/complex/catan.c b/newlib/libm/complex/catan.c
index 77510ec2f..34d75b849 100644
--- a/newlib/libm/complex/catan.c
+++ b/newlib/libm/complex/catan.c
@@ -105,8 +105,6 @@ catan(double complex z)
x2 = x * x;
a = 1.0 - x2 - (y * y);
- if (a == 0.0)
- goto ovrf;
t = 0.5 * atan2(2.0 * x, a);
w = _redupi(t);
--
2.34.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/1] newlib: libm: fix complex atan for +/- 1 + 0i
2023-10-09 10:47 ` Joseph Faulls
@ 2023-10-10 19:26 ` Jeff Johnston
0 siblings, 0 replies; 3+ messages in thread
From: Jeff Johnston @ 2023-10-10 19:26 UTC (permalink / raw)
To: Joseph Faulls; +Cc: newlib
[-- Attachment #1: Type: text/plain, Size: 1700 bytes --]
Hi Joseph,
Sorry for the delay. I did a check and the current NetBSD sources still
have that check in them and that was where
this code was taken from.
However, I created a test case and tried it with glibc and also tested with
newlib versions of catan/catanf minus the checks. They
match without the check so I pushed the change to all 3 of the catan
functions.
-- Jeff J.
On Mon, Oct 9, 2023 at 6:47 AM Joseph Faulls <Joseph.Faulls@imgtec.com>
wrote:
> Ping
>
>
>
> *From:* Joseph Faulls
> *Sent:* Tuesday, September 26, 2023 12:07 PM
> *To:* newlib@sourceware.org
> *Subject:* [PATCH 1/1] newlib: libm: fix complex atan for +/- 1 + 0i
>
>
>
> Delete check which ensured atan2 was not called with x=0. This is not
>
> necessary as atan2 is defined for x=0 when y != 0. The check incorrectly
>
> resulted in catan returning nan + inf i for when real part is +/- 1 and
>
> imaginary part is 0.
>
>
>
> The check could also have implications when called with imaginary number
>
> x + yi where x^2 + y^2 == 1.0. Although this is unlikely due to floating
>
> point precision.
>
> ---
>
> newlib/libm/complex/catan.c | 2 --
>
> 1 file changed, 2 deletions(-)
>
>
>
> diff --git a/newlib/libm/complex/catan.c b/newlib/libm/complex/catan.c
>
> index 77510ec2f..34d75b849 100644
>
> --- a/newlib/libm/complex/catan.c
>
> +++ b/newlib/libm/complex/catan.c
>
> @@ -105,8 +105,6 @@ catan(double complex z)
>
>
>
> x2 = x * x;
>
> a = 1.0 - x2 - (y * y);
>
> - if (a == 0.0)
>
> - goto ovrf;
>
>
>
> t = 0.5 * atan2(2.0 * x, a);
>
> w = _redupi(t);
>
> --
>
> 2.34.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-09-26 11:07 [PATCH 1/1] newlib: libm: fix complex atan for +/- 1 + 0i Joseph Faulls
2023-10-09 10:47 ` Joseph Faulls
2023-10-10 19:26 ` Jeff Johnston
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