* Re: sf_gamma questions
@ 2002-12-31 9:55 Dherminder Kainth
2002-01-03 2:18 ` Dherminder Kainth
2002-12-31 9:55 ` Brian Gough
0 siblings, 2 replies; 16+ messages in thread
From: Dherminder Kainth @ 2002-12-31 9:55 UTC (permalink / raw)
To: bjg; +Cc: gsl-discuss
Happy new year !
I have been using the Levin U transform routines within a C++ program and
have been getting memory leaks - for example the program crashes
when I attempt to deallocate the U transform workspace. A simpler
example program written in C seems to run fine. Is there any information
as to why this may be the case ? I can send both programs if somebody would
like to have a look.
The coding is done on a RH 7.2 Linux box.
Thanks,
Dherminder Kainth
_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: sf_gamma questions
2002-12-31 9:55 sf_gamma questions Dherminder Kainth
@ 2002-01-03 2:18 ` Dherminder Kainth
2002-12-31 9:55 ` Brian Gough
1 sibling, 0 replies; 16+ messages in thread
From: Dherminder Kainth @ 2002-01-03 2:18 UTC (permalink / raw)
To: bjg; +Cc: gsl-discuss
Happy new year !
I have been using the Levin U transform routines within a C++ program and
have been getting memory leaks - for example the program crashes
when I attempt to deallocate the U transform workspace. A simpler
example program written in C seems to run fine. Is there any information
as to why this may be the case ? I can send both programs if somebody would
like to have a look.
The coding is done on a RH 7.2 Linux box.
Thanks,
Dherminder Kainth
_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: sf_gamma questions
2002-12-31 9:55 sf_gamma questions Dherminder Kainth
2002-01-03 2:18 ` Dherminder Kainth
@ 2002-12-31 9:55 ` Brian Gough
2002-01-05 11:37 ` Brian Gough
1 sibling, 1 reply; 16+ messages in thread
From: Brian Gough @ 2002-12-31 9:55 UTC (permalink / raw)
To: Dherminder Kainth; +Cc: gsl-discuss
Dherminder Kainth writes:
> I have been using the Levin U transform routines within a C++ program and
> have been getting memory leaks - for example the program crashes
> when I attempt to deallocate the U transform workspace. A simpler
> example program written in C seems to run fine. Is there any information
> as to why this may be the case ? I can send both programs if somebody would
> like to have a look.
>
> The coding is done on a RH 7.2 Linux box.
Hi,
I recommend recompiling your program and GSL with
checkerg++/checkergcc.
That will trap any stack or malloc errors at the point where they
occur.
regards
Brian Gough
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: sf_gamma questions
2002-12-31 9:55 ` Brian Gough
@ 2002-01-05 11:37 ` Brian Gough
0 siblings, 0 replies; 16+ messages in thread
From: Brian Gough @ 2002-01-05 11:37 UTC (permalink / raw)
To: Dherminder Kainth; +Cc: gsl-discuss
Dherminder Kainth writes:
> I have been using the Levin U transform routines within a C++ program and
> have been getting memory leaks - for example the program crashes
> when I attempt to deallocate the U transform workspace. A simpler
> example program written in C seems to run fine. Is there any information
> as to why this may be the case ? I can send both programs if somebody would
> like to have a look.
>
> The coding is done on a RH 7.2 Linux box.
Hi,
I recommend recompiling your program and GSL with
checkerg++/checkergcc.
That will trap any stack or malloc errors at the point where they
occur.
regards
Brian Gough
^ permalink raw reply [flat|nested] 16+ messages in thread
* sf_gamma questions
@ 2001-12-19 13:20 Jonathan Leto
2001-11-26 23:50 ` Jonathan Leto
` (3 more replies)
0 siblings, 4 replies; 16+ messages in thread
From: Jonathan Leto @ 2001-12-19 13:20 UTC (permalink / raw)
To: gsl-discuss
[-- Attachment #1: Type: text/plain, Size: 1895 bytes --]
I was writing some test cases for Math::Gsl, when I saw some
failing, because gamma(19) was off by 1 and gamma(20) is off by
16. So I wrote a little test program to compare absolute difference
between gamma(x) and factorial(x-1) . The output was:
-------------- Actual error vs. Theoretical Error
Difference (1):0 vs 2.22044604925031308e-16
Difference (2):0 vs 2.22044604925031308e-16
Difference (3):1.77635683940025046e-15 vs 1.4246133846675888e-14
Difference (4):7.99360577730112709e-15 vs 4.71293383088833937e-14
Difference (5):1.06581410364015028e-14 vs 6.92426984602974577e-14
Difference (6):2.84217094304040074e-14 vs 2.96806016881859386e-13
Difference (7):1.1368683772161603e-13 vs 1.45976589371855462e-12
Difference (8):9.09494701772928238e-13 vs 1.02398955184829092e-11
Difference (9):7.2759576141834259e-12 vs 1.01934226616975847e-10
Difference (10):5.82076609134674072e-11 vs 1.00719432793994222e-09
Difference (11):4.65661287307739258e-10 vs 1.08776987417513721e-08
Difference (12):0 vs 1.28517996245136601e-07
Difference (13):5.9604644775390625e-08 vs 1.64857567597209688e-06
Difference (14):0 vs 2.28141601610332145e-05
Difference (15):1.52587890625e-05 vs 0.000338755711482008391
Difference (16):0 vs 0.00537169771064327506
Difference (17):0 vs 0.090592955984902801
Difference (18):0.0625 vs 1.61905872619172486
Difference (19):1 vs 30.5646696115218255
Difference (20):16 vs 607.739360880259596
Difference (21):0 vs 12694.999982832087
Difference (22):0 vs 277939.467709238641
Difference (23):131072 vs 6364246.58713807818
Difference (24):1572864 vs 152117972.34747678
Difference (25):104857600 vs 3788598556.57866812
Why is the error so large for gamma(x>18) ? Would it be possible
to just return factorial(x-1) if gamma is given an integer argument?
Test program (perl) is attached.
--
jonathan@leto.net
"Wir muessen wissen. Wir werden wissen."
-- David Hilbert, 1931
[-- Attachment #2: a --]
[-- Type: text/plain, Size: 318 bytes --]
#!/usr/bin/perl -w
use strict;
use Math::Gsl::Sf qw(gamma gamma_e);
my $r = new Math::Gsl::Sf::Result;
for (1 .. 25 ){
gamma_e( $_ , $r );
print "Difference ($_):" . abs( $r->val - fact($_- 1) ) . " vs ";
print $r->err . "\n";
}
sub fact {
my $x = shift;
return 1 if $x == 0;
return $x * fact( $x - 1 );
}
^ permalink raw reply [flat|nested] 16+ messages in thread* sf_gamma questions
2001-12-19 13:20 Jonathan Leto
@ 2001-11-26 23:50 ` Jonathan Leto
2001-12-19 13:20 ` Jonathan Leto
` (2 subsequent siblings)
3 siblings, 0 replies; 16+ messages in thread
From: Jonathan Leto @ 2001-11-26 23:50 UTC (permalink / raw)
To: gsl-discuss
[-- Attachment #1: Type: text/plain, Size: 1895 bytes --]
I was writing some test cases for Math::Gsl, when I saw some
failing, because gamma(19) was off by 1 and gamma(20) is off by
16. So I wrote a little test program to compare absolute difference
between gamma(x) and factorial(x-1) . The output was:
-------------- Actual error vs. Theoretical Error
Difference (1):0 vs 2.22044604925031308e-16
Difference (2):0 vs 2.22044604925031308e-16
Difference (3):1.77635683940025046e-15 vs 1.4246133846675888e-14
Difference (4):7.99360577730112709e-15 vs 4.71293383088833937e-14
Difference (5):1.06581410364015028e-14 vs 6.92426984602974577e-14
Difference (6):2.84217094304040074e-14 vs 2.96806016881859386e-13
Difference (7):1.1368683772161603e-13 vs 1.45976589371855462e-12
Difference (8):9.09494701772928238e-13 vs 1.02398955184829092e-11
Difference (9):7.2759576141834259e-12 vs 1.01934226616975847e-10
Difference (10):5.82076609134674072e-11 vs 1.00719432793994222e-09
Difference (11):4.65661287307739258e-10 vs 1.08776987417513721e-08
Difference (12):0 vs 1.28517996245136601e-07
Difference (13):5.9604644775390625e-08 vs 1.64857567597209688e-06
Difference (14):0 vs 2.28141601610332145e-05
Difference (15):1.52587890625e-05 vs 0.000338755711482008391
Difference (16):0 vs 0.00537169771064327506
Difference (17):0 vs 0.090592955984902801
Difference (18):0.0625 vs 1.61905872619172486
Difference (19):1 vs 30.5646696115218255
Difference (20):16 vs 607.739360880259596
Difference (21):0 vs 12694.999982832087
Difference (22):0 vs 277939.467709238641
Difference (23):131072 vs 6364246.58713807818
Difference (24):1572864 vs 152117972.34747678
Difference (25):104857600 vs 3788598556.57866812
Why is the error so large for gamma(x>18) ? Would it be possible
to just return factorial(x-1) if gamma is given an integer argument?
Test program (perl) is attached.
--
jonathan@leto.net
"Wir muessen wissen. Wir werden wissen."
-- David Hilbert, 1931
[-- Attachment #2: a --]
[-- Type: text/plain, Size: 318 bytes --]
#!/usr/bin/perl -w
use strict;
use Math::Gsl::Sf qw(gamma gamma_e);
my $r = new Math::Gsl::Sf::Result;
for (1 .. 25 ){
gamma_e( $_ , $r );
print "Difference ($_):" . abs( $r->val - fact($_- 1) ) . " vs ";
print $r->err . "\n";
}
sub fact {
my $x = shift;
return 1 if $x == 0;
return $x * fact( $x - 1 );
}
^ permalink raw reply [flat|nested] 16+ messages in thread* sf_gamma questions
2001-12-19 13:20 Jonathan Leto
2001-11-26 23:50 ` Jonathan Leto
@ 2001-12-19 13:20 ` Jonathan Leto
2001-12-19 13:20 ` Brian Gough
2001-12-19 13:20 ` Dan, Ho-Jin
3 siblings, 0 replies; 16+ messages in thread
From: Jonathan Leto @ 2001-12-19 13:20 UTC (permalink / raw)
To: gsl-discuss
I was writing some test cases for Math::Gsl, when I saw some
failing, because gamma(19) was off by 1 and gamma(20) is off by
16. So I wrote a little test program to compare absolute difference
between gamma(x) and factorial(x-1) . The output was:
-------------- Actual error vs. Theoretical Error
Difference (1):0 vs 2.22044604925031308e-16
Difference (2):0 vs 2.22044604925031308e-16
Difference (3):1.77635683940025046e-15 vs 1.4246133846675888e-14
Difference (4):7.99360577730112709e-15 vs 4.71293383088833937e-14
Difference (5):1.06581410364015028e-14 vs 6.92426984602974577e-14
Difference (6):2.84217094304040074e-14 vs 2.96806016881859386e-13
Difference (7):1.1368683772161603e-13 vs 1.45976589371855462e-12
Difference (8):9.09494701772928238e-13 vs 1.02398955184829092e-11
Difference (9):7.2759576141834259e-12 vs 1.01934226616975847e-10
Difference (10):5.82076609134674072e-11 vs 1.00719432793994222e-09
Difference (11):4.65661287307739258e-10 vs 1.08776987417513721e-08
Difference (12):0 vs 1.28517996245136601e-07
Difference (13):5.9604644775390625e-08 vs 1.64857567597209688e-06
Difference (14):0 vs 2.28141601610332145e-05
Difference (15):1.52587890625e-05 vs 0.000338755711482008391
Difference (16):0 vs 0.00537169771064327506
Difference (17):0 vs 0.090592955984902801
Difference (18):0.0625 vs 1.61905872619172486
Difference (19):1 vs 30.5646696115218255
Difference (20):16 vs 607.739360880259596
Difference (21):0 vs 12694.999982832087
Difference (22):0 vs 277939.467709238641
Difference (23):131072 vs 6364246.58713807818
Difference (24):1572864 vs 152117972.34747678
Difference (25):104857600 vs 3788598556.57866812
Why is the error so large for gamma(x>18) ? Would it be possible
to just return factorial(x-1) if gamma is given an integer argument?
Test program (perl) is attached.
--
jonathan@leto.net
"Wir muessen wissen. Wir werden wissen."
-- David Hilbert, 1931
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: sf_gamma questions
2001-12-19 13:20 Jonathan Leto
2001-11-26 23:50 ` Jonathan Leto
2001-12-19 13:20 ` Jonathan Leto
@ 2001-12-19 13:20 ` Brian Gough
2001-11-29 1:08 ` Brian Gough
2001-12-19 13:20 ` Jonathan Leto
2001-12-19 13:20 ` Dan, Ho-Jin
3 siblings, 2 replies; 16+ messages in thread
From: Brian Gough @ 2001-12-19 13:20 UTC (permalink / raw)
To: jonathan; +Cc: gsl-discuss
Jonathan Leto writes:
> Why is the error so large for gamma(x>18) ?
It's computed with an approximation so the relative error is the
appropriate measure. Note that 1/Gamma(19) is the first value which is
less than DBL_EPSILON.
> Would it be possible to just return factorial(x-1) if gamma is
> given an integer argument?
Sounds reasonable to me.
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: sf_gamma questions
2001-12-19 13:20 ` Brian Gough
@ 2001-11-29 1:08 ` Brian Gough
2001-12-19 13:20 ` Jonathan Leto
1 sibling, 0 replies; 16+ messages in thread
From: Brian Gough @ 2001-11-29 1:08 UTC (permalink / raw)
To: jonathan; +Cc: gsl-discuss
Jonathan Leto writes:
> Why is the error so large for gamma(x>18) ?
It's computed with an approximation so the relative error is the
appropriate measure. Note that 1/Gamma(19) is the first value which is
less than DBL_EPSILON.
> Would it be possible to just return factorial(x-1) if gamma is
> given an integer argument?
Sounds reasonable to me.
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: sf_gamma questions
2001-12-19 13:20 ` Brian Gough
2001-11-29 1:08 ` Brian Gough
@ 2001-12-19 13:20 ` Jonathan Leto
2001-12-01 18:46 ` Jonathan Leto
` (2 more replies)
1 sibling, 3 replies; 16+ messages in thread
From: Jonathan Leto @ 2001-12-19 13:20 UTC (permalink / raw)
To: Brian Gough; +Cc: gsl-discuss
Patch is attached to implement my idea. I am not a C programmer
by trade, so let me know if I am tickling Nyarlathotep or
something.
New output of my difference program:
-------------- Actual error vs. Theoretical Error
Difference (1):0 vs 0
Difference (2):0 vs 0
Difference (3):0 vs 0
Difference (4):0 vs 0
Difference (5):0 vs 0
Difference (6):0 vs 0
Difference (7):0 vs 0
Difference (8):0 vs 0
Difference (9):0 vs 0
Difference (10):0 vs 0
Difference (11):0 vs 0
Difference (12):0 vs 0
Difference (13):0 vs 0
Difference (14):0 vs 0
Difference (15):0 vs 0
Difference (16):0 vs 0
Difference (17):0 vs 0
Difference (18):0 vs 0
Difference (19):0 vs 2.84322508014156
Difference (20):0 vs 54.0212765226897
Difference (21):0 vs 1080.42553045379
Difference (22):0 vs 22688.9361395297
Difference (23):0 vs 499156.595069653
Difference (24):0 vs 11480601.686602
Difference (25):0 vs 275534440.478449
Brian Gough (bjg@network-theory.co.uk) was saying:
> Jonathan Leto writes:
> > Why is the error so large for gamma(x>18) ?
>
> It's computed with an approximation so the relative error is the
> appropriate measure. Note that 1/Gamma(19) is the first value which is
> less than DBL_EPSILON.
>
> > Would it be possible to just return factorial(x-1) if gamma is
> > given an integer argument?
>
> Sounds reasonable to me.
--
jonathan@leto.net
"Wir muessen wissen. Wir werden wissen."
-- David Hilbert, 1931
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: sf_gamma questions
2001-12-19 13:20 ` Jonathan Leto
@ 2001-12-01 18:46 ` Jonathan Leto
2001-12-19 13:20 ` Jonathan Leto
2001-12-19 13:20 ` Brian Gough
2 siblings, 0 replies; 16+ messages in thread
From: Jonathan Leto @ 2001-12-01 18:46 UTC (permalink / raw)
To: Brian Gough; +Cc: gsl-discuss
[-- Attachment #1: Type: text/plain, Size: 1412 bytes --]
Patch is attached to implement my idea. I am not a C programmer
by trade, so let me know if I am tickling Nyarlathotep or
something.
New output of my difference program:
-------------- Actual error vs. Theoretical Error
Difference (1):0 vs 0
Difference (2):0 vs 0
Difference (3):0 vs 0
Difference (4):0 vs 0
Difference (5):0 vs 0
Difference (6):0 vs 0
Difference (7):0 vs 0
Difference (8):0 vs 0
Difference (9):0 vs 0
Difference (10):0 vs 0
Difference (11):0 vs 0
Difference (12):0 vs 0
Difference (13):0 vs 0
Difference (14):0 vs 0
Difference (15):0 vs 0
Difference (16):0 vs 0
Difference (17):0 vs 0
Difference (18):0 vs 0
Difference (19):0 vs 2.84322508014156
Difference (20):0 vs 54.0212765226897
Difference (21):0 vs 1080.42553045379
Difference (22):0 vs 22688.9361395297
Difference (23):0 vs 499156.595069653
Difference (24):0 vs 11480601.686602
Difference (25):0 vs 275534440.478449
Brian Gough (bjg@network-theory.co.uk) was saying:
> Jonathan Leto writes:
> > Why is the error so large for gamma(x>18) ?
>
> It's computed with an approximation so the relative error is the
> appropriate measure. Note that 1/Gamma(19) is the first value which is
> less than DBL_EPSILON.
>
> > Would it be possible to just return factorial(x-1) if gamma is
> > given an integer argument?
>
> Sounds reasonable to me.
--
jonathan@leto.net
"Wir muessen wissen. Wir werden wissen."
-- David Hilbert, 1931
[-- Attachment #2: gsl-1.0_gamma.patch --]
[-- Type: text/plain, Size: 565 bytes --]
--- gamma.c.orig Mon Dec 3 23:21:36 2001
+++ gamma.c Mon Dec 3 23:53:27 2001
@@ -1247,7 +1247,14 @@
int
gsl_sf_gamma_e(const double x, gsl_sf_result * result)
{
- if(x < 0.5) {
+ int y;
+ y = abs((int)x - x );
+
+ /* if x is an integer as far as we can tell, return factorial(x-1)
+ this gives us much better precision when x>19 or so */
+ if(y < GSL_DBL_EPSILON ){
+ gsl_sf_fact_e((int) x - 1,result);
+ } else if(x < 0.5) {
int rint_x = (int)floor(x+0.5);
double f_x = x - rint_x;
double sgn = ( GSL_IS_EVEN(rint_x) ? 1.0 : -1.0 );
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: sf_gamma questions
2001-12-19 13:20 ` Jonathan Leto
2001-12-01 18:46 ` Jonathan Leto
@ 2001-12-19 13:20 ` Jonathan Leto
2001-12-19 13:20 ` Brian Gough
2 siblings, 0 replies; 16+ messages in thread
From: Jonathan Leto @ 2001-12-19 13:20 UTC (permalink / raw)
To: Brian Gough; +Cc: gsl-discuss
[-- Attachment #1: Type: text/plain, Size: 1412 bytes --]
Patch is attached to implement my idea. I am not a C programmer
by trade, so let me know if I am tickling Nyarlathotep or
something.
New output of my difference program:
-------------- Actual error vs. Theoretical Error
Difference (1):0 vs 0
Difference (2):0 vs 0
Difference (3):0 vs 0
Difference (4):0 vs 0
Difference (5):0 vs 0
Difference (6):0 vs 0
Difference (7):0 vs 0
Difference (8):0 vs 0
Difference (9):0 vs 0
Difference (10):0 vs 0
Difference (11):0 vs 0
Difference (12):0 vs 0
Difference (13):0 vs 0
Difference (14):0 vs 0
Difference (15):0 vs 0
Difference (16):0 vs 0
Difference (17):0 vs 0
Difference (18):0 vs 0
Difference (19):0 vs 2.84322508014156
Difference (20):0 vs 54.0212765226897
Difference (21):0 vs 1080.42553045379
Difference (22):0 vs 22688.9361395297
Difference (23):0 vs 499156.595069653
Difference (24):0 vs 11480601.686602
Difference (25):0 vs 275534440.478449
Brian Gough (bjg@network-theory.co.uk) was saying:
> Jonathan Leto writes:
> > Why is the error so large for gamma(x>18) ?
>
> It's computed with an approximation so the relative error is the
> appropriate measure. Note that 1/Gamma(19) is the first value which is
> less than DBL_EPSILON.
>
> > Would it be possible to just return factorial(x-1) if gamma is
> > given an integer argument?
>
> Sounds reasonable to me.
--
jonathan@leto.net
"Wir muessen wissen. Wir werden wissen."
-- David Hilbert, 1931
[-- Attachment #2: gsl-1.0_gamma.patch --]
[-- Type: text/plain, Size: 565 bytes --]
--- gamma.c.orig Mon Dec 3 23:21:36 2001
+++ gamma.c Mon Dec 3 23:53:27 2001
@@ -1247,7 +1247,14 @@
int
gsl_sf_gamma_e(const double x, gsl_sf_result * result)
{
- if(x < 0.5) {
+ int y;
+ y = abs((int)x - x );
+
+ /* if x is an integer as far as we can tell, return factorial(x-1)
+ this gives us much better precision when x>19 or so */
+ if(y < GSL_DBL_EPSILON ){
+ gsl_sf_fact_e((int) x - 1,result);
+ } else if(x < 0.5) {
int rint_x = (int)floor(x+0.5);
double f_x = x - rint_x;
double sgn = ( GSL_IS_EVEN(rint_x) ? 1.0 : -1.0 );
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: sf_gamma questions
2001-12-19 13:20 ` Jonathan Leto
2001-12-01 18:46 ` Jonathan Leto
2001-12-19 13:20 ` Jonathan Leto
@ 2001-12-19 13:20 ` Brian Gough
2001-12-03 15:28 ` Brian Gough
2 siblings, 1 reply; 16+ messages in thread
From: Brian Gough @ 2001-12-19 13:20 UTC (permalink / raw)
To: jonathan; +Cc: gsl-discuss
Jonathan Leto writes:
> --- gamma.c.orig Mon Dec 3 23:21:36 2001
> +++ gamma.c Mon Dec 3 23:53:27 2001
> @@ -1247,7 +1247,14 @@
> int
> gsl_sf_gamma_e(const double x, gsl_sf_result * result)
> {
> + /* if x is an integer as far as we can tell, return factorial(x-1)
> + this gives us much better precision when x>19 or so */
> + if(y < GSL_DBL_EPSILON ){
> + gsl_sf_fact_e((int) x - 1,result);
Thanks. I've added something along these lines but in the function
gamma_xgthalf, which is used in several places and so gives some other
opportunities to gain from a bit of extra accuracy.
Brian
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: sf_gamma questions
2001-12-19 13:20 ` Brian Gough
@ 2001-12-03 15:28 ` Brian Gough
0 siblings, 0 replies; 16+ messages in thread
From: Brian Gough @ 2001-12-03 15:28 UTC (permalink / raw)
To: jonathan; +Cc: gsl-discuss
Jonathan Leto writes:
> --- gamma.c.orig Mon Dec 3 23:21:36 2001
> +++ gamma.c Mon Dec 3 23:53:27 2001
> @@ -1247,7 +1247,14 @@
> int
> gsl_sf_gamma_e(const double x, gsl_sf_result * result)
> {
> + /* if x is an integer as far as we can tell, return factorial(x-1)
> + this gives us much better precision when x>19 or so */
> + if(y < GSL_DBL_EPSILON ){
> + gsl_sf_fact_e((int) x - 1,result);
Thanks. I've added something along these lines but in the function
gamma_xgthalf, which is used in several places and so gives some other
opportunities to gain from a bit of extra accuracy.
Brian
^ permalink raw reply [flat|nested] 16+ messages in thread
* Re: sf_gamma questions
2001-12-19 13:20 Jonathan Leto
` (2 preceding siblings ...)
2001-12-19 13:20 ` Brian Gough
@ 2001-12-19 13:20 ` Dan, Ho-Jin
2001-11-28 12:19 ` Dan, Ho-Jin
3 siblings, 1 reply; 16+ messages in thread
From: Dan, Ho-Jin @ 2001-12-19 13:20 UTC (permalink / raw)
To: jonathan; +Cc: gsl-discuss
I found that the results from slatec are slightly accurate compare to
that of slatec.
The relative error of the order O(1.e-15) shows that both routines are
very accurate.
[17!] error slatec: 1.875000 [rel:0.000000]
gsl : -0.062500 [rel:-0.000000]
[18!] error slatec: 6.000000 [rel:0.000000]
gsl : -1.000000 [rel:-0.000000]
[19!] error slatec: -80.000000 [rel:-0.000000]
gsl : -16.000000 [rel:-0.000000]
[20!] error slatec: 0.000000 [rel:0.000000]
gsl : 0.000000 [rel:0.000000]
[21!] error slatec: -344064.000000 [rel:-0.000000]
gsl : 0.000000 [rel:0.000000]
[22!] error slatec: 4194304.000000 [rel:0.000000]
gsl : -131072.000000 [rel:-0.000000]
[23!] error slatec: -83886080.000000 [rel:-0.000000]
gsl : 0.000000 [rel:0.000000]
[24!] error slatec: 4697620480.000000 [rel:0.000000]
gsl : -134217728.000000 [rel:-0.000000]
[25!] error slatec: -79456894976.000000 [rel:-0.000000]
gsl : -2147483648.000000 [rel:-0.000000]
Jonathan Leto wrote:
>I was writing some test cases for Math::Gsl, when I saw some
>failing, because gamma(19) was off by 1 and gamma(20) is off by
>16. So I wrote a little test program to compare absolute difference
>between gamma(x) and factorial(x-1) . The output was:
>
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: sf_gamma questions
2001-12-19 13:20 ` Dan, Ho-Jin
@ 2001-11-28 12:19 ` Dan, Ho-Jin
0 siblings, 0 replies; 16+ messages in thread
From: Dan, Ho-Jin @ 2001-11-28 12:19 UTC (permalink / raw)
To: jonathan; +Cc: gsl-discuss
I found that the results from slatec are slightly accurate compare to
that of slatec.
The relative error of the order O(1.e-15) shows that both routines are
very accurate.
[17!] error slatec: 1.875000 [rel:0.000000]
gsl : -0.062500 [rel:-0.000000]
[18!] error slatec: 6.000000 [rel:0.000000]
gsl : -1.000000 [rel:-0.000000]
[19!] error slatec: -80.000000 [rel:-0.000000]
gsl : -16.000000 [rel:-0.000000]
[20!] error slatec: 0.000000 [rel:0.000000]
gsl : 0.000000 [rel:0.000000]
[21!] error slatec: -344064.000000 [rel:-0.000000]
gsl : 0.000000 [rel:0.000000]
[22!] error slatec: 4194304.000000 [rel:0.000000]
gsl : -131072.000000 [rel:-0.000000]
[23!] error slatec: -83886080.000000 [rel:-0.000000]
gsl : 0.000000 [rel:0.000000]
[24!] error slatec: 4697620480.000000 [rel:0.000000]
gsl : -134217728.000000 [rel:-0.000000]
[25!] error slatec: -79456894976.000000 [rel:-0.000000]
gsl : -2147483648.000000 [rel:-0.000000]
Jonathan Leto wrote:
>I was writing some test cases for Math::Gsl, when I saw some
>failing, because gamma(19) was off by 1 and gamma(20) is off by
>16. So I wrote a little test program to compare absolute difference
>between gamma(x) and factorial(x-1) . The output was:
>
^ permalink raw reply [flat|nested] 16+ messages in thread
end of thread, other threads:[~2002-01-05 19:37 UTC | newest]
Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2002-12-31 9:55 sf_gamma questions Dherminder Kainth
2002-01-03 2:18 ` Dherminder Kainth
2002-12-31 9:55 ` Brian Gough
2002-01-05 11:37 ` Brian Gough
-- strict thread matches above, loose matches on Subject: below --
2001-12-19 13:20 Jonathan Leto
2001-11-26 23:50 ` Jonathan Leto
2001-12-19 13:20 ` Jonathan Leto
2001-12-19 13:20 ` Brian Gough
2001-11-29 1:08 ` Brian Gough
2001-12-19 13:20 ` Jonathan Leto
2001-12-01 18:46 ` Jonathan Leto
2001-12-19 13:20 ` Jonathan Leto
2001-12-19 13:20 ` Brian Gough
2001-12-03 15:28 ` Brian Gough
2001-12-19 13:20 ` Dan, Ho-Jin
2001-11-28 12:19 ` Dan, Ho-Jin
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