This repository has been archived by the owner on Nov 20, 2020. It is now read-only.
-
Notifications
You must be signed in to change notification settings - Fork 26
/
Copy pathBUGS
704 lines (570 loc) · 21.6 KB
/
BUGS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
The GSL Bugs Database is at http://savannah.gnu.org/bugs/?group=gsl
This file was generated from it at Tue Aug 25 15:52:36 2009
------------------------------------------------------------------------
BUG-ID: 21828
STATUS: Open/Confirmed
CATEGORY: Performance
SUMMARY: suboptimal performance of gsl_fdfsolver_lmsder
From: "Alexander Usov" <[email protected]>
Subject: [Help-gsl] Strange performance of gsl_fdfsolver_lmsder
Date: Wed, 24 Oct 2007 20:45:01 +0200
Hi all,
I am currently working on the problem involving source extraction from
astronomical images, which essentially boils down to fitting a number of
2d gaussians to the image.
One of the traditionally used fitters in this field is a Levenberg-Marquardt,
which gsl_fdfsolver_lmsder is and implementation of.
At some moment I have notices that for the bigger images (about 550
pixels, 20-30 parameters) gsl's lmsder algorithm spends a large fraction
of the run-time (about 50%) doing household transform.
While looking around for are different minimization algorithms I have made
a surprising finding that original netlib/minpack/lmder is almost twice faster
that that of gsl.
Could anyone explain such a big difference in performace?
--
Best regards,
Alexander.
_______________________________________________
Help-gsl mailing list
http://lists.gnu.org/mailman/listinfo/help-gsl
Reply-To: [email protected]
From: Brian Gough <[email protected]>
To: "Alexander Usov" <[email protected]>
Subject: Re: [Help-gsl] Strange performance of gsl_fdfsolver_lmsder
Date: Thu, 25 Oct 2007 21:57:08 +0100
At Wed, 24 Oct 2007 20:45:01 +0200,
Alexander Usov wrote:
> At some moment I have notices that for the bigger images (about 550
> pixels, 20-30 parameters) gsl's lmsder algorithm spends a large fraction
> of the run-time (about 50%) doing household transform.
>
> While looking around for are different minimization algorithms I have made
> a surprising finding that original netlib/minpack/lmder is almost twice faster
> that that of gsl.
>
> Could anyone explain such a big difference in performace?
I have a vague memory that there was some quantity (Jacobian?) that
MINPACK only computes fully at the end, but in GSL it is accessible to
the user at each step so I felt I had to update it on each iteration
in the absence of some alternate scheme. Sorry this is not a great
answer but I am not able to look at it in detail now.
--
Brian Gough
_______________________________________________
Help-gsl mailing list
http://lists.gnu.org/mailman/listinfo/help-gsl
------------------------------------------------------------------------
BUG-ID: 21831
STATUS: Open
CATEGORY: Accuracy problem
SUMMARY: Levý random number generator for alpha < 1
From: [email protected]
Subject: [Bug-gsl] Levý random number generator
Date: Mon, 26 Mar 2007 19:48:01 -0300
The Levý skew random number generator (gsl_ran_levy_skew) does not
procuce a Levý random number when beta=0 (symmetric case), and the
gsl_ran_levy function does not work as stated in the docs. I made some
histograms from 10^6 samples to check the accuracy of the algorithms,
by comparison agaisnt the numerical integration of the equation of
Levý's PDF. For the gsl_ran_levy function there is a good precison for
alpha [1,2], for alpha (0.3,1) you must sum a series of random numbers
to get the same precision (tipicaly 100 or more gsl_ran_levy numbers).
For alpha<=0.3 the algorithm does not work properly, even worse, the
error increases as you add more random numbers. This contradicts the
manual that says "the algoritm only works for alpha (0,2]". The
function gsl_ran_levy_skew does not produce levy random numbers when
beta=0, instead the pdf of the random numbers is a linear (?!?!) one.
----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.
_______________________________________________
Bug-gsl mailing list
http://lists.gnu.org/mailman/listinfo/bug-gsl
From: [email protected]
To: Brian Gough <[email protected]>
Cc:
Subject: Re: [Bug-gsl] Lev? random number generator
Date: Tue, 27 Mar 2007 09:35:15 -0300
Thanks for your quick answer, and sorry about my poor english, it is
not my natural language.
The code below generates 10^6 random numbers, and makes a normalized
histogram wich is compared to the levy pdf. To get the levy pdf, it
numericaly integrates the characteristic function for levy process
(the function f in the code). The n parameter just adds a series of
levy numbers to get better precision. The code saves 2 files:
lhist-$alpha-$n (the normalized histogram) and lpdf-$alpha (the pdf
for the levy process). It also prints to the stdout the absolute error
(square of the difference) between the histogram and the pdf.
The function levy skew shows problems for alpha<1.
With this code, you can also check the problems related to the
gsl_ran_levy function (just change gsl_ran_levy_skew by gsl_ran_levy,
cutting the last paramenter).
I am using the pre-compiled gsl that comes with debian etch (gsl
version 1.8.2).
If you are interested, I also encoded a routine to generate levy skew
random numbers, it is not fully tested, but it works for beta=0 and
alpha<1 (it suffers from the same precision problem as gsl_ran_levy
function for small alpha)
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <sys/time.h>
#include <unistd.h>
#include <string.h>
#include <gsl/gsl_rng.h>
#include <gsl/gsl_randist.h>
#include <gsl/gsl_statistics_double.h>
#include <gsl/gsl_histogram.h>
#include <gsl/gsl_integration.h>
double f (double x, void *params)
{
double alpha = *(double *) params;
double f = exp(-pow(x,alpha))/M_PI;
return f;
}
double *levy_pdf(double alpha,int hist_size,double a,double b)
{
double abserr,*lpdf,dx;
gsl_function F;
int i;
gsl_integration_workspace *w=gsl_integration_workspace_alloc(1000);
gsl_integration_workspace *cw=gsl_integration_workspace_alloc(1000);
gsl_integration_qawo_table
*wf=gsl_integration_qawo_table_alloc(0.0,1.0,GSL_INTEG_COSINE,200);
lpdf=(double*)calloc(hist_size,sizeof(double));
F.function=&f;
F.params=α
dx=(double)(b-a)/(double)hist_size;
for (i=0;i<hist_size;i++)
{
gsl_integration_qawo_table_set(wf,i*dx+a,1.0,GSL_INTEG_COSINE);
gsl_integration_qawf (&F,0.0,1e-10,1000,w,cw,wf,&lpdf[i],&abserr);
}
gsl_integration_qawo_table_free(wf);
gsl_integration_workspace_free(w);
gsl_integration_workspace_free(cw);
return (lpdf);
}
int main (int argc,char *argv[])
{
double *l,*lpdf,a=-20,b=20,alpha,dx,n,errabs=0.0;
unsigned long int rnd_seed;
int i,j,rand_numbers=1e6,hist_size=400;
gsl_histogram *h;
gsl_rng *r;
struct timeval *tv;
struct timezone *tz;
char filename[50];
FILE *f1,*f2;
if(argc!=3)
{
printf("\nThe program must be called with 2 parameters: alpha and n\n \n");
exit(1);
}
dx=(double)(b-a)/(double)hist_size;
h=gsl_histogram_alloc(hist_size);
alpha=atof(argv[1]);
n=atof(argv[2]);
strcpy(filename,"lhist-");
strcat(filename,argv[1]);
strcat(filename,"-");
strcat(filename,argv[2]);
f1=fopen(filename,"w+");
strcpy(filename,"lpdf-");
strcat(filename,argv[1]);
f2=fopen(filename,"w+");
l=(double*)calloc(rand_numbers,sizeof(double));
lpdf=(double*)calloc(hist_size,sizeof(double));
r=gsl_rng_alloc (gsl_rng_mt19937);
gettimeofday(tv,tz);
rnd_seed=(unsigned long int)tv->tv_usec;
gsl_rng_set(r,rnd_seed);
i=0;
do
{
l[i]=0.0;
for (j=1;j<n;j++) l[i]+=gsl_ran_levy_skew(r,1.0,alpha,0.0);
l[i]=l[i]/pow(n,1.0/alpha);
if (abs(l[i])<=20) i++;//picks only random numbers in the interval
[a,b] to get good precision in the histogram
}while(i<rand_numbers);
gsl_histogram_set_ranges_uniform(h,a,b);
for(i=0;i<rand_numbers;i++) gsl_histogram_increment(h,l[i]);
gsl_histogram_scale(h,(double)hist_size/((b-a)*gsl_histogram_sum(h)));
gsl_histogram_fprintf(f1,h,"%g","%g");
lpdf=levy_pdf(alpha,hist_size,a,b);
for (i=0;i<hist_size;i++) fprintf(f2,"%e\t%e\n",i*dx+a,lpdf[i]);
for (i=0;i<hist_size;i++) errabs+=pow((gsl_histogram_get(h,i)-lpdf[i]),2.0);
printf("%e\n",errabs/(double)hist_size);
gsl_histogram_free(h);
gsl_rng_free(r);
fclose(f1);
exit (0);
}
> At Mon, 26 Mar 2007 19:48:01 -0300,
> [email protected] wrote:
>>
>> The Lev? skew random number generator (gsl_ran_levy_skew) does not
>> procuce a Lev? random number when beta=0 (symmetric case), and the
>> gsl_ran_levy function does not work as stated in the docs. I made some
>> histograms from 10^6 samples to check the accuracy of the algorithms,
>> by comparison agaisnt the numerical integration of the equation of
>> Lev?'s PDF. For the gsl_ran_levy function there is a good precison for
>> alpha [1,2], for alpha (0.3,1) you must sum a series of random numbers
>> to get the same precision (tipicaly 100 or more gsl_ran_levy numbers).
>> For alpha<=0.3 the algorithm does not work properly, even worse, the
>> error increases as you add more random numbers. This contradicts the
>> manual that says "the algoritm only works for alpha (0,2]". The
>> function gsl_ran_levy_skew does not produce levy random numbers when
>> beta=0, instead the pdf of the random numbers is a linear (?!?!) one.
>
> Thanks for your email. Please can you send a small example program
> which demonstrates the problem.
>
> Note that the Levy skew generator is tested in the GSL test suite for
> several cases where beta=0 -- if you have not done so, can you run
> "make check" and confirm that it works for these cases.
>
> --
> Brian Gough
> (GSL Maintainer)
>
> Network Theory Ltd,
> Publishing the GSL Manual - http://www.network-theory.co.uk/gsl/manual/
>
----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.
_______________________________________________
Bug-gsl mailing list
http://lists.gnu.org/mailman/listinfo/bug-gsl
-
------------------------------------------------------------------------
BUG-ID: 21833
STATUS: Open
CATEGORY: Performance
SUMMARY: suboptimal performance of gsl permutation?
From: "djamel anonymous" <[email protected]>
Subject: gsl permutation
Date: Wed, 24 Jan 2007 07:42:06 +0000
Hi.
i am sending you this email about a possible issue in glibc permutation
algorithm.i think it has qudratic worst case running time.for example if we
have the permutation
1,2,3,4,,,,,n,0
we will permute all elements in first iteration then for each iteration we
will traverse on average half the cycle (which is of size n) before we know
that the elements of cycle have already been permuted.there is two possible
solutions to make the algorithm linear:
1-at each step we traverse the full cycle and permute all elements in the
cycle.for each permuted element i we assign p[i]=i.the disavantage of this
is that it will destroy the original permutation.
2-use a bit array of size n bits.each time we permute an element we set the
relevant bit.if at iteration i we find that bit i is already set we skip to
next iteration.the disavantage of this is that it equires additional storage
allocation.
best regards.
_________________________________________________________________
MSN Hotmail sur i-mode? : envoyez et recevez des e-mails depuis votre
téléphone portable ! http://www.msn.fr/hotmailimode/
3 - Normal
------------------------------------------------------------------------
BUG-ID: 21835
STATUS: Open
CATEGORY: Accuracy problem
SUMMARY: gsl_sf_hyperg_2F1 problematic arguments
BUG#1 -- gsl_sf_hyperg_2F1_e fails for some arguments
From: [email protected]
Subject: gsl_sf_hyperg_2F1 bug report
Date: Thu, 31 Jan 2002 12:30:04 -0000
gsl_sf_hyperg_2F1_e fails with arguments (1,13,14,0.999227196008978,&r).
It should return 53.4645... .
#include <gsl/gsl_sf.h>
#include <stdio.h>
int main (void)
{
gsl_sf_result r;
gsl_sf_hyperg_2F1_e (1,13,14,0.999227196008978,&r);
printf("r = %g %g\n", r.val, r.err);
}
NOTES: The program overflows the maximum number of iterations in
gsl_sf_hyperg_2F1, due to the presence of a nearby singularity at
(c=a+b,x=1) so the sum is slowly convergent.
The exact result is 53.46451441879150950530608621 as calculated by
gp-pari using sumpos(k=0,gamma(a+k)*gamma(b+k)*gamma(c)*gamma(1)/
(gamma(c+k)*gamma(1+k)*gamma(a)*gamma(b))*x^k)
The code needs to be extended to handle the case c=a+b. This is the
main problem. The case c=a+b is special and needs to be computed
differently. There is a special formula given for it in Abramowitz &
Stegun 15.3.10
As reported by Lee Warren <[email protected]> another set of
arguments which fail are:
#include <gsl/gsl_sf.h>
#include <stdio.h>
int main (void)
{
gsl_sf_result r;
gsl_sf_hyperg_2F1_e (-1, -1, -0.5, 1.5, &r);
printf("r = %g %g\n", r.val, r.err);
}
The correct value is -2.
See also,
From: Olaf Wucknitz <[email protected]>
Subject: [Bug-gsl] gsl_sf_hyperg_2F1
Hi,
I am having a problem with gsl_sf_hyperg_2F1.
With the parameters (-0.5, 0.5, 1, x) the returned values show a jump at
x=0.5. For x<0.5 the results seem to be correct, while for x>0.5 they
aren't.
The function gsl_sf_hyperg_2F1_e calls hyperg_2F1_series for x<0.5, but
hyperg_2F1_reflect for x>0.5. The latter function checks for c-a-b being
an integer (which it is in my case). If I change one of the parameters
a,b,c by a small amount, the other branch of the function is taken and the
results are correct again.
Unfortunately I know too little about the numerics of 2F1 to suggest a
patch at the moment.
Regards,
Olaf Wucknitz
--
Joint Institute for VLBI in Europe [email protected]
------------------------------------------------------------------------
BUG-ID: 21836
STATUS: Open/Confirmed
CATEGORY: Accuracy problem
SUMMARY: gamma_inc_P and gamma_inc_Q only satisfy P+Q=1 within errors
BUG#44 -- gamma_inc_P and gamma_inc_Q only satisfy P+Q=1 within errors
The sum of gamma_inc_P and gamma_inc_Q doesn't always satisfy the
identity P+Q=1 exactly (although it is correct within errors), due the
slightly different branch conditions for the series and continued
fraction expansions. These could be made identical so that P+Q=1 exactly.
#include <stdio.h>
#include <gsl/gsl_sf_gamma.h>
int
main (void)
{
gsl_sf_result r1, r2;
double a = 0.3, x = 1.0;
gsl_sf_gamma_inc_P_e (a, x, &r1);
gsl_sf_gamma_inc_Q_e (a, x, &r2);
printf("%.18e\n", r1.val);
printf("%.18e\n", r2.val);
printf("%.18e\n", r1.val + r2.val);
}
$ ./a.out
9.156741562411074842e-01
8.432584375889111417e-02
9.999999999999985567e-01
3 - NormalNone
------------------------------------------------------------------------
BUG-ID: 21837
STATUS: Open/Confirmed
CATEGORY: Runtime error
SUMMARY: gsl_linalg_solve_symm_tridiag requires positive definite matrix
A zero on the diagonal will cause NaNs even though a reasonable
solution could be computed in principle.
#include <gsl/gsl_linalg.h>
int main (void)
{
double d[] = { 0.00, 1.21, 0.80, 1.55, 0.76 } ;
double e[] = { 0.82, 0.39, 0.09, 0.68 } ;
double b[] = { 0.07, 0.62, 0.81, 0.11, 0.65} ;
double x[] = { 0.00, 0.00, 0.00, 0.00, 0.00} ;
gsl_vector_view dv = gsl_vector_view_array(d, 5);
gsl_vector_view ev = gsl_vector_view_array(e, 4);
gsl_vector_view bv = gsl_vector_view_array(b, 5);
gsl_vector_view xv = gsl_vector_view_array(x, 5);
gsl_linalg_solve_symm_tridiag(&dv.vector, &ev.vector, &bv.vector, &xv.vector);
gsl_vector_fprintf(stdout, &xv.vector, "% .5f");
d[0] += 1e-5;
gsl_linalg_solve_symm_tridiag(&dv.vector, &ev.vector, &bv.vector, &xv.vector);
gsl_vector_fprintf(stdout, &xv.vector, "% .5f");
}
$ ./a.out
nan
nan
nan
nan
nan
0.13626
0.08536
1.03840
-0.60009
1.39219
AUG 2007: We now return an error code for this case. To return a solution
we would need to do a permutation, see slatec/dgtsl.f
3 - NormalNone
------------------------------------------------------------------------
BUG-ID: 24252
STATUS: Open/Confirmed
CATEGORY: None
SUMMARY: suggestion: add gamma tail distribution
From: Laedermann Jean-Pascal <[email protected]>
To: Brian Gough <[email protected]>
Subject: RE : RE : tail gamma
Date: Thu, 11 Sep 2008 08:45:41 +0200
Hello,
It's only a piece of C code I attach here.
The source is the excellent book of Devroye (chapter nine p 420), see attachments.
Hoping this will be useful.
Jean-Pascal Laedermann, PhD
ing. phys. EPFL, math. UNIL
--None
------------------------------------------------------------------------
BUG-ID: 24812
STATUS: Open/Confirmed
CATEGORY: Runtime error
SUMMARY: gsl_sf_hyperg_2F1(11, -1 ; 11/2; 0.125) fails
From: "Didier Pinchon" <[email protected]>
To: <[email protected]>
Subject: [Bug-gsl] Bug in gsl_sf_hyperg_2F1 ??
Date: Sat, 8 Nov 2008 03:00:41 +0100
Hello,
I have tried to compute 2F1(11, -1 ; 11/2; 0.125) and I got an error message (below is my sample program).
However 2F1(-1, 11 ; 11/2; 0.125) provides the right result 0.75
Am I wrong somewhere ?
I did not find any indication in archives.
Thank you for your help.
All the best,
Didier
/* Compilation and execution:
$ gcc -o bug_gsl -I/usr/local/include/gsl bug_gsl.c -L/usr/local/lib -lgsl -lm
$ ./bug_gsl
gsl: hyperg_2F1.c:750: ERROR: error
Default GSL error handler invoked.
Abandon
*/
-line 732:
if(GSL_MAX_DBL(fabs(a),1.0)*fabs(bp)*fabs(x) < 2.0*fabs(c)) {
line 740:
if(fabs(bp*bp*x*x) < 0.001*fabs(bp) && fabs(a) < 10.0) {
I think these should have a=>ap for consistency
------------------------------------------------------------------------
BUG-ID: 24871
STATUS: Open/Confirmed
CATEGORY: None
SUMMARY: suggestion, add support for E_n
Dear GSL group,
Thank you very much for your work on GSL. I use it much in Octave.
I think it would be great if you could improve the GSL routines
for computations of exponential integrals so that they can accept complex arguments too. A good algorithm for this was published in
ACM Transactions on Mathematical Software
Donald E. Amos, Computation of Exponential Integrals of a Complex Argument, vol.16, no. 2, p.169--177, 1990,
http://doi.acm.org/10.1145/78928.78933
ACM Transactions on Mathematical Software
Donald E. Amos, Algorithm 683: A Portable FORTRAN Subroutine for Exponential Integrals of a Complex Argument, vol.16, no. 2,
p.178--182, 1990,
http://doi.acm.org/10.1145/78928.78934
The fortran code is available at
http://www.netlib.org/toms/683
http://www.netlib.no/netlib/toms/683
http://www.mirrorservice.org/sites/netlib.bell-labs.com/netlib/toms/683.gz
http://scicomp.ewha.ac.kr/netlib/toms/683
With best wishes,
Oleg
---
D.Sc. Oleg V. Motygin,
Institute of Problems in Mech Engineering
Russian Academy of Sciences
V.O., Bol'shoj pr. 61
199178 St.Petersburg
Russia
email: [email protected], [email protected]
_______________________________________________
Bug-gsl mailing list
http://lists.gnu.org/mailman/listinfo/bug-gsl
------------------------------------------------------------------------
BUG-ID: 25320
STATUS: Open
CATEGORY: Accuracy problem
SUMMARY: Import fresnel, bugs on GSL Extension Fresnel
The fresnel extension should be imported for the next release, with the following bug report checked.
From: "Toshiro Ohsaki" <[email protected]>
To: <[email protected]>
Subject: [Bug-gsl] Bugs on GSL Extension Fresnel
Date: Wed, 26 Nov 2008 21:07:02 +0900
Dear staff of GNU
I found bugs on GSL Extensions/Applications Fresnel by Andrew Steiner.
This program does not return a correct value, if x is negative.
The original function fresnel_c is coded as,
double fresnel_c(double x)
{
double xx = x*x*pi_2;
double ret_val;
if(xx<=8.0)
ret_val = fresnel_cos_0_8(xx);
else
ret_val = fresnel_cos_8_inf(xx);
return (x<0.0) ? -ret_val : ret_val;
}
.
I think it should be coded as,
double fresnel_c(double x)
{
double xx = x*x*pi_2;
double ret_val;
double sign;
if(xx < 0.0){
xx*=-1.0;
sign=-1.0;
}
else{
sign=1.0;
}
if(xx<=8.0)
ret_val = fresnel_cos_0_8(xx);
else
ret_val = fresnel_cos_8_inf(xx);
ret_val*=sign;
return(ret_val);
}
.
The same correction should be done on the function fresnel_s.
Sincerely yours,
Toshiro Ohsaki
from Tokyo Japan.
_______________________________________________
Bug-gsl mailing list
http://lists.gnu.org/mailman/listinfo/bug-gsl
------------------------------------------------------------------------
BUG-ID: 25383
STATUS: Open/Postponed
CATEGORY: None
SUMMARY: use GSL_ENOPROG instead of GSL_CONTINUE in lmiterate.c
[I think we should use GSL_ENOPROG in lmiterate.c although it could break existing code I guess]
From: "Mark M. Ito" <[email protected]>
Subject: [Bug-gsl] non-linear LS fit example in documentation: bug?
Date: Tue, 20 Jan 2009 15:16:26 -0500
Dear GSL folks,
In section 37.9 "Example programs for Nonlinear Least-Squares Fitting"
in the gsl manual, the main loop says:
do
{
iter++;
status = gsl_multifit_fdfsolver_iterate (s);
printf ("status = %s\n", gsl_strerror (status));
print_state (iter, s);
if (status)
break;
status = gsl_multifit_test_delta (s->dx, s->x,
1e-4, 1e-4);
}
while (status == GSL_CONTINUE && iter < 500);
gsl_multifit_covar (s->J, 0.0, covar);
Shouldn't the "if (status) break;" be an "if (status) continue;"? It is
normal for the solver to return GSL_CONTINUE in which case you want to
continue to iterate. Break exits the do loop completely, no?
-- Mark Ito
________________________________
This has been documented in the manual. Will change in a future release (1.14)3 - NormalConfirmed
------------------------------------------------------------------------