bugGNU Scientific Library - Bugs: bug #30947, Please, include fixed step size...

 
 

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bug #30947: Please, include fixed step size control object for ode suite

Submitted by:  Sergey B Kirpichev <skirpichev>
Submitted on:  Thu 02 Sep 2010 11:49:47 AM UTC  
 
Category:  None Severity:  3 - Normal
Operating System:  Status:  None
Assigned to:  None Open/Closed:  Open
Release: 

Sun 01 May 2011 11:16:21 AM UTC, comment #2:

> one important reason for the evolve level functions is to allow
> for variable step size.


No. Just to allow adaptive step size control. Why don't
consider the *evolve_apply with fixed step as just a special case?

> If you really require a fixed step size for the stepper level, then
> you can use the for loop around step_apply function shown in the manual.


Of cource, I can (it WAS noted in bugreport). Sometimes it's just not
convinient, e.g. to use different loops for fixed and variable step sizes.

> Also, I'm afraid that using your cfxd may not guarantee the use of a
> fixed step size; also evolve_apply can change the step length,
> so you might have to have a function something like
> "evolve_apply_fixed_step_size" to do the job.


Why? fc_control_hadjust() always returns GSL_ODEIV_HADJ_NIL - there
is no reason to change step size.

See also thread in bug-gsl:
http://lists.gnu.org/archive/html/bug-gsl/2010-09/msg00001.html

Sergey B Kirpichev <skirpichev>
Fri 03 Sep 2010 07:51:53 AM UTC, comment #1:

Hi,

one important reason for the evolve level functions is to allow for variable step size. If you really require a fixed step size for the stepper level, then you can use the for loop around step_apply function shown in the manual.

Also, I'm afraid that using your cfxd may not guarantee the use of a fixed step size; also evolve_apply can change the step length, so you might have to have a function something like "evolve_apply_fixed_step_size" to do the job.

BR,
Tuomo

Tuomo Keskitalo <tkeskita>
Project Member
Thu 02 Sep 2010 11:49:47 AM UTC, original submission:

For now fixed step size and adaptive iterations uses different routines (low level gsl_odeiv_step_apply for fixed step size vs gsl_odeiv_evolve_apply).

Attached patch add the control object for the first case.

Sergey B Kirpichev <skirpichev>

 

Attached Files

 

Depends on the following items: None found

Items that depend on this one: None found

 

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    Follows 1 latest change.

    Date Changed by Updated Field Previous Value => Replaced by
    2010-09-02 skirpichev Attached File- => Added 0001-Fixed-step-size-control-object.patch, #21376

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