odeoptions
set options for ode solvers
Syntax
odeoptions()
Description
This function interactively displays a command which should be
executed to set various options of ode solvers. The context variable
%ODEOPTIONS
sets the options.
The ode function checks if this variable
exists and in this case it uses it. For using default values you should
clear this variable. To create it you must execute the instruction
%ODEOPTIONS=odeoptions() . |
The variable %ODEOPTIONS
is a vector with the
following elements:
[itask, tcrit, h0, hmax, hmin, jactyp, mxstep, maxordn, maxords, ixpr, ml, mu]
.
The default value is: [1,0,0,%inf,0,2,500,12,5,0,-1,-1].
The meaning of the elements is described below.
itask
sets the integration mode:- 1: normal computation at specified times
- 2 : computation at mesh points (given in first row of output of
ode
) - 3 : one step at one internal mesh point and return
- 4 : normal computation without overshooting
tcrit
- 5 : one step, without passing
tcrit
, and return
tcrit
critical time used only ifitask
equals 4 or 5 as described aboveh0
first step triedhmax
max step sizehmin
min step sizejactype
set jacobian properties:- 0: functional iterations, no jacobian used
(
"adams"
or"stiff"
only) - 1 : user-supplied full jacobian
- 2 : internally generated full jacobian
- 3: internally generated diagonal jacobian
(
"adams"
or"stiff"
only) - 4 : user-supplied banded jacobian (see
ml
andmu
below) - 5 : internally generated banded jacobian
(see
ml
andmu
below)
- 0: functional iterations, no jacobian used
(
maxordn
maximum non-stiff order allowed, at most 12maxords
maximum stiff order allowed, at most 5ixpr
print level, 0 or 1ml
,mu
If
jactype
equals 4 or 5,ml
andmu
are the lower and upper half-bandwidths of the banded jacobian: the band is thei,j
's withi-ml
<=j
<=ny-1
.If
jactype
equals 4 the jacobian function must return a matrixJ
which isml+mu+1 x ny
(whereny=dim
ofy
inydot=f(t,y))
such that column 1 ofJ
is made ofmu
zeros followed bydf1/dy1
,df2/dy1
,df3/dy1
, ... (1+ml
possibly non-zero entries), column 2 is made ofmu-1
zeros followed bydf1/dx2
,df2/dx2
, etc.
Examples
In the following example, we solve the Ordinary Differential Equation
dy/dt=y^2-y sin(t)+cos(t)
with the initial
condition y(0)=0
claiming the solution be stored at each mesh value.
See also
- ode — solveur d'équations différentielles ordinaires
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