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# 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 if`itask`

equals 4 or 5 as described above`h0`

first step tried`hmax`

max step size`hmin`

min step size`jactype`

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`

and`mu`

below) - 5 : internally generated banded jacobian
(see
`ml`

and`mu`

below)

- 0: functional iterations, no jacobian used
(
`maxordn`

maximum non-stiff order allowed, at most 12`maxords`

maximum stiff order allowed, at most 5`ixpr`

print level, 0 or 1`ml`

,`mu`

If

`jactype`

equals 4 or 5,`ml`

and`mu`

are the lower and upper half-bandwidths of the banded jacobian: the band is the`i,j`

's with`i-ml`

<=`j`

<=`ny-1`

.If

`jactype`

equals 4 the jacobian function must return a matrix`J`

which is`ml+mu+1 x ny`

(where`ny=dim`

of`y`

in`ydot=f(t,y))`

such that column 1 of`J`

is made of`mu`

zeros followed by`df1/dy1`

,`df2/dy1`

,`df3/dy1`

, ... (`1+ml`

possibly non-zero entries), column 2 is made of`mu-1`

zeros followed by`df1/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 — ordinary differential equation solver

## Comments

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