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# ode_optional_output

ode solvers optional outputs description

### Description

This page describes the most important values returned in the
optional lhs ode function arguments `w`

and
`iw`

.
These are valid only for the `lsode`

,
`lsoda`

and `lsodar`

ode solver.
For more details, one can look at the solvers fortran code comments in `SCI/modules/differential_equations/src/fortran/lsod*.f`

.

- w(11)
the step size in t last used (successfully).

- w(12)
the step size to be attempted on the next step.

- w(13)
the current value of the independent variable which the solver has actually reached, i.e. the current internal mesh point in t. On output, tcur will always be at least as far as the argument t, but may be farther (if interpolation was done).

- w(14)
a tolerance scale factor, greater than 1.0, computed when a request for too much accuracy was detected (istate = -3 if detected at the start of the problem, istate = -2 otherwise). If itol is left unaltered but rtol and atol are uniformly scaled up by a factor of

`tolsf=w(14)`

for the next call, then the solver is deemed likely to succeed. (The user may also ignore`tolsf`

and alter the tolerance parameters in any other way appropriate.)- w(15)
the value of t at the time of the last method switch, if any. This value is not significant with

`lsode`

solver.- iw(10)
the number of

`g`

evaluations for the problem so far. This value is only significant for`lsodar`

solver.- iw(11)
the number of steps taken for the problem so far.

- iw(12)
the number of f evaluations for the problem so far.

- iw(13)
the number of jacobian evaluations (and of matrix lu decompositions) for the problem so far.

- iw(14)
the method order last used (successfully).

- iw(15)
the order to be attempted on the next step.

- iw(16)
the index of the component of largest magnitude in the weighted local error vector ( e(i)/ewt(i) ), on an error return with istate = -4 or -5.

- iw(17)
the length of

`w`

actually required, assuming that the length of rwork is to be fixed for the rest of the problem, and that switching may occur. This is defined on normal returns and on an illegal input return for insufficient storage.- iw(18)
the length of

`iw`

actually required, assuming that the length of`iw`

is to be fixed for the rest of the problem, and that switching may occur. This is defined on normal returns and on an illegal input return for insufficient storage.- iw(19)
the method indicator for the last successful step. 1 means adams (nonstiff), 2 means bdf (stiff). This value is not significant with

`lsode`

solver.- iw(20)
the current method indicator. 1 means adams (nonstiff), 2 means bdf (stiff). This is the method to be attempted on the next step. Thus it differs from

`iw(19)`

only if a method switch has just been made. This value is not significant with`lsode`

solver.

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