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C++ API

: dassl_options ()
: val = dassl_options (opt)
: dassl_options (opt, val)

Query or set options for the function dassl.

When called with no arguments, the names of all available options and their current values are displayed.

Given one argument, return the value of the option opt.

When called with two arguments, dassl_options sets the option opt to value val.

Options include

"absolute tolerance"

Absolute tolerance. May be either vector or scalar. If a vector, it must match the dimension of the state vector, and the relative tolerance must also be a vector of the same length.

"relative tolerance"

Relative tolerance. May be either vector or scalar. If a vector, it must match the dimension of the state vector, and the absolute tolerance must also be a vector of the same length.

The local error test applied at each integration step is 

 abs (local error in x(i))
      <= rtol(i) * abs (Y(i)) + atol(i)
"compute consistent initial condition"

If nonzero, dassl will attempt to compute a consistent set of initial conditions. This is generally not reliable, so it is best to provide a consistent set and leave this option set to zero.

"enforce nonnegativity constraints"

If you know that the solutions to your equations will always be non-negative, it may help to set this parameter to a nonzero value. However, it is probably best to try leaving this option set to zero first, and only setting it to a nonzero value if that doesn’t work very well.

"initial step size"

Differential-algebraic problems may occasionally suffer from severe scaling difficulties on the first step. If you know a great deal about the scaling of your problem, you can help to alleviate this problem by specifying an initial stepsize.

"maximum order"

Restrict the maximum order of the solution method. This option must be between 1 and 5, inclusive.

"maximum step size"

Setting the maximum stepsize will avoid passing over very large regions (default is not specified).

"step limit"

Maximum number of integration steps to attempt on a single call to the underlying Fortran code.

Package: octave