solver_settings

**This is an old revision of the document!**

The solver tab lets you choose which Ordinary Differential Equation (ODE) solver is to be used in the simulation.

Absolute error tolerances that apply to the individual components of the solution vector. Absolute tolerance is a threshold value below which the value of the solution component is unimportant. The absolute error tolerances determine the accuracy when the solution approaches zero. The setting is globally defined in the solver tab but can be overridden if defined explicitly in a compartment.

*Default value = auto*

Number of step size violations before displaying warning messages.

*Default value = 1*

==Enable saturation== – When saturation is enabled, non-negativeness in Compartments are imposed. If imposed and non-negative is defined in the Compartment the inventory cannot be negative.

_Default value = disabled_

**Fixed-step size (fundamental sample time)** - Step size for the fixed-step solver. The default is one-fiftieth of the simulation interval.

_Default value = auto_

**Initial step size** - Suggested initial step size. Initial step size sets an upper bound on the magnitude of the first step size the solver tries. If you do not set Initial step size, the initial step size is based on the slope of the solution at the initial time, and if the slope of all solution components is zero, the procedure might try a step size that is much too large. If you know this is happening or you want to be sure that the solver resolves important behaviour at the start of the integration, help the code start by providing a suitable Initial step size.

_Default value = auto_

**Limit data points to last** - Maximum number of data-points to store at workspace variables.

_Default value = 1000_

**LU decomposition matrix format** - Data format while solving the LU-decomposition.

_Alternatives = Auto, Dense and Sparse_

_Default value = Dense_

**Max order** - Maximum order formula used to compute the solution.

_Default value = 5_

**Max step size** - Maximum step size for variable-step solver. The default is one-fiftieth of the simulation interval.

_Default value = auto_

**Min step size** - Minimum step size for variable-step solver.

_Default value = auto_

**Norm control** - Control the error relative to the norm of the solution.

_Default value = disabled_

**Refine** - Increases the number of output points by a factor of Refine. If Refine is 1, the solver returns solutions only at the end of each time step. If Refine is n >1, the solver subdivides each time step into n smaller intervals and returns solutions at each time point. The extra values produced for Refine are computed by means of continuous extension formulas. These are specialized formulas used by the ODE solvers to obtain accurate solutions between computed time steps without significant increase in computation time.

_Default value = 1_

**Relative tolerance** - Relative error tolerance that applies to all components of the solution vector y. This tolerance is a measure of the error relative to the size of each solution component. Roughly, it controls the number of correct digits in all solution components, except those smaller than thresholds defined in Absolute tolerance. The default, 1e-3, corresponds to 0.1% accuracy.

_Default value = 0.0010_

solver_settings.1439475090.txt.gz · Last modified: 2015/08/13 15:11 (external edit)