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Solver Pane

The Solver category includes parameters for configuring a solver for a model. A solver computes a dynamic system's states at successive time steps over a specified time span. You also use these parameters to specify the simulation start and stop times.

Once the model compiles, the Solver Information tooltip displays

  • Compiled solver name

  • Step size (Max step size or Fixed step size)

Once the model compiles, the status bar displays the solver used for compiling and a carat (^) when:

  • Simulink® selects a different solver during compilation.

  • You set the step size to auto. The Solver Information tooltip displays the step size that Simulink calculated.

When configuring the solver, note that:

  • Simulation time is not the same as clock time. For example, running a simulation for 10 seconds usually does not take 10 seconds. Total simulation time depends on factors such as model complexity, solver step sizes, and computer speed.

  • Fixed-step solver type is required for code generation, unless you use an S-function or RSim target.

  • Variable-step solver type can significantly shorten the time required to simulate models in which states change rapidly or which contain discontinuities.


Start time

Specify the start time for the simulation or generated code as a double-precision value, scaled to seconds.

Stop time

Specify the stop time for the simulation or generated code as a double-precision value, scaled to seconds.


Select the type of solver you want to use to simulate your model.


Select the solver you want to use to compute the states of the model during simulation or code generation.

Max step size

Specify the largest time step that the solver can take.

Integration method

Specify the integration order of the odeN solver

Initial step size

Specify the size of the first time step that the solver takes.

Min step size

Specify the smallest time step that the solver can take.

Relative tolerance

Specify the largest acceptable solver error, relative to the size of each state during each time step. If the relative error exceeds this tolerance, the solver reduces the time step size.

Absolute tolerance

Specify the largest acceptable solver error, as the value of the measured state approaches zero. If the absolute error exceeds this tolerance, the solver reduces the time step size.

Shape preservation

At each time step use derivative information to improve integration accuracy.

Maximum order

Select the order of the numerical differentiation formulas (NDFs) used in the ode15s solver.

Solver reset method

Select how the solver behaves during a reset, such as when it detects a zero crossing.

Number of consecutive min steps

Specify the maximum number of consecutive minimum step size violations allowed during simulation.

Solver Jacobian Method

Specify the method to compute the Jacobian matrix for an implicit solver.

Daessc mode

Fine-tune the daessc solver performance.

Treat each discrete rate as a separate task

Specify whether Simulink executes blocks with periodic sample times individually or in groups.

Automatically handle rate transition for data transfer

Specify whether Simulink software automatically inserts hidden Rate Transition blocks between blocks that have different sample rates to ensure: the integrity of data transfers between tasks; and optional determinism of data transfers for periodic tasks.

Deterministic data transfer

Control whether the Rate Transition block parameter Ensure deterministic data transfer (maximum delay) is set for auto-inserted Rate Transition blocks.

Higher priority value indicates higher task priority

Specify whether the real-time system targeted by the model assigns higher or lower priority values to higher priority tasks when implementing asynchronous data transfers.

Zero-crossing control

Enables zero-crossing detection during model simulation. For most models, this speeds up simulation by enabling the solver to take larger time steps.

Time tolerance

Specify a tolerance factor that controls how closely zero-crossing events must occur to be considered consecutive.

Number of consecutive zero crossings

Specify the number of consecutive zero crossings that can occur before Simulink software displays a warning or an error.


Specifies the algorithm to detect zero crossings when a variable-step solver is used.

Signal threshold

Specifies the deadband region used during the detection of zero crossings. Signals falling within this region are defined as having crossed through zero.

Periodic sample time constraint

Select constraints on the sample times defined by this model. If the model does not satisfy the specified constraints during simulation, Simulink software displays an error message.

Fixed-step size (fundamental sample time)

Specify the step size used by the selected fixed-step solver.

Sample time properties

Specify and assign priorities to the sample times that this model implements.

Extrapolation order

Select the extrapolation order used by the ode14x solver to compute a model's states at the next time step from the states at the current time step.

Number of Newton's iterations

Specify the number of Newton's method iterations used by the ode14x solver to compute a model's states at the next time step from the states at the current time step.

Allow tasks to execute concurrently on target

Enable concurrent tasking behavior for model.

Auto scale absolute tolerance

Enable automatic absolute tolerance adaptation

Allow multiple tasks to access inputs and outputs

Enable Branched Input Multiple Outputs in rate-based models

Enable zero-crossing detection for fixed-step solver

Enable zero-crossing detection with fixed step

Maximum number of bracketing iterations

Specify maximum number of bracketing iterations that will be performed when locating a zero crossing

Maximum number of zero-crossings per step

Specify the maximum number of zero-crossings Simulink will locate in one fixed-step

Use local solver when referencing model

Speed up simulation in model references using local solvers

These configuration parameters are in the Advanced parameters section.


Enable decoupled continuous integration

Removes the coupling between continuous and discrete rates.

Enable minimal zero-crossing impact integration

Minimizes the impact of zero-crossings on the integration of continuous states.

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