Variant Sink

R2026b

Route amongst multiple outputs using variants

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Variant Sink block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Simulink / Signal Routing

Description

The Variant Sink block enables you to include multiple implementations of a component on the destination (sink) of a signal in a single layer.

For example, suppose you want to simulate this model to control the speed of the car windshield wiper by using different rain sensors. The Variant Source block switches between different rain sensors. The control logic uses this information to output the result to the Variant Sink block. The Variant Sink then switches between the wiper motor model during simulation and the D/A (Digital-to-Analog) block output during code generation. The variant blocks switch between choices based on the Types of Variant Control Modes in Variant Blocks you select. For more information, see Introduction to Variant Controls.

Note

At most, one variant choice connected to output port of the Variant Sink block is active during simulation.

The Variant Sink block has only one input port and one or more output ports. You can connect the varying choices to the output port of the block so that, at most, one choice is active during model execution.

The Variant Sink block is associated with a Variant control mode and a Variant activation time. The variant control mode determines how to specify the variant control. The variant activation time determines a time to activate the choices and to decide whether to include only the active choice or both active and inactive choices in the generated code. During simulation, Simulink^® connects the active choice directly to the input port of the Variant Sink block and ignores the inactive choices.

Using a Variant Sink block allows you to:

• Propagate variant conditions throughout the model.

• Visualize all possible implementations of variant choices in a single layer of your model, which improves model readability.

• Simulink eliminates inactive blocks throughout the model, which improves runtime performance. If all the variant choices are inactive, Simulink removes the variant region completely from your model.

• Variant sources and sinks provide variant component interfaces that you can use to quickly model variant choices.

The color and icon of the variant badge on the block icon changes depending on the values of the Variant activation time, Variant control mode, and Allow zero active variant controls parameters set on the block. For more information, see Variant Badges.

Examples

Variant Source and Variant Sink Blocks

Consider the slexVariantSourceAndSink model containing two Variant Source blocks Variant Source1 and Variant Source2, and a Variant Sink block. The variant conditions at the inports and the outports of the Variant Source and the Variant Sink blocks determine the activation and deactivation of the blocks connected to them. V and W are the variant control variables and are defined in the PostLoadFcn callback of the model.

• Open Script

Limitations

The Variant Sink block works with time-based, function-call, and action signals. You cannot use SimEvents^®, Simscape™ Multibody™, or other non-time-based signals with these blocks.

Ports

Input

Port_1 — Input signal

scalar | vector | matrix

Input signal to be connected to the active output port.

You can auto insert inport on the Variant Sink block by hovering the mouse over the block side or by dragging the signal near the block boundary. You can delete the port by either clicking delete on the keyboard or with a mouse click.

Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus | struct

Output

Port_1 — Output from first variant

scalar | vector | matrix

Output signal from the first variant. The variant control that evaluates to true determines which output port is active.

You can auto insert outport on the Variant Sink block by hovering the mouse over the block side or by dragging the signal near the block boundary. You can delete the port by either clicking delete on the keyboard or with a mouse click.

Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Port_N — Output from Nth variant

scalar | vector | matrix

Output signal from the Nth variant. The variant control that evaluates to true determines which output port is active.

Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Parameters

Variant control mode — Variant control mode

expression (default) | label | sim codegen switching

The variant control that determines the active variant choice can be any of these types.

• expression — The software chooses the active variant based on the evaluation of the variant conditions. When a condition expression evaluates to true, the corresponding variant choice becomes active. When a condition expression evaluates to false, the corresponding variant choice becomes inactive. See Switch Between Choices Using Condition Expressions in Variant Blocks.

• label — The software chooses the active variant based on the name of the variant. The variant control is a string and does not require you to create any variable in any workspaces. See Switch Between Choices Using Labels in Variant Blocks.

• sim codegen switching — Automatically switch between the variants for simulation and code generation workflows without creating any workspace variable. When you simulate a model, the software automatically chooses the sim branch as the active choice. Similarly, when you do a software-in-the-loop (SIL) or processor-In-Loop (PIL) simulation, generate code, or use external mode, the software automatically chooses the codegen branch. See Switch Between Choices for Simulation and Code Generation Workflows Without Using Control Variables in Variant Blocks.

For more information on variant control modes, see Introduction to Variant Controls. For a comparison between different types of variant control modes, see Compare Different Types of Variant Control Modes in Variant Blocks.

Dependencies

The availability of different variant activation times depends on the type of the Variant control mode that you specify. The Variant activation time parameter determines the time when the software sets the active choice. The parameter also determines which variability to include in the generated code. This table explains the variant activation time supported by each variant control mode.

Variant activation time
Variant control mode	update diagram	update diagram analyze all choices	code compile	startup
expression	✓	✓	✓	✓
label	✓	x	x	x
sim codegen switching	✓	✓	x	x

Programmatic Use

Block Parameter: VariantControlMode

Type: character vector

Values: 'expression' | 'label' | 'sim codegen switching'

Default: 'expression'

Variant activation time — Time when software chooses active variant choice

update diagram (default) | update diagram analyze all choices | code compile | startup | inherit from Simulink.VariantControl

This parameter determines which variability to include in the simulation and code generation workflows. For more information, see Activate Variant During Different Stages of Simulation and Code Generation Workflow.

• update diagram — When you execute the model, only the active choice is included in the simulation and the code generation workflow. Generated code contains only the active choice.

• update diagram analyze all choices — When you execute the model, both active and inactive choices are analyzed for consistency across the model. However, only the active choice is included in the simulation and the code generation workflow. Generated code contains only the active choice.

• code compile — When you execute the model, both active and inactive choices are analyzed for consistency across the model, and all choices are included in the simulation and the code generation workflow. Generated code contains both the active and inactive choices enclosed in the preprocessor conditionals #if and #elif. However, the executable built from the generated code contains only active choice.

• startup — When you execute the model, both active and inactive choices are analyzed for consistency across the model, and all choices are included in the simulation and the code generation workflow. With this option, you can improve the speed of iterative simulations using fast restart. For more information, see Run Iterative Simulations Without Recompiling Model for Variant Systems Using Fast Restart. Code generated from the model contains both the active and inactive choices that are enclosed in regular if conditions. The executable built from the generated code also contains both active and inactive choices.

• inherit from Simulink.VariantControl — When you execute the model, the block inherits the activation time from its variant control variables of type Simulink.VariantControl. If a variant block has multiple variant control variables of type Simulink.VariantControl, then all those variables must have the same activation time.

Dependencies

The availability of different variant activation times depends on the type of the variant control mode that you specify. The Variant activation time parameter determines when the software sets the active choice. The parameter also determines which variability to include in the generated code. This table explains the variant activation time supported by each variant control mode.

Variant activation time
Variant control mode	update diagram	update diagram analyze all choices	code compile	startup
expression	✓	✓	✓	✓
label	✓	x	x	x
sim codegen switching	✓	✓	x	x

Programmatic Use

Block Parameter: VariantActivationTime

Type: character vector

Values: 'update diagram' | 'update diagram analyze all choices' | 'code compile' | 'startup'

Default: 'update diagram'

Port and associated conditions — Table of variant choices, variant controls, and conditions

empty table (default)

The table has a row for each variant choice connected to the output port of the Variant Sink block. If there are no variant choices, the table is empty.

You can use buttons to the left of the Port and associated conditions table to modify the elements in the table.

To...	Click...
Add a new output port: Create a new output port as a variant choice and add an entry for the new choice in the table.
Delete selected port: Delete the selected variant choices from the block and their entries from the table. Alternatively, you can remove the selected variant choices by pressing the Delete key on your keyboard.
Create/Edit selected variant object: Create or edit a Simulink.VariantExpression object for the selected variant choice in the global workspace and specify the variant condition using the Simulink.VariantExpression object parameter dialog box. Note For a model that uses the base workspace, this operation creates the Simulink.VariantExpression object in the base workspace, and the object is available only for the current MATLAB® session. To permanently store the data, save the object in a MAT file or MATLAB script.

Port — Number of connected output port

no default

Number of the output port that is connected to one variant choice upstream of the Variant Sink block. This value is read-only.

Click to add a port or to delete an existing one.

Variant control label — Name of choice in label mode

true or false (default) | string

A name for a choice, specified as a string.

Dependencies

To enable this parameter, set Variant control mode to label.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	VariantControls
Values:	variant controls that are associated with variant choices
Data Types:	char

Example: set_param(gcb, 'VariantControls', {'A == 1','A == 2'}), where gcb is the Variant Sink or Variant Source block.

Example: get_param(gcb, 'VariantControls'), where gcb is the Variant Sink or Variant Source block.

Variant control switch — Variant choices for simulation and code generation workflows

(sim) | (codegen)

Specify (sim) to activate the corresponding variant choice during simulation. Specify (codegen) to activate the corresponding variant choice while performing code generation workflows such as SIL, PIL, external mode, and so on.

Dependencies

To enable this parameter, set Variant control mode to sim codegen switching.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	VariantControls
Values:	variant controls that are associated with variant choices
Data Types:	char

Example: set_param(gcb, 'VariantControls', {'(sim)','(codegen)'}), where gcb is the Variant Sink or Variant Source block.

Example: get_param(gcb, 'VariantControls'), where gcb is the Variant Sink or Variant Source block.

Variant control expression — Condition expression that determines the active choice

true or false (default) | boolean condition expression | a Simulink.VariantExpression object representing a boolean condition expression | (default)

Specify the condition expression to determine the active choice. When a condition expression evaluates to true, the software activates the corresponding variant choice. When a condition expression evaluates to false, the software deactivates the corresponding variant choice.

The variant controls can be:

• Boolean condition expression for rapid prototyping. For example, A == 1, A ~= B, A && B == 1, and so on.

• A Simulink.VariantExpression object that contains a condition expression for condition reuse. See Use Simulink.VariantExpression Objects for Variant Condition Reuse of Variant Blocks.

• Default Variant Choice if none of the choices evaluates to true.

Here, A and B are operands called as variant control variables. ==, ~=, and && are operators in the condition expression. The condition expression can contain one or more such variant control variables and operators. For information on supported types and storage location of variant control variables, see Types of Variant Control Variables (Operands) in Variant Blocks. For information on operators, see Types of Operators in Variant Blocks for Different Activation Times.

For more information, see Switch Between Choices Using Condition Expressions in Variant Blocks.

In Variant Assembly Subsystem block, this parameter is a list of auto-generated boolean expressions with Variant control variable on the left-hand side and the members of the Variant enumeration choice are on the right-hand side of the expressions. Both the sides of the expressions are connected with ==. This parameter is read-only.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

The programmatic parameter name is VariantControl for Variant Subsystem blocks, and VariantControls for Variant Source, Variant Sink, and Variant Start blocks. See Hierarchical Variant Block Parameters and Inline Variant Block Parameters.

Variant Subsystem block:

Parameter:	VariantControl
Values:	variant control that is associated with the variant choice
Data Types:	char

Example: set_param(gcb, 'VariantControl', 'V == 3'), where gcb is the variant choice of the Variant Subsystem block.

Example: get_param(gcb, 'VariantControl'), where gcb is the variant choice of the Variant Subsystem block.

Variant Source, Variant Sink, and Variant Start blocks:

Parameter:	VariantControls
Values:	variant controls that are associated with variant choices
Data Types:	char

Example: set_param(gcb, 'VariantControls', {'A == 1','A == 2'}), where gcb is the Variant Sink, Variant Source, or Variant Start block.

Example: get_param(gcb, 'VariantControls'), where gcb is the Variant Sink, Variant Source, or Variant Start block.

Condition (read-only) — Condition expression in Simulink.VariantExpression object

Read-only: N/A (default)

This parameter is read-only.

This parameter displays the condition expression specified as Simulink.VariantExpression object. To change or edit the condition expression, use the Simulink.VariantExpression parameter dialog box that appears when you double-click the object in the workspace.

Note

The operands that you specify in a condition expression of type Simulink.VariantExpression must be defined in the base workspace or a data dictionary. Specifying operands that are defined in the mask or model workspace is not supported.

Label mode active choice — Name of active choice in label mode

true (Subsystem) (default) | false (Subsystem1)

This list contains the labels of all the variant choices. To set an active choice, select a label from the list. The corresponding choice becomes active. Alternatively, to change the active choice in label mode, you can follow the approaches described in Set Active Choices Using Variant Control Labels.

Dependencies

To enable this parameter, set Variant control mode to label.

Programmatic Use

Parameter: LabelModeActiveChoice

Type: character vector

Value: If no label mode active choice is specified, the value is empty. If a label mode active choice is specified, the value is the variant control label for the active choice.

Default: ''

Allow zero active variant controls — Simulate model without active variant choice

off (default) | on

• off — Simulink generates an error when there is no active variant choice.

• on — When you select this parameter and if there is no active variant choice, Simulink simulates the model without any active variant choice connected to the Variant Sink block. Simulink disconnects all the blocks connected to the input and output stream of Variant Sink block, thus removing the variant regions completely from the model execution.

Consider the car windshield wiper example in the Description section. Suppose you do not want to pass the wiper speed to either of the variant choices, wiper motor and D/A. When you simulate the model with Allow zero active variant controls set to on and if there is no active variant choice in the Variant Sink controlled by mode block, Simulink disconnects the Variant Sink controlled by mode block and all its connected blocks, which removes the variant region completely from the model.

This table shows the code that you generate with and without the Allow zero active variant controls parameter for the code compile activation time. In the code that you generate with Allow zero active variant controls set to off, only the variant choices wiper motor and D/A are conditional, whereas the Gain block is unconditional. The Gain block is unconditional, and so it executes for either of the choices. This code support only scenarios where either of the choices evaluate to true. If none of the choices evaluate to true, both the choices are removed from compilation. The output of the Gain remains unused and this results in an error. In the code that you generate with Allow zero active variant controls set to on, the variant choices wiper motor, D/A, and the connected Gain blocks are conditional. So, if none of the choices evaluate to true, the Gain block is also removed, thus enabling you to completely remove the variant region from code compilation.

Generated code without Allow zero active variant controls	Generated code with Allow zero active variant controls
/* If none of the conditions Mode == 1 or Mode == 2 evaluate to true, the output of Gain remains unused which resuls in an error.*/ /* logic for Gain; */ # if Mode == 1 /* logic for wiper motor; */ # elif Mode == 2 /* logic for digital to analog conversion; */ # endif	# if Mode == 1 /* logic for wiper motor; */ # elif Mode == 2 /* logic digital to analog conversion; */ # endif /* The logic for Gain is executed only if either of the conditions evaluate to true. Gain is removed from code compilation if none of the condition evaluates to true. */ # if (Mode == 1) ∥ (Mode == 2) /* logic for Gain; */ # endif

Dependencies

This parameter is available only if you set Variant control mode to expression.

Programmatic Use

Block Parameter: AllowZeroVariantControls

Type: character vector

Values: 'off' | 'on'

Default: 'off'

Show variant condition on block — Annotate block ports

off (default) | on

When you select this option, Simulink annotates the variant condition expression on each port of the Variant Sink block.

Programmatic Use

Block Parameter: ShowConditionOnBlock

Type: character vector

Values: 'off' | 'on'

Default: 'off'

Block Characteristics

Data Types	Boolean | bus | double | enumerated | fixed point | half | image | integer | single | string
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"simulink/Signal Routing/Variant Sink"

Example: add_block("simulink/Signal Routing/Variant Sink","myModel/myBlock",MakeNameUnique="on")

For information about programmatic access to individual block parameters, see the Programmatic Use section of parameter descriptions on this page.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced in R2016a

R2026b: Delete key support for removing variant choices

To remove variant choices from the Variant Source and Variant Sink blocks, select the entries for the variant choices in the Port and associated conditions table and press the Delete key on your keyboard. This action is equivalent to clicking the Delete selected port button in the Port and associated conditions table.

R2025a: Detect undefined variant control variables during edit-time

The Variant Source and Variant Sink blocks issue errors by displaying a red border for undefined variant control variables during model editing. To see a description of the error, pause on the highlighted block, and then click the error symbol to open the notification dialog box with predefined fixes. Select the most appropriate fix, and click the Fix button. You may need to provide additional information to resolve the error. If successful, the red border disappears. If not, a failure message appears.