Product

Multiply and divide scalars and nonscalars or multiply and invert matrices

Library

Math Operations

Description

Default Product Block Use

By default, the Product block outputs the result of multiplying two inputs: two scalars, a scalar and a nonscalar, or two nonscalars that have the same dimensions. The default parameter values that specify this behavior are:

  • Multiplication: Element-wise(.*)

  • Number of inputs: 2

Setting non-default values for either of these parameters can change a Product block to function as a Divide block or a Product of Elements block. See the documentation of those two blocks for more information.

If all you need is to multiply two inputs to create an output, you can use the Product block with default parameter values. If you need additional capabilities, see Product Block Capabilities.

The following table shows the output of the Product block for example inputsexample inputs using default block parameter values.

Inputs and BehaviorExample

Scalar X Scalar

Output the product of the two inputs.

Scalar X Nonscalar

Output a nonscalar having the same dimensions as the input nonscalar. Each element of the output nonscalar is the product of the input scalar and the corresponding element of the input nonscalar.

Nonscalar X Nonscalar

Output a nonscalar having the same dimensions as the inputs. Each element of the output is the product of corresponding elements of the inputs.

Product Block Capabilities

The Product block, the Divide block, and the Product of Elements block are actually the same underlying block with different default values for the Number of inputs parameter. All three blocks can therefore provide the same capabilities. The Product block (or the Divide block or Product of Elements block if appropriately configured) can:

  • Numerically multiply and divide any number of scalar, vector, or matrix inputs

  • Perform matrix multiplication and division on any number of matrix inputs

The Product block performs scalar or matrix multiplication, depending on the value of the Multiplication parameter. The block accepts one or more inputs, depending on the Number of inputs parameter. The Number of inputs parameter also specifies the operation to perform on each input.

The Product block can input any combination of scalars, vectors, and matrices for which the operation to perform has a mathematically defined result. The block performs the specified operations on the inputs, then outputs the result.

The Product block has two modes: Element-wise mode, which processes nonscalar inputs element by element, and Matrix mode, which processes nonscalar inputs as matrices. The next two sections describe these two modes.

Element-wise Mode

When the value of the Multiplication parameter is Element-wise(.*), the Product block is in Element-wise mode, in which it operates on the individual numeric elements of any nonscalar inputs. The MATLAB® equivalent is the .* operator. In element-wise mode, the Product block can perform a variety of multiplication, division, and arithmetic inversion operations.

The value of the Number of inputs parameter controls both how many inputs exist and whether each is multiplied or divided to form the output. When the Product block in Element-wise mode has only one input, it is functionally equivalent to a Product of Elements block. When the block has multiple inputs, any nonscalar inputs must have identical dimensions, and the block outputs a nonscalar with those dimensions. To calculate the output, the block first expands any scalar input to a nonscalar that has the same dimensions as the nonscalar inputs.

This table shows the output of the Product block for example inputsexample inputs, using the indicated values for the Number of inputs parameter.

Parameter ValuesExamples

Number of inputs: 2

Number of inputs: */

Number of inputs: /**/

Number of inputs: **

Number of inputs: */*

Matrix Mode

When the value of the Multiplication parameter is Matrix(*), the Product block is in Matrix mode, in which it processes nonscalar inputs as matrices. The MATLAB equivalent is the * operator. In Matrix mode, the Product block can invert a single square matrix, or multiply and divide any number of matrices that have dimensions for which the result is mathematically defined.

The value of the Number of inputs parameter controls both how many inputs exist and whether each input matrix is multiplied or divided to form the output. The syntax of Number of inputs is the same as in Element-wise mode. The difference between the modes is in the type of multiplication and division that occur.

Expected Differences Between Simulation and Code Generation

For element-wise operations on complex floating-point inputs, simulation and code generation results might differ in near-overflow cases. Although complex numbers is selected and non-finite numbers is not selected on the Code Generation > Interface pane of the Configuration Parameters dialog box, the code generator does not emit special case code for intermediate overflows. This method improves the efficiency of embedded operations for the general case that does not include extreme values. If the inputs might include extreme values, please manage these cases explicitly.

The generated code might not produce the exact same pattern of NaN and inf values as simulation when these values are mathematically meaningless. For example, if the simulation output contains a NaN, output from the generated code also contains a NaN, but not necessarily in the same place.

Data Type Support

The Product block accepts real or complex signals of any numeric data type that Simulink® supports, including fixed-point data types. For more information, see Data Types Supported by Simulink in the Simulink documentation.

The Product block does not support numeric division for complex signals with boolean or fixed-point data types. For other types, the block accepts complex signals as divisors only when the input and output signals all specify the same built-in data type. In this case, however, the block ignores its specified rounding mode.

The Product block accepts multidimensional signals when operating in Element-wise mode, but not when operating in Matrix mode. See Signal Dimensions, Element-wise Mode, and Matrix Mode for more information.

Parameters and Dialog Box

The Main pane of the Product block dialog box appears as follows:

Signal Attributes Pane

The Signal Attributes pane of the Product block dialog box appears as follows:

Show data type assistant

Display the Data Type Assistant.

Settings

The Data Type Assistant helps you set the Output data type parameter.

For more information, see Specify Block Output Data Types.

Number of inputs

Control two properties of the Product block:

  • The number of input ports on the block

  • Whether each input is multiplied or divided into the output

Settings

Default:2

  • 1 or * or /

    Has one input. In Element-wise mode, the input is processed as described for the Product of Elements block. In Matrix mode, if the parameter value is 1 or * the block outputs the input value. If the value is / the input must be a square matrix (including a scalar as a degenerate case) and the block outputs the matrix inverse. See Element-wise Mode and Matrix Mode for more information.

  • An integer value > 1

    Has number of inputs given by the integer value. The inputs are multiplied together in Element-wise mode or Matrix mode, as specified by the Multiplication parameter. See Element-wise Mode and Matrix Mode for more information.

  • An unquoted string of two or more * and / characters

    Has the number of inputs given by the length of the string. Each input that corresponds to a * character is multiplied into the output. Each input that corresponds to a / character is divided into the output. The operations occur in Element-wise mode or Matrix mode, as specified by the Multiplication parameter. See Element-wise Mode and Matrix Mode for more information.

Dependency

Setting Number of inputs to * and selecting Element-wise(.*) for Multiplication enable the following parameter:

  • Multiply over

Command-Line Information

See Block-Specific Parameters for the command-line information.

Multiplication

Specify whether the Product block operates in Element-wise mode or Matrix mode.

Settings

Default: Element-wise(.*)

Element-wise(.*)

Operate in Element-wise mode.

Matrix(*)

Operate in Matrix mode.

Dependency

Selecting Element-wise(.*) and setting Number of inputs to * enable the following parameter:

  • Multiply over

Command-Line Information

See Block-Specific Parameters for the command-line information.

Multiply over

Affect multiplication on matrix input.

Settings

Default: All dimensions

All dimensions

Output a scalar that is product of all elements of the matrix, or the product of their inverses, depending on the value of Number of inputs.

Specified dimension

Output a vector, the composition of which depends on the value of the Dimension parameter.

Dependencies

  • Enable this parameter by selecting Element-wise(.*) for Multiplication and setting Number of inputs to * or 1 or /.

  • Setting this parameter to Specified dimension enables the Dimension parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Dimension

Affect multiplication on matrix input.

Settings

Default: 1

Minimum: 1

Maximum: 2

1

Output a vector that contains an element for each column of the input matrix.

2

Output a vector that contains an element for each row of the input matrix.

Tips

Each element of the output vector contains the product of all elements in the corresponding column or row of the input matrix, or the product of the inverses of those elements, depending on the value of Number of inputs:

  • 1 or *

    Multiply the values of the column or row elements

  • /

    Multiply the inverses of the column or row elements

Dependency

Enable this parameter by selecting Specified dimension for Multiply over.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Sample time (-1 for inherited)

Enter the discrete interval between sample time hits or specify another appropriate sample time such as continuous or inherited.

Settings

Default: -1

By default, the block inherits its sample time based upon the context of the block within the model. To set a different sample time, enter a valid sample time based upon the table in Types of Sample Time.

See also Specify Sample Time in the online documentation for more information.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Require all inputs to have the same data type

Require that all inputs have the same data type.

Settings

Default: Off

On

Require that all inputs have the same data type.

Off

Do not require that all inputs have the same data type.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Lock output data type setting against changes by the fixed-point tools

Select to lock the output data type setting of this block against changes by the Fixed-Point Tool and the Fixed-Point Advisor.

Settings

Default: Off

On

Locks the output data type setting for this block.

Off

Allows the Fixed-Point Tool and the Fixed-Point Advisor to change the output data type setting for this block.

Command-Line Information

Parameter: LockScale
Type: string
Value: 'off' | 'on'
Default: 'off'

See Also

For more information, see Use Lock Output Data Type Setting.

Integer rounding mode

Specify the rounding mode for fixed-point operations.

Settings

Default: Floor

Ceiling

Rounds both positive and negative numbers toward positive infinity. Equivalent to the MATLAB ceil function.

Convergent

Rounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™ convergent function.

Floor

Rounds both positive and negative numbers toward negative infinity. Equivalent to the MATLAB floor function.

Nearest

Rounds number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer nearest function.

Round

Rounds number to the nearest representable value. If a tie occurs, rounds positive numbers toward positive infinity and rounds negative numbers toward negative infinity. Equivalent to the Fixed-Point Designer round function.

Simplest

Automatically chooses between round toward floor and round toward zero to generate rounding code that is as efficient as possible.

Zero

Rounds number toward zero. Equivalent to the MATLAB fix function.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

For more information, see Rounding.

Saturate on integer overflow

Specify whether overflows saturate.

Settings

Default: Off

On

Overflows saturate to either the minimum or maximum value that the data type can represent.

For example, an overflow associated with a signed 8-bit integer can saturate to -128 or 127.

Off

Overflows wrap to the appropriate value that is representable by the data type.

For example, the number 130 does not fit in a signed 8-bit integer and wraps to -126.

Tips

  • Consider selecting this check box when your model has possible overflow and you want explicit saturation protection in the generated code.

  • Consider clearing this check box when you want to optimize efficiency of your generated code.

    Clearing this check box also helps you avoid overspecifying how a block handles out-of-range signals. For more information, see Checking for Signal Range Errors.

  • When you select this check box, saturation applies to every internal operation on the block, not just the output or result.

  • In general, the code generation process can detect when overflow is not possible. In this case, the code generator does not produce saturation code.

Command-Line Information

Parameter: SaturateOnIntegerOverflow
Type: string
Value: 'off' | 'on'
Default: 'off'

Output minimum

Lower value of the output range that Simulink checks.

Settings

Default: [] (unspecified)

Specify this number as a finite, real, double, scalar value.

    Note:   If you specify a bus object as the data type for this block, do not set the minimum value for bus data on the block. Simulink ignores this setting. Instead, set the minimum values for bus elements of the bus object specified as the data type. For information on the Minimum parameter for a bus element, see Simulink.BusElement.

Simulink uses the minimum to perform:

    Note:   Output minimum does not saturate or clip the actual output signal. Use the Saturation block instead.

Command-Line Information

Parameter: OutMin
Type: string
Value: '[ ]'
Default: '[ ]'

Output maximum

Upper value of the output range that Simulink checks.

Settings

Default: [] (unspecified)

Specify this number as a finite, real, double, scalar value.

    Note:   If you specify a bus object as the data type for this block, do not set the maximum value for bus data on the block. Simulink ignores this setting. Instead, set the maximum values for bus elements of the bus object specified as the data type. For information on the Maximum parameter for a bus element, see Simulink.BusElement.

Simulink uses the maximum value to perform:

    Note:   Output maximum does not saturate or clip the actual output signal. Use the Saturation block instead.

Command-Line Information

Parameter: OutMax
Type: string
Value: '[ ]'
Default: '[ ]'

Output data type

Specify the output data type.

Settings

Default: Inherit: Inherit via internal rule

Inherit: Inherit via internal rule

Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware. If you change the embedded target settings, the data type selected by the internal rule might change. It is not always possible for the software to optimize code efficiency and numerical accuracy at the same time. If the internal rule doesn't meet your specific needs for numerical accuracy or performance, use one of the following options:

  • Specify the output data type explicitly.

  • Use the simple choice of Inherit: Same as first input.

  • Explicitly specify a default data type such as fixdt(1,32,16) and then use the Fixed-Point Tool to propose data types for your model. For more information, see fxptdlg.

  • To specify your own inheritance rule, use Inherit: Inherit via back propagation and then use a Data Type Propagation block. Examples of how to use this block are available in the Signal Attributes library Data Type Propagation Examples block.

Inherit: Inherit via back propagation

Use data type of the driving block.

Inherit: Same as first input

Use data type of the first input signal.

double

Output data type is double.

single

Output data type is single.

int8

Output data type is int8.

uint8

Output data type is uint8.

int16

Output data type is int16.

uint16

Output data type is uint16.

int32

Output data type is int32.

uint32

Output data type is uint32.

fixdt(1,16,0)

Output data type is fixed point fixdt(1,16,0).

fixdt(1,16,2^0,0)

Output data type is fixed point fixdt(1,16,2^0,0).

<data type expression>

Use a data type object, for example, Simulink.NumericType.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

For more information, see Specify Block Output Data Types.

Mode

Select the category of data to specify.

Settings

Default: Inherit

Inherit

Inheritance rules for data types. Selecting Inherit enables a second menu/text box to the right. Select one of the following choices:

  • Inherit via internal rule (default)

  • Inherit via back propagation

  • Same as first input

Built in

Built-in data types. Selecting Built in enables a second menu/text box to the right. Select one of the following choices:

  • double (default)

  • single

  • int8

  • uint8

  • int16

  • uint16

  • int32

  • uint32

Fixed point

Fixed-point data types.

Expression

Expressions that evaluate to data types. Selecting Expression enables a second menu/text box to the right, where you can enter the expression.

Dependency

Clicking the Show data type assistant button enables this parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specify Data Types Using Data Type Assistant.

Data type override

Specify data type override mode for this signal.

Settings

Default: Inherit

Inherit

Inherits the data type override setting from its context, that is, from the block, Simulink.Signal object or Stateflow® chart in Simulink that is using the signal.

Off

Ignores the data type override setting of its context and uses the fixed-point data type specified for the signal.

Tip

The ability to turn off data type override for an individual data type provides greater control over the data types in your model when you apply data type override. For example, you can use this option to ensure that data types meet the requirements of downstream blocks regardless of the data type override setting.

Dependency

This parameter appears only when the Mode is Built in or Fixed point.

Signedness

Specify whether you want the fixed-point data as signed or unsigned.

Settings

Default: Signed

Signed

Specify the fixed-point data as signed.

Unsigned

Specify the fixed-point data as unsigned.

Dependencies

Selecting Mode > Fixed point enables this parameter.

See Also

For more information, see Specifying a Fixed-Point Data Type.

Word length

Specify the bit size of the word that holds the quantized integer.

Settings

Default: 16

Minimum: 0

Maximum: 32

Dependencies

Selecting Mode > Fixed point enables this parameter.

See Also

For more information, see Specifying a Fixed-Point Data Type.

Scaling

Specify the method for scaling your fixed-point data to avoid overflow conditions and minimize quantization errors.

Settings

Default: Best precision

Binary point

Specify binary point location.

Slope and bias

Enter slope and bias.

Best precision

Specify best-precision values.

Dependencies

Selecting Mode > Fixed point enables this parameter.

Selecting Binary point enables:

  • Fraction length

  • Calculate Best-Precision Scaling

Selecting Slope and bias enables:

  • Slope

  • Bias

  • Calculate Best-Precision Scaling

See Also

For more information, see Specifying a Fixed-Point Data Type.

Fraction length

Specify fraction length for fixed-point data type.

Settings

Default: 0

Binary points can be positive or negative integers.

Dependencies

Selecting Scaling > Binary point enables this parameter.

See Also

For more information, see Specifying a Fixed-Point Data Type.

Slope

Specify slope for the fixed-point data type.

Settings

Default: 2^0

Specify any positive real number.

Dependencies

Selecting Scaling > Slope and bias enables this parameter.

See Also

For more information, see Specifying a Fixed-Point Data Type.

Bias

Specify bias for the fixed-point data type.

Settings

Default: 0

Specify any real number.

Dependencies

Selecting Scaling > Slope and bias enables this parameter.

See Also

For more information, see Specifying a Fixed-Point Data Type.

Characteristics

Direct Feedthrough

Yes

Sample Time

Specified in the Sample time parameter

Scalar Expansion

Yes

Dimensionalized

Yes

Multidimensionalized

Yes, only when the Multiplication parameter specifies Element-wise(.*)

Zero-Crossing Detection

No

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