Resource Sharing Parameters for Adders and Multipliers

This page describes configuration parameters that reside in the HDL Code Generation > Optimization > Resource sharing tab of the Configuration Parameters dialog box. Enable these parameters to save resources on the target device by specifying whether to share adders and multipliers in your design, and the minimum sharing bitwidth.

Share Adders

Enable this parameter to share adders with the resource sharing optimization. Resource sharing identifies Add or Sum blocks in your design that have two inputs and replaces them with a single Add or Sum block. This optimization saves area on the target FPGA device.

Settings

Default: Off

On: When resource sharing is enabled, this optimization shares adders with a bit width greater than or equal to the Adder sharing minimum bitwidth.
Off: Do not share adders.

Dependency

To share adders in your design, in the HDL Block Properties for the DUT Subsystem, specify the SharingFactor.
When you specify the Adder sharing minimum bitwidth, the code generator shares adders that have a bit width greater than or equal to the minimum bit width. The default minimum bit width for sharing adders is zero.

Command-Line Information

Property: ShareAdders

Type: character vector

Value: 'on' | 'off'

Default: 'off'

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can use the ShareAdders setting when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'ShareAdders','on')

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdl.
```
hdlset_param('sfir_fixed','ShareAdders','on')
makehdl('sfir_fixed/symmetric_fir')
```

Adder sharing minimum bitwidth

Use this parameter to specify the minimum bit width that is required to share adders with the resource sharing optimization.

Settings

Default: 0

0, 1: No minimum bit width for shared adders.
N, where N is an integer greater than 1: When resource sharing and adder sharing are enabled, share adders with a bit width greater than or equal to N.

Dependency

To share adders in your design:

In the Resource Sharing tab, enable the Adders setting.
In the HDL Block Properties for the DUT Subsystem, specify the SharingFactor.

Command-Line Information

Property: AdderSharingMinimumBitwidth

Type: integer

Value: integer greater than or equal to 0

Default: 0

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can use the AdderSharingMinimumBitwidth setting when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'AdderSharingMinimumBitwidth',16)

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdl.
```
hdlset_param('sfir_fixed','AdderSharingMinimumBitwidth',16)
makehdl('sfir_fixed/symmetric_fir')
```

Share Multipliers

Enable this parameter to share multipliers with the resource sharing optimization. Resource sharing identifies Product or Gain blocks in your design that have two inputs and replaces them with a single Product or Gain block. This optimization saves area on the target FPGA device.Share multipliers with the resource sharing optimization.

Settings

Default: On

On: When resource sharing is enabled, share multipliers with a bit width greater than or equal to the Multiplier sharing minimum bitwidth. For successfully sharing multipliers, the input fixed-point data types must have the same wordlength. The fraction lengths and signs of the fixed-point data types can be different.
Off: Do not share multipliers.

Dependency

To share multipliers in your design, in the HDL Block Properties for the DUT Subsystem, specify the SharingFactor.
When you specify the Multiplier sharing minimum bitwidth, the code generator shares multipliers that have a bit width greater than or equal to the minimum bit width. The default minimum bit width for sharing multipliers is zero.

Command-Line Information

Property: ShareMultipliers

Type: character vector

Value: 'on' | 'off'

Default: 'on'

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can use the ShareMultipliers setting when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'ShareMultipliers','on')

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdl.
```
hdlset_param('sfir_fixed','ShareMultipliers','on')
makehdl('sfir_fixed/symmetric_fir')
```

Multiplier sharing minimum bitwidth

Use this parameter to specify the minimum bit width that is required to share multipliers with the resource sharing optimization.

Settings

Default: 0

0, 1: No minimum bit width for shared multipliers.
N, where N is an integer greater than 1: When resource sharing and multiplier sharing are enabled, share multipliers with a bit width greater than or equal to N.

Dependency

To share multipliers in your design:

In the Resource Sharing tab, make sure that the Multipliers check box is selected.
In the HDL Block Properties for the DUT Subsystem, specify the SharingFactor.

Command-Line Information

Property: MultiplierSharingMinimumBitwidth

Type: integer

Value: integer greater than or equal to 0

Default: 0

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can use the MultiplierSharingMinimumBitwidth setting when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'MultiplierSharingMinimumBitwidth',16)

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdl.
```
hdlset_param('sfir_fixed','MultiplierSharingMinimumBitwidth',16)
makehdl('sfir_fixed/symmetric_fir')
```

Multiplier promotion threshold

To share smaller multipliers with other larger multipliers by using the resource sharing optimization, specify the multiplier promotion threshold. This threshold specifies the maximum word length by which HDL Coder™ promotes a multiplier for sharing with other multipliers. For example, if you have a multiplier whose input word lengths sum to 28 bits and you want to share that multiplier with another multiplier whose input word lengths sum to 34 bits, subtract the total bits from each other, and set the multiplier promotion threshold to at least as large as the difference. In this example, the difference is 6 bits.

Settings

Default: 0

0

No difference in word length between the multipliers, meaning that HDL Coder shares multipliers that have the same word length.

N, where N is an integer greater than 0

Maximum word length by which HDL Coder promotes a multiplier for sharing with other multipliers. If the difference in word lengths is less than or equal to N, HDL Coder promotes and shares multipliers that have different word lengths.

To determine N:

Calculate the sum of the input word lengths for the multipliers that you want to share.
Set N to be at least as large as the difference between the summation of input word lengths for the different multipliers.

Dependency

To share multipliers in your design:

In the Resource Sharing tab, make sure that you select the Multipliers check box.
In the HDL Block Properties for the DUT Subsystem, specify the SharingFactor.

Command-Line Information

Property: MultiplierPromotionThreshold

Type: integer

Value: integer greater than or equal to 0

Default: 0

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can use the MultiplierPromotionThreshold setting when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model by using either of these methods:

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'MultiplierPromotionThreshold',8)

When you use hdlset_param, you can set the parameter on the model, and then generate HDL code by using makehdl.
```
hdlset_param('sfir_fixed','MultiplierPromotionThreshold',8)
makehdl('sfir_fixed/symmetric_fir')
```

Multiplier partitioning threshold

Settings

Default: Inf

N, where N is an integer greater than or equal to 2

Partition multipliers so that N is the maximum multiplier input bit width.

This parameter specifies the maximum input bit width for a multiplier. If at least one of the inputs to the multiplier has a bit width greater than the threshold value, the code generator splits the multiplier into smaller multipliers.

To improve hardware mapping results, set the multiplier partitioning threshold to the input bit width of the DSP or multiplier hardware on your target device.

Inf

Do not partition multipliers.

Command-Line Information

Property: MultiplierPartitioningThreshold

Type: integer

Value: integer greater than or equal to 0

Default: Inf

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can set the MultiplierPartitioningThreshold to 16 when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'MultiplierPartitioningThreshold',16)

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdl.
```
hdlset_param('sfir_fixed', 'MultiplierPartitioningThreshold',16)
makehdl('sfir_fixed/symmetric_fir')
```

Share Multiply-Add blocks

Share Multiply-Add blocks with the resource sharing optimization.

Settings

Default: On

On: When resource sharing is enabled, share Multiply-Add blocks with a bit width greater than or equal to Multiply-Add block sharing minimum bitwidth.
Off: Do not share Multiply-Add blocks.

Dependency

To share Multiply-Add blocks in your design, in the HDL Block Properties for the DUT Subsystem, specify the SharingFactor.
When you specify the Multiply-Add block sharing minimum bitwidth, the code generator shares Multiply-Add blocks that have a bit width greater than or equal to the minimum bit width. The default minimum bit width for sharing Multiply-Add blocks is zero.

Command-Line Information

Property: ShareMultiplyAdds

Type: character vector

Value: 'on' | 'off'

Default: 'on'

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can use the ShareMultiplyAdds setting when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'ShareMultiplyAdds','on')

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdl.
```
hdlset_param('sfir_fixed','ShareMultiplyAdds','on')
makehdl('sfir_fixed/symmetric_fir')
```

Multiply-Add block sharing minimum bitwidth

Use this parameter to specify the minimum bit width that is required to share Multiply-Add with the resource sharing optimization.

Settings

Default: 0

0, 1: No minimum bit width for shared Multiply-Add blocks.
N, where N is an integer greater than 1: When resource sharing and Multiply-Add block sharing are enabled, share Multiply-Add blocks with a bit width greater than or equal to N.

Dependency

To share Multiply-Add blocks in your design:

In the Resource Sharing tab, make sure that the Multiply-Add blocks check box is selected.
In the HDL Block Properties for the DUT Subsystem, specify the SharingFactor.

Command-Line Information

Property: MultiplierAddSharingMinimumBitwidth

Type: integer

Value: integer greater than or equal to 0

Default: 0

To set this property, use the functions hdlset_param or makehdl. To view the property value, use the function hdlget_param.

For example, you can use the MultiplierAddSharingMinimumBitwidth setting when you generate HDL code for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdl function.

makehdl('sfir_fixed/symmetric_fir', ... 
        'MultiplierAddSharingMinimumBitwidth',16)

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdl.
```
hdlset_param('sfir_fixed',MultiplierAddSharingMinimumBitwidth',16)
makehdl('sfir_fixed/symmetric_fir')
```