## Use algorithms optimized for row-major array layout

### Description

For certain blocks, enable optimized algorithms for row-major format code generation and corresponding row-major algorithms for model simulation.

Category: Math and Data Types

### Settings

Default: Off

When Array layout (Simulink Coder) is set to `Row-major`, the code generator uses algorithms to maintain consistency of numeric results between the simulation and the generated code. Sometimes, the generated code for these algorithms might be inefficient. You can enable the Use algorithms optimized for row-major array layout configuration parameter to enable efficient algorithms that are optimized for certain blocks. The Use algorithms optimized for row-major array layout parameter affects the simulation and the generated code.

This parameter affects only these blocks:

• Sum of Elements

• Product of Elements

• n-D Lookup Table

• Interpolation Using Prelookup

• Direct Lookup Table (n-D)

For these blocks, the column-major and row-major algorithms might differ in the order of output calculations, possibly resulting in slightly different numeric values.

On
• When Array layout is set to `Row-major`, this parameter enables the use of efficient algorithms that traverse the data in row-major order. The generated code is efficient.

• When Array layout is set to `Column-major`, this parameter enables the use of algorithms that traverse the data in row-major order. The generated code is inefficient.

Off
• When Array layout is set to `Row-major`, the code generator uses algorithms that traverse the data in column-major order. The generated code is inefficient.

• When Array layout is set to `Column-major`, the code generator uses algorithms that traverse the data in column-major order. The generated code is efficient.

### Tips

When Array layout is set to `Row-major`, the row-major algorithm operates on table data that is contiguous in memory. This table data leads to faster cache access, making these algorithms cache-friendly.

This table summarizes the relationship between array layout and cache-friendly algorithms. It is a best practice to use the algorithm that is optimized for the specified array layout to achieve good performance. For example, select Use algorithms optimized for row-major array layout when the Array layout is set to `Row-major` for code generation.

`ArrayLayout``UseRowMajorAlgorithm`Algorithm Applied
`Column-major``'off'`

Efficient column-major algorithm

Recommended

`Row-major``'off'`

Inefficient column-major algorithm

Not recommended

`Column-major``'on'`

Inefficient row-major algorithm

Not recommended

`Row-major``'on'`

Efficient row-major algorithm

Recommended

### Command-Line Information

 Parameter: `UseRowMajorAlgorithm` Type: character vector Value: `'on'` | `'off'` Default: `'off'`

### Recommended Settings

ApplicationSetting
DebuggingNo impact
TraceabilityNo impact
EfficiencyNo impact
Safety precautionNo impact