coder.loop.reverse

Reverse loop iteration order in generated code

Since R2023a

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Syntax

coder.loop.reverse("loopID")

coder.loop.reverse

loopObj = coder.loop.reverse(___)

Description

example

coder.loop.reverse("loopID") prompts the code generator to reverse the loop iteration order for the for-loop whose index name is loopID in the generated code.

For more information about loop optimizations, see Optimize Loops in Generated Code.

coder.loop.reverse prompts the code generator to reverse the loop iteration order for the for loop defined immediately after this function call in the generated code. Use this transform when you know the upper bound of the loop iterator.

loopObj = coder.loop.reverse(___) returns a loop control object with transformSchedule property set to coder.loop.reverse. Use the apply method to apply the transform to the specified loop.

Examples

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Reverse for-Loop Iteration Order in Generated Code

Use the coder.loop.reverse function to the reverse iteration order of for loops in the generated code.

Define a MATLAB^® function applyReverseTransform that performs an addition operation on an array.

function out = applyReverseTransform
out = zeros(1,100);

coder.loop.reverse('i');
for i = 1:100
    out(i) = out(i) + i;
end

Generate code for this function by running the following command:

codegen applyReverseTransform -config:lib -launchreport

Inspect the code generated for the function in the code generation report. Notice that the for-loop index in the generated function reduces from 99 to 0. This optimization can be beneficial if the upper-bound of the index is known.

void applyReverseTransform(double out[100])
{
  int i;
  memset(&out[0], 0, 100U * sizeof(double));
  for (i = 99; i >= 0; i--) {
    out[i] += (double)i + 1.0;
  }
}