coder.unroll

In one file, write the entry-point function call_getrand and a local function getrand. getrand unrolls a for-loop that assigns random numbers to an n-by-1 array. call_getrand calls getrand with the value 3.

function z = call_getrand 
%#codegen
z = getrand(3);
end

function y = getrand(n)
coder.inline('never');
y = zeros(n, 1);
coder.unroll();
for i = 1:n
    y(i) = rand();
end
end

Generate a static library.

codegen -config:lib call_getrand -report

In the generated code, the code generator produces a copy of the for-loop body for each of the three loop iterations.

static void getrand(double y[3])
{
  y[0] = b_rand();
  y[1] = b_rand();
  y[2] = b_rand();
}

In one file, write the entry-point function call_getrand_unrollflag and a local function getrand_unrollflag. When the number of loop iterations is less than 10, getrand_unrollflag unrolls the for-loop. call_getrand calls getrand with the value 50.

function z = call_getrand_unrollflag
%#codegen
z = getrand_unrollflag(50);
end

function y = getrand_unrollflag(n)
coder.inline('never');
unrollflag = n < 10;
y = zeros(n, 1);
coder.unroll(unrollflag)
for i = 1:n
    y(i) = rand();
end
end

Generate a static library.

codegen -config:lib call_getrand_unrollflag -report

static void getrand_unrollflag(double y[50])
{
  int i;
  for (i = 0; i < 50; i++) {
    y[i] = b_rand();
  }
}

The number of iterations is not less than 10. Therefore, the code generator does not unroll the for-loop. It produces a for-loop in the generated code.

• function z = call_getrand 
  %#codegen
  z = getrand(3);
  end
  
  function y = getrand(n)
  coder.inline('never');
  y = zeros(n, 1);
  for i = coder.unroll(1:n)
      y(i) = rand();
  end
  end

• function z = call_getrand_unrollflag
  %#codegen
  z = getrand_unrollflag(50);
  end
  
  function y = getrand_unrollflag(n)
  coder.inline('never');
  unrollflag = n < 10;
  y = zeros(n, 1);
  for i = coder.unroll(1:n, unrollflag)
      y(i) = rand();
  end
  end