.. highlight:: c

.. _pragma_loop_unroll:

Unroll Loop
-------------------------------

**Syntax**

``#pragma LEGUP loop unroll factor(<int>)``

**Description**

Specifies a loop to be unrolled.

**Parameters**

The factor indicates how many times to unroll the loop. 
If it is not specified, or specified as N (the total number of loop iterations), the loop will be fully unrolled. 
If it is specified as 2, the loop will be unrolled 2 times, where the number of loop iterations will be halved and the loop body will be replicated twice. 
If it is specified as 1, the loop will *NOT* be unrolled.

+------------+---------+----------+------------------+--------------+
| Parameter  |  Value  | Optional | Default          | Description  |
+============+=========+==========+==================+==============+
| ``factor`` | Integer | Yes      | N (fully unroll) | Unroll count |
+------------+---------+----------+------------------+--------------+

**Position**

Before the beginning of the loop.

.. Note::

  If there is a loop label, the pragma should be placed after the label.


**Examples**

Fully unroll a loop.

.. code-block:: c

  #pragma LEGUP loop unroll
  for (int i = 0; i < 10; i++) {
    ...
  }

Unroll the loop by 2 times only.

.. code-block:: c

  LOOP_LABEL:
  #pragma LEGUP loop unroll factor(2)
  while (i < 10) {
    ...
  }

Small loops may be unrolled even without the unroll pragma. Make sure the loop is not unrolled. 

.. code-block:: c

  #pragma LEGUP loop unroll factor(1)
  for (int i = 0; i < 10; i++) {
    ...
  }

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