Free Running Pipeline - Free Running Pipeline - 2026.1 English - UG1448

Vitis HLS Messaging (UG1448)

Document ID
UG1448
Release Date
2026-06-23
Version
2026.1 English

Description

Warning: [HLS 200-1965] Disabling free running pipeline (frp) architecture on pipeline 'VITIS_LOOP_11_2' in module 'COM_Pipeline_VITIS_LOOP_11_2', because it has II equal to pipeline depth (will fall back to a sequential design).

Explanation

In this example, the pipelined loop's II is the same as its depth (2), meaning the loop is sequential. Applying FRP to this loop will not help.

Example

void COM(int a[SIZE])
{
  int i,j,temp;

  for(i = 0; i < SIZE-1; i++)
  {
    for(j = 0; j < SIZE-1-i; j++)
    {
        #pragma HLS pipeline style=frp
        if(a[j] < a[j+1])
         {
              temp = a[j+1];
              a[j+1] = a[j];
              a[j] = temp;
         }
     }
  }
        for(i = 0; i < SIZE; i++)
            printf("%d\n",a[i]);
}