Unmet Latency Constraint - 2023.2 English

Vitis HLS Messaging (UG1448)

Document ID
UG1448
Release Date
2023-10-18
Version
2023.2 English

Description

Warning: [200-892] Unable to satisfy the latency directive.

This message reports that the user-specified latency constraint is being ignored.

Explanation

The LATENCY pragma specified is un-realistic with the code and it will ignore the latency pragma.

This behavior can be seen in the following code example where the floating-point add A[i] + 5 takes more than one cycle and it is unable to meet this constraint.

void example_label(float A[50], int B[50]) {
  int i;
  int C[50];
 LOOP_1: for(i = 0; i < 50; i++){
#pragma HLS LATENCY max=1
        C[i] = A[i] + 5;
  }
...
}

Solution

Relax the user latency constraint as per the code.