Intel® High Level Synthesis Compiler Pro Edition: Best Practices Guide

ID 683152
Date 12/13/2021

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4.1. Choose the Right Interface for Your Component

Different component interfaces can affect the quality of results (QoR) of your component without changing your component algorithm. Consider the effects of different interfaces before choosing the interface between your component and the rest of your design.

The best interface for your component might not be immediately apparent, so you might need to try different interfaces for your component to achieve the optimal QoR. Take advantage of the rapid component compilation time provided by the Intel® HLS Compiler Pro Edition and the resulting High Level Design reports to determine which interface gives you the optimal QoR for your component.

This section uses a vector addition example to illustrate the impact of changing the component interface while keeping the component algorithm the same. The example has two input vectors, vector a and vector b, and stores the result to vector c. The vectors have a length of N (which could be very large).

The core algorithm is as follows:
  #pragma unroll 8
  for (int i = 0; i < N; ++i) {
    c[i] = a[i] + b[i];

The Intel® HLS Compiler Pro Edition extracts the parallelism of this algorithm by pipelining the loops if no loop dependency exists. In addition, by unrolling the loop (by a factor of 8), more parallelism can be extracted.

Ideally, the generated component has a latency of N/8 cycles. In the examples in the following section, a value of 1024 is used for N, so the ideal latency is 128 cycles (1024/8).

The following sections present variations of this example that use different interfaces. Review these sections to learn how different interfaces affect the QoR of this component.

You can work your way through the variations of these examples by reviewing the tutorial available in <quartus_installdir>/hls/examples/tutorials/interfaces/overview.