Guidance - 2021.2 English

Vitis Unified Software Platform Documentation: Application Acceleration Development (UG1393)

Document ID
UG1393
ft:locale
English (United States)
Release Date
2021-12-15
Version
2021.2 English

The Vitis core development kit has a comprehensive design guidance tool that provides immediate, actionable guidance to the software developer for issues detected in their designs. These issues might be related to the source code, or due to missed tool optimizations. Also, the rules are generic rules based on an extensive set of reference designs. Therefore, these rules might not be applicable for your specific design. It is up to you to understand the specific guidance rules and take appropriate action based on your specific algorithm and requirements.

Guidance is generated from the Vitis HLS, Vitis profiler, and Vivado Design Suite when invoked by the v++ compiler. The generated design guidance can have several severity levels; warning messages, informational messages and design rule checks are provided during software emulation, hardware emulation, and system builds. The profile design guidance helps you interpret the profiling results which allows you to focus on improving performance.

Guidance includes message text for reported violations, a brief suggested resolution, and a detailed resolution provided as a web link. You can determine your next course of action based on the suggested resolution. This helps improves productivity by quickly highlighting issues and directing you to additional information in using the Vitis technology.

Design guidance is automatically generated after building or running an application from the command line or Vitis IDE.

You can open the Guidance report as discussed in Using the Vitis Analyzer. To access the Guidance report, open the Compile Summary, the Link Summary, or the Run Summary, and open the Guidance report.

  • Kernel Guidance is generated by the Vitis HLS tool after kernel is built using v++ compile command. This can be viewed in the Vitis analyzer by opening the Compile Summary report. Kernel guidance as well as Compile Summary files are generated for each kernel compiled. Kernel guidance includes recommendations on using Dataflow; and possible reasons why the expected throughout could not be achieved.
  • System Guidance is generated after kernel is built using the v++ link command. This can be viewed in the Vitis analyzer by opening the Link Summary report. System guidance includes all Kernel Guidance checks, and provides comprehensive review before running your application.
  • Run Guidance is generated when your generated .xclbin is run, and is a feature of the XRT. This can be viewed by opening the Run Summary in the Vitis analyzer. Run Guidance includes checks like if Kernel Stall is above 50%, recommendations if PLRAM can be used instead of DDR, etc.

With the Guidance report open, the Guidance view displays the messages along with resolution columns. The resolutions also have extended weblink help available.

The following image shows an example of the Guidance report displayed in the Vitis analyzer. For example, clicking a link in the Name column opens a description of the rule check. Links in the Details column can open source code, select a design object such as a kernel, or navigate to another report.

Figure 1. Design Guidance Example
Tip: As described in Setting Guidance Thresholds, you can manually edit the values in the Threshold column of the Run Guidance report to customize the report.

There is one HTML guidance report for each run of the v++ command, including compile and link. The report files are located in the --report_dir under the specific output name. For example:

  • v++_compile_<output>_guidance.html for v++ compilation
  • v++_link_<output>_guidance.html for v++ linking

You can click the web link in the Resolution column to get additional details about the resolution. The Guidance Messaging web page lists all of the current messages for your review.

Figure 2. Guidance Messaging Web Page

Kernel and Compute Unit objects, as well as profile reported data values, can also be cross-probed to other views like the System Diagram or Profile Report. Refer to Working with Reports for more information.