When closing timing on challenging designs, users may choose to run many different place_design directives in order to select the best timing result. Auto directives use machine learning to predict the best directives to run. Users can benefit by only running these directives instead of the full sweep of directives listed in Available Directives.
Note: When running with the Auto directives, the directive setup happens slightly later in the flow than when the directive is directly specified which can result is slightly different results.
Machine learning prediction of directives have a margin of error. As a consequence, it is recommended to run 3 Auto_n directives and take the best result. The directives predicted are equivalent to the ones mentioned in Available Directives, so there is no benefit in running auto directives in addition to these. The directive selected by the tool is reported in the log file. An example of the message is as follows:
INFO: [Place 30-1947] Predicted directive using ML models is: EarlyBlockPlacement
To enable the feature, set the
<value> where value is:
- High performing predicted directive
- Second best predicted directive
- Third best predicted directive