Non-sequential Passes

‍TO BE IMPLEMENTED

By default each pass within a node depends on the previous pass. If a node can parallelize the computation across multiple hardware engines, e.g. two CPU cores, custom inter-pass dependencies can be defined.

‍The functions implementing the passes which might run concurrently need to be thread-safe.

Example

In the following example the two passes PROCESS_EVEN and PROCESS_ODD can run in parallel to perform their work concurrently.

Example of Non-Sequential Passes

The corresponding C++ snippet describing the passes:

static constexpr auto describePasses()
{
    return describePassCollection(
        // the first pass has no (default) dependency
        describePass("SETUP"_sv, DW_PROCESSOR_TYPE_CPU),
 
        // the default dependency is the previous SETUP pass
        describePass("PROCESS_EVEN"_sv, DW_PROCESSOR_TYPE_CPU),
 
        // the default dependency would be the PROCESS_EVEN pass which is not desired
        // hence providing a custom dependency on the SETUP pass
        describePass("PROCESS_ODD"_sv, DW_PROCESSOR_TYPE_CPU, describePassDependencies("SETUP"_sv)),
 
        // the default dependency would be only the PROCESS_ODD pass which is not desired
        // hence providing custom dependencies on the PROCESS_EVEN and PROCESS_ODD pass
        describePass("POSTPROCESS"_sv, DW_PROCESSOR_TYPE_CPU, describePassDependencies("PROCESS_EVEN"_sv, "PROCESS_ODD"_sv)),
 
        // the default dependency is the previous POSTPROCESS pass
        describePass("TEARDOWN"_sv, DW_PROCESSOR_TYPE_CPU));
};

References

• The schema for .node.json files captures the description of custom pass dependencies under passes -> dependencies.
• The C++ API dw::framework::describePass() has an optional parameter to define custom inter-pass dependencies.