What is the efficiency of SC_THREAD?

[katang]

What is exactly the  relation and the efficiency of SC_THREAD, SC_METHOD and system thread? I am making a simulator, where both the exact timing and the execution speed counts. I addition, I might need a separate Qt5 GUI thread. What are the means either in Qt5 or SystemC to support those synchronization requirements?

[David Black]

This question cannot be answered with respect to the SystemC standard as the issue is heavily implementation dependent. I am aware of implementations where SC_THREAD is faster than SC_METHOD and visa versa. It is also not a good basis for evaluating SystemC itself since the issue of simulation performance almost always comes down to how SystemC was used and how the modeler wrote their SystemC model. I do know an awful lot of folks use SystemC inappropriately (e.g. using it for modeling RTL, where VHDL or SystemVerilog are much better suited). IEEE 1666-2011 calls out the desired behavior, and not the implementation.

Note: I did a presentation on SystemC myths many years ago at NASCUG that included the myth about whether or not one should favor SC_METHOD over SC_THREAD for performance reasons. It is quite simply a poor way of making a decision when attempting to obtain performance.