Time resolution in SystemC 3.0.0

[Julien]

Hi SystemC experts.

SystemC 3.0.0 supports new time units: attoseconds, zeptoseconds and yoctoseconds.

As a consequence, the field time_resolution (which is a double) of the sc_time_params structure has a different unit compared to SystemC 2.3.4. The unit is yoctoseconds and no longer femtoseconds. The comment on line 475 of the file sc_time.h is thus probably wrong.

When sc_set_time_resolution is called with 1 second, time_resolution is set to 1e24.

The function sc_time_tuple::init() converts the time_resolution from double to sc_dt::int64: see sc_time.cpp line 84.

But the 64-bit sc_dt::int64 type is not large enough to contain values like 1e24, and this causes an overflow.

Example:

#include <systemc>

int sc_main(int, char **) {
  sc_core::sc_set_time_resolution(1, sc_core::SC_SEC);
  sc_core::sc_time t = sc_core::sc_time(1, sc_core::SC_SEC);
  sc_core::sc_time_tuple time_tuple(t);
  return 0;
}

The execution of the above code results into an assertion failure:

        SystemC 3.0.0-Accellera --- Sep 30 2024 14:19:10
        Copyright (c) 1996-2024 by all Contributors,
        ALL RIGHTS RESERVED

Warning: (W516) default time unit changed to time resolution
In file: kernel/sc_time.cpp:393

Fatal: (F4) assertion failed: tr == 1
In file: kernel/sc_time.cpp:90

Info: (I99) simulation aborted
Aborted (core dumped)

The above example works fine with SystemC 2.3.4.

The function sc_time_tuple::init() should probably be modified to use a larger type than sc_dt::int64.

Or maybe the computation of the scale could be done using the log10() function.