AMREX_DEVICE_PRINTF: Host

[ax3l]

Summary

In AMReX, device means host if compiled for CPUs.
Add support for printf debugging on CPUs for AMREX_DEVICE_PRINTF.

Currently, the macro was undefined, unless for the special case of SYCL compilation for host code paths where it worked.

Additional background

Checklist

The proposed changes:

• fix a bug or incorrect behavior in AMReX
• add new capabilities to AMReX
• changes answers in the test suite to more than roundoff level
• are likely to significantly affect the results of downstream AMReX users
• include documentation in the code and/or rst files, if appropriate

[WeiqunZhang]

It was intentional, because AMREX_DEVICE_PRINTF really should be for debugging only.

[WeiqunZhang]

It was intended as a feature, not a bug.

[ax3l]

Yes, but both on host as well as on device this is breaking compiler optimizations and bloating registers.

I want to use it exclusively inside a

#if defined(AMREX_DEBUG) || defined(DEBUG)
#endif

block.

[ax3l]

A common construct where this macro is used that I saw is this:

#if defined(AMREX_DEBUG)
    AMREX_IF_ON_DEVICE((
        AMREX_DEVICE_PRINTF("Message %d\n", n);
    ))
    AMREX_IF_ON_HOST((
        std::stringstream ss;
        ss << "Message " << n << "\n";
        amrex::Abort(ss.str());
    ))
#endif

Maybe we could provide a macro for this?
The difference is:

• only defined in debug
• will abort on the host, too

#define AMREX_DEBUG_DEVICE_PRINTF(Format,...) ...