[M3devel] Thread.HardwareConcurrency()?

[Rodney M. Bates]

On 07/04/2017 02:27 AM, Jay K wrote:
> Clearing out more backlog...
>
>
> I suggest, for example, the cm3 compiler should use
> a thread per "processor" for the backend.
>
>
> I acknowledge that "processor" isn't well defined, such as with Intel
> hyperthreading and in general with various resources (registers, integer ALU,
> floating point ALU, branch predictor memory, cache) not being equally duplicated.
>
>
> I acknowledge that hogging all the CPU is deleterious to interactive
> performance, or overall system performance if anything else is running.
>

When I have the option, I usually use one fewer threads than processors, so
I can read email, etc. while waiting.  The compiler could alternatively be
set up to do this.

>
> Adapting to overall system load and being good citizen is quite difficult
> unless you are the semi-omniscient operating system kernel.
>
>
> I believe C++11 exposes this notion and Boost did before it.
> (C++11 finally acknowledged the existance of threads and has
> a memory model and library for them, 20 years late)
>
>
> I propose that we can freely integrate Boost code into our runtime.
> That its license is close in spirit to ours.
>
>
> edit m3-libs/m3core/src/thread/Common/BoostThread.cpp
>
>
> #ifndef _WIN32
> // Copyright (C) 2001-2003
> // William E. Kempf
> // Copyright (C) 2007-8 Anthony Williams
> // (C) Copyright 2011-2012 Vicente J. Botet Escriba
> //
> //  Distributed under the Boost Software License, Version 1.0. (See accompanying
> //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
> #ifdef __GLIBC__
> #include <sys/sysinfo.h>
> #elif defined(__APPLE__) || defined(__FreeBSD__)
> #include <sys/types.h>
> #include <sys/sysctl.h>
> #else // if defined BOOST_HAS_UNISTD_H
> #include <unistd.h>
> #endif
> #endif
>
>
> extern "C"
>     unsigned m3_thread_hardware_concurrency()
>     {
> #if defined(PTW32_VERSION) || defined(__hpux)
>         return pthread_num_processors_np();
> #elif defined(__APPLE__) || defined(__FreeBSD__)
>         int count;
>         size_t size = sizeof(count);
>         return sysctlbyname("hw.ncpu", &count, &size, NULL, 0) ? 0 : count;
> #elif defined(BOOST_HAS_UNISTD_H) && defined(_SC_NPROCESSORS_ONLN)
>         int const count = sysconf(_SC_NPROCESSORS_ONLN);
>         return (count > 0) ? count : 0;
> #elif defined(__GLIBC__)
>         return get_nprocs();
> #else
>         return 0;
> #endif
>     }
> #else
> #include <windows.h>
> // Distributed under the Boost Software License, Version 1.0. (See
> // accompanying file LICENSE_1_0.txt or copy at
> // http://www.boost.org/LICENSE_1_0.txt)
> // (C) Copyright 2007 Anthony Williams
> // (C) Copyright 2007 David Deakins
> // (C) Copyright 2011-2013 Vicente J. Botet Escriba
> extern "C"
>     unsigned m3_m3_thread_hardware_concurrency()
>     {
>         SYSTEMINFO info;
>         GetSystemInfo(&info);
>         return info.dwNumberOfProcessors;
>     }
> #endif
>
>
>
> and then something in Thread.i3.
>
>
>  <* external m3_thread_hardware_concurrent *>
>  PROCEDURE Thread.HardwareConcurrency(): INTEGER;
>
>
> ?
>
>
>  - Jay
>
>
>
>
>
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>

-- 
Rodney Bates
rodney.m.bates at acm.org