[Scons-users] SCons popularity

Mon Jun 15 09:14:12 EDT 2015

Thanks Russel, that fills in some technical gaps.  I don't have any
experience in that area so your experience helps.
On Jun 15, 2015 6:51 AM, "Russel Winder" <russel at winder.org.uk> wrote:

> On Sun, 2015-06-14 at 03:10 -0400, Ray Sheppard wrote:
> > Hello again William,
> >    I am giving you my impressions of the product. I already said I am
> >
> > not a developer.  I will address some of your comments.  Today's
> > supercomputers seldom permit serial code.  All code is parallelized.
> > Usage of 10's of thousands of ranks is not uncommon.  The general
> > build
> > directory is a working scratch file system.  Installations must put
> > their executables in a different file system.  Several systems do not
> >
> > even have home directory access during the execution of a job.  While
> >
> > computer scientists seem to love shared libraries, in a modern
> > system,
>
> I am not sure "computer scientists" really care. The whole shared
> library thing comes from a period in history when disc space and main
> memory were scarce. Running multiple executables with copies of all the
> same code was seen as a violation of "do not repeat yourself" (DRY) and
> so the shared library system was created. Saves disc space and memory
> space at the expense of severe dependency management problems.
>
> There is a move now, exemplified in Go, to always do static
> compilation. Having 60MB or 100MB executables is seen as small penalty
> for the lack of dependency management.
>
> > they needlessly light up the network fabric in order to slow down
> > execution.  Often, shared expectations (as in *.so) must be
> > accomplished
> > as a a static import from a *.a library. This creates complicated
> > compiling systems.  Using a Cray as an example, the underlying
> > compiler
>
> For MPI-based, cluster-based systems, it makes a great deal of sense to
> statically compile all the executables, especially for SPMD style
> parallelism.
>
> > might be gcc/gfortran.  However, the actual compiler has a name like
> > ftn.  It has a section for putting ftn specific flags (first section
> > of
> > the compile line) as well as native compiler flags (middle section of
> >
> > the compile line). Code which is looking for a clue, like mpicc to
> > decide if it is an MPI code is out of luck because the compilers
> > parse
> > the code and auto link in its version of message passing as well as
> > most
> > common math libraries without specific links. Adding in unnecessary
> > links (like -lmpi) only result in an aborted compilation. All of this
> >
> > requires modifications (from my experience) deep in the SCons
> > specific
> > files.  When I use the term "head" I am referring to the framework's
> > ability to divine its surroundings and make decisions. Your framework
> >
> > certainly does try to do that. I have read and even hard copied
> > printed
> > your user guide. Were I creating a project and trying to use SCons to
> >
> > write it, your user guide would be very helpful. If I have a package
> > that thinks it has write permissions to /usr/local and needs to have
> > specific flag structures, it is not so much.  I do not wish to write
> > my
> > own builder or scanner.  I just want to invoke a build with something
> > like:
> > scons all INSTALL_ROOT=/somewhere CC=something CFLAGS= "-x -y -z"
> > FC=something_else FFLAGS="-a -b -c"
> > Reading variables like LD_LIBRARY_PATH and CFLAGS rather than making
> > up
> > a new ones like LIBPATH  (or at least aliasing one to another) would
> > be
> > a nice touch.  I seem to have missed that section of the UG. Again,
> > this
> > is just the impression of someone who uses your product.  You can do
> > with these comments as you wish.
>
> I haven't done any hard core parallel programming on real
> supercomputers using C++ for 20 years, but with my tinkering using C++
> with MPI, OpenMP, OpenCL, etc. on stock Linux and OSX platforms, I have
> never found I had to delve into the internals of SCons to get things
> working. I have had to experiment a lot due to lack of tutorial and
> manual material, and to find idiomatic and Pythonic ways of expressing
> things in SConscript and SConstruct files, but generally all the
> variations have been handled at the Python level and not at the "get
> inside SCons" level.
>
> For a really trivial example:
> https://github.com/russel/Pi_Quadrature/tree/master/C%2B%2B
>
> --
> Russel.
>
> =============================================================================
> Dr Russel Winder      t: +44 20 7585 2200   voip:
> sip:russel.winder at ekiga.net
> 41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel at winder.org.uk
> London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
>
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