Re: [boost] [1.44] Beta progress?

27 Jul 2010

      Matthias Troyer wrote:
...
...
If you say that really need to know about each type I'm not
going to dispute it.  But I will say I'm not seeing it.
I sort of expect to see something like:
class mpi_oprimitive ... {
   mpioutputfunction m_out;
   template<typename T, std::size_t s>
   mpi_out{
       // uh-oh programming error - no mpi size
       BOOST_STATIC_ASSERT(0 == s);
   }
mpiout_int<int, 2>(int t){
       mpi_out(MPI_SHORT_INT(t)));
   }
   mpiout_int<int, 4>(int t){
       mpi_out(MPI_LONG_INT(t)));
   }
   ...?
   void save(int t){
       mpiout_int(t, sizeof(t));
   }
   void save(short int t){
       mpiout_int(t, sizeof(t));
   }
   void save(long int t){
       mpiout_int(t, sizeof(t));
   }
   ..?
mpiout_uint<int, 2>(unsigned int t){
       mpi_out(MPI_SHORT_INT(t)));
   }
   mpiout_uint<int, 4>(unsigned int t){
       mpi_out(MPI_LONG_INT(t)));
   }
   ...?
   void save(unsigned int t){
       mpiout_uint(t, sizeof(t));
   }
   void save(const unsigned short int t){
       mpiout_uint(t, sizeof(t));
   }
   void save(const unsigned long int t){
       mpiout_int(t, sizeof(t));
   }
   ..?
   }
   ...
I'm not even suggesting this, I'm just explaining
why adding "more" to the documentation or
spec or whatever would have occurred to me.
Unfortunately it is not as easy since an arbitrary number of
datatypes can be created by the user, e.g. for pairs, structs,
arrays, ... . Hence there is not a limited list of types but a
general template, and thus no automatic conversion takes place.
Ahh but these aren't handled in the mpi_?primitive class but
rather in the mpi_archive class - assuming it were to follow
the pattern in text and binary archives.

here's what I envisioned when I factored the code in my
archives.

class text_archives
    template
    save_override(
        invoke code in oserialize
            if it's a primitive - redirect (eventually) to text_primitive
            if its an array - invoke array code
            if its an enum - invoke enum code
            if it's a pointer - invoke pionter code
            else
                invoke serialize code - this would handle all the types you 
mentin above - pairs, structs. etc.
...

That is ONLY types marked primitive and C++ primitives have to be considered 
here.
Since the types in questions are marked primitive and convertible to 
primitive, I believe
that ONLY C++ integer types have to be considered in the mpi_?primitive 
classes.

Looking at text_primitive and binary_primitive you can see this.  A couple
of types needed special handling.  The can be filtered out in either
the archive class or the primitive class.  But most types need no special
treatment.  A couple do - bool is rendered as a character, char is rendered
as a small binary number.  But mostly this gets handled transparently.
It also handles most of the hassle with different sizes for built-in types.

Robert Ramey
...
Matthias
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