Memory and disk layout of real*10 variables

[Erik Schnetter]

The memory layout of a real*10 variable on an i386 processor requires 12 
or 16 bytes per variable, depending on the flag -m128bit-long-double.  
The disk layout for unformatted (binary) writing occupies 10 bytes per 
variable.

This has several disadvantages.  It is different from I would naively 
expect (which does not mean much), and it is different from binary C 
I/O (which could also be ignored).  However, it is likely also rather 
inefficient if large arrays are written to disk, because a single call 
to write() or fwrite() now has to be split up into one call per array 
element, so that the padding is removed.

It is also questionable whether having a real*10 variable occupy 12 or 
16 bytes in memory is what people expect; again, this could be ignored 
since the standard permits this.

I have opened a PR for this because this set of behaviours is very 
different from other compilers and detrimental to performance.

-erik

-- 
Erik Schnetter <schnetter@aei.mpg.de>   http://www.aei.mpg.de/~eschnett/

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