paper on OO performance with gfortran

[Jerry DeLisle]

On 08/11/2015 09:02 AM, Damian Rouson wrote:
> 
>> On Aug 11, 2015, at 3:58 AM, Paul Richard Thomas <paul.richard.thomas@gmail.com> wrote:
>>
>> Dear Damian,
>>
>> That is fascinating. The fact that g++ is issuing SMD instructions and
>> gfortran is not is concerning. Funnily enough, I have just started
>> looking into precisely this area and so will follow it up.
> 
> Performance analysis is very tricky business — particularly when language comparisons are involved, 
> but I’m glad this sparked some thought and that you’re already addressing this issue.   I find
> that most authors of such comparisons don’t write Fortran code that fully exploits the most
> powerful idioms and they often miss some of the semantic of value of features.  For example,
> I’ve seen the ability to define new operators dismissed as “syntactic sugar’ without accounting
> for the requirement that operator arguments have the “intent(in)” attribute, which naturally lends
> itself to writing PURE procedures, which in turn opens up optimization opportunities, including
> easing the path to asynchronous parallel evaluation.
> 
> Furthermore, there are differences in the cultures around the languages that make the comparisons 
> even more difficult.  For example, many important Fortran programs are self-contained, whereas
> nearly any significant C++ program links to libraries that are not part of the language. 
> 
>>
>> Parameterized Derived Types are much, much more complicated to
>> implement than I ever imagined.
> 
> At last week’s Fortran standards committee meeting, it was the consensus that PDTs were
> much, much more complicated to implement than anyone ever imagined.  Would it make more
> sense to knock out DTIO first?  At least then gfortran would only be missing one major feature
> for Fortran 2008 compliance. :)

Many moons ago I started digging into DTIO for gfortran and at the time I
thought it would not be that difficult to do, but tedious.  Its been so long
since I looked at it I will have to start over from scratch and try to
understand it again.  I want to restart soon, now that I am home and no longer
commuting 1200 miles to work.  PaulT, I may be contacting you to bounce some ideas.

Jerry