Performance Ada and C, was Re: Size code Ada and C

[vsnyder@gyre.jpl.nasa.gov (Van Snyder)]

In article <dewar.899298949@merv>, dewar@merv.cs.nyu.edu (Robert Dewar) writes:
|> 
|> But to think there is a significant difference here between C, Ada or
|> C++ is I think a delusion.
|> 

Bolek Szymanski (http://www.cs.rpi.edu/szymansk) has noticed substantial
performance differences between C and Fortran, and even more substantial
differences between C++ and Fortran, at least in plasma particle-in-cell
simulation codes.  The reason that Fortran is usually faster than C is
the reason that Ada ought to be faster:  Pointers in Fortran are more
disciplined -- no pointer arithmetic, and non-pointer thing-o's must have
the TARGET attribute to get a pointer landing on them. Barbara Ryder, from
AT&T Bell Labs (I don't know what fragment she's in now, if any) has shown
that pointer optimization in C is NP-hard, while pointer optimization in
Fortran and Ada is "only" polynomially hard.

Only loosely relatedly, Les Hatton of PR-QA in Esher, Surrey, England has
noticed that defect densities and lifetime costs of equivalent programs in
Fortran, C and Ada are roughly the same, whereas defect densities and
lifetime costs of C++ programs are roughly three times as large.

One of my colleagues reminded me of a study, for which neither of us
could remember the author, that observed that 3 out of 4 C++ projects
that are initiated are cancelled before completion.

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