Re: Numerical Computation and Ada95

[Jeffrey Carter <jeffrey.carter@boeing.com>]

David Starner wrote:
> 
> There's always the question on whether you want fast programs or
> correct programs. (-: Most Ada compilers offer switches to turn off
> run-time checks, so there should be practically no difference
> between the speed of Fortran, C++ and Ada. (In practice, Ada seems
> to be slightly slower (10-20%) even with the checks turned off. This
> will of course vary widely depending on your program and enviroment.)

This, I am glad to say, is simply wrong. Robert Dewar has a suite of
equivalent Ada and C programs that generate *identical* object code when
compiled with gcc. Back in the dark days of Ada 83, the highly optimized
Tartan Ada compiler produced faster code than the C benchmarks Tartan
used to convince people to buy their *C* compilers instead of using the
free one that TI shipped with their DSPs. An article in _Ada Letters_
described the features of Ada and C that allowed them to do better
optimization for Ada than for C.

There was also a case of a Tartan Ada compiler producing faster code
than hand-optimized assembler. This was described in a TRI-Ada
presentation. The people developing the Ada made no special effort to
make the code fast, because the purpose of the project was to prove that
Ada was NOT fast enough. The project failed, sort of like the Tuskegee
Airman project.

In general, using modern compilers and modern processors, equivalent
programs will produce equivalent execution times.

--
Jeffrey Carter