CP vs C++

From: Fyodor Tkachov <"Fyodor>
Date: Wed, 28 Jan 2004 15:58:23 +0100

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Hi All!

I'd like to share an interesting experience -- someone asked a while ago about the cost of array boundary checks etc.

A pretty complex algorithm was developed in Component Pascal for the needs of physics at CERN (the so-called optimal jet finder). The algorithmic experimentation required was significant, and I cannot imagine how it could have been done within the time it took in Blackbox (4 focused weeks) with any other language.

The program is not very large, consists of 4 modules and contains a nice mix of normal numerical stuff (arrays, sin's etc.), bit manipulation, records, pointers and lists (the data structures remain static once initialized -- this was possible and needed for the port), true object stuff (so that "dynamic dispatch" had to be used in the C++ version).
So it's quite representative -- on top of being fully real-life.

Now, since CERN physicists use all possible kinds of hardware, the algorithm was ported to Fortran 77 and recently to C++.

The C++ version is a straightforward copy of the CP version.
The tests were run on Win XP, and MS Visual C++ compiler was used.

The C++ variant compiled as a "Debug" version was 3 times slower than CP -- 9.x : 3.6 (sec).
The C++ variant compiled as "Release" with full optimization clocked in at 3.5 sec.
The time measurement fluctuations in all cases was 0.1.

The compilation time in the last case was noticeable -- must be >10 times more than for CP where it is barely noticeable.

A CERN C++ guru insists that the resulting C++ code is not good, too many friends and typedefs, etc. -- I am not sure as the CP version is neat and nice, and the earlier Fortran version produced from the same CP original is said to be very good by the same guru.

So, make your conclusions.
I have no numbers for Fortran yet.

Cheers
-------------------------
Fyodor Tkachov

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Received on Wed Jan 28 2004 - 15:58:23 UTC