Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!watmath!watdragon!dvadura
From: dvadura@watdragon.waterloo.edu (Dennis Vadura)
Newsgroups: comp.lang.c++
Subject: Efficiency of C++ relative to C??
Message-ID: <16493@watdragon.waterloo.edu>
Date: 19 Sep 89 01:43:33 GMT
Reply-To: dvadura@watdragon.waterloo.edu (Dennis Vadura)
Organization: Computer Science Dept., University of Waterloo
Lines: 45

I have the following question:

	Has anyone performed a study comparing the execution time cost
	of C++ language features compared to C?  In particular I am
	interested in the following problem.  Given a particular program,
	code it in C and code it in C++ using the full power of C++.
	Time the execution speed of both programs on the same input
	data.

	Then ask how much of the cost of the C++ program is due to the
	use of virtual functions, and what is the call overhead for
	a virtual function when compared to the call overhead for a
	normal call in C?

This may not be the best way to determine what I am after, but I want
a feel for how much of a penalty (if any, although I suspect it's there
and may be quite large) using C++ is going to incur if I switch from using C
to using C++ for large software projects because I want to use the
enhanced expressive power of C++ over C.

As an example there exist companies that spend 100's of thousands a year
to improve the efficiency of their code by 5%.  If on average C++ language
features incur high overhead then the cost in efficiency
for them to switch to a language like C++ with its enhanced expressive
power is too prohibitive.  Such a move would represent a large
step backward in their product.

So I am looking for paper references to such studies, or even anecdotal
experience, as I don't think many such studies exist.

ie. what is the net consensus on this?  If I care about the efficiency
    of my code and want to keep it as efficient as it is presently but
    switch to C++, is this a realistic expectation.  If not, then why
    is my expectation unrelistic, and how do I address a solution?
    Is a clever optimizer sufficient?

Send mail and I will collect the responses and summarize to the net.

-thanks
-dennis
-- 
--------------------------------------------------------------------------------
The only happy people are Single MEN   |Dennis  UUCP,BITNET:    dvadura@water
and Married WOMEN.                     |Vadura  EDU,CDN,CSNET:  dvadura@waterloo
================================================================================