Re: [boost] Safety over efficiency guideline

From: Kevin Atkinson (kevinatk_at_[hidden])
Date: 2000-06-09 12:19:57

On Fri, 9 Jun 2000, Beman Dawes wrote:

> At 03:42 PM 6/9/00 +0200, Branko wrote:
> 
> >Right. IMHO this could be another general Boost guideline: Always
> choose
> >safety over efficiency. When providing both, make the safer
> implementation
> >the default.
> 
> Interesting suggestion!
> 
> But I don't think it is quite that simple.  There are a fair number
> of cases (portions of the STL for example) where efficiency wins.
> 
> Like so many engineering decisions, it is really a cost versus
> benefits decision.  We aren't, for example, willing to execute
> everything interpretively so more safety checks can be applied.
> 
> Let's see if there is a safety versus efficiency guideline we can
> agree on.  How about:
> 
> "Choose safety over efficiency, particularly when the risk is great
> or the cost of safety is low.  If separate safe or efficient
> variations are provided, the safer should be the default."

I think that safety should be the default when debugging a program, but
when compiling for production use efficiency should be the default
*unless* the cost of safety is cheap as for as efficiency goes.  For
example when debugging bounds checking is a very good thing however when
creating the executable for production use bounds checking should be
turned off as it is rather costly as far as performance goes.

How about a debug_assert.  That is an assert than can be turned off when
not debugging.  I don't recommend using assert because I often use assert
for non-costly checks.  Asserts are better than throwing exceptions for
debugging because they don't unwind the stack.

-- 
Kevin Atkinson
kevinatk_at_[hidden]
http://metalab.unc.edu/kevina/