Re: Hoare's dictum in the real world [was: std::vector slow?]

From:

Ulrich Eckhardt <eckhardt@satorlaser.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Mon, 12 Nov 2007 09:36:28 CST

Message-ID:

<lqgl05-g37.ln1@satorlaser.homedns.org>

Tom Lynch wrote:

I have worked on two projects dealing with large datasets in which
caching some data from large files was added after the initial
implementation had revealed it to be a necessary optimisation. Don't
most reasonable abstractions of datasets allow this sort of change
without massive subsequent refactoring of other parts of the code?

Who says that anyone is doing any abstraction? "It's just a few records that
we simply read into a vector. Since $OTHERPROGRAMMER prefers C we pass
those to a C interface then as a pointer/length combo. No need for fancy
stuff there."

Many programs start out with this approach, in particular when you have to
seek in the records it is way easier than writing an abstract interface
that allows seeking in some yet unimaginably large recordset.

You simply sometimes don't know up front what will be needed and then you
have to decide between an algorithm that has little overhead and
complication and scales bad or one that has greater overhead, is more
complicated and scales better. Since development time and time to market is
a significant thing in a real hacker's life, the most elegant design is not
always also the best design.

Uli

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