Re: What difference (object and sequence)
A few days ago Doug Edmunds asked:
> Is there any difference (size, performance, etc.)
> between declaring a variable as an object
> and declaring it as a sequence,
> other than type checking?
Using *very* rough numbers:
90% of the time you will see a slight (1% to 5%)
improvement in speed if you declare a heavily-used
variable as a sequence, rather than an object.
10% of the time you may see a very slight loss (1% to 2%).
It's not something that most people should worry about.
As a rule of thumb, you should declare variables using
the most restrictive of the pre-defined types that you can.
This will catch more bugs, make your code easier to understand,
and probably make it run a few percent faster. For instance
it's usually faster to declare something as an integer
rather than an atom.
As for memory consumption, it only matters what the
current *value* of a variable is, not how it is declared.
If you are serious about performance, you need to
make measurements. As we saw from some postings
a while back, it isn't always obvious which way of
coding something is going to be faster. Even though
I know how things are implemented, I am often surprised.
Put small code fragments into for-loops up to a million
and time them. Profile your program. Don't assume that
you know which statement is the "bottleneck".
For instance, most people assume that it must be faster
to perform arithmetic on a whole sequence in one statement,
rather than looping. This is not a good assumption. You have
to measure it.
There's a lot of invisible, but significant stuff going on when
your program executes. Storage allocation and deallocation
are important, but there are subtle hardware effects such as
caching that can be very significant and hard to predict.
Regards,
Rob Craig
Rapid Deployment Software
Regards,
Rob Craig
Rapid Deployment Software
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