The performance cost associated with std::vector.

[Jason Heyes]

What harmful effects can using std::vector have on the performance of my
program? How do I protect my program from these effects? Thanks.

[Bob Hairgrove]

On Mon, 15 Dec 2003 00:58:50 +1100, "Jason Heyes"
<ge******@optusnet.com.au> wrote:

What harmful effects can using std::vector have on the performance of my
program? How do I protect my program from these effects? Thanks.

I think a more appropriate question would be:

"What harmful effects can NOT using std::vector have on the
performance of my program? How do I protect my program from these
effects?"
--
Bob Hairgrove
No**********@Home.com

[Bob Jacobs]

"Jason Heyes" <ge******@optusnet.com.au> wrote in message
news:3f***********************@news.optusnet.com.a u...

What harmful effects can using std::vector have on the performance of my
program? How do I protect my program from these effects? Thanks.

Performance compared with what?

[Samuele Armondi]

"Jason Heyes" <ge******@optusnet.com.au> wrote in message
news:3f***********************@news.optusnet.com.a u...

What harmful effects can using std::vector have on the performance of my
program? How do I protect my program from these effects? Thanks.

On most implementations, perfomance is similar to an array, but it should
not be hard to code a little test to find out how your particular
implementation measures up... The advantages of using a vector (like safety
from memory management problems and the like) far outweigh any perfomance
penalties for all but the most time-critical applications.
HTH,
S. Armondi

[tom_usenet]

On Mon, 15 Dec 2003 00:58:50 +1100, "Jason Heyes"
<ge******@optusnet.com.au> wrote:

What harmful effects can using std::vector have on the performance of my
program? How do I protect my program from these effects? Thanks.

Compared against dynamic allocation using malloc/new[], you really
only have minor concerns that I can think of.

1. Vector elements are initialized when you resize. You can avoid this
where it has caused a performance problem by using push_back to add
elements (having reserved enough space).

2. Avoid copying vectors (or passing by value) unless you really want
to perform a deep copy.

Apart from that, performance should be close to identical to a
hand-coded hand-optimized malloc-based array using exponential
expansion.

Tom

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