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Newsgroups: comp.lang.c++
Subject: Re: STL vector
References: <op.v4z6q8m5vc68pg@hp2011.workgroup> <KGFwq.32258$zC6.5650@en-nntp-15.dc1.easynews.com>
Date: Wed, 16 Nov 2011 08:58:04 +0100
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From: "Peter Liedermann" <peter09876@hispeed.ch>
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On Wed, 16 Nov 2011 03:59:56 +0100, Joe Gottman  
<josephgottman@comcast.net> wrote:

> On 11/15/2011 2:50 PM, Peter Liedermann wrote:
>> Hi there,
>>
>> Let "Jumbo" be the name of a class whose instances consume substantial
>> storage.
>>
>> A vector of typically 1000 such Jumbo-instances is needed. It must be
>> sorted by a simple int criterium, but not often.
>>
>> Is there a substantial performance difference between vector <Jumbo> and
>> vector <Jumbo *>, provided that everything else is adapted accordingly?
>> Is there a difference at all?
>>
>> Thanx a lot,
>> Peter
>>
>
>    1) If you know in advance the size of the vector, you can reserve the  
> right amount of capacity before you start filling it and thus avoid the  
> costs of reallocation.

yes, I do

>
>    2) If you can define an efficient swap() function for your class,  
> then sorting a vector<Jumbo> would not involve any copying whatever.
>
I can certainly swap Jumbo * (pointers) easily, swapping Jumbo objects  
themselves is certainly (much?) more difficult.
So I am determined to use Jumbo * as of now.
Thanx for the clarification
Peter