[OT] gcc: maximum length of an array?

[P.U.Kruppa]

On Sun, 23 Jul 2006, Andrew Brampton wrote:

> Can you show me the line you are using to malloc with, and the lines you are 
> using to access the array...
>
> The smallest unit you can malloc on is a byte, and if you are mallocing 
> 100000000 bytes, and using each byte as a single boolean value then you are 
> wasting 7/8 of your array.
>
> It might be better to do some bit masking to gain access to the other 7 bits.
Thanks for this idea Andrew!
it took me some time to implement it - since I am quite a n00b 
and never heard about bitmasking - but with the help of
 	http://c-faq.com/misc/bitsets.html
I could do 10^9 .

Uli.

>
> Andrew
>
> ----- Original Message ----- From: "P.U.Kruppa" <root at pukruppa.de>
> To: <freebsd-questions at freebsd.org>
> Sent: Monday, July 24, 2006 7:49 PM
> Subject: [OT] gcc: maximum length of an array?
>
>
>> Hi,
>> 
>> sorry for posting an [OT], but usually people on this list know everything 
>> :-)
>> 
>> Since I don't know too much about programming I am frequently fascinated by 
>> simple things like Eratosthenes' sieve.
>> As you might remember, one has to create a boolean array for that. The 
>> longer the array the more primes can be found.
>> 
>> With malloc() I can create an array of length 100000000 (10^8)
>> and the first 5761455 primes are calculated in a few seconds.
>> So of course I would like to test length 10^9 but here my program crashes.
>> 
>> So my questions:
>>  - is there some way to create a longer array?
>>  - or what are the alternatives?
>>  - do you know some kind of fine manual about this?
>> 
>> Regards and thanks for all answers,
>> 
>> Uli.
>> 
>> 
>> *********************************************
>> * Peter Ulrich Kruppa - Wuppertal - Germany *
>> *********************************************
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>
>



*********************************************
* Peter Ulrich Kruppa - Wuppertal - Germany *
*********************************************