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" <[EMAIL PROTECTED]>
To: <freebsd-questions@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.
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* Peter Ulrich Kruppa - Wuppertal - Germany *
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