Date: Thu, 27 Jul 2006 15:50:09 +0200 (CEST) From: "P.U.Kruppa" <root@pukruppa.de> To: Andrew Brampton <andrew@bramp.freeserve.co.uk> Cc: freebsd-questions@freebsd.org Subject: Re: [OT] gcc: maximum length of an array? Message-ID: <20060727154218.W84312@www.pukruppa.net> In-Reply-To: <009d01c6ae6f$ec017840$0a00a8c0@Andrew> References: <20060724200535.G84312@www.pukruppa.net> <009d01c6ae6f$ec017840$0a00a8c0@Andrew>
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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@pukruppa.de> > 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. >> >> >> ********************************************* >> * Peter Ulrich Kruppa - Wuppertal - Germany * >> ********************************************* >> _______________________________________________ >> freebsd-questions@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-questions >> To unsubscribe, send any mail to >> "freebsd-questions-unsubscribe@freebsd.org" >> >> > > ********************************************* * Peter Ulrich Kruppa - Wuppertal - Germany * *********************************************
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