Alice, Bob and Mallory comments

"Finding primes in parallel" by Jonas Elfström

Wed, 20 Jan 2010 09:11:22 +0100

http://coding-time.blogspot.com/2008/03/implement-your-own-parallelfor-in-c.html - makes it possible to run FindPrimesBySieveOfAtkins unchanged in C# 2.0-3.5.

"Finding primes in parallel" by Svish

Tue, 19 Jan 2010 18:33:16 +0100

So should maybe use the Set method instead then? Or doesn’t make much difference perhaps…

Thanks for the link. Will check it out :)

"Find primes in regexp" by Jonas Elfström

Mon, 18 Jan 2010 21:46:43 +0100

http://stackoverflow.com/questions/20448/what-is-the-most-brilliant-regex-youve-ever-used/20546#20546

And it was created by http://www.abigail.be/

"Finding primes in parallel" by Jonas Elfström

Sat, 16 Jan 2010 16:11:21 +0100

“I was wondering if it could be done in a nice way without using Parallel.”

Check out: http://www.codeproject.com/KB/dotnet/PoorMansParallelForEach.aspx

"Finding primes in parallel" by Jonas Elfström

Fri, 15 Jan 2010 17:24:41 +0100

If Holterman is correct then my usage is thread safe: http://stackoverflow.com/questions/1213997/is-there-a-generic-type-safe-bitarray-in-net/1214686#1214686

"Finding primes in parallel" by Jonas Elfström

Fri, 15 Jan 2010 16:23:15 +0100

That’s for “long, ulong, double, and decimal”. Read/write of booleans is atomic. I’m just not sure that isPrime[n] = !isPrime[n]; is the same as Boolean test = false; test = !test; which would be atomic.

"Finding primes in parallel" by Svish

Fri, 15 Jan 2010 15:50:13 +0100

From that link you posted: “Aside from the library functions designed for that purpose, there is no guarantee of atomic read-modify-write, such as in the case of increment or decrement.” – Wouldn’t that mean that it is not thread-safe? or?

"Finding primes in parallel" by Svish

Fri, 15 Jan 2010 15:47:57 +0100

But that would remove the parallelism :p I was wondering if it could be done in a nice way without using Parallel.For, but still have the parallelism. (So do whatever Parallel.For does yourself)

"Finding primes in parallel" by Jonas Elfström

Fri, 15 Jan 2010 13:33:16 +0100

Replace the Parallel.For with for (int x = 1; x <= sqrt; x++) and remove ); from row 24 and you should be good to go.

If I understand http://bit.ly/8lZagW correctly the isPrime[n] = !isPrime[n]; is an atomic operation but I have to investigate the matter of thread safety further. Thanks!

"Finding primes in parallel" by Svish

Fri, 15 Jan 2010 11:03:18 +0100

Are BitArrays thread-safe, or how does that work?

Is it possible to write a version of this without the Parrallel.For method? Well, I suppose it is possible of course, but would it be a big mess? :p