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An improved version Sieve32FastV2 is available.

I don’t consider the code to be complicated but is quite a bit longer than a simple sieve. If a simple sieve is more of your speed, stick with Sieve31 or Sieve32.

Sieve31 a simple sieve for 31 bit primes, or int. Uses BitArray. Likely candidate for ToList().

Sieve32 a simple sieve for 32 bit primes, or uint. Uses BitArray. Due to memory needs, a bool[] version is not possible.

EBrown’s answer to Sieve31. Uses a bool[]. Over 40% faster than Sieve31 but uses 600% the memory. Due to memory constraints, cannot use ToList().

The version below is as fast if not faster than EBrown’s answer (depends on number of cores) but requires only 4% more memory than Sieve31.

• Sieve31 took 37.97 seconds and used 143 MB memory.

• EBrown’s answer took 22.18 seconds and used 1 GB memory.

• Sieve32Fast above took 20.38 seconds and used 149 MB.

• Sieve32 took 77.10 seconds and used 283 MB memory.
• Sieve32Fast above took 41.23 seconds and used 293 MB memory.

An improved version Sieve32FastV2 is available.

I don’t consider the code to be complicated but is quite a bit longer than a simple sieve. If a simple sieve is more of your speed, stick with Sieve31 or Sieve32.

Sieve31 a simple sieve for 31 bit primes, or int. Uses BitArray. Likely candidate for ToList().

Sieve32 a simple sieve for 32 bit primes, or uint. Uses BitArray. Due to memory needs, a bool[] version is not possible.

EBrown’s answer to Sieve31. Uses a bool[]. Over 40% faster than Sieve31 but uses 600% the memory. Due to memory constraints, cannot use ToList().

The version below is as fast if not faster than EBrown’s answer (depends on number of cores) but requires only 4% more memory than Sieve31.

• Sieve31 took 37.97 seconds and used 143 MB memory.

• EBrown’s answer took 22.18 seconds and used 1 GB memory.

• Sieve32Fast above took 20.38 seconds and used 149 MB.

• Sieve32 took 77.10 seconds and used 283 MB memory.
• Sieve32Fast above took 41.23 seconds and used 293 MB memory.

An improved version Sieve32FastV2 is available.

`var prime32 = ToNumber(bitIndex, rootVector.StartingNumber);`

var prime32 = ToNumber(bitIndex, rootVector.StartingNumber);