optimize parallel methods

[ashWhiteHat]

Abstract

I optimized parallelize method.
This is depending on #595.

I did experiment about pallalelize here.
I changed parallelize method according to following result.

Summary

Words

Word	Explanation
Turning Degree	The minimum degree k that the parallel starts to get benefit.
Task Size	The task that per thread processes.
Task Point	The point that expresses concrete task size as the addition is 1 and the multiplication is 5~6.
Base Turning Point	The turning degree when we perform 1 task point and degree is 13.
Chunk Size	The task point that per thread processes.

Fact

• The thread number is almost nothing to do with turning degree.
  Benched with thread number 2 and 8.
• The bigger task size, the lower turning degree.
• The bigger task size, the more the parallel speeds up.
• The bigger task size, degree and thread number, the smaller chunk size is efficient.
• The task size is 5 times addition < 1 time multiplication < 6 times addition.
• The influence rate is Task Point > Degree > Thread Number.

Variables

The turning degree can be computed approximately (Base Turning Degree) - (log(Task Point)).
The chunk size can be computed approximately n / 2^{[8 * (log(Task Point)) + 2 *(k - (Base Turning Degree)) + log(thread_number)] / 8}.

I would appreciate it if you could confirm.
Thank you.