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Re: Add uniform_inside_sphere_distribution

From: Ed Smith-Rowland <3dw4rd at verizon dot net>
To: libstdc++ at gcc dot gnu dot org
Cc: gcc-patches <gcc-patches at gcc dot gnu dot org>
Date: Thu, 06 Nov 2014 08:08:23 -0500
Subject: Re: Add uniform_inside_sphere_distribution
Authentication-results: sourceware.org; auth=none
References: <545A6BD6 dot 5050706 at verizon dot net> <alpine dot DEB dot 2 dot 11 dot 1411052223020 dot 1572 at laptop-mg dot saclay dot inria dot fr> <545AB59D dot 3080906 at verizon dot net> <alpine dot DEB dot 2 dot 11 dot 1411060814090 dot 1570 at laptop-mg dot saclay dot inria dot fr>

On 11/06/2014 02:23 AM, Marc Glisse wrote:

On Wed, 5 Nov 2014, Ed Smith-Rowland wrote:
On 11/05/2014 04:25 PM, Marc Glisse wrote:
On Wed, 5 Nov 2014, Ed Smith-Rowland wrote:
Like the uniform_on_sphere_distribution which is used inside, the2-dimensional case uses rejection
Could you point out where in the code you are special-casingdimension 2? Somehow I can't see it in the patch.
My miscommunication.  Sorry.
The special casing - and all the hard work - is done by the containeduniform_on_sphere_distribution.
In dimension 2, uniform_on_sphere_distribution generates a uniformrandom point in the unit disk and projects it to the circle. Usingthat + one more random number to regenerate a uniform random point inthe disk seems wasteful to me.

Good point. I'll check out a direct rejection and see what that gets metime-wise. The ratio is pi/4 which is pretty good.

References:
- Add uniform_inside_sphere_distribution
  - From: Ed Smith-Rowland
- Re: Add uniform_inside_sphere_distribution
  - From: Marc Glisse
- Re: Add uniform_inside_sphere_distribution
  - From: Ed Smith-Rowland
- Re: Add uniform_inside_sphere_distribution
  - From: Marc Glisse

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