I need some feedback from some of the math nerds on the list.

The functions gammaf and lgammaf are not reentrant and set a global 'signgam' to indicate the sign.

Currently it looks like druntime/phobos2 use these non-reentrant versions, which could cause some issues in a threaded environment.

My questions for the math nerds are:

How important is this signgam value?

Should we provide a safe way of getting this value?

In std.math should we wrap the reentrant versions and store signgam in TLS, or should we expose the *_r reentrant versions in std.math directly?

I think now in D2 global variables are stored thread-local by default, so providing a safe signgam would be trivial (of course only accessible to the thread that called the lgamma/gamma).

Another option is to just leave it alone.  Personally I couldn't care less since I have never used the functions.

-- tbone

On Wed, 05 Jan 2011 11:33:30 -0700, Travis Boucher wrote:

> I need some feedback from some of the math nerds on the list.
> 
> The functions gammaf and lgammaf are not reentrant and set a global 'signgam' to indicate the sign.
> 
> Currently it looks like druntime/phobos2 use these non-reentrant versions, which could cause some issues in a threaded environment.
> 
> My questions for the math nerds are:
> 
> How important is this signgam value?
> 
> Should we provide a safe way of getting this value?
> 
> In std.math should we wrap the reentrant versions and store signgam in TLS, or should we expose the *_r reentrant versions in std.math directly?
> 
> I think now in D2 global variables are stored thread-local by default, so providing a safe signgam would be trivial (of course only accessible to the thread that called the lgamma/gamma).
> 
> Another option is to just leave it alone.  Personally I couldn't care less since I have never used the functions.
> 
> -- tbone

Phobos does not use the C gamma functions anymore.  Instead, there are native D implementations in the std.mathspecial module (as of the latest release), that don't have this problem.  See:

http://www.digitalmars.com/d/2.0/phobos/std_mathspecial.html

http://www.dsource.org/projects/phobos/browser/trunk/phobos/std/ mathspecial.d

-Lars