[CppAD] Multi-Threading

[Jey Kottalam]

Specifically, when using GCC on linux, the malloc linked in by GCC is
threadsafe when using the "-pthreads" option, and other threadsafe
mallocs such as TCMalloc are available from third-parties.

-Jey

On Thu, Mar 8, 2012 at 7:51 AM, Jey Kottalam <cppad at jey.kottalam.net> wrote:
>> The system memory allocator is
>> exclusive; i.e., only one thread can use it at a time. For this reason, the
>> old simpler version of CppAD would loose performance when more than 5
>> threads where used in parallel. A new multi-threading memory allocator was
>> added to solve this problem.
>>
>
> This is not true as far as I know. Even if it is, it's not an issue to
> be solved at the level of CppAD, but instead needs to be solved
> application-wide by any program that uses threads, so CppAD should
> just assume that the memory allocator provided by the system is
> thread-safe and performant. I'd like to at least see a preprocessor
> flag that can be used to disable CppAD's custom memory management
> layer to have it use operator new and operator new directly.
>
> Generally, CppAD's multi-threading API is rather clumsy and confusing
> right now, and could at least use some clearer documentation. (E.g.
> it's not clear what "multi-threading mode" is, whether it refers to
> using one tape from multiple threads, or if it creates a tape per
> thread. It was also not immediately clear whether "multi-threading
> mode" needed to be enabled to simply pass ADFun objects between
> threads.)
>
> -Jey