TempAlloc (Was: Library Development: What to finish/flesh out?)

[dsimcha]

On 3/18/2011 2:56 AM, Don wrote:
>> 3. TempAlloc: A memory allocator based on a thread-local segmented stack,
>> useful for allocating large temporary buffers in things like numerics
>> code.
>> Also comes with a hash table, hash set and AVL tree optimized for this
>> allocation scheme. The advantages over plain old stack allocation are
>> that
>> it's independent of function calls (meaning you can return pointers to
>> TempAlloc-allocated memory from a function, etc.) and it's segmented,
>> meaning
>> you can allocate huge buffers w/o risking stack overflow. Its main
>> weakness
>> is that this stack is not scanned by the GC, meaning that you can't
>> store the
>> only reference to a GC-allocated piece of memory here. However, in
>> practice
>> large arrays of primitives are an extremely common case in
>> performance-critical code. I find this module immensely useful in
>> dstats and
>> Lars Kyllingstad uses it in SciD. Getting it into Phobos would make it
>> easy
>> for other scientific/numerics code to use it. Completion state:
>> Working and
>> used. Needs a litte cleanup and documentation. (Phobos candidate)
>
> This is #1. Far and away. Belongs in druntime.
> I would use it instantly in BigInt.

This is not up for "official" review yet because std.net.isemail and 
std.parallelism (and possibly more stuff depending on how we manage the 
review queue) are ahead of it.  If you want a sneak preview:

Code:

https://github.com/dsimcha/TempAlloc

Docs:

http://cis.jhu.edu/~dsimcha/d/phobos/core_tempalloc.html

I put in a few small, tangentially related memory allocation functions 
that I've wanted in druntime/Phobos for awhile in this proposal, too. 
alignedMalloc() and alignedFree() are used by TempAlloc but can be made 
private if people don't like them.  newVoid() is not used by TempAlloc 
and might fit better in std.array, but I think it belongs somewhere in 
Phobos or druntime.