[SciPy-dev] Memory mapped files in scipy core
oliphant at ee.byu.edu
Mon Nov 21 14:12:07 CST 2005
Paul Barrett wrote:
> On 11/20/05, *Travis Oliphant* <oliphant at ee.byu.edu
> <mailto:oliphant at ee.byu.edu>> wrote:
> On a related, but orthogonal note:
> My understanding is that using memory-mapped files for *very* large
> files will require modification to the mmap module in Python ---
> something I think we should push. One part of that process would
> be to
> add the C-struct array interface to the mmap module and the buffer
> object -- perhaps this is how we get the array interface into Python
> quickly. Then, if we could make a base-type mmap that did not
> use the
> buffer interface or the sequence interface (similar to the
> bigndarray in
> scipy_core) and therefore by-passed the problems with Python in those
> areas, then the current mmap object could inherit from the base class
> and provide current functionality while still exposing the array
> interface for access to >2GB files on 64-bit systems.
> Is it really necessary to embed the C-struct array interface in mmap?
> I thought that Python array interface was the standard mechanism for
> interfacing with array objects. Or do I misunderstand you.
The C-struct interface is faster and a bit easier to code in C.
Currently the C-struct interface is how numarray/ Numeric and scipy
core are all talking to each other.
One can use either the C-struct interface or the Python interface for
implementing the array interface. I suspect we would want both on the
memory-mapped object. The most important element of the proposal is
elimination of the buffer and sequence protocols on a new base-class
mmap object. Then users could use this object to memory-map very large
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