Version française
Home     About     Download     Resources     Contact us    

This site is updated infrequently. For up-to-date information, please visit the new OCaml website at

Browse thread
Documentation request: allocation of bigarrays in C
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: 2006-04-02 (14:05)
From: Dmitry Bely <dbely@m...>
Subject: Re: [Caml-list] Documentation request: allocation of bigarrays in C
Li-Thiao-Té Sébastien <> writes:

>>>If you want to be GC-friendly, use the bigarray
>>>allocation macros with a NULL pointer to allocate memory then get a
>>>pointer to the data array.
>> If you need GC-controlled bigarray, why simply not to use
>> Bigarray.Genarray.create?
> Why is there a C bigarray allocation function at all then ? :)

alloc_bigarray_xxx()? Their primary purpose is to allocate a proxy
structure for an external C-allocated data (that cannot be finalized).
data==NULL behaviour IMHO is not for the final user but only for
Bigarray.Genarray.create internal use.

> In my case, I want to read a relatively big file (50MB) containing
> arrays of floats . I use C functions for the raw speed then pass the
> bigarrays to OCaml to do some reordering of the data, and higher-level
> processing.

You should use Bigarray.Genarray.create then pass the created bigarray to C
side using Data_bigarray_val(). Note that the bigarray is allocated with
malloc() outside the Ocaml heap.

> I do not open the file in Ocaml then send a string to C for parsing,
> but rather open the file in C and return the bigarray list to
> Ocaml. (cf my previous mistake on creating Ocaml lists in C on this
> mailing-list)
> I have hundreds of such files that I may want to load and compare
> interactively, so reclaiming unused memory is a big bonus.

Sure - Ocaml-allocated bigarrays will be finalized as usual.

- Dmitry Bely