module Bigarray: sig .. end
Large, multi-dimensional, numerical arrays.
This module implements multi-dimensional arrays of integers and
floating-point numbers, thereafter referred to as 'big arrays'.
The implementation allows efficient sharing of large numerical
arrays between OCaml code and C or Fortran numerical libraries.
Concerning the naming conventions, users of this module are encouraged
to do
open Bigarray in their source, then refer to array types and
operations via short dot notation, e.g.
Array1.t or
Array2.sub.
Big arrays support all the OCaml ad-hoc polymorphic operations:
Element kinds
Big arrays can contain elements of the following kinds:
- IEEE single precision (32 bits) floating-point numbers
(
Bigarray.float32_elt),
- IEEE double precision (64 bits) floating-point numbers
(
Bigarray.float64_elt),
- IEEE single precision (2 * 32 bits) floating-point complex numbers
(
Bigarray.complex32_elt),
- IEEE double precision (2 * 64 bits) floating-point complex numbers
(
Bigarray.complex64_elt),
- 8-bit integers (signed or unsigned)
(
Bigarray.int8_signed_elt or Bigarray.int8_unsigned_elt),
- 16-bit integers (signed or unsigned)
(
Bigarray.int16_signed_elt or Bigarray.int16_unsigned_elt),
- OCaml integers (signed, 31 bits on 32-bit architectures,
63 bits on 64-bit architectures) (
Bigarray.int_elt),
- 32-bit signed integer (
Bigarray.int32_elt),
- 64-bit signed integers (
Bigarray.int64_elt),
- platform-native signed integers (32 bits on 32-bit architectures,
64 bits on 64-bit architectures) (
Bigarray.nativeint_elt).
Each element kind is represented at the type level by one
of the abstract types defined below.
type float32_elt
type float64_elt
type complex32_elt
type complex64_elt
type int8_signed_elt
type int8_unsigned_elt
type int16_signed_elt
type int16_unsigned_elt
type int_elt
type int32_elt
type int64_elt
type nativeint_elt
type ('a, 'b) kind
To each element kind is associated an OCaml type, which is
the type of OCaml values that can be stored in the big array
or read back from it. This type is not necessarily the same
as the type of the array elements proper: for instance,
a big array whose elements are of kind float32_elt contains
32-bit single precision floats, but reading or writing one of
its elements from OCaml uses the OCaml type float, which is
64-bit double precision floats.
The abstract type ('a, 'b) kind captures this association
of an OCaml type 'a for values read or written in the big array,
and of an element kind 'b which represents the actual contents
of the big array. The following predefined values of type
kind list all possible associations of OCaml types with
element kinds:
val char : (char, int8_unsigned_elt) kind
As shown by the types of the values above,
big arrays of kind
float32_elt and
float64_elt are
accessed using the OCaml type
float. Big arrays of complex kinds
complex32_elt,
complex64_elt are accessed with the OCaml type
Complex.t. Big arrays of
integer kinds are accessed using the smallest OCaml integer
type large enough to represent the array elements:
int for 8- and 16-bit integer bigarrays, as well as OCaml-integer
bigarrays;
int32 for 32-bit integer bigarrays;
int64
for 64-bit integer bigarrays; and
nativeint for
platform-native integer bigarrays. Finally, big arrays of
kind
int8_unsigned_elt can also be accessed as arrays of
characters instead of arrays of small integers, by using
the kind value
char instead of
int8_unsigned.
Array layouts
type fortran_layout
To facilitate interoperability with existing C and Fortran code,
this library supports two different memory layouts for big arrays,
one compatible with the C conventions,
the other compatible with the Fortran conventions.
In the C-style layout, array indices start at 0, and
multi-dimensional arrays are laid out in row-major format.
That is, for a two-dimensional array, all elements of
row 0 are contiguous in memory, followed by all elements of
row 1, etc. In other terms, the array elements at
(x,y)
and
(x, y+1) are adjacent in memory.
In the Fortran-style layout, array indices start at 1, and
multi-dimensional arrays are laid out in column-major format.
That is, for a two-dimensional array, all elements of
column 0 are contiguous in memory, followed by all elements of
column 1, etc. In other terms, the array elements at
(x,y)
and
(x+1, y) are adjacent in memory.
Each layout style is identified at the type level by the
abstract types
Bigarray.c_layout and
fortran_layout respectively.
Supported layouts
The abstract values
c_layout and
fortran_layout represent
the two supported layouts at the level of values.
Generic arrays (of arbitrarily many dimensions)
One-dimensional arrays
module Array1: sig .. end
One-dimensional arrays.
Two-dimensional arrays
module Array2: sig .. end
Two-dimensional arrays.
Three-dimensional arrays
module Array3: sig .. end
Three-dimensional arrays.
Coercions between generic big arrays and fixed-dimension big arrays
val genarray_of_array1 : ('a, 'b, 'c) Array1.t -> ('a, 'b, 'c) Genarray.t
Return the generic big array corresponding to the given one-dimensional
big array.
val genarray_of_array2 : ('a, 'b, 'c) Array2.t -> ('a, 'b, 'c) Genarray.t
Return the generic big array corresponding to the given two-dimensional
big array.
val genarray_of_array3 : ('a, 'b, 'c) Array3.t -> ('a, 'b, 'c) Genarray.t
Return the generic big array corresponding to the given three-dimensional
big array.
val array1_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array1.t
Return the one-dimensional big array corresponding to the given
generic big array. Raise Invalid_argument if the generic big array
does not have exactly one dimension.
val array2_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array2.t
Return the two-dimensional big array corresponding to the given
generic big array. Raise Invalid_argument if the generic big array
does not have exactly two dimensions.
val array3_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array3.t
Return the three-dimensional big array corresponding to the given
generic big array. Raise Invalid_argument if the generic big array
does not have exactly three dimensions.
Re-shaping big arrays
val reshape : ('a, 'b, 'c) Genarray.t ->
int array -> ('a, 'b, 'c) Genarray.t
reshape b [|d1;...;dN|] converts the big array b to a
N-dimensional array of dimensions d1...dN. The returned
array and the original array b share their data
and have the same layout. For instance, assuming that b
is a one-dimensional array of dimension 12, reshape b [|3;4|]
returns a two-dimensional array b' of dimensions 3 and 4.
If b has C layout, the element (x,y) of b' corresponds
to the element x * 3 + y of b. If b has Fortran layout,
the element (x,y) of b' corresponds to the element
x + (y - 1) * 4 of b.
The returned big array must have exactly the same number of
elements as the original big array b. That is, the product
of the dimensions of b must be equal to i1 * ... * iN.
Otherwise, Invalid_argument is raised.