Module Stdlib.Bigarray

module Bigarray: Bigarray;

Element kinds

Bigarrays can contain elements of the following kinds:

Each element kind is represented at the type level by one of the *_elt types defined below (defined with a single constructor instead of abstract types for technical injectivity reasons).

type float32_elt = 
| Float32_elt
type float64_elt = 
| Float64_elt
type int8_signed_elt = 
| Int8_signed_elt
type int8_unsigned_elt = 
| Int8_unsigned_elt
type int16_signed_elt = 
| Int16_signed_elt
type int16_unsigned_elt = 
| Int16_unsigned_elt
type int32_elt = 
| Int32_elt
type int64_elt = 
| Int64_elt
type int_elt = 
| Int_elt
type nativeint_elt = 
| Nativeint_elt
type complex32_elt = 
| Complex32_elt
type complex64_elt = 
| Complex64_elt
type ('a, 'b) kind = 
| Float32 : (float, float32_elt) kind
| Float64 : (float, float64_elt) kind
| Int8_signed : (int, int8_signed_elt) kind
| Int8_unsigned : (int, int8_unsigned_elt) kind
| Int16_signed : (int, int16_signed_elt) kind
| Int16_unsigned : (int, int16_unsigned_elt) kind
| Int32 : (int32, int32_elt) kind
| Int64 : (int64, int64_elt) kind
| Int : (int, int_elt) kind
| Nativeint : (nativeint, nativeint_elt) kind
| Complex32 : (Complex.t, complex32_elt) kind
| Complex64 : (Complex.t, complex64_elt) kind
| Char : (char, int8_unsigned_elt) kind

To each element kind is associated an OCaml type, which is the type of OCaml values that can be stored in the Bigarray or read back from it. This type is not necessarily the same as the type of the array elements proper: for instance, a Bigarray 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 GADT type ('a, 'b) kind captures this association of an OCaml type 'a for values read or written in the Bigarray, and of an element kind 'b which represents the actual contents of the Bigarray. Its constructors list all possible associations of OCaml types with element kinds, and are re-exported below for backward-compatibility reasons.

Using a generalized algebraic datatype (GADT) here allows writing well-typed polymorphic functions whose return type depend on the argument type, such as:

  let zero : type a b. (a, b) kind -> a = function
    | Float32 -> 0.0 | Complex32 -> Complex.zero
    | Float64 -> 0.0 | Complex64 -> Complex.zero
    | Int8_signed -> 0 | Int8_unsigned -> 0
    | Int16_signed -> 0 | Int16_unsigned -> 0
    | Int32 -> 0l | Int64 -> 0L
    | Int -> 0 | Nativeint -> 0n
    | Char -> '\000'
let float32: kind(float, float32_elt);
let float64: kind(float, float64_elt);
let complex32: kind(Complex.t, complex32_elt);
let complex64: kind(Complex.t, complex64_elt);
let int8_signed: kind(int, int8_signed_elt);
let int8_unsigned: kind(int, int8_unsigned_elt);
let int16_signed: kind(int, int16_signed_elt);
let int16_unsigned: kind(int, int16_unsigned_elt);
let int: kind(int, int_elt);
let int32: kind(int32, int32_elt);
let int64: kind(int64, int64_elt);
let nativeint: kind(nativeint, nativeint_elt);
let char: kind(char, int8_unsigned_elt);

As shown by the types of the values above, Bigarrays of kind float32_elt and float64_elt are accessed using the OCaml type float. Bigarrays of complex kinds complex32_elt, complex64_elt are accessed with the OCaml type Complex.t. Bigarrays 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, Bigarrays 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.

let kind_size_in_bytes: kind('a, 'b) => int;

kind_size_in_bytes k is the number of bytes used to store an element of type k.

Array layouts

type c_layout = 
| C_layout_typ
type fortran_layout = 
| Fortran_layout_typ

To facilitate interoperability with existing C and Fortran code, this library supports two different memory layouts for Bigarrays, 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 phantom types Bigarray.c_layout and Bigarray.fortran_layout respectively.

Supported layouts

The GADT type 'a layout represents one of the two supported memory layouts: C-style or Fortran-style. Its constructors are re-exported as values below for backward-compatibility reasons.

type 'a layout = 
| C_layout : c_layout layout
| Fortran_layout : fortran_layout layout
let c_layout: layout(c_layout);
let fortran_layout: layout(fortran_layout);

Generic arrays (of arbitrarily many dimensions)

module Genarray: sig .. end

Zero-dimensional arrays

module Array0: sig .. end

Zero-dimensional arrays.

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 Bigarrays and fixed-dimension Bigarrays

let genarray_of_array0: Array0.t('a, 'b, 'c) => Genarray.t('a, 'b, 'c);

Return the generic Bigarray corresponding to the given zero-dimensional Bigarray.

let genarray_of_array1: Array1.t('a, 'b, 'c) => Genarray.t('a, 'b, 'c);

Return the generic Bigarray corresponding to the given one-dimensional Bigarray.

let genarray_of_array2: Array2.t('a, 'b, 'c) => Genarray.t('a, 'b, 'c);

Return the generic Bigarray corresponding to the given two-dimensional Bigarray.

let genarray_of_array3: Array3.t('a, 'b, 'c) => Genarray.t('a, 'b, 'c);

Return the generic Bigarray corresponding to the given three-dimensional Bigarray.

let array0_of_genarray: Genarray.t('a, 'b, 'c) => Array0.t('a, 'b, 'c);

Return the zero-dimensional Bigarray corresponding to the given generic Bigarray.

let array1_of_genarray: Genarray.t('a, 'b, 'c) => Array1.t('a, 'b, 'c);

Return the one-dimensional Bigarray corresponding to the given generic Bigarray.

let array2_of_genarray: Genarray.t('a, 'b, 'c) => Array2.t('a, 'b, 'c);

Return the two-dimensional Bigarray corresponding to the given generic Bigarray.

let array3_of_genarray: Genarray.t('a, 'b, 'c) => Array3.t('a, 'b, 'c);

Return the three-dimensional Bigarray corresponding to the given generic Bigarray.

Re-shaping Bigarrays

let reshape: (Genarray.t('a, 'b, 'c), array(int)) => Genarray.t('a, 'b, 'c);

reshape b [|d1;...;dN|] converts the Bigarray 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 Bigarray must have exactly the same number of elements as the original Bigarray b. That is, the product of the dimensions of b must be equal to i1 * ... * iN. Otherwise, Invalid_argument is raised.

let reshape_0: Genarray.t('a, 'b, 'c) => Array0.t('a, 'b, 'c);

Specialized version of Bigarray.reshape for reshaping to zero-dimensional arrays.

let reshape_1: (Genarray.t('a, 'b, 'c), int) => Array1.t('a, 'b, 'c);

Specialized version of Bigarray.reshape for reshaping to one-dimensional arrays.

let reshape_2: (Genarray.t('a, 'b, 'c), int, int) => Array2.t('a, 'b, 'c);

Specialized version of Bigarray.reshape for reshaping to two-dimensional arrays.

let reshape_3:
  (Genarray.t('a, 'b, 'c), int, int, int) => Array3.t('a, 'b, 'c);

Specialized version of Bigarray.reshape for reshaping to three-dimensional arrays.