Bigarray.Genarray(3) OCaml library Bigarray.Genarray(3)NAMEBigarray.Genarray - no description
Module
Module Bigarray.GenarrayDocumentation
Module Genarray
: sig end
type ('a, 'b, 'c) t
The type Genarray.t is the type of big arrays with variable numbers of
dimensions. Any number of dimensions between 1 and 16 is supported.
The three type parameters to Genarray.t identify the array element kind
and layout, as follows:
-the first parameter, 'a , is the OCaml type for accessing array ele‐
ments ( float , int , int32 , int64 , nativeint );
-the second parameter, 'b , is the actual kind of array elements (
float32_elt , float64_elt , int8_signed_elt , int8_unsigned_elt , etc);
-the third parameter, 'c , identifies the array layout ( c_layout or
fortran_layout ).
For instance, (float, float32_elt, fortran_layout) Genarray.t is the
type of generic big arrays containing 32-bit floats in Fortran layout;
reads and writes in this array use the OCaml type float .
val create : ('a, 'b) Bigarray.kind -> 'c Bigarray.layout -> int array
-> ('a, 'b, 'c) t
Genarray.create kind layout dimensions returns a new big array whose
element kind is determined by the parameter kind (one of float32 ,
float64 , int8_signed , etc) and whose layout is determined by the
parameter layout (one of c_layout or fortran_layout ). The dimensions
parameter is an array of integers that indicate the size of the big
array in each dimension. The length of dimensions determines the num‐
ber of dimensions of the bigarray.
For instance, Genarray.create int32 c_layout [|4;6;8|] returns a fresh
big array of 32-bit integers, in C layout, having three dimensions, the
three dimensions being 4, 6 and 8 respectively.
Big arrays returned by Genarray.create are not initialized: the initial
values of array elements is unspecified.
Genarray.create raises Invalid_argument if the number of dimensions is
not in the range 1 to 16 inclusive, or if one of the dimensions is neg‐
ative.
val num_dims : ('a, 'b, 'c) t -> int
Return the number of dimensions of the given big array.
val dims : ('a, 'b, 'c) t -> int array
Genarray.dims a returns all dimensions of the big array a , as an array
of integers of length Genarray.num_dims a .
val nth_dim : ('a, 'b, 'c) t -> int -> int
Genarray.nth_dim a n returns the n -th dimension of the big array a .
The first dimension corresponds to n = 0 ; the second dimension corre‐
sponds to n = 1 ; the last dimension, to n = Genarray.num_dims a - 1 .
Raise Invalid_argument if n is less than 0 or greater or equal than
Genarray.num_dims a .
val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
Return the kind of the given big array.
val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
Return the layout of the given big array.
val get : ('a, 'b, 'c) t -> int array -> 'a
Read an element of a generic big array. Genarray.get a [|i1; ...; iN|]
returns the element of a whose coordinates are i1 in the first dimen‐
sion, i2 in the second dimension, ..., iN in the N -th dimension.
If a has C layout, the coordinates must be greater or equal than 0 and
strictly less than the corresponding dimensions of a . If a has For‐
tran layout, the coordinates must be greater or equal than 1 and less
or equal than the corresponding dimensions of a . Raise Invalid_argu‐
ment if the array a does not have exactly N dimensions, or if the coor‐
dinates are outside the array bounds.
If N > 3 , alternate syntax is provided: you can write a.{i1, i2, ...,
iN} instead of Genarray.get a [|i1; ...; iN|] . (The syntax a.{...}
with one, two or three coordinates is reserved for accessing one-, two-
and three-dimensional arrays as described below.)
val set : ('a, 'b, 'c) t -> int array -> 'a -> unit
Assign an element of a generic big array. Genarray.set a [|i1; ...;
iN|] v stores the value v in the element of a whose coordinates are i1
in the first dimension, i2 in the second dimension, ..., iN in the N
-th dimension.
The array a must have exactly N dimensions, and all coordinates must
lie inside the array bounds, as described for Genarray.get ; otherwise,
Invalid_argument is raised.
If N > 3 , alternate syntax is provided: you can write a.{i1, i2, ...,
iN} <- v instead of Genarray.set a [|i1; ...; iN|] v . (The syntax
a.{...} <- v with one, two or three coordinates is reserved for updat‐
ing one-, two- and three-dimensional arrays as described below.)
val sub_left : ('a, 'b, Bigarray.c_layout) t -> int -> int -> ('a, 'b,
Bigarray.c_layout) t
Extract a sub-array of the given big array by restricting the first
(left-most) dimension. Genarray.sub_left a ofs len returns a big array
with the same number of dimensions as a , and the same dimensions as a
, except the first dimension, which corresponds to the interval [ofs
... ofs + len - 1] of the first dimension of a . No copying of ele‐
ments is involved: the sub-array and the original array share the same
storage space. In other terms, the element at coordinates [|i1; ...;
iN|] of the sub-array is identical to the element at coordinates
[|i1+ofs; ...; iN|] of the original array a .
Genarray.sub_left applies only to big arrays in C layout. Raise
Invalid_argument if ofs and len do not designate a valid sub-array of a
, that is, if ofs < 0 , or len < 0 , or ofs + len > Genarray.nth_dim a
0 .
val sub_right : ('a, 'b, Bigarray.fortran_layout) t -> int -> int ->
('a, 'b, Bigarray.fortran_layout) t
Extract a sub-array of the given big array by restricting the last
(right-most) dimension. Genarray.sub_right a ofs len returns a big
array with the same number of dimensions as a , and the same dimensions
as a , except the last dimension, which corresponds to the interval
[ofs ... ofs + len - 1] of the last dimension of a . No copying of
elements is involved: the sub-array and the original array share the
same storage space. In other terms, the element at coordinates [|i1;
...; iN|] of the sub-array is identical to the element at coordinates
[|i1; ...; iN+ofs|] of the original array a .
Genarray.sub_right applies only to big arrays in Fortran layout. Raise
Invalid_argument if ofs and len do not designate a valid sub-array of a
, that is, if ofs < 1 , or len < 0 , or ofs + len > Genarray.nth_dim a
(Genarray.num_dims a - 1) .
val slice_left : ('a, 'b, Bigarray.c_layout) t -> int array -> ('a, 'b,
Bigarray.c_layout) t
Extract a sub-array of lower dimension from the given big array by fix‐
ing one or several of the first (left-most) coordinates. Genar‐
ray.slice_left a [|i1; ... ; iM|] returns the 'slice' of a obtained by
setting the first M coordinates to i1 , ..., iM . If a has N dimen‐
sions, the slice has dimension N - M , and the element at coordinates
[|j1; ...; j(N-M)|] in the slice is identical to the element at coordi‐
nates [|i1; ...; iM; j1; ...; j(N-M)|] in the original array a . No
copying of elements is involved: the slice and the original array share
the same storage space.
Genarray.slice_left applies only to big arrays in C layout. Raise
Invalid_argument if M >= N , or if [|i1; ... ; iM|] is outside the
bounds of a .
val slice_right : ('a, 'b, Bigarray.fortran_layout) t -> int array ->
('a, 'b, Bigarray.fortran_layout) t
Extract a sub-array of lower dimension from the given big array by fix‐
ing one or several of the last (right-most) coordinates. Genar‐
ray.slice_right a [|i1; ... ; iM|] returns the 'slice' of a obtained by
setting the last M coordinates to i1 , ..., iM . If a has N dimen‐
sions, the slice has dimension N - M , and the element at coordinates
[|j1; ...; j(N-M)|] in the slice is identical to the element at coordi‐
nates [|j1; ...; j(N-M); i1; ...; iM|] in the original array a . No
copying of elements is involved: the slice and the original array share
the same storage space.
Genarray.slice_right applies only to big arrays in Fortran layout.
Raise Invalid_argument if M >= N , or if [|i1; ... ; iM|] is outside
the bounds of a .
val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
Copy all elements of a big array in another big array. Genarray.blit
src dst copies all elements of src into dst . Both arrays src and dst
must have the same number of dimensions and equal dimensions. Copying
a sub-array of src to a sub-array of dst can be achieved by applying
Genarray.blit to sub-array or slices of src and dst .
val fill : ('a, 'b, 'c) t -> 'a -> unit
Set all elements of a big array to a given value. Genarray.fill a v
stores the value v in all elements of the big array a . Setting only
some elements of a to v can be achieved by applying Genarray.fill to a
sub-array or a slice of a .
val map_file : Unix.file_descr -> ?pos:int64 -> ('a, 'b) Bigarray.kind
-> 'c Bigarray.layout -> bool -> int array -> ('a, 'b, 'c) t
Memory mapping of a file as a big array. Genarray.map_file fd kind
layout shared dims returns a big array of kind kind , layout layout ,
and dimensions as specified in dims . The data contained in this big
array are the contents of the file referred to by the file descriptor
fd (as opened previously with Unix.openfile , for example). The
optional pos parameter is the byte offset in the file of the data being
mapped; it defaults to 0 (map from the beginning of the file).
If shared is true , all modifications performed on the array are
reflected in the file. This requires that fd be opened with write per‐
missions. If shared is false , modifications performed on the array
are done in memory only, using copy-on-write of the modified pages; the
underlying file is not affected.
Genarray.map_file is much more efficient than reading the whole file in
a big array, modifying that big array, and writing it afterwards.
To adjust automatically the dimensions of the big array to the actual
size of the file, the major dimension (that is, the first dimension for
an array with C layout, and the last dimension for an array with For‐
tran layout) can be given as -1 . Genarray.map_file then determines
the major dimension from the size of the file. The file must contain
an integral number of sub-arrays as determined by the non-major dimen‐
sions, otherwise Failure is raised.
If all dimensions of the big array are given, the file size is matched
against the size of the big array. If the file is larger than the big
array, only the initial portion of the file is mapped to the big array.
If the file is smaller than the big array, the file is automatically
grown to the size of the big array. This requires write permissions on
fd .
Array accesses are bounds-checked, but the bounds are determined by the
initial call to map_file . Therefore, you should make sure no other
process modifies the mapped file while you're accessing it, or a SIGBUS
signal may be raised. This happens, for instance, if the file is
shrinked.
OCamldoc 2013-10-24 Bigarray.Genarray(3)
