Module Array
: sigend
Float arrays with packed representation.
typet = floatarray
The type of float arrays with packed representation.
Since 4.08
vallength : t->int
Return the length (number of elements) of the given floatarray.
valget : t->int->floatgetan returns the element number n of floatarray a .
RaisesInvalid_argument if n is outside the range 0 to (lengtha-1) .
valset : t->int->float->unitsetanx modifies floatarray a in place, replacing element number n with x .
RaisesInvalid_argument if n is outside the range 0 to (lengtha-1) .
valmake : int->float->tmakenx returns a fresh floatarray of length n , initialized with x .
RaisesInvalid_argument if n<0 or n>Sys.max_floatarray_length .
valcreate : int->tcreaten returns a fresh floatarray of length n , with uninitialized data.
RaisesInvalid_argument if n<0 or n>Sys.max_floatarray_length .
valinit : int->(int->float)->tinitnf returns a fresh floatarray of length n , with element number i initialized to the result of fi
. In other terms, initnf tabulates the results of f applied to the integers 0 to n-1 .
RaisesInvalid_argument if n<0 or n>Sys.max_floatarray_length .
valmake_matrix : int->int->float->tarraymake_matrixdimxdimye returns a two-dimensional array (an array of arrays) with first dimension dimx
and second dimension dimy , where all elements are initialized with e .
Since 5.2
RaisesInvalid_argument if dimx or dimy is negative or greater than Sys.max_floatarray_length .
valinit_matrix : int->int->(int->int->float)->tarrayinit_matrixdimxdimyf returns a two-dimensional array (an array of arrays) with first dimension dimx
and second dimension dimy , where the element at index ( x,y ) is initialized with fxy .
Since 5.2
RaisesInvalid_argument if dimx or dimy is negative or greater than Sys.max_floatarray_length .
valappend : t->t->tappendv1v2 returns a fresh floatarray containing the concatenation of the floatarrays v1 and v2 .
RaisesInvalid_argument if lengthv1+lengthv2>Sys.max_floatarray_length .
valconcat : tlist->t
Same as Float.Array.append , but concatenates a list of floatarrays.
valsub : t->int->int->tsubaposlen returns a fresh floatarray of length len , containing the elements number pos to pos+len-1 of floatarray a .
RaisesInvalid_argument if pos and len do not designate a valid subarray of a ; that is, if pos<0 , or
len<0 , or pos+len>lengtha .
valcopy : t->tcopya returns a copy of a , that is, a fresh floatarray containing the same elements as a .
valfill : t->int->int->float->unitfillaposlenx modifies the floatarray a in place, storing x in elements number pos to pos+len-1 .
RaisesInvalid_argument if pos and len do not designate a valid subarray of a .
valblit : t->int->t->int->int->unitblitsrcsrc_posdstdst_poslen copies len elements from floatarray src , starting at element number
src_pos , to floatarray dst , starting at element number dst_pos . It works correctly even if src and
dst are the same floatarray, and the source and destination chunks overlap.
RaisesInvalid_argument if src_pos and len do not designate a valid subarray of src , or if dst_pos and
len do not designate a valid subarray of dst .
valto_list : t->floatlistto_lista returns the list of all the elements of a .
valof_list : floatlist->tof_listl returns a fresh floatarray containing the elements of l .
RaisesInvalid_argument if the length of l is greater than Sys.max_floatarray_length .
Iteratorsvaliter : (float->unit)->t->unititerfa applies function f in turn to all the elements of a . It is equivalent to fa.(0);fa.(1);...;fa.(lengtha-1);() .
valiteri : (int->float->unit)->t->unit
Same as Float.Array.iter , but the function is applied with the index of the element as first argument,
and the element itself as second argument.
valmap : (float->float)->t->tmapfa applies function f to all the elements of a , and builds a floatarray with the results returned
by f .
valmap_inplace : (float->float)->t->unitmap_inplacefa applies function f to all elements of a , and updates their values in place.
Since 5.1
valmapi : (int->float->float)->t->t
Same as Float.Array.map , but the function is applied to the index of the element as first argument, and
the element itself as second argument.
valmapi_inplace : (int->float->float)->t->unit
Same as Float.Array.map_inplace , but the function is applied to the index of the element as first
argument, and the element itself as second argument.
Since 5.1
valfold_left : ('acc->float->'acc)->'acc->t->'accfold_leftfxinit computes f(...(f(fxinit.(0))init.(1))...)init.(n-1) , where n is the length of
the floatarray init .
valfold_right : (float->'acc->'acc)->t->'acc->'accfold_rightfainit computes fa.(0)(fa.(1)(...(fa.(n-1)init)...)) , where n is the length of
the floatarray a .
Iteratorsontwoarraysvaliter2 : (float->float->unit)->t->t->unitArray.iter2fab applies function f to all the elements of a and b .
RaisesInvalid_argument if the floatarrays are not the same size.
valmap2 : (float->float->float)->t->t->tmap2fab applies function f to all the elements of a and b , and builds a floatarray with the results
returned by f : [|fa.(0)b.(0);...;fa.(lengtha-1)b.(lengthb-1)|] .
RaisesInvalid_argument if the floatarrays are not the same size.
Arrayscanningvalfor_all : (float->bool)->t->boolfor_allf[|a1;...;an|] checks if all elements of the floatarray satisfy the predicate f . That is, it
returns (fa1)&&(fa2)&&...&&(fan) .
valexists : (float->bool)->t->boolexistsf[|a1;...;an|] checks if at least one element of the floatarray satisfies the predicate f .
That is, it returns (fa1)||(fa2)||...||(fan) .
valmem : float->t->boolmemaset is true if and only if there is an element of set that is structurally equal to a , i.e. there
is an x in set such that compareax=0 .
valmem_ieee : float->t->bool
Same as Float.Array.mem , but uses IEEE equality instead of structural equality.
Arraysearchingvalfind_opt : (float->bool)->t->floatoptionvalfind_index : (float->bool)->t->intoptionfind_indexfa returns Somei , where i is the index of the first element of the array a that satisfies fx , if there is such an element.
It returns None if there is no such element.
Since 5.1
valfind_map : (float->'aoption)->t->'aoptionvalfind_mapi : (int->float->'aoption)->t->'aoption
Same as find_map , but the predicate is applied to the index of the element as first argument (counting
from 0), and the element itself as second argument.
Since 5.1
Sortingandshufflingvalsort : (float->float->int)->t->unit
Sort a floatarray in increasing order according to a comparison function. The comparison function must
return 0 if its arguments compare as equal, a positive integer if the first is greater, and a negative
integer if the first is smaller (see below for a complete specification). For example, compare is a
suitable comparison function. After calling sort , the array is sorted in place in increasing order.
sort is guaranteed to run in constant heap space and (at most) logarithmic stack space.
The current implementation uses Heap Sort. It runs in constant stack space.
Specification of the comparison function: Let a be the floatarray and cmp the comparison function. The
following must be true for all x , y , z in a :
- cmpxy > 0 if and only if cmpyx < 0
- if cmpxy >= 0 and cmpyz >= 0 then cmpxz >= 0
When sort returns, a contains the same elements as before, reordered in such a way that for all i and j
valid indices of a :
- cmpa.(i)a.(j) >= 0 if i >= j
valstable_sort : (float->float->int)->t->unit
Same as Float.Array.sort , but the sorting algorithm is stable (i.e. elements that compare equal are
kept in their original order) and not guaranteed to run in constant heap space.
The current implementation uses Merge Sort. It uses a temporary floatarray of length n/2 , where n is the
length of the floatarray. It is usually faster than the current implementation of Float.Array.sort .
valfast_sort : (float->float->int)->t->unit
Same as Float.Array.sort or Float.Array.stable_sort , whichever is faster on typical input.
valshuffle : rand:(int->int)->t->unitshuffleranda randomly permutes a 's elements using rand for randomness. The distribution of
permutations is uniform.
rand must be such that a call to randn returns a uniformly distributed random number in the range [ 0 ;
n-1 ]. Random.int can be used for this (do not forget to Random.self_init the generator).
Since 5.2
FloatarraysandSequencesvalto_seq : t->floatSeq.t
Iterate on the floatarray, in increasing order. Modifications of the floatarray during iteration will be
reflected in the sequence.
valto_seqi : t->(int*float)Seq.t
Iterate on the floatarray, in increasing order, yielding indices along elements. Modifications of the
floatarray during iteration will be reflected in the sequence.
valof_seq : floatSeq.t->t
Create an array from the generator.
valmap_to_array : (float->'a)->t->'aarraymap_to_arrayfa applies function f to all the elements of a , and builds an array with the results
returned by f : [|fa.(0);fa.(1);...;fa.(lengtha-1)|] .
valmap_from_array : ('a->float)->'aarray->tmap_from_arrayfa applies function f to all the elements of a , and builds a floatarray with the results
returned by f .
Arraysandconcurrencysafety
Care must be taken when concurrently accessing float arrays from multiple domains: accessing an array
will never crash a program, but unsynchronized accesses might yield surprising
(non-sequentially-consistent) results.
Atomicity
Every float array operation that accesses more than one array element is not atomic. This includes
iteration, scanning, sorting, splitting and combining arrays.
For example, consider the following program:
letsize=100_000_000leta=Float.Array.makesize1.letupdateaf()=Float.Array.iteri(funix->Float.Array.setai(fx))aletd1=Domain.spawn(updatea(funx->x+.1.))letd2=Domain.spawn(updatea(funx->2.*.x+.1.))let()=Domain.joind1;Domain.joind2
After executing this code, each field of the float array a is either 2. , 3. , 4. or 5. . If
atomicity is required, then the user must implement their own synchronization (for example, using Mutex.t
).
Dataraces
If two domains only access disjoint parts of the array, then the observed behaviour is the equivalent to
some sequential interleaving of the operations from the two domains.
A data race is said to occur when two domains access the same array element without synchronization and
at least one of the accesses is a write. In the absence of data races, the observed behaviour is
equivalent to some sequential interleaving of the operations from different domains.
Whenever possible, data races should be avoided by using synchronization to mediate the accesses to the
array elements.
Indeed, in the presence of data races, programs will not crash but the observed behaviour may not be
equivalent to any sequential interleaving of operations from different domains. Nevertheless, even in the
presence of data races, a read operation will return the value of some prior write to that location with
a few exceptions.
Tearing
Float arrays have two supplementary caveats in the presence of data races.
First, the blit operation might copy an array byte-by-byte. Data races between such a blit operation and
another operation might produce surprising values due to tearing: partial writes interleaved with other
operations can create float values that would not exist with a sequential execution.
For instance, at the end of
letzeros=Float.Array.makesize0.letmax_floats=Float.Array.makesizeFloat.max_floatletres=Float.Array.copyzerosletd1=Domain.spawn(fun()->Float.Array.blitzeros0res0size)letd2=Domain.spawn(fun()->Float.Array.blitmax_floats0res0size)let()=Domain.joind1;Domain.joind2
the res float array might contain values that are neither 0. nor max_float .
Second, on 32-bit architectures, getting or setting a field involves two separate memory accesses. In the
presence of data races, the user may observe tearing on any operation.
OCamldoc 2025-06-12 Float.Array(3o)
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