.. default-domain:: chpl .. module:: ChapelArray :synopsis: Operations on Domains and Arrays. Domain and Array Operations =========================== Operations on Domains and Arrays. ================================================= Distribution, Domain and Array Equality operators ================================================= Equality operators are defined to test if two distributions are equivalent or not: .. code-block:: chapel dist1 == dist2 dist1 != dist2 Or to test if two domains are equivalent or not: .. code-block:: chapel dom1 == dom2 dom1 != dom2 Arrays are promoted, so the result of the equality operators is an array of booleans. To get a single result use the ``equals`` method instead. .. code-block:: chapel arr1 == arr2 // compare each element resulting in an array of booleans arr1 != arr2 // compare each element resulting in an array of booleans arr1.equals(arr2) // compare entire arrays resulting in a single boolean ======================================== Miscellaneous Domain and Array Operators ======================================== The domain count operator ``#`` ------------------------------- The ``#`` operator can be applied to dense rectangular domains with a tuple argument whose size matches the rank of the domain (or optionally an integer in the case of a 1D domain). The operator is equivalent to applying the ``#`` operator to the component ranges of the domain and then using them to slice the domain. The array count operator ``#`` ------------------------------ The ``#`` operator can be applied to dense rectangular arrays with a tuple argument whose size matches the rank of the array (or optionally an integer in the case of a 1D array). The operator is equivalent to applying the ``#`` operator to the array's domain and using the result to slice the array. The array swap operator ``<=>`` ------------------------------- The ``<=>`` operator can be used to swap the contents of two arrays with the same shape. ================================================ Set Operations on Associative Domains and Arrays ================================================ Associative domains and arrays support a number of operators for set manipulations. The supported set operators are: ======= ==================== \+ , \| Union & Intersection \- Difference ^ Symmetric Difference ======= ==================== Consider the following code where ``A`` and ``B`` are associative arrays: .. code-block:: chapel var C = A op B; The result ``C`` is a new associative array backed by a new associative domain. The domains of ``A`` and ``B`` are not modified by ``op``. There are also ``op=`` variants that store the result into the first operand. Consider the following code where ``A`` and ``B`` are associative arrays: .. code-block:: chapel A op= B; ``A`` must not share its domain with another array, otherwise the program will halt with an error message. For the ``+=`` and ``|=`` operators, the value from ``B`` will overwrite the existing value in ``A`` when indices overlap. ================================================== Parallel Safety with respect to Arrays and Domains ================================================== Users must take care when applying operations to arrays and domains concurrently from distinct tasks. For instance, if one task is modifying the index set of a domain while another task is operating on either the domain itself or an array declared over that domain, this represents a race and could have arbitrary consequences including incorrect results and program crashes. While making domains and arrays safe with respect to such concurrent operations would be appealing, Chapel's current position is that such safety guarantees would be prohibitively expensive. Chapel arrays do support concurrent reads, writes, iterations, and operations as long as their domains are not being modified simultaneously. Such operations are subject to Chapel's memory consistency model like any other memory accesses. Similarly, tasks may make concurrent queries and iterations on a domain as long as another task is not simultaneously modifying the domain's index set. By default, associative domains permit multiple tasks to modify their index sets concurrently. This adds some amount of overhead to these operations. If the user knows that all such modifications will be done serially or in a parallel-safe context, the overheads can be avoided by setting ``parSafe`` to ``false`` in the domain's type declaration. For example, the following declaration creates an associative domain of strings where the implementation will do nothing to ensure that simultaneous modifications to the domain are parallel-safe: .. code-block:: chapel var D: domain(string, parSafe=false); As with any other domain type, it is not safe to access an associative array while its domain is changing, regardless of whether ``parSafe`` is set to ``true`` or ``false``. =========================================== Functions and Methods on Arrays and Domains =========================================== .. function:: proc isRectangularDom(d: domain) param Return true if the argument ``d`` is a rectangular domain. Otherwise return false. .. function:: proc isRectangularArr(a: []) param Return true if the argument ``a`` is an array with a rectangular domain. Otherwise return false. .. function:: proc isIrregularDom(d: domain) param Return true if ``d`` is an irregular domain; e.g. is not rectangular. Otherwise return false. .. function:: proc isIrregularArr(a: []) param Return true if ``a`` is an array with an irregular domain; e.g. not rectangular. Otherwise return false. .. function:: proc isAssociativeDom(d: domain) param Return true if ``d`` is an associative domain. Otherwise return false. .. function:: proc isAssociativeArr(a: []) param Return true if ``a`` is an array with an associative domain. Otherwise return false. .. function:: proc isSparseDom(d: domain) param Return true if ``d`` is a sparse domain. Otherwise return false. .. function:: proc isSparseArr(a: []) param Return true if ``a`` is an array with a sparse domain. Otherwise return false. .. type:: domain The domain type .. method:: proc init(_pid: int, _instance, _unowned: bool) .. method:: proc init(value) .. method:: proc init(d: _distribution, param rank: int, type idxType = int, param stridable: bool = false, definedConst: bool = false) .. method:: proc init(d: _distribution, param rank: int, type idxType = int, param stridable: bool = false, ranges: rank*(range(idxType, BoundedRangeType.bounded, stridable)), definedConst: bool = false) .. method:: proc init(d: _distribution, type idxType, param parSafe: bool = true, definedConst: bool = false) .. method:: proc init(d: _distribution, dom: domain, definedConst: bool = false) .. method:: proc init=(const ref other: domain) .. method:: proc init=(const ref other: domain) .. method:: proc dist Return the domain map that implements this domain .. method:: proc rank param Return the number of dimensions in this domain .. method:: proc idxType type Return the type of the indices of this domain .. method:: proc intIdxType type The ``idxType`` as represented by an integer type. When ``idxType`` is an enum type, this evaluates to ``int``. Otherwise, it evaluates to ``idxType``. .. method:: proc stridable param Return true if this is a stridable domain .. itermethod:: iter these() Yield the domain indices .. method:: proc this(i: integral ...rank) .. method:: proc dims() Return a tuple of ranges describing the bounds of a rectangular domain. For a sparse domain, return the bounds of the parent domain. .. method:: proc dim(d: int) Return a range representing the boundary of this domain in a particular dimension. .. method:: proc shape Return a tuple of :proc:`intIdxType` describing the size of each dimension. For a sparse domain, return the shape of the parent domain. .. method:: proc clear() Remove all indices from this domain, leaving it empty .. method:: proc add(in i) Add index ``i`` to this domain. This method is also available as the ``+=`` operator. The domain must be irregular. .. method:: proc makeIndexBuffer(size: int) Creates an index buffer which can be used for faster index addition. For example, instead of: .. code-block:: chapel var spsDom: sparse subdomain(parentDom); for i in someIndexIterator() do spsDom += i; You can use `SparseIndexBuffer` for better performance: .. code-block:: chapel var spsDom: sparse subdomain(parentDom); var idxBuf = spsDom.makeIndexBuffer(size=N); for i in someIndexIterator() do idxBuf.add(i); idxBuf.commit(); The above snippet will create a buffer of size N indices, and will automatically commit indices to the sparse domain as the buffer fills up. Indices are also committed when the buffer goes out of scope. .. note:: The interface and implementation is not stable and may change in the future. :arg size: Size of the buffer in number of indices. :type size: int .. method:: proc bulkAdd(inds: [] _value.rank*(_value.idxType), dataSorted = false, isUnique = false, preserveInds = true, addOn = nilLocale) Adds indices in ``inds`` to this domain in bulk. For sparse domains, an operation equivalent to this method is available with the ``+=`` operator, where the right-hand-side is an array. However, in that case, default values will be used for the flags ``dataSorted``, ``isUnique``, and ``preserveInds``. This method is available because in some cases, expensive operations can be avoided by setting those flags. To do so, ``bulkAdd`` must be called explicitly (instead of ``+=``). .. note:: Right now, this method and the corresponding ``+=`` operator are only available for sparse domains. In the future, we expect that these methods will be available for all irregular domains. .. note:: ``nilLocale`` is a sentinel value to denote that the locale where this addition should occur is unknown. We expect this to change in the future. :arg inds: Indices to be added. ``inds`` can be an array of ``rank*idxType`` or an array of ``idxType`` for 1-D domains. :arg dataSorted: ``true`` if data in ``inds`` is sorted. :type dataSorted: bool :arg isUnique: ``true`` if data in ``inds`` has no duplicates. :type isUnique: bool :arg preserveInds: ``true`` if data in ``inds`` needs to be preserved. :type preserveInds: bool :arg addOn: The locale where the indices should be added. Default value is ``nil`` which indicates that locale is unknown or there are more than one. :type addOn: locale :returns: Number of indices added to the domain :rtype: int .. method:: proc remove(i) Remove index ``i`` from this domain .. method:: proc requestCapacity(i) Request space for a particular number of values in an domain. Currently only applies to associative domains. .. method:: proc size Return the number of indices in this domain .. method:: proc low Return the lowest index in this domain .. method:: proc high Return the highest index in this domain .. method:: proc stride Return the stride of the indices in this domain .. method:: proc alignment Return the alignment of the indices in this domain .. method:: proc first Return the first index in this domain .. method:: proc last Return the last index in this domain .. method:: proc alignedLow Return the low index in this domain factoring in alignment .. method:: proc alignedHigh Return the high index in this domain factoring in alignment .. method:: proc contains(i: _value.idxType ...rank) Return true if this domain contains ``i``. Otherwise return false. For sparse domains, only indices with a value are considered to be contained in the domain. .. method:: proc isSubset(super: domain) Return true if this domain is a subset of ``super``. Otherwise returns false. .. method:: proc isSuper(sub: domain) Return true if this domain is a superset of ``sub``. Otherwise returns false. .. method:: proc orderToIndex(order: int) Returns the `ith` index in the domain counting from 0. For example, ``{2..10 by 2}.orderToIndex(2)`` would return ``6``. The order of a multidimensional domain follows its serial iterator. For example, ``{1..3, 1..2}.orderToIndex(3)`` would return ``(2, 2)``. .. note:: Right now, this method supports only dense rectangular domains with numeric indices :arg order: Order for which the corresponding index in the domain has to be found. :returns: Domain index for a given order in the domain. .. method:: proc expand(off: rank*(intIdxType)) Return a new domain that is the current domain expanded by ``off(d)`` in dimension ``d`` if ``off(d)`` is positive or contracted by ``off(d)`` in dimension ``d`` if ``off(d)`` is negative. .. method:: proc expand(off: intIdxType) Return a new domain that is the current domain expanded by ``off`` in all dimensions if ``off`` is positive or contracted by ``off`` in all dimensions if ``off`` is negative. .. method:: proc exterior(off: rank*(intIdxType)) Return a new domain that is the exterior portion of the current domain with ``off(d)`` indices for each dimension ``d``. If ``off(d)`` is negative, compute the exterior from the low bound of the dimension; if positive, compute the exterior from the high bound. .. method:: proc exterior(off: intIdxType) Return a new domain that is the exterior portion of the current domain with ``off`` indices for each dimension. If ``off`` is negative, compute the exterior from the low bound of the dimension; if positive, compute the exterior from the high bound. .. method:: proc interior(off: rank*(intIdxType)) Return a new domain that is the interior portion of the current domain with ``off(d)`` indices for each dimension ``d``. If ``off(d)`` is negative, compute the interior from the low bound of the dimension; if positive, compute the interior from the high bound. .. method:: proc interior(off: intIdxType) Return a new domain that is the interior portion of the current domain with ``off`` indices for each dimension. If ``off`` is negative, compute the interior from the low bound of the dimension; if positive, compute the interior from the high bound. .. method:: proc translate(off) Return a new domain that is the current domain translated by ``off(d)`` in each dimension ``d``. .. method:: proc translate(off) Return a new domain that is the current domain translated by ``off`` in each dimension. .. method:: proc isEmpty(): bool Return true if the domain has no indices .. method:: proc localSlice(r ...rank) Return a local view of the sub-array (slice) defined by the provided range(s), halting if the slice contains elements that are not local. Indexing into this local view is cheaper, because the indices are known to be local. .. method:: proc localSlice(d: domain) Return a local view of the sub-array (slice) defined by the provided domain, halting if the slice contains elements that are not local. Indexing into this local view is cheaper, because the indices are known to be local. .. itermethod:: iter sorted(comparator: ?t = chpl_defaultComparator()) Yield the domain indices in sorted order .. method:: proc safeCast(type t: domain) Cast a rectangular domain to another rectangular domain type. If the old type is stridable and the new type is not stridable, ensure that the stride was 1. .. method:: proc targetLocales() const ref Return an array of locales over which this domain has been distributed. .. method:: proc hasSingleLocalSubdomain() param Return true if the local subdomain can be represented as a single domain. Otherwise return false. .. method:: proc localSubdomain(loc: locale = here) Return the subdomain that is local to `loc`. :arg loc: indicates the locale for which the query should take place (defaults to `here`) :type loc: locale .. itermethod:: iter localSubdomains(loc: locale = here) Yield the subdomains that are local to `loc`. :arg loc: indicates the locale for which the query should take place (defaults to `here`) :type loc: locale .. method:: proc supportsAutoLocalAccess() param .. type:: array The array type .. method:: proc eltType type The type of elements contained in the array .. method:: proc idxType type The type of indices used in the array's domain .. method:: proc rank param The number of dimensions in the array .. method:: proc indices return the array's indices as its domain .. itermethod:: iter these() ref Yield the array elements .. method:: proc size Return the number of elements in the array .. method:: proc reindex(newDomain: domain) Return an array view over a new domain. The new domain must be of the same rank and size as the original array's domain. For example: .. code-block:: chapel var A: [1..10] int; const D = {6..15}; ref reA = A.reindex(D); reA[6] = 1; // updates A[1] .. method:: proc reindex(newDims ...) Return an array view over a new domain defined implicitly by one or more `newDims`, which must be ranges. The new domain must be of the same rank and size as the original array's domain. For example: .. code-block:: chapel var A: [3..4, 5..6] int; ref reA = A.reindex(13..14, 15..16); reA[13,15] = 1; // updates A[3,5] .. method:: proc IRV Return the Implicitly Represented Value for sparse arrays .. itermethod:: iter sorted(comparator: ?t = chpl_defaultComparator()) Yield the array elements in sorted order. .. method:: proc targetLocales() const ref Return an array of locales over which this array has been distributed. .. method:: proc hasSingleLocalSubdomain() param Return true if the local subdomain can be represented as a single domain. Otherwise return false. .. method:: proc localSubdomain(loc: locale = here) Return the subdomain that is local to `loc`. :arg loc: indicates the locale for which the query should take place (defaults to `here`) :type loc: locale .. itermethod:: iter localSubdomains(loc: locale = here) Yield the subdomains that are local to `loc`. :arg loc: indicates the locale for which the query should take place (defaults to `here`) :type loc: locale .. method:: proc isEmpty(): bool Return true if the array has no elements .. method:: proc back() Return the last element in the array. The array must be a rectangular 1-D array. .. method:: proc front() Return the first element in the array. The array must be a rectangular 1-D array. .. method:: proc reverse() Reverse the order of the values in the array. .. method:: proc find(val: this.eltType): (bool, index(this.domain)) Return a tuple containing ``true`` and the index of the first instance of ``val`` in the array, or if ``val`` is not found, a tuple containing ``false`` and an unspecified value is returned. .. method:: proc count(val: this.eltType): int Return the number of times ``val`` occurs in the array. .. method:: proc shape Return a tuple of integers describing the size of each dimension. For a sparse array, returns the shape of the parent domain. .. method:: proc iteratorYieldsLocalElements() param .. method:: proc array.equals(that: [] ): bool Return true if all this array is the same size and shape as argument ``that`` and all elements of this array are equal to the corresponding element in ``that``. Otherwise return false. .. function:: proc isDmapType(type t) param Return true if ``t`` is a domain map type. Otherwise return false. .. function:: proc isDmapValue(e) param Return true if ``e`` is a domain map. Otherwise return false. .. function:: proc isDomainType(type t) param Return true if ``t`` is a domain type. Otherwise return false. .. function:: proc isDomainValue(e) param Return true if ``e`` is a domain. Otherwise return false. .. function:: proc isArrayType(type t) param Return true if ``t`` is an array type. Otherwise return false. .. function:: proc isArrayValue(e) param Return true if ``e`` is an array. Otherwise return false. .. function:: proc reshape(A: [], D: domain) Return a copy of the array ``A`` containing the same values but in the shape of the domain ``D``. The number of indices in the domain must equal the number of elements in the array. The elements of ``A`` are copied into the new array using the default iteration orders over ``D`` and ``A``.