r"""Module that defines indexed objects. The classes ``IndexedBase``, ``Indexed``, and ``Idx`` represent a matrix element ``M[i, j]`` as in the following diagram:: 1) The Indexed class represents the entire indexed object. | ___|___ ' ' M[i, j] / \__\______ | | | | | 2) The Idx class represents indices; each Idx can | optionally contain information about its range. | 3) IndexedBase represents the 'stem' of an indexed object, here `M`. The stem used by itself is usually taken to represent the entire array. There can be any number of indices on an Indexed object. No transformation properties are implemented in these Base objects, but implicit contraction of repeated indices is supported. Note that the support for complicated (i.e. non-atomic) integer expressions as indices is limited. (This should be improved in future releases.) Examples ======== To express the above matrix element example you would write: >>> from sympy import symbols, IndexedBase, Idx >>> M = IndexedBase('M') >>> i, j = symbols('i j', cls=Idx) >>> M[i, j] M[i, j] Repeated indices in a product implies a summation, so to express a matrix-vector product in terms of Indexed objects: >>> x = IndexedBase('x') >>> M[i, j]*x[j] M[i, j]*x[j] If the indexed objects will be converted to component based arrays, e.g. with the code printers or the autowrap framework, you also need to provide (symbolic or numerical) dimensions. This can be done by passing an optional shape parameter to IndexedBase upon construction: >>> dim1, dim2 = symbols('dim1 dim2', integer=True) >>> A = IndexedBase('A', shape=(dim1, 2*dim1, dim2)) >>> A.shape (dim1, 2*dim1, dim2) >>> A[i, j, 3].shape (dim1, 2*dim1, dim2) If an IndexedBase object has no shape information, it is assumed that the array is as large as the ranges of its indices: >>> n, m = symbols('n m', integer=True) >>> i = Idx('i', m) >>> j = Idx('j', n) >>> M[i, j].shape (m, n) >>> M[i, j].ranges [(0, m - 1), (0, n - 1)] The above can be compared with the following: >>> A[i, 2, j].shape (dim1, 2*dim1, dim2) >>> A[i, 2, j].ranges [(0, m - 1), None, (0, n - 1)] To analyze the structure of indexed expressions, you can use the methods get_indices() and get_contraction_structure(): >>> from sympy.tensor import get_indices, get_contraction_structure >>> get_indices(A[i, j, j]) ({i}, {}) >>> get_contraction_structure(A[i, j, j]) {(j,): {A[i, j, j]}} See the appropriate docstrings for a detailed explanation of the output. """ # TODO: (some ideas for improvement) # # o test and guarantee numpy compatibility # - implement full support for broadcasting # - strided arrays # # o more functions to analyze indexed expressions # - identify standard constructs, e.g matrix-vector product in a subexpression # # o functions to generate component based arrays (numpy and sympy.Matrix) # - generate a single array directly from Indexed # - convert simple sub-expressions # # o sophisticated indexing (possibly in subclasses to preserve simplicity) # - Idx with range smaller than dimension of Indexed # - Idx with stepsize != 1 # - Idx with step determined by function call from collections.abc import Iterable from sympy.core.numbers import Number from sympy.core.assumptions import StdFactKB from sympy.core import Expr, Tuple, sympify, S from sympy.core.symbol import _filter_assumptions, Symbol from sympy.core.logic import fuzzy_bool, fuzzy_not from sympy.core.sympify import _sympify from sympy.functions.special.tensor_functions import KroneckerDelta from sympy.multipledispatch import dispatch from sympy.utilities.iterables import is_sequence, NotIterable from sympy.utilities.misc import filldedent class IndexException(Exception): pass class Indexed(Expr): """Represents a mathematical object with indices. >>> from sympy import Indexed, IndexedBase, Idx, symbols >>> i, j = symbols('i j', cls=Idx) >>> Indexed('A', i, j) A[i, j] It is recommended that ``Indexed`` objects be created by indexing ``IndexedBase``: ``IndexedBase('A')[i, j]`` instead of ``Indexed(IndexedBase('A'), i, j)``. >>> A = IndexedBase('A') >>> a_ij = A[i, j] # Prefer this, >>> b_ij = Indexed(A, i, j) # over this. >>> a_ij == b_ij True """ is_Indexed = True is_symbol = True is_Atom = True def __new__(cls, base, *args, **kw_args): from sympy.tensor.array.ndim_array import NDimArray from sympy.matrices.matrixbase import MatrixBase if not args: raise IndexException("Indexed needs at least one index.") if isinstance(base, (str, Symbol)): base = IndexedBase(base) elif not hasattr(base, '__getitem__') and not isinstance(base, IndexedBase): raise TypeError(filldedent(""" The base can only be replaced with a string, Symbol, IndexedBase or an object with a method for getting items (i.e. an object with a `__getitem__` method). """)) args = list(map(sympify, args)) if isinstance(base, (NDimArray, Iterable, Tuple, MatrixBase)) and all(i.is_number for i in args): if len(args) == 1: return base[args[0]] else: return base[args] base = _sympify(base) obj = Expr.__new__(cls, base, *args, **kw_args) IndexedBase._set_assumptions(obj, base.assumptions0) return obj def _hashable_content(self): return super()._hashable_content() + tuple(sorted(self.assumptions0.items())) @property def name(self): return str(self) @property def _diff_wrt(self): """Allow derivatives with respect to an ``Indexed`` object.""" return True def _eval_derivative(self, wrt): from sympy.tensor.array.ndim_array import NDimArray if isinstance(wrt, Indexed) and wrt.base == self.base: if len(self.indices) != len(wrt.indices): msg = "Different # of indices: d({!s})/d({!s})".format(self, wrt) raise IndexException(msg) result = S.One for index1, index2 in zip(self.indices, wrt.indices): result *= KroneckerDelta(index1, index2) return result elif isinstance(self.base, NDimArray): from sympy.tensor.array import derive_by_array return Indexed(derive_by_array(self.base, wrt), *self.args[1:]) else: if Tuple(self.indices).has(wrt): return S.NaN return S.Zero @property def assumptions0(self): return {k: v for k, v in self._assumptions.items() if v is not None} @property def base(self): """Returns the ``IndexedBase`` of the ``Indexed`` object. Examples ======== >>> from sympy import Indexed, IndexedBase, Idx, symbols >>> i, j = symbols('i j', cls=Idx) >>> Indexed('A', i, j).base A >>> B = IndexedBase('B') >>> B == B[i, j].base True """ return self.args[0] @property def indices(self): """ Returns the indices of the ``Indexed`` object. Examples ======== >>> from sympy import Indexed, Idx, symbols >>> i, j = symbols('i j', cls=Idx) >>> Indexed('A', i, j).indices (i, j) """ return self.args[1:] @property def rank(self): """ Returns the rank of the ``Indexed`` object. Examples ======== >>> from sympy import Indexed, Idx, symbols >>> i, j, k, l, m = symbols('i:m', cls=Idx) >>> Indexed('A', i, j).rank 2 >>> q = Indexed('A', i, j, k, l, m) >>> q.rank 5 >>> q.rank == len(q.indices) True """ return len(self.args) - 1 @property def shape(self): """Returns a list with dimensions of each index. Dimensions is a property of the array, not of the indices. Still, if the ``IndexedBase`` does not define a shape attribute, it is assumed that the ranges of the indices correspond to the shape of the array. >>> from sympy import IndexedBase, Idx, symbols >>> n, m = symbols('n m', integer=True) >>> i = Idx('i', m) >>> j = Idx('j', m) >>> A = IndexedBase('A', shape=(n, n)) >>> B = IndexedBase('B') >>> A[i, j].shape (n, n) >>> B[i, j].shape (m, m) """ if self.base.shape: return self.base.shape sizes = [] for i in self.indices: upper = getattr(i, 'upper', None) lower = getattr(i, 'lower', None) if None in (upper, lower): raise IndexException(filldedent(""" Range is not defined for all indices in: %s""" % self)) try: size = upper - lower + 1 except TypeError: raise IndexException(filldedent(""" Shape cannot be inferred from Idx with undefined range: %s""" % self)) sizes.append(size) return Tuple(*sizes) @property def ranges(self): """Returns a list of tuples with lower and upper range of each index. If an index does not define the data members upper and lower, the corresponding slot in the list contains ``None`` instead of a tuple. Examples ======== >>> from sympy import Indexed,Idx, symbols >>> Indexed('A', Idx('i', 2), Idx('j', 4), Idx('k', 8)).ranges [(0, 1), (0, 3), (0, 7)] >>> Indexed('A', Idx('i', 3), Idx('j', 3), Idx('k', 3)).ranges [(0, 2), (0, 2), (0, 2)] >>> x, y, z = symbols('x y z', integer=True) >>> Indexed('A', x, y, z).ranges [None, None, None] """ ranges = [] sentinel = object() for i in self.indices: upper = getattr(i, 'upper', sentinel) lower = getattr(i, 'lower', sentinel) if sentinel not in (upper, lower): ranges.append((lower, upper)) else: ranges.append(None) return ranges def _sympystr(self, p): indices = list(map(p.doprint, self.indices)) return "%s[%s]" % (p.doprint(self.base), ", ".join(indices)) @property def free_symbols(self): base_free_symbols = self.base.free_symbols indices_free_symbols = { fs for i in self.indices for fs in i.free_symbols} if base_free_symbols: return {self} | base_free_symbols | indices_free_symbols else: return indices_free_symbols @property def expr_free_symbols(self): from sympy.utilities.exceptions import sympy_deprecation_warning sympy_deprecation_warning(""" The expr_free_symbols property is deprecated. Use free_symbols to get the free symbols of an expression. """, deprecated_since_version="1.9", active_deprecations_target="deprecated-expr-free-symbols") return {self} class IndexedBase(Expr, NotIterable): """Represent the base or stem of an indexed object The IndexedBase class represent an array that contains elements. The main purpose of this class is to allow the convenient creation of objects of the Indexed class. The __getitem__ method of IndexedBase returns an instance of Indexed. Alone, without indices, the IndexedBase class can be used as a notation for e.g. matrix equations, resembling what you could do with the Symbol class. But, the IndexedBase class adds functionality that is not available for Symbol instances: - An IndexedBase object can optionally store shape information. This can be used in to check array conformance and conditions for numpy broadcasting. (TODO) - An IndexedBase object implements syntactic sugar that allows easy symbolic representation of array operations, using implicit summation of repeated indices. - The IndexedBase object symbolizes a mathematical structure equivalent to arrays, and is recognized as such for code generation and automatic compilation and wrapping. >>> from sympy.tensor import IndexedBase, Idx >>> from sympy import symbols >>> A = IndexedBase('A'); A A >>> type(A) When an IndexedBase object receives indices, it returns an array with named axes, represented by an Indexed object: >>> i, j = symbols('i j', integer=True) >>> A[i, j, 2] A[i, j, 2] >>> type(A[i, j, 2]) The IndexedBase constructor takes an optional shape argument. If given, it overrides any shape information in the indices. (But not the index ranges!) >>> m, n, o, p = symbols('m n o p', integer=True) >>> i = Idx('i', m) >>> j = Idx('j', n) >>> A[i, j].shape (m, n) >>> B = IndexedBase('B', shape=(o, p)) >>> B[i, j].shape (o, p) Assumptions can be specified with keyword arguments the same way as for Symbol: >>> A_real = IndexedBase('A', real=True) >>> A_real.is_real True >>> A != A_real True Assumptions can also be inherited if a Symbol is used to initialize the IndexedBase: >>> I = symbols('I', integer=True) >>> C_inherit = IndexedBase(I) >>> C_explicit = IndexedBase('I', integer=True) >>> C_inherit == C_explicit True """ is_symbol = True is_Atom = True @staticmethod def _set_assumptions(obj, assumptions): """Set assumptions on obj, making sure to apply consistent values.""" tmp_asm_copy = assumptions.copy() is_commutative = fuzzy_bool(assumptions.get('commutative', True)) assumptions['commutative'] = is_commutative obj._assumptions = StdFactKB(assumptions) obj._assumptions._generator = tmp_asm_copy # Issue #8873 def __new__(cls, label, shape=None, *, offset=S.Zero, strides=None, **kw_args): from sympy.matrices.matrixbase import MatrixBase from sympy.tensor.array.ndim_array import NDimArray assumptions, kw_args = _filter_assumptions(kw_args) if isinstance(label, str): label = Symbol(label, **assumptions) elif isinstance(label, Symbol): assumptions = label._merge(assumptions) elif isinstance(label, (MatrixBase, NDimArray)): return label elif isinstance(label, Iterable): return _sympify(label) else: label = _sympify(label) if is_sequence(shape): shape = Tuple(*shape) elif shape is not None: shape = Tuple(shape) if shape is not None: obj = Expr.__new__(cls, label, shape) else: obj = Expr.__new__(cls, label) obj._shape = shape obj._offset = offset obj._strides = strides obj._name = str(label) IndexedBase._set_assumptions(obj, assumptions) return obj @property def name(self): return self._name def _hashable_content(self): return super()._hashable_content() + tuple(sorted(self.assumptions0.items())) @property def assumptions0(self): return {k: v for k, v in self._assumptions.items() if v is not None} def __getitem__(self, indices, **kw_args): if is_sequence(indices): # Special case needed because M[*my_tuple] is a syntax error. if self.shape and len(self.shape) != len(indices): raise IndexException("Rank mismatch.") return Indexed(self, *indices, **kw_args) else: if self.shape and len(self.shape) != 1: raise IndexException("Rank mismatch.") return Indexed(self, indices, **kw_args) @property def shape(self): """Returns the shape of the ``IndexedBase`` object. Examples ======== >>> from sympy import IndexedBase, Idx >>> from sympy.abc import x, y >>> IndexedBase('A', shape=(x, y)).shape (x, y) Note: If the shape of the ``IndexedBase`` is specified, it will override any shape information given by the indices. >>> A = IndexedBase('A', shape=(x, y)) >>> B = IndexedBase('B') >>> i = Idx('i', 2) >>> j = Idx('j', 1) >>> A[i, j].shape (x, y) >>> B[i, j].shape (2, 1) """ return self._shape @property def strides(self): """Returns the strided scheme for the ``IndexedBase`` object. Normally this is a tuple denoting the number of steps to take in the respective dimension when traversing an array. For code generation purposes strides='C' and strides='F' can also be used. strides='C' would mean that code printer would unroll in row-major order and 'F' means unroll in column major order. """ return self._strides @property def offset(self): """Returns the offset for the ``IndexedBase`` object. This is the value added to the resulting index when the 2D Indexed object is unrolled to a 1D form. Used in code generation. Examples ========== >>> from sympy.printing import ccode >>> from sympy.tensor import IndexedBase, Idx >>> from sympy import symbols >>> l, m, n, o = symbols('l m n o', integer=True) >>> A = IndexedBase('A', strides=(l, m, n), offset=o) >>> i, j, k = map(Idx, 'ijk') >>> ccode(A[i, j, k]) 'A[l*i + m*j + n*k + o]' """ return self._offset @property def label(self): """Returns the label of the ``IndexedBase`` object. Examples ======== >>> from sympy import IndexedBase >>> from sympy.abc import x, y >>> IndexedBase('A', shape=(x, y)).label A """ return self.args[0] def _sympystr(self, p): return p.doprint(self.label) class Idx(Expr): """Represents an integer index as an ``Integer`` or integer expression. There are a number of ways to create an ``Idx`` object. The constructor takes two arguments: ``label`` An integer or a symbol that labels the index. ``range`` Optionally you can specify a range as either * ``Symbol`` or integer: This is interpreted as a dimension. Lower and upper bounds are set to ``0`` and ``range - 1``, respectively. * ``tuple``: The two elements are interpreted as the lower and upper bounds of the range, respectively. Note: bounds of the range are assumed to be either integer or infinite (oo and -oo are allowed to specify an unbounded range). If ``n`` is given as a bound, then ``n.is_integer`` must not return false. For convenience, if the label is given as a string it is automatically converted to an integer symbol. (Note: this conversion is not done for range or dimension arguments.) Examples ======== >>> from sympy import Idx, symbols, oo >>> n, i, L, U = symbols('n i L U', integer=True) If a string is given for the label an integer ``Symbol`` is created and the bounds are both ``None``: >>> idx = Idx('qwerty'); idx qwerty >>> idx.lower, idx.upper (None, None) Both upper and lower bounds can be specified: >>> idx = Idx(i, (L, U)); idx i >>> idx.lower, idx.upper (L, U) When only a single bound is given it is interpreted as the dimension and the lower bound defaults to 0: >>> idx = Idx(i, n); idx.lower, idx.upper (0, n - 1) >>> idx = Idx(i, 4); idx.lower, idx.upper (0, 3) >>> idx = Idx(i, oo); idx.lower, idx.upper (0, oo) """ is_integer = True is_finite = True is_real = True is_symbol = True is_Atom = True _diff_wrt = True def __new__(cls, label, range=None, **kw_args): if isinstance(label, str): label = Symbol(label, integer=True) label, range = list(map(sympify, (label, range))) if label.is_Number: if not label.is_integer: raise TypeError("Index is not an integer number.") return label if not label.is_integer: raise TypeError("Idx object requires an integer label.") elif is_sequence(range): if len(range) != 2: raise ValueError(filldedent(""" Idx range tuple must have length 2, but got %s""" % len(range))) for bound in range: if (bound.is_integer is False and bound is not S.Infinity and bound is not S.NegativeInfinity): raise TypeError("Idx object requires integer bounds.") args = label, Tuple(*range) elif isinstance(range, Expr): if range is not S.Infinity and fuzzy_not(range.is_integer): raise TypeError("Idx object requires an integer dimension.") args = label, Tuple(0, range - 1) elif range: raise TypeError(filldedent(""" The range must be an ordered iterable or integer SymPy expression.""")) else: args = label, obj = Expr.__new__(cls, *args, **kw_args) obj._assumptions["finite"] = True obj._assumptions["real"] = True return obj @property def label(self): """Returns the label (Integer or integer expression) of the Idx object. Examples ======== >>> from sympy import Idx, Symbol >>> x = Symbol('x', integer=True) >>> Idx(x).label x >>> j = Symbol('j', integer=True) >>> Idx(j).label j >>> Idx(j + 1).label j + 1 """ return self.args[0] @property def lower(self): """Returns the lower bound of the ``Idx``. Examples ======== >>> from sympy import Idx >>> Idx('j', 2).lower 0 >>> Idx('j', 5).lower 0 >>> Idx('j').lower is None True """ try: return self.args[1][0] except IndexError: return @property def upper(self): """Returns the upper bound of the ``Idx``. Examples ======== >>> from sympy import Idx >>> Idx('j', 2).upper 1 >>> Idx('j', 5).upper 4 >>> Idx('j').upper is None True """ try: return self.args[1][1] except IndexError: return def _sympystr(self, p): return p.doprint(self.label) @property def name(self): return self.label.name if self.label.is_Symbol else str(self.label) @property def free_symbols(self): return {self} @dispatch(Idx, Idx) def _eval_is_ge(lhs, rhs): # noqa:F811 other_upper = rhs if rhs.upper is None else rhs.upper other_lower = rhs if rhs.lower is None else rhs.lower if lhs.lower is not None and (lhs.lower >= other_upper) == True: return True if lhs.upper is not None and (lhs.upper < other_lower) == True: return False return None @dispatch(Idx, Number) # type:ignore def _eval_is_ge(lhs, rhs): # noqa:F811 other_upper = rhs other_lower = rhs if lhs.lower is not None and (lhs.lower >= other_upper) == True: return True if lhs.upper is not None and (lhs.upper < other_lower) == True: return False return None @dispatch(Number, Idx) # type:ignore def _eval_is_ge(lhs, rhs): # noqa:F811 other_upper = lhs other_lower = lhs if rhs.upper is not None and (rhs.upper <= other_lower) == True: return True if rhs.lower is not None and (rhs.lower > other_upper) == True: return False return None