Improve QOL when reshaping array symbols

docs/reference/symbols.rst

@@ -47,6 +47,8 @@ are inherited by the :ref:`model symbols <symbols_model_symbols>`.
 
     ~ArraySymbol.all
     ~ArraySymbol.any
+    ~ArraySymbol.copy
+    ~ArraySymbol.flatten
     ~ArraySymbol.has_state
     ~ArraySymbol.max
     ~ArraySymbol.maybe_equals

dwave/optimization/_model.pyi

@@ -103,6 +103,8 @@ class ArraySymbol(Symbol):
     def __truediv__(self, rhs: ArraySymbol) -> Divide: ...
     def all(self) -> All: ...
     def any(self) -> Any: ...
+    def copy(self) -> Copy: ...
+    def flatten(self) -> Reshape: ...
     def max(self) -> Max: ...
     def min(self) -> Min: ...
     def ndim(self) -> int: ...

dwave/optimization/_model.pyx

@@ -1280,6 +1280,24 @@ cdef class ArraySymbol(Symbol):
         from dwave.optimization.symbols import Any  # avoid circular import
         return Any(self)
 
+    def copy(self):
+        """Return an array symbol that is a copy of the array.
+
+        See Also:
+            :class:`~dwave.optimization.symbols.Copy` Equivalent class.
+
+        .. versionadded:: 0.5.1
+        """
+        from dwave.optimization.symbols import Copy  # avoid circular import
+        return Copy(self)
+
+    def flatten(self):
+        """Return an array symbol collapsed into one dimension.
+
+        Equivalent to ``symbol.reshape(-1)``.
+        """
+        return self.reshape(-1)
+
     def max(self):
         """Create a :class:`~dwave.optimization.symbols.Max` symbol.
 
@@ -1350,11 +1368,14 @@ cdef class ArraySymbol(Symbol):
             (1, 3)
         """
         from dwave.optimization.symbols import Reshape  # avoid circular import
-        if len(shape) > 1:
-            return Reshape(self, shape)
-        else:
-            return Reshape(self, shape[0])
+        if len(shape) <= 1:
+            shape = shape[0]
+
+        if not self.array_ptr.contiguous():
+            return Reshape(self.copy(), shape)
 
+        return Reshape(self, shape)
+
     def shape(self):
         """Return the shape of the symbol.
 

dwave/optimization/include/dwave-optimization/array.hpp

@@ -915,10 +915,11 @@ class ArrayOutputMixin : public Base {
     explicit ArrayOutputMixin(ssize_t n) : ArrayOutputMixin({n}) {}
 
     explicit ArrayOutputMixin(std::initializer_list<ssize_t> shape)
-            : ndim_(shape.size()), shape_(make_shape(shape)) {}
+            : ArrayOutputMixin(std::span(shape)) {}
 
-    explicit ArrayOutputMixin(std::span<const ssize_t> shape)
-            : ndim_(shape.size()), shape_(make_shape(shape)) {}
+    template <std::ranges::sized_range Range>
+    explicit ArrayOutputMixin(Range&& shape)
+            : ndim_(shape.size()), shape_(make_shape(std::forward<Range>(shape))) {}
 
     ssize_t ndim() const noexcept final { return ndim_; }
 
@@ -941,7 +942,7 @@ class ArrayOutputMixin : public Base {
     constexpr bool contiguous() const noexcept final { return true; }
 
  private:
-    template <class Range>
+    template <std::ranges::sized_range Range>
     static std::unique_ptr<ssize_t[]> make_shape(Range&& shape) noexcept {
         if (shape.size() == 0) return nullptr;
         auto ptr = std::make_unique<ssize_t[]>(shape.size());

dwave/optimization/include/dwave-optimization/nodes/manipulation.hpp

@@ -46,6 +46,55 @@ class ConcatenateNode : public ArrayOutputMixin<ArrayNode> {
     std::vector<ssize_t> array_starts_;
 };
 
+/// An array node that is a contiguous copy of its predecessor.
+class CopyNode : public ArrayOutputMixin<ArrayNode> {
+ public:
+    explicit CopyNode(ArrayNode* array_ptr);
+
+    /// @copydoc Array::buff()
+    double const* buff(const State& state) const override;
+
+    /// @copydoc Node::commit()
+    void commit(State& state) const override;
+
+    /// @copydoc Array::diff()
+    std::span<const Update> diff(const State& state) const override;
+
+    /// @copydoc Node::initialize_state()
+    void initialize_state(State& state) const override;
+
+    /// @copydoc Array::integral()
+    bool integral() const override;
+
+    /// @copydoc Array::max()
+    double max() const override;
+
+    /// @copydoc Array::min()
+    double min() const override;
+
+    /// @copydoc Node::propagate()
+    void propagate(State& state) const override;
+
+    /// @copydoc Node::revert()
+    void revert(State& state) const override;
+
+    using ArrayOutputMixin::shape;
+
+    /// @copydoc Array::shape()
+    std::span<const ssize_t> shape(const State& state) const override;
+
+    using ArrayOutputMixin::size;
+
+    /// @copydoc Array::size()
+    ssize_t size(const State& state) const override;
+
+    /// @copydoc Array::size_diff()
+    ssize_t size_diff(const State& state) const override;
+
+ private:
+    const Array* array_ptr_;
+};
+
 /// Replaces specified elements of an array with the given values.
 ///
 /// The indexing works on the flattened array. Translated to NumPy, PutNode is
@@ -104,14 +153,43 @@ class PutNode : public ArrayOutputMixin<ArrayNode> {
     const Array* values_ptr_;
 };
 
+
+/// Propagates the values of its predecessor, interpreted into a different shape.
 class ReshapeNode : public ArrayOutputMixin<ArrayNode> {
  public:
-    ReshapeNode(ArrayNode* node_ptr, std::span<const ssize_t> shape);
+    /// Constructor for ReshapeNode.
+    ///
+    /// @param array_ptr The array to be reshaped. May not be dynamic.
+    /// @param shape The new shape. Must have the same size as the original shape.
     ReshapeNode(ArrayNode* array_ptr, std::vector<ssize_t>&& shape);
 
+    /// Constructor for ReshapeNode.
+    ///
+    /// @param array_ptr The array to be reshaped. May not be dynamic.
+    /// @param shape The new shape. Must have the same size as the original shape.
+    template <std::ranges::range Range>
+    ReshapeNode(ArrayNode* node_ptr, Range&& shape)
+            : ReshapeNode(node_ptr, std::vector<ssize_t>(shape.begin(), shape.end())) {}
+
+    /// @copydoc Array::buff()
     double const* buff(const State& state) const override;
+
+    /// @copydoc Node::commit()
     void commit(State& state) const override;
+
+    /// @copydoc Array::diff()
     std::span<const Update> diff(const State& state) const override;
+
+    /// @copydoc Array::integral()
+    bool integral() const override;
+
+    /// @copydoc Array::max()
+    double max() const override;
+
+    /// @copydoc Array::min()
+    double min() const override;
+
+    /// @copydoc Node::revert()
     void revert(State& state) const override;
 
  private:

dwave/optimization/libcpp/array.pxd

@@ -24,6 +24,7 @@ __all__ = ["Array"]
 cdef extern from "dwave-optimization/array.hpp" namespace "dwave::optimization" nogil:
     cdef cppclass Array:
         double* buff(State&)
+        bint contiguous() const
         bint dynamic() const
         const string& format() const
         Py_ssize_t itemsize() const

dwave/optimization/libcpp/nodes.pxd

@@ -78,6 +78,9 @@ cdef extern from "dwave-optimization/nodes/manipulation.hpp" namespace "dwave::o
     cdef cppclass ConcatenateNode(ArrayNode):
         Py_ssize_t axis()
 
+    cdef cppclass CopyNode(ArrayNode):
+        pass
+
     cdef cppclass PutNode(ArrayNode):
         pass
 

dwave/optimization/src/nodes/_state.hpp

@@ -35,6 +35,10 @@ class ArrayStateData {
     explicit ArrayStateData(std::vector<double>&& values) noexcept
             : buffer(std::move(values)), previous_size_(buffer.size()) {}
 
+    template <std::ranges::range Range>
+    explicit ArrayStateData(Range&& values) noexcept
+            : ArrayStateData(std::vector<double>(values.begin(), values.end())) {}
+
     // Assign new values to the state, tracking the changes from the previous state to the new
     // one. Including resizes.
     bool assign(std::ranges::sized_range auto&& values) {
@@ -193,6 +197,10 @@ class ArrayNodeStateData: public ArrayStateData, public NodeStateData {
     explicit ArrayNodeStateData(std::vector<double>&& values) noexcept
             : ArrayStateData(std::move(values)), NodeStateData() {}
 
+    template <std::ranges::range Range>
+    explicit ArrayNodeStateData(Range&& values) noexcept
+            : ArrayNodeStateData(std::vector<double>(values.begin(), values.end())) {}
+
     std::unique_ptr<NodeStateData> copy() const override {
         return std::make_unique<ArrayNodeStateData>(*this);
     }

dwave/optimization/src/nodes/manipulation.cpp

@@ -156,6 +156,50 @@ void ConcatenateNode::propagate(State& state) const {
 
 void ConcatenateNode::revert(State& state) const { data_ptr<ArrayNodeStateData>(state)->revert(); }
 
+CopyNode::CopyNode(ArrayNode* array_ptr)
+        : ArrayOutputMixin(array_ptr->shape()), array_ptr_(array_ptr) {
+    this->add_predecessor(array_ptr);
+}
+
+double const* CopyNode::buff(const State& state) const {
+    return data_ptr<ArrayNodeStateData>(state)->buff();
+}
+
+void CopyNode::commit(State& state) const { data_ptr<ArrayNodeStateData>(state)->commit(); }
+
+std::span<const Update> CopyNode::diff(const State& state) const {
+    return data_ptr<ArrayNodeStateData>(state)->diff();
+}
+
+bool CopyNode::integral() const { return array_ptr_->integral(); }
+
+void CopyNode::initialize_state(State& state) const {
+    int index = this->topological_index();
+    assert(index >= 0 && "must be topologically sorted");
+    assert(static_cast<int>(state.size()) > index && "unexpected state length");
+    assert(state[index] == nullptr && "already initialized state");
+
+    state[index] = std::make_unique<ArrayNodeStateData>(array_ptr_->view(state));
+}
+
+double CopyNode::max() const { return array_ptr_->max(); }
+
+double CopyNode::min() const { return array_ptr_->min(); }
+
+void CopyNode::propagate(State& state) const {
+    data_ptr<ArrayNodeStateData>(state)->update(array_ptr_->diff(state));
+}
+
+void CopyNode::revert(State& state) const { data_ptr<ArrayNodeStateData>(state)->revert(); }
+
+std::span<const ssize_t> CopyNode::shape(const State& state) const {
+    return array_ptr_->shape(state);
+}
+
+ssize_t CopyNode::size(const State& state) const { return array_ptr_->size(state); }
+
+ssize_t CopyNode::size_diff(const State& state) const { return array_ptr_->size_diff(state); }
+
 // A PutNode needs to track its buffer as well as a mask of which elements in the
 // original array are currently overwritten.
 // We use ArrayStateData for the buffer
@@ -442,8 +486,34 @@ void PutNode::propagate(State& state) const {
 
 void PutNode::revert(State& state) const { return data_ptr<PutNodeState>(state)->revert(); }
 
-ReshapeNode::ReshapeNode(ArrayNode* node_ptr, std::span<const ssize_t> shape)
-        : ArrayOutputMixin(shape), array_ptr_(node_ptr) {
+// Reshape allows one shape dimension to be -1. In that case the size is inferred.
+// We do that inference here.
+std::vector<ssize_t> infer_reshape(Array* array_ptr, std::vector<ssize_t>&& shape) {
+    // if the base array is dynamic, we might allow the first dimension to be negative
+    // 1. So let's defer to the various constructors.
+    if (array_ptr->dynamic()) return shape;
+
+    // Check if there are any -1s, and if not fallback to other input checking.
+    auto it = std::ranges::find(shape, -1);
+    if (it == shape.end()) return shape;
+
+    // Get the product of the shape and negate it (to exclude the -1)
+    auto prod = -std::reduce(shape.begin(), shape.end(), 1, std::multiplies<ssize_t>());
+
+    // If the product is <=0, then we have another negative number or a 0. In which
+    // case we just fall back to other error checking.
+    if (prod <= 0) return shape;
+
+    // Ok, we can officially overwrite the -1.
+    // Don't worry about the case that prod doesn't divide array_ptr->size(), other
+    // error checking will catch that case.
+    *it = array_ptr->size() / prod;
+
+    return shape;
+}
+
+ReshapeNode::ReshapeNode(ArrayNode* node_ptr, std::vector<ssize_t>&& shape)
+        : ArrayOutputMixin(infer_reshape(node_ptr, std::move(shape))), array_ptr_(node_ptr) {
     // Don't (yet) support non-contiguous predecessors.
     // In some cases with non-contiguous predecessors we need to make a copy.
     // See https://github.com/dwavesystems/dwave-optimization/issues/200
@@ -468,6 +538,12 @@ ReshapeNode::ReshapeNode(ArrayNode* node_ptr, std::span<const ssize_t> shape)
         throw std::invalid_argument("cannot reshape to a dynamic array");
     }
 
+    // one -1 was already replaced by infer_shape
+    if (std::ranges::any_of(this->shape() | std::views::drop(1),
+                            [](const ssize_t& dim) { return dim < 0; })) {
+        throw std::invalid_argument("can only specify one unknown dimension");
+    }
+
     if (this->size() != array_ptr_->size()) {
         // Use the same error message as NumPy
         throw std::invalid_argument("cannot reshape array of size " +
@@ -478,9 +554,6 @@ ReshapeNode::ReshapeNode(ArrayNode* node_ptr, std::span<const ssize_t> shape)
     this->add_predecessor(node_ptr);
 }
 
-ReshapeNode::ReshapeNode(ArrayNode* node_ptr, std::vector<ssize_t>&& shape)
-        : ReshapeNode(node_ptr, std::span(shape)) {}
-
 double const* ReshapeNode::buff(const State& state) const { return array_ptr_->buff(state); }
 
 void ReshapeNode::commit(State& state) const {}  // stateless node
@@ -489,6 +562,12 @@ std::span<const Update> ReshapeNode::diff(const State& state) const {
     return array_ptr_->diff(state);
 }
 
+bool ReshapeNode::integral() const { return array_ptr_->integral(); }
+
+double ReshapeNode::max() const { return array_ptr_->max(); }
+
+double ReshapeNode::min() const { return array_ptr_->min(); }
+
 void ReshapeNode::revert(State& state) const {}  // stateless node
 
 class SizeNodeData : public ScalarNodeStateData {

dwave/optimization/symbols.pyi

@@ -76,6 +76,10 @@ class Constant(ArraySymbol):
     def __le__(self, rhs: numpy.typing.ArrayLike) -> numpy.typing.NDArray[numpy.bool]: ...
 
 
+class Copy(ArraySymbol):
+    ...
+
+
 class DisjointBitSets(Symbol):
     def set_state(self, index: int, state: numpy.typing.ArrayLike): ...