Class AbstractSparseNdArray<T, U extends NdArray<T>>

java.lang.Object
org.tensorflow.ndarray.impl.sparse.AbstractSparseNdArray<T,U>
Type Parameters:
T - the type that the array contains
U - the type of dense NdArray
All Implemented Interfaces:
NdArray<T>, Shaped, SparseNdArray<T,U>
Direct Known Subclasses:
BooleanSparseNdArray, ByteSparseNdArray, DoubleSparseNdArray, FloatSparseNdArray, IntSparseNdArray, LongSparseNdArray, ShortSparseNdArray, SparseNdArray, SparseSlice
public abstract class AbstractSparseNdArray<T, U extends NdArray<T>> extends Object implements SparseNdArray<T,U>
Abstract base class for sparse array.

A sparse array as two separate dense arrays: indices, values, and a shape that represents the dense shape.

NOTE: all Sparse Arrays are readonly for the set(NdArray, long...) and setObject(Object, long...) methods 

FloatSparseNdArray st = new FloatSparseNdArray(
     StdArrays.of(new long[][] {{0, 0}, {1, 2}}),
     NdArrays.vectorOf(1f, 2f),
     Shape.of(3, 4));

represents the dense array: 

[[1, 0, 0, 0]
 [0, 0, 2, 0]
 [0, 0, 0, 0]]

  • Field Details

  • Constructor Details

    • AbstractSparseNdArray

      protected AbstractSparseNdArray(LongNdArray indices, U values, T defaultValue, DimensionalSpace dimensions)
      Creates an abstract SparseNdArray
      Parameters:
      indices - A 2-D LongNdArray of shape [N, ndims], that specifies the indices of the elements in the sparse array that contain non-default values (elements are zero-indexed). For example, indices=[[1,3], [2,4]] specifies that the elements with indexes of [1,3] and [2,4] have non-default values.
      values - A 1-D NdArray of any type and shape [N], which supplies the values for each element in indices. For example, given indices=[[1,3], [2,4]], the parameter values=[18, 3.6] specifies that element [1,3] of the sparse NdArray has a value of 18, and element [2,4] of the NdArray has a value of 3.6.
      defaultValue - Scalar value to set for indices not specified in indices
      dimensions - the dimensional space for the dense object represented by this sparse array.

    • AbstractSparseNdArray

      protected AbstractSparseNdArray(T defaultValue, DimensionalSpace dimensions)
      Creates an abstract SparseNdArray
      Parameters:
      defaultValue - Scalar value to set for indices not specified in getIndices()
      dimensions - the dimensional space for the dense object represented by this sparse array,

  • Method Details

    • elements

      public NdArraySequence<U> elements(int dimensionIdx)
      Returns a sequence of all elements at a given dimension.

      Logically, the N-dimensional array can be flatten in a single vector, where the scalars of the (n - 1)th element precedes those of the (n)th element, for a total of Shaped.size() values.

      For example, given a n x m matrix on the [x, y] axes, elements are iterated in the following order:

      x0y0, x0y1, ..., x0ym-1, x1y0, x1y1, ..., xn-1ym-1

      The returned sequence can then be iterated to visit each elements, either by calling Iterable.forEach(Consumer) or NdArraySequence.forEachIndexed(BiConsumer). 

         // Iterate matrix for initializing each of its vectors
   matrixOfFloats.elements(0).forEach(v -> {
     v.set(vector(1.0f, 2.0f, 3.0f));
   });

   // Iterate a vector for reading each of its scalar
   vectorOfFloats.scalars().forEachIdx((coords, s) -> {
     System.out.println("Value " + s.getFloat() + " found at " + coords);
   });
      Specified by:
      elements in interface NdArray<T>
      Parameters:
      dimensionIdx - index of the dimension
      Returns:
      an NdArray sequence

    • toCoordinates

      protected long[] toCoordinates(DimensionalSpace dimensions, long position)
      Computes the coordinates based on a relative position to the beginning of the dimension space.
      Parameters:
      dimensions - the dimension space
      position - relative position to the beginning of the dimension space.
      Returns:
      the coordinates

    • getIndicesCoordinates

      protected long[] getIndicesCoordinates(LongNdArray l)
      Converts the given set of indices coordinates to a long array of coordinates.

      The shape of the NdArray is [ndims]

      Parameters:
      l - the LongNdArray containing the coordinates
      Returns:
      the long array containing the coordinates.

    • toDense

      public abstract U toDense()
      Converts this sparse array to a dense array.
      Returns:
      the dense array.

    • withShape

      public U withShape(Shape shape)
      Description copied from interface: NdArray
      Returns a new N-dimensional view of this array with the given shape.

      The provided shape must comply to the following characteristics:

      • new shape is known (i.e. has no unknown dimension)
      • new shape size is equal to the size of the current shape (i.e. same number of elements)
      For example, 
         NdArrays.ofInts(Shape.scalar()).withShape(Shape.of(1, 1));  // ok
   NdArrays.ofInts(Shape.of(2, 3).withShape(Shape.of(3, 2));   // ok
   NdArrays.ofInts(Shape.scalar()).withShape(Shape.of(1, 2));  // not ok, sizes are different (1 != 2)
   NdArrays.ofInts(Shape.of(2, 3)).withShape(Shape.unknown()); // not ok, new shape unknown

      Any changes applied to the returned view affect the data of this array as well, as there is no copy involved.

      Specified by:
      withShape in interface NdArray<T>
      Parameters:
      shape - the new shape to apply
      Returns:
      a new array viewing the data according to the new shape, or this array if shapes are the same

    • slice

      public NdArray<T> slice(Index... indices)
      Creates a multi-dimensional view (or slice) of this array by mapping one or more dimensions to the given index selectors.

      Slices allow to traverse an N-dimensional array in any of its axis and/or to filter only elements of interest. For example, for a given matrix on the [x, y] axes, it is possible to iterate elements at y=0 for all x.

      Any changes applied to the returned slice affect the data of this array as well, as there is no copy involved.

      Example of usage: 

         FloatNdArray matrix3d = NdArrays.ofFloats(shape(3, 2, 4));  // with [x, y, z] axes

   // Iterates elements on the x axis by preserving only the 3rd value on the z axis,
   // (i.e. [x, y, 2])
   matrix3d.slice(all(), all(), at(2)).elements(0).forEach(m -> {
     assertEquals(shape(2), m); // y=2, z=0 (scalar)
   });

   // Creates a slice that contains only the last element of the y axis and elements with an
   // odd `z` coordinate.
   FloatNdArray slice = matrix3d.slice(all(), at(1), odd());
   assertEquals(shape(3, 2), slice.shape());  // x=3, y=0 (scalar), z=2 (odd coordinates)

   // Iterates backward the elements on the x axis
   matrix3d.slice(flip()).elements(0).forEach(m -> {
     assertEquals(shape(2, 4), m);  // y=2, z=4
   });
      Specified by:
      slice in interface NdArray<T>
      Parameters:
      indices - index selectors per dimensions, starting from dimension 0 of this array.
      Returns:
      the element resulting of the index selection

    • get

      public NdArray<T> get(long... coordinates)
      Returns the N-dimensional element of this array at the given coordinates.

      Elements of any of the dimensions of this array can be retrieved. For example, if the number of coordinates is equal to the number of dimensions of this array, then a rank-0 (scalar) array is returned, which value can then be obtained by calling `array.getObject()`.

      Any changes applied to the returned elements affect the data of this array as well, as there is no copy involved.

      Note that invoking this method is an equivalent and more efficient way to slice this array on single scalar, i.e. array.get(x, y, z) is equal to array.slice(at(x), at(y), at(z))

      Specified by:
      get in interface NdArray<T>
      Parameters:
      coordinates - coordinates of the element to access, none will return this array
      Returns:
      the element at this index

    • getObject

      public T getObject(long... coordinates)
      Returns the value of the scalar found at the given coordinates.

      To access the scalar element, the number of coordinates provided must be equal to the number of dimensions of this array (i.e. its rank). For example: 

       FloatNdArray matrix = NdArrays.ofFloats(shape(2, 2));  // matrix rank = 2
 matrix.getObject(0, 1);  // succeeds, returns 0.0f
 matrix.getObject(0);  // throws IllegalRankException

 FloatNdArray scalar = matrix.get(0, 1);  // scalar rank = 0
 scalar.getObject();  // succeeds, returns 0.0f
      Note: if this array stores values of a primitive type, prefer the usage of the specialized method in the subclass for that type. For example, floatArray.getFloat(0); .
      Specified by:
      getObject in interface NdArray<T>
      Parameters:
      coordinates - coordinates of the scalar to resolve
      Returns:
      value of that scalar

    • setObject

      public NdArray<T> setObject(T value, long... coords)
      Assigns the value of the scalar found at the given coordinates.

      To access the scalar element, the number of coordinates provided must be equal to the number of dimensions of this array (i.e. its rank). For example: 

       FloatNdArray matrix = NdArrays.ofFloats(shape(2, 2));  // matrix rank = 2
 matrix.setObject(10.0f, 0, 1);  // succeeds
 matrix.setObject(10.0f, 0);  // throws IllegalRankException

 FloatNdArray scalar = matrix.get(0, 1);  // scalar rank = 0
 scalar.setObject(10.0f);  // succeeds
      Note: if this array stores values of a primitive type, prefer the usage of the specialized method in the subclass for that type. For example, floatArray.setFloat(10.0f, 0);
      Specified by:
      setObject in interface NdArray<T>
      Parameters:
      value - the value to assign
      coords - coordinates of the scalar to assign
      Returns:
      this array

    • set

      public NdArray<T> set(NdArray<T> src, long... coordinates)
      Assigns the value of the N-dimensional element found at the given coordinates.

      The number of coordinates provided can be anywhere between 0 and rank - 1. For example: 

       FloatNdArray matrix = NdArrays.ofFloats(shape(2, 2));  // matrix rank = 2
 matrix.set(vector(10.0f, 20.0f), 0);  // success
 matrix.set(scalar(10.0f), 1, 0); // success
      Specified by:
      set in interface NdArray<T>
      Parameters:
      src - an array of the values to assign
      coordinates - coordinates of the element to assign
      Returns:
      this array

    • createValues

      public abstract U createValues(Shape shape)
      Creates a dense array of the type that this sparse array represents.
      Parameters:
      shape - the shape of the dense array.
      Returns:
      the dense of the type that this sparse array represents.

    • copyTo

      public NdArray<T> copyTo(NdArray<T> dst)
      Copy the content of this array to the destination array.

      The Shaped.shape() of the destination array must be equal to the shape of this array, or an exception is thrown. After the copy, the content of both arrays can be altered independently, without affecting each other.

      Specified by:
      copyTo in interface NdArray<T>
      Parameters:
      dst - array to receive a copy of the content of this array
      Returns:
      this array

    • positionOf

      protected long positionOf(long[] coords, boolean isValue)
      Computes the position within the dense array given by the coordinates
      Parameters:
      coords - the coordinates within the dense array
      isValue - indicator whether the coordinates represents a value or higher level dimension.
      Returns:
      the position within the array

    • slowCopyTo

      protected void slowCopyTo(NdArray<T> array)

    • getIndices

      public LongNdArray getIndices()
      Gets the Indices
      Specified by:
      getIndices in interface SparseNdArray<T, U extends NdArray<T>>
      Returns:
      the Indices

    • setIndices

      public void setIndices(LongNdArray indices)
      Sets the Indices
      Parameters:
      indices - the Indices

    • getValues

      public U getValues()
      Gets the values
      Specified by:
      getValues in interface SparseNdArray<T, U extends NdArray<T>>
      Returns:
      the values

    • setValues

      public void setValues(U values)
      Sets the values
      Parameters:
      values - the values

    • locateIndex

      protected long locateIndex(long[] coordinates)
      Gets the values index by coordinates
      Parameters:
      coordinates - the coordinates to locate
      Returns:
      index of the coordinates, if the coordinates are contained in the indices array; otherwise, (-(insertion point) - 1). The insertion point is defined as the point at which the coordinates would be inserted into the indices array: the index of the first element greater than the key, or indices.shape().get(0); if all elements in the array are less than the specified key. Note that this guarantees that the return value will be >= 0, only if the coordinates are found.

    • hashCode

      public int hashCode()

    • equals

      public boolean equals(Object obj)
      Checks equality between n-dimensional arrays.

      An array is equal to another object if this object is another NdArray of the same shape, type and the elements are equal and in the same order. For example: 

      IntNdArray array = NdArrays.ofInts(Shape.of(2, 2))
   .set(NdArrays.vectorOf(1, 2), 0)
   .set(NdArrays.vectorOf(3, 4), 1);

assertEquals(array, StdArrays.ndCopyOf(new int[][] {{1, 2}, {3, 4}}));  // true
assertEquals(array, StdArrays.ndCopyOf(new Integer[][] {{1, 2}, {3, 4}}));  // true, as Integers are equal to ints
assertNotEquals(array, NdArrays.vectorOf(1, 2, 3, 4));  // false, different shapes
assertNotEquals(array, StdArrays.ndCopyOf(new int[][] {{3, 4}, {1, 2}}));  // false, different order
assertNotEquals(array, StdArrays.ndCopyOf(new long[][] {{1L, 2L}, {3L, 4L}}));  // false, different types

      Note that the computation required to verify equality between two arrays can be expensive in some cases and therefore, it is recommended to not use this method in a critical path where performances matter.

      Specified by:
      equals in interface NdArray<T>
      Parameters:
      obj - object to compare this array with
      Returns:
      true if this array is equal to the provided object

    • toString

      public String toString()
      A String showing the type, default value, number of elements and the dense shape of this sparse ndarray.
      Overrides:
      toString in class Object
      Returns:
      A string containing the type, default value, number of elements and shape.

    • sortIndicesAndValues

      public AbstractSparseNdArray<T,U> sortIndicesAndValues()
      Sorts the indices and values in ascending row-major coordinates.
      Returns:
      this instance

    • getDefaultValue

      public T getDefaultValue()
      Scalar value to set for indices not specified in indices, defaults to zero, false, or the empty String depending on the data type.

    • setDefaultValue

      public void setDefaultValue(T defaultValue)
      Sets the defaultValue
      Parameters:
      defaultValue - the default value

    • createDefaultArray

      public abstract U createDefaultArray()
      Creates the NdArray with the default value as a scalar
      Returns:
      the default NdArray of the default value as a scalar

    • getDefaultArray

      public U getDefaultArray()
      Scalar NdArray to use for indices not specified in getIndices() This will default to zero, false, or the empty string depending on the data type of the values, otherwise it will contain the defaultValue.

    • slice

      public abstract U slice(long position, DimensionalSpace dimensions)

    • dimensions

      public DimensionalSpace dimensions()

    • shape

      public Shape shape()
      Specified by:
      shape in interface Shaped
      Returns:
      the shape of this container

    • scalars

      public NdArraySequence<U> scalars()
      Description copied from interface: NdArray
      Returns a sequence of all scalars in this array.

      This is equivalent to call elements(shape().numDimensions() - 1)

      Specified by:
      scalars in interface NdArray<T>
      Returns:
      an NdArray sequence

    • slowHashCode

      protected int slowHashCode()

    • slowEquals

      protected boolean slowEquals(NdArray<?> array)