Shape

public final class Shape

The shape of a Tensor or NdArray.

A Shape defines sizes along its axes. It may contain an unknown size for one of the axes or may be totally unknown, in which case not even the number of axes is known. If the size of an axis is unknown, UNKNOWN_SIZE should be used as its size.

Fields

public static long UNKNOWN_SIZE The size of an unknown axis or the total unknown size for an unknown Shape.

Public Methods

Shape	append(long lastDimension) Returns a new Shape, with a new last dimension added.
Shape	append(Shape other) Returns a new Shape, with another Shapes' dimensions appended.
long[]	asArray() Returns a defensive copy of the this Shape's axes.
boolean	equals(Object obj) Equals implementation for Shapes.
boolean	hasUnknownDimension() Returns whether one or more dimensions of this Shape have an unknown size.
int	hashCode()
Shape	head() Returns a 1-dimensional Shape with first dimension matching the first dimension of this Shape.
static boolean	isCompatible(long dim, long otherDim) Test to see if two shape dimensions are compatible.
boolean	isCompatibleWith(Shape shape) Determines whether another shape is compatible with this one.
boolean	isMatrix() Returns whether this Shape is the shape of a matrix
boolean	isScalar() Returns whether this Shape represents a scalar.
boolean	isUnknown() Returns whether the number of dimensions of this Shape is unknown.
boolean	isVector() Returns whether this Shape is the shape of a vector.
int	numDimensions() Returns the number of dimensions of this Shape.
static Shape	of(long... dimensionSizes) Create a Shape representing a scalar or an N-dimensional value.
Shape	prepend(Shape other) Returns a new Shape, with another Shape's dimensions prepended.
Shape	prepend(long firstDimension) Returns a new Shape, with a new first dimension added.
static Shape	scalar() Creates a Shape representing a scalar value.
long	size(int i) The size of the dimension with the given index.
long	size() Returns the total number of elements a Tensor with this Shape would have.
Shape	subShape(int begin, int end) Return a `end - begin` dimensional shape with dimensions matching this Shape from `begin` to `end`.
Shape	tail() Returns a new Shape, with this Shape's first dimension removed.
Shape	take(int n) Returns an n-dimensional Shape with the dimensions matching the first n dimensions of this shape
Shape	takeLast(int n) Returns an n-dimensional Shape with the dimensions matching the last n dimensions of this Shape.
String	toString() Succinct description of the Shape meant for debugging.
static Shape	unknown() Creates a Shape representing an unknown number of dimensions.

Inherited Methods

From class java.lang.Object

boolean	equals(Object arg0)
final Class<?>	getClass()
int	hashCode()
final void	notify()
final void	notifyAll()
String	toString()
final void	wait(long arg0, int arg1)
final void	wait(long arg0)
final void	wait()

Fields

public static long UNKNOWN_SIZE

The size of an unknown axis or the total unknown size for an unknown Shape.

Public Methods

public Shape append (long lastDimension)

Returns a new Shape, with a new last dimension added. In order for this call to succeed, isUnknown() must be false.

Parameters

lastDimension	the dimension to append

Returns

a new Shape with this Shape's dimensions followed by the given dimension, never null

public Shape append (Shape other)

Returns a new Shape, with another Shapes' dimensions appended. For both this Shape and the other Shape, isUnknown() must return false. E.g. @code Shape.of(3,4).append(Shape.of(1,2)) => Shape.of(3,4,1,2) }

Parameters

other	another Shape, must not be `null`, must not be unknown

Returns

A new Shape consisting of this Shape's dimensions followed by the given Shape's dimensions

public long[] asArray ()

Returns a defensive copy of the this Shape's axes. Changes to the returned array to not change this Shape's state. Returns null if isUnknown() is true.

public boolean equals (Object obj)

Equals implementation for Shapes. Two Shapes are considered equal iff:

the number of dimensions is defined and equal for both
the size of each dimension is defined and equal for both

If either Shape has unknown dimensions (even if they are the same in both) or if either shape has an unknown number of dimensions (even if both return true for isUnknown()), they are not considered equal! However, a shape will always equal itself, even if it is unknown or contains unknown dimensions.

public boolean hasUnknownDimension ()

Returns whether one or more dimensions of this Shape have an unknown size.

public int hashCode ()

public Shape head ()

Returns a 1-dimensional Shape with first dimension matching the first dimension of this Shape.

public static boolean isCompatible (long dim, long otherDim)

Test to see if two shape dimensions are compatible.

The dimensions are compatible if either dimension is Shape.UNKNOWN_SIZE or both dimensions are equal

Parameters

dim	the first dimension
otherDim	the second dimension

Returns

true, if both dimensions are compatible

public boolean isCompatibleWith (Shape shape)

Determines whether another shape is compatible with this one.

Two possibly-partially-defined shapes are compatible if there exists a fully-defined shape that both shapes can represent. Thus, compatibility allows the shape inference code to reason about partially-defined shapes. For example:

Shape.unknown() is compatible with all shapes.
Shape(UNKNOWN_SIZE, UNKNOWN_SIZE) is compatible with all two-dimensional shapes, such as Shape(32, 784), and also Shape.unknown(). It is not compatible with, for example, Shape(UNKNOWN_SIZE) or Shape(UNKNOWN_SIZE, UNKNOWN_SIZE, UNKNOWN_SIZE).
Shape(32, UNKNOWN_SIZE) is compatible with all two-dimensional shapes with size 32 in the 0th dimension, and also Shape(UNKNOWN_SIZE, UNKNOWN_SIZE) and Shape.unknown(). It is not compatible with, for example, Shape(32), Shape(32, UNKNOWN_SIZE, 1) or Shape(64, UNKNOWN_SIZE).
Shape(32, 784) is compatible with itself, and also Shape(32, UNKNOWN_SIZE), Shape(UNKNOWN_SIZE, 784), Shape(UNKNOWN_SIZE, UNKNOWN_SIZE) and Shape.unknown(). It is not compatible with, for example, Shape(32, 1, 784) or Shape(UNKNOWN_SIZE).

The compatibility relation is reflexive and symmetric, but not transitive. For example, Shape(32, 784) is compatible with Shape.unknown(), and Shape.unknown() is compatible with Shape(4, 4), but Shape(32, 784) is not compatible with Shape(4, 4).

Compatibility is not the same as broadcasting. Compatible shapes must have the same number of dimensions and for each dimension pair, one dimension has to equal the other dimensions or at least one of the dimensions in the pair has to be UNKNOWN_SIZE.

Broadcasting allows different dimensions, but paired dimensions have to either be equal, or one dimension must be 1. If one shape has less dimensions than another shape, the smaller shape is "stretched" with dimensions of 1.

Parameters

shape	The other shape

Returns

true, if the two shapes are compatible.

public boolean isMatrix ()

Returns whether this Shape is the shape of a matrix

public boolean isScalar ()

Returns whether this Shape represents a scalar.

public boolean isUnknown ()

Returns whether the number of dimensions of this Shape is unknown.

public boolean isVector ()

Returns whether this Shape is the shape of a vector.

public int numDimensions ()

Returns the number of dimensions of this Shape. -1 if unknown, 0 for a scalar, 1 for a vector, 2 for a matrix etc.

public static Shape of (long... dimensionSizes)

Create a Shape representing a scalar or an N-dimensional value.

Creates a Shape representing a scalar or an N-dimensional value (N being at least 1), with the provided size for each dimension. A -1 indicates that the size of the corresponding dimension is unknown. If no sizes are provided, a Shape representing a scalar is created. For example:

// A 2-element vector.
 Shape vector = Shape.of(2);

 // A 2x3 matrix.
 Shape matrix = Shape.of(2, 3);

 // A matrix with 4 columns but an unknown number of rows.
 // This is typically used to indicate the shape of tensors that represent
 // a variable-sized batch of values. The Shape below might represent a
 // variable-sized batch of 4-element vectors.
 Shape batch = Shape.of(-1, 4);

 // A scalar. For readability, you should prefer calling Shape.scalar()
 Shape scalar = Shape.of()

Parameters

dimensionSizes	number of elements in each dimension of this shape, if any, or `UNKNOWN_SIZE` if unknown.

Returns

a new shape

public Shape prepend (Shape other)

Returns a new Shape, with another Shape's dimensions prepended. For both this Shape and the other Shape, isUnknown() must return false. E.g. Shape.of(3,4).prepend(Shape.of(1,2)) => Shape.of(1,2,3,4)

Parameters

other	another Shape, must not be `null`, must not be unknown

Returns

A new Shape consisting of the given Shape's dimensions followed by this Shape's dimensions, never null

public Shape prepend (long firstDimension)

Returns a new Shape, with a new first dimension added. In order for this call to succeed, isUnknown() must be false.

Parameters

firstDimension	the dimension to prepend

Returns

a new shape with the given dimension first, followed by this Shape's dimensions, never null

public static Shape scalar ()

Creates a Shape representing a scalar value.

Returns

A Shape without dimensions for which isScalar() is true, never null.

public long size (int i)

The size of the dimension with the given index.

If isUnknown() is true or the size of the dimension with the given index has an unknown size, UNKNOWN_SIZE is returned.

Parameters

i	the index of the dimension to get the size for. If this Shape has a known number of dimensions, it must be < `numDimensions()`. The index may be negative, in which case the position is counted from the end of the shape. E.g.: `size(-1)` returns the size of the last dimension, `size(-2)` the size of the second to last dimension etc.

Returns

The size of the dimension with the given index if known, UNKNOWN_SIZE otherwise.

public long size ()

Returns the total number of elements a Tensor with this Shape would have.

If isUnknown() is true or hasUnknownDimension() is true, UNKNOWN_SIZE is returned.

Returns

The total number of elements a Tensor with this shape would have if it can be calculated, else UNKNOWN_SIZE.

public Shape subShape (int begin, int end)

Return a end - begin dimensional shape with dimensions matching this Shape from begin to end.

Parameters

begin	Where to start the sub-shape.
end	Where to end the sub-shape, exclusive.

Returns

the sub-shape bounded by begin and end.

public Shape tail ()

Returns a new Shape, with this Shape's first dimension removed.

public Shape take (int n)

Returns an n-dimensional Shape with the dimensions matching the first n dimensions of this shape

Parameters

n	the number of leading dimensions to get, must be <= than `numDimensions()`

Returns

an n-dimensional Shape with the first n dimensions matching the first n dimensions of this Shape

public Shape takeLast (int n)

Returns an n-dimensional Shape with the dimensions matching the last n dimensions of this Shape.

Parameters

n	the number of trailing dimensions to get, must be <= than `numDimensions()`

Returns

an n-dimensional shape with the dimensions matching the last n dimensions of this Shape, never null

public String toString ()

Succinct description of the Shape meant for debugging.

public static Shape unknown ()

Creates a Shape representing an unknown number of dimensions.

Returns

A Shape for which isUnknown() is true, never null.