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 | |
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 | |
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 | |
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
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 asShape(32, 784)
, and alsoShape.unknown()
. It is not compatible with, for example,Shape(UNKNOWN_SIZE)
orShape(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 alsoShape(UNKNOWN_SIZE, UNKNOWN_SIZE)
andShape.unknown()
. It is not compatible with, for example,Shape(32)
,Shape(32, UNKNOWN_SIZE, 1)
orShape(64, UNKNOWN_SIZE)
.Shape(32, 784)
is compatible with itself, and alsoShape(32, UNKNOWN_SIZE)
,Shape(UNKNOWN_SIZE, 784)
,Shape(UNKNOWN_SIZE, UNKNOWN_SIZE)
andShape.unknown()
. It is not compatible with, for example,Shape(32, 1, 784)
orShape(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 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.