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/OpenJDK 21

Class VectorMask<E>

java.lang.Object
jdk.incubator.vector.VectorMask<E>
Type Parameters:
E - the boxed version of ETYPE, the element type of a vector

Value-based classes and identity operations

VectorMask, along with Vector, is a value-based class. With VectorMask, identity-sensitive operations such as == may yield unpredictable results, or reduced performance. Oddly enough, v.equals(w) is likely to be faster than v==w, since equals is not an identity sensitive method. (Neither is toString nor hashCode.) Also, vector mask objects can be stored in locals and parameters and as static final constants, but storing them in other Java fields or in array elements, while semantically valid, may incur performance penalties.
public abstract class VectorMask<E> extends Object
A VectorMask represents an ordered immutable sequence of boolean values.

A VectorMask and Vector of the same element type (ETYPE) and shape have the same number of lanes, and are therefore compatible (specifically, their vector species are compatible).

Some vector operations accept (compatible) masks to control the selection and operation of lane elements of input vectors.

The number of values in the sequence is referred to as the VectorMask length. The length also corresponds to the number of VectorMask lanes. The lane element at lane index N (from 0, inclusive, to length, exclusive) corresponds to the N + 1'th value in the sequence.

A lane is said to be set if the lane element is true, otherwise a lane is said to be unset if the lane element is false.

VectorMask declares a limited set of unary, binary and reduction operations.

  • A lane-wise unary operation operates on one input mask and produces a result mask. For each lane of the input mask the lane element is operated on using the specified scalar unary operation and the boolean result is placed into the mask result at the same lane. The following pseudocode illustrates the behavior of this operation category: 
    
 VectorMask<E> a = ...;
 boolean[] ar = new boolean[a.length()];
 for (int i = 0; i < a.length(); i++) {
     ar[i] = scalar_unary_op(a.laneIsSet(i));
 }
 VectorMask<E> r = VectorMask.fromArray(a.vectorSpecies(), ar, 0);
  • A lane-wise binary operation operates on two input masks to produce a result mask. For each lane of the two input masks a and b, the corresponding lane elements from a and b are operated on using the specified scalar binary operation and the boolean result is placed into the mask result at the same lane. The following pseudocode illustrates the behavior of this operation category: 
    
 VectorMask<E> a = ...;
 VectorMask<E> b = ...;
 boolean[] ar = new boolean[a.length()];
 for (int i = 0; i < a.length(); i++) {
     ar[i] = scalar_binary_op(a.laneIsSet(i), b.laneIsSet(i));
 }
 VectorMask<E> r = VectorMask.fromArray(a.vectorSpecies(), ar, 0);
  • A cross-lane reduction operation accepts an input mask and produces a scalar result. For each lane of the input mask the lane element is operated on, together with a scalar accumulation value, using the specified scalar binary operation. The scalar result is the final value of the accumulator. The following pseudocode illustrates the behaviour of this operation category: 
    
 Mask<E> a = ...;
 int acc = zero_for_scalar_binary_op;  // 0, or 1 for &
 for (int i = 0; i < a.length(); i++) {
      acc = scalar_binary_op(acc, a.laneIsSet(i) ? 1 : 0);  // & | +
 }
 return acc;  // maybe boolean (acc != 0)

Method Summary

Modifier and Type Method Description
abstract boolean allTrue()
Returns true if all of the mask lanes are set.
abstract VectorMask<E> and(VectorMask<E> m)
Computes the logical intersection (as a&b) between this mask and a second input mask.
abstract VectorMask<E> andNot(VectorMask<E> m)
Logically subtracts a second input mask from this mask (as a&~b).
abstract boolean anyTrue()
Returns true if any of the mask lanes are set.
abstract <F> VectorMask<F> cast(VectorSpecies<F> species)
Converts this mask to a mask of the given species of element type F.
abstract <F> VectorMask<F> check(Class<F> elementType)
Checks that this mask applies to vectors with the given element type, and returns this mask unchanged.
abstract <F> VectorMask<F> check(VectorSpecies<F> species)
Checks that this mask has the given species, and returns this mask unchanged.
abstract VectorMask<E> compress()
Compresses set lanes from this mask.
abstract VectorMask<E> eq(VectorMask<E> m)
Determines logical equivalence of this mask to a second input mask (as boolean a==b or a^~b).
final boolean equals(Object obj)
Indicates whether this mask is identical to some other object.
abstract int firstTrue()
Returns the index of the first mask lane that is set.
static <E> VectorMask<E> fromArray(VectorSpecies<E> species, boolean[] bits, int offset)
Loads a mask from a boolean array starting at an offset.
static <E> VectorMask<E> fromLong(VectorSpecies<E> species, long bits)
Returns a mask where each lane is set or unset according to the bits in the given bitmask, starting with the least significant bit, and continuing up to the sign bit.
static <E> VectorMask<E> fromValues(VectorSpecies<E> species, boolean... bits)
Returns a mask where each lane is set or unset according to given boolean values.
protected final Object getPayload()
final int hashCode()
Returns a hash code value for the mask, based on the mask bit settings and the vector species.
abstract VectorMask<E> indexInRange(int offset, int limit)
Removes lanes numbered N from this mask where the adjusted index N+offset, is not in the range [0..limit-1].
abstract VectorMask<E> indexInRange(long offset, long limit)
Removes lanes numbered N from this mask where the adjusted index N+offset, is not in the range [0..limit-1].
abstract void intoArray(boolean[] a, int offset)
Stores this mask into a boolean array starting at offset.
abstract boolean laneIsSet(int i)
Tests if the lane at index i is set
abstract int lastTrue()
Returns the index of the last mask lane that is set.
final int length()
Returns the number of mask lanes.
abstract VectorMask<E> not()
Logically negates this mask.
abstract VectorMask<E> or(VectorMask<E> m)
Computes the logical union (as a|b) of this mask and a second input mask.
abstract boolean[] toArray()
Returns an boolean array containing the lane elements of this mask.
abstract long toLong()
Returns the lane elements of this mask packed into a long value for at most the first 64 lane elements.
final String toString()
Returns a string representation of this mask, of the form "Mask[T.TT...]", reporting the mask bit settings (as 'T' or '.' characters) in lane order.
abstract Vector<E> toVector()
Returns a vector representation of this mask, the lane bits of which are set or unset in correspondence to the mask bits.
abstract int trueCount()
Returns the number of mask lanes that are set.
abstract VectorSpecies<E> vectorSpecies()
Returns the vector species to which this mask applies.
abstract VectorMask<E> xor(VectorMask<E> m)
Determines logical symmetric difference (as a^b) of this mask and a second input mask.

Methods declared in class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Details

vectorSpecies

public abstract VectorSpecies<E> vectorSpecies()
Returns the vector species to which this mask applies. This mask applies to vectors of the same species, and the same number of lanes.
Returns:
the vector species of this mask

length

public final int length()
Returns the number of mask lanes. This mask applies to vectors of the same number of lanes, and the same species.
Returns:
the number of mask lanes

fromValues

public static <E> VectorMask<E> fromValues(VectorSpecies<E> species, boolean... bits)
Returns a mask where each lane is set or unset according to given boolean values.

For each mask lane, where N is the mask lane index, if the given boolean value at index N is true then the mask lane at index N is set, otherwise it is unset.

The given species must have a number of lanes that is compatible with the given array.

Type Parameters:
E - the boxed element type
Parameters:
species - vector species for the desired mask
bits - the given boolean values
Returns:
a mask where each lane is set or unset according to the given boolean value
Throws:
IllegalArgumentException - if bits.length != species.length()
See Also:

fromArray

public static <E> VectorMask<E> fromArray(VectorSpecies<E> species, boolean[] bits, int offset)
Loads a mask from a boolean array starting at an offset.

For each mask lane, where N is the mask lane index, if the array element at index offset + N is true then the mask lane at index N is set, otherwise it is unset.

Type Parameters:
E - the boxed element type
Parameters:
species - vector species for the desired mask
bits - the boolean array
offset - the offset into the array
Returns:
the mask loaded from the boolean array
Throws:
IndexOutOfBoundsException - if offset < 0, or offset > bits.length - species.length()
See Also:

fromLong

public static <E> VectorMask<E> fromLong(VectorSpecies<E> species, long bits)
Returns a mask where each lane is set or unset according to the bits in the given bitmask, starting with the least significant bit, and continuing up to the sign bit.

For each mask lane, where N is the mask lane index, if the expression (bits>>min(63,N))&1 is non-zero, then the mask lane at index N is set, otherwise it is unset.

If the given species has fewer than 64 lanes, the high 64-VLENGTH bits of the bit-mask are ignored. If the given species has more than 64 lanes, the sign bit is replicated into lane 64 and beyond.

Type Parameters:
E - the boxed element type
Parameters:
species - vector species for the desired mask
bits - the given mask bits, as a 64-bit signed integer
Returns:
a mask where each lane is set or unset according to the bits in the given integer value
See Also:

cast

public abstract <F> VectorMask<F> cast(VectorSpecies<F> species)
Converts this mask to a mask of the given species of element type F. The species.length() must be equal to the mask length. The various mask lane bits are unmodified.

For each mask lane, where N is the lane index, if the mask lane at index N is set, then the mask lane at index N of the resulting mask is set, otherwise that mask lane is not set.

Type Parameters:
F - the boxed element type of the species
Parameters:
species - vector species for the desired mask
Returns:
a mask converted by shape and element type
Throws:
IllegalArgumentException - if this mask length and the species length differ

toLong

public abstract long toLong()
Returns the lane elements of this mask packed into a long value for at most the first 64 lane elements.

The lane elements are packed in the order of least significant bit to most significant bit. For each mask lane where N is the mask lane index, if the mask lane is set then the Nth bit is set to one in the resulting long value, otherwise the Nth bit is set to zero. The mask must have no more than 64 lanes.

Returns:
the lane elements of this mask packed into a long value.
Throws:
UnsupportedOperationException - if there are more than 64 lanes in this mask

toArray

public abstract boolean[] toArray()
Returns an boolean array containing the lane elements of this mask.

This method behaves as if it stores this mask into an allocated array (using intoArray(boolean[], int)) and returns that array as follows: 


 boolean[] a = new boolean[this.length()];
 this.intoArray(a, 0);
 return a;
Returns:
an array containing the lane elements of this vector

intoArray

public abstract void intoArray(boolean[] a, int offset)
Stores this mask into a boolean array starting at offset.

For each mask lane, where N is the mask lane index, the lane element at index N is stored into the array element a[offset+N].

Parameters:
a - the array, of type boolean[]
offset - the offset into the array
Throws:
IndexOutOfBoundsException - if offset < 0 or offset > a.length - this.length()

anyTrue

public abstract boolean anyTrue()
Returns true if any of the mask lanes are set.
Returns:
true if any of the mask lanes are set, otherwise false.

allTrue

public abstract boolean allTrue()
Returns true if all of the mask lanes are set.
Returns:
true if all of the mask lanes are set, otherwise false.

trueCount

public abstract int trueCount()
Returns the number of mask lanes that are set.
Returns:
the number of mask lanes that are set.

firstTrue

public abstract int firstTrue()
Returns the index of the first mask lane that is set. Returns VLENGTH if none of them are set.
Returns:
the index of the first mask lane that is set, or VLENGTH

lastTrue

public abstract int lastTrue()
Returns the index of the last mask lane that is set. Returns -1 if none of them are set.
Returns:
the index of the last mask lane that is set, or -1

and

public abstract VectorMask<E> and(VectorMask<E> m)
Computes the logical intersection (as a&b) between this mask and a second input mask.

This is a lane-wise binary operation which applies the logical AND operation (&) to each corresponding pair of mask bits.

Parameters:
m - the second input mask
Returns:
the result of logically conjoining the two input masks

or

public abstract VectorMask<E> or(VectorMask<E> m)
Computes the logical union (as a|b) of this mask and a second input mask.

This is a lane-wise binary operation which applies the logical OR operation (|) to each corresponding pair of mask bits.

Parameters:
m - the input mask
Returns:
the result of logically disjoining the two input masks

xor

public abstract VectorMask<E> xor(VectorMask<E> m)
Determines logical symmetric difference (as a^b) of this mask and a second input mask.

This is a lane-wise binary operation which applies the logical XOR operation (^) to each corresponding pair of mask bits.

Parameters:
m - the input mask
Returns:
the result of logically disjunctively disjoining the two input masks

andNot

public abstract VectorMask<E> andNot(VectorMask<E> m)
Logically subtracts a second input mask from this mask (as a&~b).

This is a lane-wise binary operation which applies the logical ANDC operation (&~) to each corresponding pair of mask bits.

Parameters:
m - the second input mask
Returns:
the result of logically subtracting the second mask from this mask

eq

public abstract VectorMask<E> eq(VectorMask<E> m)
Determines logical equivalence of this mask to a second input mask (as boolean a==b or a^~b).

This is a lane-wise binary operation tests each corresponding pair of mask bits for equality. It is also equivalent to the logical XNOR operation (^~) to each corresponding pair of mask bits.

Parameters:
m - the input mask
Returns:
a mask showing where the two input masks were equal
See Also:

not

public abstract VectorMask<E> not()
Logically negates this mask.

This is a lane-wise binary operation which applies the logical NOT operation (~) to each mask bit.

Returns:
the result of logically negating this mask

indexInRange

public abstract VectorMask<E> indexInRange(int offset, int limit)
Removes lanes numbered N from this mask where the adjusted index N+offset, is not in the range [0..limit-1].

In all cases the series of set and unset lanes is assigned as if by using infinite precision or VLENGTH-saturating additions or subtractions, without overflow or wrap-around.

API Note:
This method performs a SIMD emulation of the check performed by Objects.checkIndex(int,int), on the index numbers in the range [offset..offset+VLENGTH-1]. If an exception is desired, the resulting mask can be compared with the original mask; if they are not equal, then at least one lane was out of range, and exception processing can be performed.

A mask which is a series of N set lanes followed by a series of unset lanes can be obtained by calling allTrue.indexInRange(0, N), where allTrue is a mask of all true bits. A mask of N1 unset lanes followed by N2 set lanes can be obtained by calling allTrue.indexInRange(-N1, N2).

Parameters:
offset - the starting index
limit - the upper-bound (exclusive) of index range
Returns:
the original mask, with out-of-range lanes unset
See Also:

indexInRange

public abstract VectorMask<E> indexInRange(long offset, long limit)
Removes lanes numbered N from this mask where the adjusted index N+offset, is not in the range [0..limit-1].

In all cases the series of set and unset lanes is assigned as if by using infinite precision or VLENGTH-saturating additions or subtractions, without overflow or wrap-around.

API Note:
This method performs a SIMD emulation of the check performed by Objects.checkIndex(long,long), on the index numbers in the range [offset..offset+VLENGTH-1]. If an exception is desired, the resulting mask can be compared with the original mask; if they are not equal, then at least one lane was out of range, and exception processing can be performed.

A mask which is a series of N set lanes followed by a series of unset lanes can be obtained by calling allTrue.indexInRange(0, N), where allTrue is a mask of all true bits. A mask of N1 unset lanes followed by N2 set lanes can be obtained by calling allTrue.indexInRange(-N1, N2).

Parameters:
offset - the starting index
limit - the upper-bound (exclusive) of index range
Returns:
the original mask, with out-of-range lanes unset
Since:
19
See Also:

toVector

public abstract Vector<E> toVector()
Returns a vector representation of this mask, the lane bits of which are set or unset in correspondence to the mask bits. For each mask lane, where N is the mask lane index, if the mask lane is set at N then the specific non-default value -1 is placed into the resulting vector at lane index N. Otherwise the default element value 0 is placed into the resulting vector at lane index N. Whether the element type (ETYPE) of this mask is floating point or integral, the lane value, as selected by the mask, will be one of the two arithmetic values 0 or -1. For every ETYPE the most significant bit of the vector lane is set if and only if the mask lane is set. In addition, for integral types, all lane bits are set in lanes where the mask is set.

The vector returned is the same as would be computed by ZERO.blend(MINUS_ONE, this), where ZERO and MINUS_ONE are vectors which replicate the default ETYPE value and the ETYPE value representing -1, respectively.

API Note:
For the sake of static type checking, users may wish to check the resulting vector against the expected integral lane type or species. If the mask is for a float-point species, then the resulting vector will have the same shape and lane size, but an integral type. If the mask is for an integral species, the resulting vector will be of exactly that species.
Returns:
a vector representation of this mask
See Also:

laneIsSet

public abstract boolean laneIsSet(int i)
Tests if the lane at index i is set
Parameters:
i - the lane index
Returns:
true if the lane at index i is set, otherwise false
Throws:
IndexOutOfBoundsException - if the index is out of range (< 0 || >= length())

check

public abstract <F> VectorMask<F> check(Class<F> elementType)
Checks that this mask applies to vectors with the given element type, and returns this mask unchanged. The effect is similar to this pseudocode: elementType == vectorSpecies().elementType() ? this : throw new ClassCastException().
Type Parameters:
F - the boxed element type of the required lane type
Parameters:
elementType - the required lane type
Returns:
the same mask
Throws:
ClassCastException - if the element type is wrong
See Also:

check

public abstract <F> VectorMask<F> check(VectorSpecies<F> species)
Checks that this mask has the given species, and returns this mask unchanged. The effect is similar to this pseudocode: species == vectorSpecies() ? this : throw new ClassCastException().
Type Parameters:
F - the boxed element type of the required species
Parameters:
species - vector species required for this mask
Returns:
the same mask
Throws:
ClassCastException - if the species is wrong
See Also:

toString

public final String toString()
Returns a string representation of this mask, of the form "Mask[T.TT...]", reporting the mask bit settings (as 'T' or '.' characters) in lane order.
Overrides:
toString in class Object
Returns:
a string of the form "Mask[T.TT...]"

equals

public final boolean equals(Object obj)
Indicates whether this mask is identical to some other object. Two masks are identical only if they have the same species and same source indexes, in the same order.
Overrides:
equals in class Object
Parameters:
obj - the reference object with which to compare.
Returns:
whether this vector is identical to some other object
See Also:

hashCode

public final int hashCode()
Returns a hash code value for the mask, based on the mask bit settings and the vector species.
Overrides:
hashCode in class Object
Returns:
a hash code value for this mask
See Also:

compress

public abstract VectorMask<E> compress()
Compresses set lanes from this mask. Returns a mask which is a series of N set lanes followed by a series of unset lanes, where N is the true count of this mask.
Returns:
the compressed mask of this mask
Since:
19

getPayload

protected final Object getPayload()

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Documentation extracted from Debian's OpenJDK Development Kit package.
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https://docs.oracle.com/en/java/javase/21/docs/api/jdk.incubator.vector/jdk/incubator/vector/VectorMask.html