tf.lookup.experimental.DenseHashTable

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A generic mutable hash table implementation using tensors as backing store.

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Compat aliases for migration

See Migration guide for more details.

tf.compat.v1.lookup.experimental.DenseHashTable

tf.lookup.experimental.DenseHashTable(
    key_dtype, value_dtype, default_value, empty_key, deleted_key,
    initial_num_buckets=None, name='MutableDenseHashTable', checkpoint=True
)

Data can be inserted by calling the insert method and removed by calling the remove method. It does not support initialization via the init method.

It uses "open addressing" with quadratic reprobing to resolve collisions. Compared to MutableHashTable the insert, remove and lookup operations in a DenseHashTable are typically faster, but memory usage can be higher. However, DenseHashTable does not require additional memory for temporary tensors created during checkpointing and restore operations.

Example usage:

table = tf.lookup.DenseHashTable(key_dtype=tf.int64,
                                 value_dtype=tf.int64,
                                 default_value=-1,
                                 empty_key=0,
                                 deleted_key=-1)

sess.run(table.insert(keys, values))
out = table.lookup(query_keys)
print(out.eval())

Args
key_dtype	the type of the key tensors.
value_dtype	the type of the value tensors.
default_value	The value to use if a key is missing in the table.
empty_key	the key to use to represent empty buckets internally. Must not be used in insert, remove or lookup operations.
deleted_key	the key to use to represent deleted buckets internally. Must not be used in insert, remove or lookup operations and be different from the empty_key.
initial_num_buckets	the initial number of buckets.
name	A name for the operation (optional).
checkpoint	if True, the contents of the table are saved to and restored from checkpoints. If shared_name is empty for a checkpointed table, it is shared using the table node name.

Raises
ValueError	If checkpoint is True and no name was specified.

Attributes
key_dtype	The table key dtype.
name	The name of the table.
resource_handle	Returns the resource handle associated with this Resource.
value_dtype	The table value dtype.

Methods

erase

View source

erase(
    keys, name=None
)

Removes keys and its associated values from the table.

If a key is not present in the table, it is silently ignored.

Args
keys	Keys to remove. Can be a tensor of any shape. Must match the table's key type.
name	A name for the operation (optional).

Returns
The created Operation.

Raises
TypeError	when keys do not match the table data types.

export

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export(
    name=None
)

Returns tensors of all keys and values in the table.

Args
name	A name for the operation (optional).

Returns
A pair of tensors with the first tensor containing all keys and the second tensors containing all values in the table.

insert

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insert(
    keys, values, name=None
)

Associates keys with values.

Args
keys	Keys to insert. Can be a tensor of any shape. Must match the table's key type.
values	Values to be associated with keys. Must be a tensor of the same shape as keys and match the table's value type.
name	A name for the operation (optional).

Returns
The created Operation.

Raises
TypeError	when keys or values doesn't match the table data types.

insert_or_assign

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insert_or_assign(
    keys, values, name=None
)

Associates keys with values.

Args
keys	Keys to insert. Can be a tensor of any shape. Must match the table's key type.
values	Values to be associated with keys. Must be a tensor of the same shape as keys and match the table's value type.
name	A name for the operation (optional).

Returns
The created Operation.

Raises
TypeError	when keys or values doesn't match the table data types.

lookup

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lookup(
    keys, name=None
)

Looks up keys in a table, outputs the corresponding values.

The default_value is used for keys not present in the table.

Args
keys	Keys to look up. Can be a tensor of any shape. Must match the table's key_dtype.
name	A name for the operation (optional).

Returns
A tensor containing the values in the same shape as keys using the table's value type.

Raises
TypeError	when keys do not match the table data types.

remove

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remove(
    keys, name=None
)

Removes keys and its associated values from the table.

If a key is not present in the table, it is silently ignored.

Args
keys	Keys to remove. Can be a tensor of any shape. Must match the table's key type.
name	A name for the operation (optional).

Returns
The created Operation.

Raises
TypeError	when keys do not match the table data types.

size

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size(
    name=None
)

Compute the number of elements in this table.

Args
name	A name for the operation (optional).

Returns
A scalar tensor containing the number of elements in this table.