gum::HashFunc< Instantiation > Class Reference

Hash function for gum::Instantiation. More...

#include <instantiation.h>

Inheritance diagram for gum::HashFunc< Instantiation >:

Collaboration diagram for gum::HashFunc< Instantiation >:

Public Member Functions
virtual Size	operator() (const Instantiation &key) const override final
	Computes the hashed value of a key.
void	resize (const Size new_size)
	Update the hash function to take into account a resize of the hash table.
Size	size () const
	Returns the hash table size as known by the hash function.

Static Public Member Functions
static Size	castToSize (const Instantiation &key)
	Returns the value of a key as a Size.

Protected Attributes
Size	hash_size_
	The size of the hash table.
unsigned int	hash_log2_size_
	Log of the number of slots of the hash table in base 2.
Size	hash_mask_
	performing y = x & hash_mask_ guarantees that y is a slot index of the hash table
unsigned int	right_shift_
	performing y = x >> right_shift_ guarantees that y is a slot index of the hash table

Detailed Description

Hash function for gum::Instantiation.

Definition at line 1247 of file instantiation.h.

Member Function Documentation

castToSize()

INLINE Size gum::HashFunc< Instantiation >::castToSize ( const Instantiation & key )

static

Returns the value of a key as a Size.

returns a hashed key for hash tables the keys of which are represented by vectors of Idx

Parameters

key	The value to return as a Size.

Returns

Returns the value of a key as a Size.

Definition at line 774 of file instantiation_inl.h.

                                                                            {
    Size h = Size(0);
    for (const DiscreteVariable* k:
         key.variablesSequence())   // k are unique only by address (not by name)
      h += HashFunc< const DiscreteVariable* >::castToSize(k) * Size(key.val(*k));
 
    return h;
  }

References castToSize(), gum::Instantiation::val(), and gum::Instantiation::variablesSequence().

Referenced by castToSize(), and operator()().

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operator()()

INLINE Size gum::HashFunc< Instantiation >::operator() ( const Instantiation & key ) const

finaloverridevirtual

Computes the hashed value of a key.

returns a hashed key for hash tables the keys of which are represented by vectors of Idx

Parameters

key	The key to compute the hashed value.

Returns

Returns the hashed value of a key.

Implements gum::HashFuncBase< Instantiation >.

Definition at line 785 of file instantiation_inl.h.

                                                                                  {
    return castToSize(key) & this->hash_mask_;
  }

References castToSize(), gum::HashFuncBase< Instantiation >::hash_mask_, and operator()().

Referenced by operator()().

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resize()

void gum::HashFuncBase< Instantiation >::resize ( const Size new_size )

inherited

Update the hash function to take into account a resize of the hash table.

When the user wishes to resize the gum::HashTable so that the array is of size s, the gum::HashTable resizes itself to the smallest power of 2 greater than or equal to s. This new size is computed by function gum::HashFuncBase::resize(gum::Size). Hence, s should be the size of the array of lists, not the number of elements stored into the gum::HashTable.

Parameters

new_size

The hashtable's size wished by the user. Actually, a hashtable of size n is an array of n lists.

Exceptions

SizeError

Raised if s is too small.

size()

Size gum::HashFuncBase< Instantiation >::size ( ) const

inherited

Returns the hash table size as known by the hash function.

Returns

Returns the size of the hash table, i.e., the number of slots (lists) it contains.

Member Data Documentation

hash_log2_size_

unsigned int gum::HashFuncBase< Instantiation >::hash_log2_size_

protectedinherited

Log of the number of slots of the hash table in base 2.

Definition at line 224 of file hashFunc.h.

{0};

hash_mask_

Size gum::HashFuncBase< Instantiation >::hash_mask_

protectedinherited

performing y = x & hash_mask_ guarantees that y is a slot index of the hash table

To transform a Size x into a slot index of the hash table, you can either use x & hash_mask_ or x >> right_shift_ depending on whether you want to exploit the least significant bits of x (&) or the most significant one (>>).

Definition at line 235 of file hashFunc.h.

{Size(0)};

Referenced by gum::HashFunc< Instantiation >::operator()().

hash_size_

Size gum::HashFuncBase< Instantiation >::hash_size_

protectedinherited

The size of the hash table.

Definition at line 221 of file hashFunc.h.

{Size(0)};

right_shift_

unsigned int gum::HashFuncBase< Instantiation >::right_shift_

protectedinherited

performing y = x >> right_shift_ guarantees that y is a slot index of the hash table

To transform a Size x into a slot index of the hash table, you can either use x & hash_mask_ or x >> right_shift_ depending on whether you want to exploit the least significant bits of x (&) or the most significant one (>>).

Definition at line 246 of file hashFunc.h.

{0};

---

The documentation for this class was generated from the following files:

• agrum/base/multidim/instantiation.h
• agrum/base/multidim/instantiation_inl.h