index_rhash Module



Derived Types

type, public ::  index_rhash_t

Components

Type Visibility Attributes Name Initial
type(shared_rhash_t), private :: shared_ht

Type-Bound Procedures

procedure, public :: hash_function
procedure, public :: alloc
procedure, public :: dealloc
procedure, public :: count_index
procedure, public :: add_index
procedure, public :: finalize_setup
procedure, public :: setup_offsets
procedure, public :: lookup
procedure, public :: known_conflicts
procedure, public :: sync

Functions

private function hash_function(this, index) result(hval)

Get the hash value for an arbitrary input value

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(in) :: this
integer(kind=int64), intent(in) :: index

input value to get the hash value for

Return Value integer(kind=int64)

private function known_conflicts(this) result(t_kc)

During initialisation, we can only start writing values once the offsets are known. This requires knowledge about the number of conflicts per hash value. This function tells us whether the conflicts have already been counted.

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(in) :: this

Return Value logical


Subroutines

private subroutine alloc(this, n_elem, htsize)

Allocate the internal (shared) memory

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(inout) :: this
integer(kind=int64), intent(in) :: n_elem

number of distinct values to store

integer(kind=int64), intent(in) :: htsize

range of the hash function

private subroutine dealloc(this)

Deallocate all arrays associated with this hash table object

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(inout) :: this

private subroutine count_index(this, index)

Log the occurence of this index in the set of indices to be stored Does not add it, only updates the offsets

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(inout) :: this
integer(kind=int64), intent(in) :: index

index value to be logged

private subroutine setup_offsets(this)

For performance reasons, we cannot directly calculate the offsets, but instead first count the number of conflicts per hash value. Then, we sum these up cumulatively Directly counting the offsets is horrifically slow

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(inout) :: this

private subroutine add_index(this, index, pos)

Add an input value to the stored values, assuming we already know the offsets

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(inout) :: this
integer(kind=int64), intent(in) :: index

value to be stored

integer(kind=int64), intent(out) :: pos

on return, the position where this value was stored

private subroutine finalize_setup(this)

Dealloates temporary arrays used for initialisation

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t) :: this

private subroutine lookup(this, index, pos, t_found)

Look up a value in this hash table. Returns whether the value is stored and if yes, where

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(in) :: this
integer(kind=int64), intent(in) :: index

value to be looked up

integer(kind=int64), intent(out) :: pos

on return, the position of index if found, else 0

logical, intent(out) :: t_found

on return, true if and only if index was found

private subroutine sync(this)

For a MPI-3 shared memory array, synchronization is required after/before each read/write epoch

Arguments

Type IntentOptional Attributes Name
class(index_rhash_t), intent(inout) :: this