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User Defined Function

samasamaan
Node Clone

Hello 

I have the following function that I found in this Ref

I want to use this function to find the minimum dominating set. How can I execute this in neo4j? 

function CYPHERGreedyAlgorithm
    MATCH(h)
    SET h.whiteness = 1
    SET h.blackness = 0
    WITH h
    OPTIONAL MATCH(j) 
    WHERE NOT (j){>()
    SET j.blackness = 1
    SET j.whiteness = 0
    WITH j
    MATCH (n){>(m)
    WHERE n.blackness <> 1
    WITH collect(m) as neighbourhood, n
    WITH reduce(totalweight = n.whiteness, j in neighbourhood | totalweight + j.whiteness) as weightings, n
    WITH n, weightings
    ORDER BY weightings desc limit 1
    MATCH (n1){>(m1)
    WHERE n1.blackness <> 1
    WITH collect(m1) as neighbourhood, n1
    WITH reduce(totalweight = n1.whiteness, j in neighbourhood | totalweight + j.whiteness) as weightings, n1
    WITH n1, weightings
    ORDER BY weightings desc limit 1
    MATCH(n1){>(m1)
    WHERE m1.blackness <> 1
    SET n1.blackness = 1
    SET n1.whiteness = 0
    SET m1.whiteness = 0
    WITH n1
    MATCH (k)
    WHERE k.whiteness = 1
    RETURN count(distinct(k)) as countOfRemainingWhiteNodes
end function
 
3 REPLIES 3

koji
Ninja
Ninja

Hi @samasamaan 

First, you can easily create functions with apoc.
After that, it is best to move to Java without apoc.

This is a sample code on the APOC doc.

CALL apoc.custom.declareProcedure(
  'powers(input::INT, power::INT) :: (answer::INT)',
  'UNWIND range(0, $power) AS power
   RETURN $input ^ power AS answer'
);

Custom, Cypher Based Procedures and Functions
https://neo4j.com/labs/apoc/4.4/cypher-execution/cypher-based-procedures-functions/

User-defined functions
https://neo4j.com/docs/java-reference/current/extending-neo4j/functions/

 

 

Thanks for your reply. My question is: Should I program the algorithm in Java? Why I can’t use the Cypher that I mentioned in the question? Please I need help in this to solve the SDN controller placement problem using neo4j and the dominating set algorithm. 

samasamaan
Node Clone

I found this link Minimum Dominating Set . Can this be a good reference to add this algorithm to the GDS library?