Running algorithms implemented with Pregel API in parallel runtime

Neo4j Graph Platform Graph Algorithms/Graph Data Science
1

I am trying to run the Pregel Shortest Path example in parallel runtime.

CYPHER runtime=parallel
CALL example.pregel.sssp.stream("countries_2018", {maxIterations: 3, startNode: 0})
YIELD nodeId, values
RETURN nodeId, values

But it is giving me the following error

Failed to invoke procedure `example.pregel.sssp.stream`: Caused by: java.lang.UnsupportedOperationException: `transaction.getMetaData' is not supported in procedures when called from parallel runtime. Please retry using another runtime.

Does this mean when this procedure is called, Pregel tries to start a new transaction and hence procedures implemented with Pregel API cannot be run in parallel runtime? Or is there another way to run the procedures using Pregel API in parallel runtime?

2

Hey @kouganepola730 ,
this looks like a bug inside GDS. We carded the problem and will work on a fix.
I will keep you updated once we found a solution.

3

Hello @kouganepola730,

Thank you for reporting this, we've taken some steps and a fix should be included in the next GDS release.
Out of curiosity, what are you trying to achieve with using the parallel runtime and GDS?

4

Hello @veselin.nikolov,

Thank you for looking into this.

I was trying to use parallel runtime in order to run the above Pregel API example in a multi-threaded setup.