Known Issues

java.util.NoSuchElementException on fetchActiveState

This issue will lead to the following output:

[] ERROR - guardian failed, shutting down system


Note that the 46 in the above error could be any number, as this error arises from parallelism

Below this, you will find one of the following errors:

java.util.NoSuchElementException: null
      at scala.collection.concurrent.TrieMap.apply(TrieMap.scala:878)
java.lang.Exception: Something went wrong, each StatefulAgent must have one active state all the times
      at com.bharatsim.engine.models.StatefulAgent.fetchActiveState(StatefulAgent.scala:69)

The error is not easily reproducible, and appears to occur randomly.

A preliminary investigation suggests a problem with the underlying TrieMap data structure. Edges on the map do not appear to be created, and cannot be referenced when called. Note that this behaviour only occurs if bharatsim is parallelized.

A potential workaround is to run bharatsim without parallelism. To do so, you need to edit the application.conf file, which can be found in /src/main/resources/. The first couple of lines should be

bharatsim {
  engine {
      execution {
          mode = "actor-based"
          mode = ${?EXECUTION_MODE}
          simulation-steps = 4000
          simulation-steps = ${?SIMULATION_STEPS}
          actor-based {
              num-processing-actors = 100

Line 4 needs to be changed to

mode = "no-parallelism"

This will fix the issue, but be aware that removing parallelism could lead to your code taking longer to run.


For the latest on the error, please check the github issue