Actions in Events

Events in both MP Prism and scalar Prism can take action clauses. For example, in MP Prism the following action clause prints x for the pset foo when the members of foo are stopped at line 10:

stop at 10 {print x} pset foo

Associating an action with an event forces a global synchronization at the breakpoint or tracepoint. In the example above, every process in pset foo must stop at line 10 before x can be printed. If a member does not stop at line 10, the action never takes place. In a trace event, all processes in the pset must stop at the specified place and synchronize; the action then takes place, and the processes automatically continue execution.

You can include an eval pset command as an event action. For example,

stop in send {eval pset sending}

evaluates the pset sending when all the members of the current pset are stopped in send. You receive error messages if it is impossible to evaluate membership in a pset (for example, because a variable in the set definition is not active).

Note these limitations in using event actions: i:

• In MP Prism, you cannot include the following commands that manipulate psets:

  • define pset

  • delete pset

  • process

  • pset

• I n MP Prism, you cannot include a pset qualifier in the action. The command in the action clause takes its pset from the pset of the event.

• In both MP Prism and scalar Prism, you cannot include commands that affect program execution, specifically:

  • cont and contw

  • run

  • step and stepi

  • next and nexti

  • wait

• In both MP Prism and scalar Prism, you cannot include the load, reload, return, and core commands.