Synchronization and exchange of data between processors

A method of operating a system comprising a first subsystem having a first processor, and a second subsystem having a second processor, the method comprising:

• arranging the second subsystem to process code over a series of steps;
• in a first one of the steps, sending a descriptor from the second subsystem to the first subsystem specifying a value of a parameter of an interaction that the second subsystem is programmed to perform with the first subsystem via an inter-processor interconnect in a subsequent one of the steps;
• and
• on the first subsystem, performing a preparatory operation based on the specified value of the parameter of the interaction as specified by the descriptor, to prepare for the interaction prior to the subsequent step.

A non-transitory computer-readable storage medium having stored thereon computer-executable code configured so as when run on a system comprising a first subsystem having a first processor and a second subsystem having a second processor, performs operations of:

• controlling the second subsystem to run the program over a series of steps;
• in a first one of the steps, controlling the second subsystem to send a descriptor to the first subsystem specifying a value of a parameter of an interaction that the second subsystem is programmed to perform with the first subsystem via an inter-processor interconnect in a subsequent one of the steps;
• and
• controlling the first subsystem to perform a preparatory operation, based on the specified value of the parameter of the interaction as specified by the descriptor, to prepare for said the interaction prior to said subsequent step.