Exchange of data between processor modules

A method of operating a processing system having an arrangement of multiple processor modules in sets and a first interconnect for exchanging data between a first processor module of a first set and a second processor module of a second set;

• the method comprising:
• arranging the first processor module and the second processor module to each operate in a series of steps, each step comprising an exchange phase and a compute phase;
• pre-programming the first processor module with a value representing a number of units of data that is to be received by the first processor module from the second processor module in an exchange phase of a first step, and arranging the first processor module, starting from the pre-programmed value, to count out units of data remaining to be received each time one of said units of data is received;
• and
• arranging the first processor module to perform an exchange synchronization whereby, before advancing from the exchange phase of the first step to a compute phase of the first step, the first processor module waits until no units of data remain to be received according to the count.

A computer program product embodied on computer readable storage and comprising a program for running on each of a first processor module and a second processor module, using a first interconnect for exchanging data between a first processor module of a first set and a second processor module of a second set;

• the computer program product being configured so as when run on first multiple processor module and the second processor to perform operations of:
• arranging the first processor module and the second processor module to each operate in a series of steps, each step comprising an exchange phase and a compute phase;
• pre-programming the first processor module with a value representing a number of units of data that is to be received by the first processor module from the second processor module in an exchange phase of a first step, and arranging the first processor module, starting from the pre-programmed value, to count out units of data remaining to be received each time one of said units of data is received;
• and
• arranging the first processor module to perform an exchange synchronization whereby, before advancing from the exchange phase of the first step to a compute phase of the first step, the first processor module waits until no units of data remain to be received according to the count.