Fault-tolerant multi-computer system

A method for controlling the operation of each computer in a fault tolerant multiple computer system wherein the system includes a communication network whereby each computer can send error, data value, task selection and task completed/started messages to every other computer in the system and each computer has an operations controller and applications computer and wherein each computer further has a set of tasks it is capable of selecting and executing, comprising the steps of:

• checking for error with said operations controller all messages received by each computer from all the computers in system to generate an error signal identifying each computer which sent the message containing an error;
• sending error messages to all of the other computers in response to said error signals identifying as a faulty computer each computer which sent a message containing an error;
• recording in said operations controller as faulty each computer which sent a message containing an error in response to said error signals and each computer identified in error messages received from a predetermined number of other computers to generate a fault status table;
• discarding all messages containing errors and messages received from computers recorded as faulty in said fault status table;
• recording in a status table contained within said operations controller the status information contained in the task data value, task selection and task completed/started messages which were not discarded, said status table listing said tasks and their associated status information in their order of execution priority;
• detecting when all the information required for the execution of any task is recorded in said status table to generate an dispatch signal;
• recording as unselected in said status table, each task which was previously recorded as selected by a computer which has subsequently been recorded as faulty in said fault status table;
• generating by said operations controller a dispatch signal to signify the tasks unselected are ready for execution;
• selecting by said operations controller from said status table the highest priority task ready for execution and not selected by another computer in response to said dispatch signal;
• recording in said operations controller the selected task as selected in said task status table;
• sending to all of the computers a task selected message containing the identity of the task selected;
• generating in said operations controller a release task signal containing the identify of the selected task in response to the computer signifying it has completed the execution of a preceeding task;
• recording in a data values table contained within said operations controller the value of the data variable contained in each non discarded data value message received from all the computers;
• communicating from said data values table to the applications computer the value of the data variables required for the execution of the selected task in response to said release task signal;
• executing in the applications computer the selected task using the communicated values of the data variables to generate values for new data variables;
• sending to all of the computers by said operations controller, data value messages containing the values of the new data variables received from the applications computer;
• and
• sending to all of the computers by said operations controller a task completed/started message identifying the computer, the task completed, and the new task started by the identified computer after the execution of the task is completed.