Method and system of aligning execution point of duplicate copies of a user program by exchanging information about instructions executed

A processor-based method comprising:

• determining by a first processor that the user program executed on the first processor has not made a system level call in a predetermined amount of time;
• determining by the first processor, using information from a second processor, whether a duplicate copy of the user program executed in the second processor has made a system level call in the predetermined amount of time;
• operating duplicate copies of the user program in the first and second processor;
• decoding at least some instructions and determining inputs of each instruction decoded, the decoding substantially simultaneously with executing in each processor;
• exchanging among the processors addresses of decoded instructions and values indicative of inputs of the decoded instructions;
• discerning that an execution point of the user program in the first processors lags with respect to an execution point of the user program in the second processor using at least the addresses of the decoded instructions;
• and
• advancing the first processor until the execution point within each user program is substantially aligned.

A system comprising:

• a first processor operable to execute a user program, the first processor coupled to a first memory;
• said first processor is operable to execute a predetermined number of instructions of its respective user program, and operable to substantially simultaneously with the executing decode at least some instructions and determine inputs of the decoded instructions, and place addresses of the decoded instructions and values indicative of the inputs in a first list;
• a second processor operable to substantially simultaneously execute a duplicate copy of the user program, the second processor coupled to a second memory;
• said second processor is operable to execute a predetermined number of instructions of its respective user program, and operable to substantially simultaneously with the executing decode at least some instructions and determine inputs of the decoded instructions, and place addresses of the decoded instructions and values indicative of the inputs in a second list;
• said first and second processor are operable to exchange lists;
• and
• said first processor is operable to match a plurality of executed instructions of its user program to a plurality of executed instructions of the user program of the second processor based on the lists and to determine a number of instructions by which the first processor lags, and the first processor is operable to execute forward until execution points of the duplicate copies of the user program are substantially the same.

A system comprising:

• a first processor operable to execute a user program, the first processor coupled to a first memory;
• a second processor operable to substantially simultaneously execute a duplicate copy of the user program, the second processor coupled to a second memory;
• said first processor is operable to execute a number of instructions of its respective user program, and operable to substantially simultaneously with the executing decode at least some instructions and determine inputs of the decoded instructions, and operable to substantially simultaneously with the executing exchange addresses of the decoded instructions and inputs with the second processor;
• said second processor is operable to execute a number of instructions of its respective user program, and operable to substantially simultaneously with the executing decode at least some instructions and determine inputs of the decoded instructions, and operable to substantially simultaneously with the executing exchange addresses of the decoded instructions and inputs with the first processor;
• and
• said first processor is operable to match a plurality of executed instructions of its user program to a plurality of executed instructions of the user program of the second processor to determine a number of instructions by which the first processor lags, and the first processor is operable to execute forward until execution points of the duplicate copies of the user program are substantially the same.