Abstract: The present invention utilizes link time code modification to instrument the code which is to be executed, typically comprising plurality of kernel operations and user programs. When the code is instrumented, wherever a data memory reference appears, the linker inserts a very short stylized subroutine call to a routine that logs the reference in a large, trace buffer. The same call is inserted at the beginning of each basic block to record instruction references. When the trace buffer fills up with recorded memory references, the contents of the buffer are processed, either by dumping the contents to an output device emptying the trace buffer, or a cache simulation routine is run to analyze the data. The results of the analysis are stored rather than storing the entire results of the tracing program.

Abstract: A parallel computer system which has a primary task processor, a second primary task processor, a secondary task processor acting as a backup for the second primary task processor transfers messages by:sending messages from the primary task processor to the second primary processor with the second primary task processor operating on the messages by initially storing a received message in a queue and thereafter reading the message from the queue for processing in accordance with the task associated therewith and accumulating a count of the messages read from its queue; and sending the same messages from the first primary task processor to the secondary task processor which stores the messages in a message queue for possible use if the second primary task processor fails. If a primary task processor fails after processing a given number of messages, the secondary task processor associated therewith starts processing the messages in its queue but after having discarded the first given number of messages.