1. A computer implemented method for debugging a parallel computer system comprising the steps of: a) initiating debugging at a point of interest execution state; b) broadcasting a data template with data block checksums of an initial execution state to all compute nodes arranged in a cluster; c) each compute node searching its own memory image for checksum matches; d) producing a template of new data blocks with checksums that didn't exist previously; e) producing reference lists to original data blocks that did exist in the previous checkpoint; f) collecting the reference lists from the compute nodes; g) collecting new unique data blocks from the nodes and storing them; h) determining differences between the data template with the initial execution state and the point of interest execution state; and i) providing data of the determined differences in step h to a system user to assist in debugging the parallel computer system.