The invention provides a processor with two or more parallel instruction paths for processing instructions. The instruction paths may be implemented with a plurality of cores on a common die. Instructions of the invention are preferably processed within a bundle of two or more instructions of a common program thread; and each of the instruction paths preferably forms a cluster to process bundled instructions. Each of the instruction paths has an array of pipelined execution units. Initially, two or more of the parallel instruction paths processes the same program thread (one or more bundles) through the execution units, but with different optimization characteristics set for each path. Assessment logic monitors the processing of the initial program thread through the execution units and selects the heuristics defining which path is in the lead. The other instruction paths are then reallocated, or synchronized, with the optimization characteristics of the lead instruction path, or with similarly optimized characteristics, to process other bundles of the program thread; preferably, the lead path continues processing of the initial thread without being disturbed. For other program threads, the process may repeat in processing like bundles through multiple instruction paths to identify the preferred heuristics; and then synchronizing the multiple instruction paths to the optimized characteristics to improve per thread performance.