1. A computer-implemented method, comprising: at a runtime system executing at a parallel-processing computer that includes multiple types of processing elements using shared memory: at runtime: receiving one or more operation requests issued by an application; choosing a respective type of processing element for at least one of the one or more operation requests, the at least one operation request corresponding to an intrinsic operation or a primitive operation, wherein the respective type of processing element is selected from the group consisting of single-core/multi-core central processing units, graphics processing units and single-core/multi-core co-processors; identifying, from a library, a precompiled, processor-specific compute kernel corresponding to the intrinsic operation or the primitive operation of the at least one operation request, the library comprising a plurality of processor-specific compute kernels corresponding to a plurality of intrinsic operations or primitive operations; and preparing one or more compute kernels for the at least one operation request, wherein the one or more compute kernels include the at least one precompiled, processor-specific compute kernel, and are configured to execute on the respective type of processing element.