1. A parallel computer for requesting shared variable directory (SVD) information from a plurality of threads, the parallel computer comprising a runtime optimizer, a plurality of threads of execution, the threads organized into tasks, the parallel computer further comprising memory partitioned to provide each thread with a private memory and a shared memory, the parallel computer comprising computer processors operatively coupled to the memory having disposed within it computer program instructions that, when executed by the computer processors, cause the parallel computer to function by: prior to detecting that a first thread requires a plurality of updated SVD information, creating a gather operation message header for each entry of an SVD associated with the first thread by storing each gather operation message header with the corresponding entry of the SVD associated with the first thread; detecting, by a runtime optimizer of the parallel computer, that the first thread requires the plurality of updated SVD information associated with shared resource data stored in a plurality of memory partitions associated with a plurality of threads, each partition associated with a different thread; in response to detecting that the first thread requires the updated SVD information, broadcasting, by the runtime optimizer, a gather operation message header corresponding to an entry of the SVD associated with the first thread to the plurality of threads using a system messaging layer of a protocol stack of the parallel computer, wherein the system messaging layer provides system-level data communications functions that support higher layers of the protocol stack, the gather operation message header indicating an SVD key corresponding to the required updated SVD information and a local address associated with the first thread to receive the plurality of updated SVD information associated with the SVD key; and receiving at the local address, the plurality of updated SVD information from the plurality of threads.