Executing an accelerator application program in a hybrid computing environment with a host computer having a host computer architecture; an accelerator having an accelerator architecture, the accelerator architecture optimized, with respect to the host computer architecture, for speed of execution of a particular class of computing functions; the host computer and the accelerator adapted to one another for data communications by a system level message passing module, where executing an accelerator application program on an accelerator includes receiving, from a host application program on the host computer, operating information for an accelerator application program; designating a directory as a CWD for the accelerator application program, separate from any other CWDs of any other applications running on the accelerator; assigning, to the CWD, a name that is unique with respect to names of other CWDs of other applications in the computing environment; and starting the accelerator application program on the accelerator.