Condor 7.9.1

Condor takes advantage of computing resources that would otherwise be wasted and puts them to good use. Condor streamlines the scientist`s tasks by allowing the submission of many jobs at the same time. In this way, tremendous amounts of computation can be done with very little intervention from the user. Moreover, Condor allows users to take advantage of idle machines that they would not otherwise have access to. Condor provides other important features to its users. Source code does not have to be modified in any way to take advantage of these benefits. Code that can be re-linked with the Condor libraries gains two further abilities: the jobs can produce checkpoints and they can perform remote system calls. A checkpoint is the complete set of information that comprises a program`s state. Given a checkpoint, a program can use the checkpoint to resume execution. For long-running computations, the ability to produce and use checkpoints can save days, or even weeks of accumulated computation time. If a machine crashes, or must be rebooted for an administrative task, a checkpoint preserves computation already completed. Condor makes checkpoints of jobs, doing so periodically, or when the machine on which a job is executing will shortly become unavailable. In this way, the job can be continued on another machine (of the same platform); this is known as process migration. A user submits a job to Condor. The job is executed on a remote machine within the pool of machines available to Condor. Minimal impact on and the security of the remote machine are preserved by Condor through remote system calls. When the job does a system call, for example to do an input or output function, the data is maintained on the machine where the job was submitted. The data is not on the remote machine, where it could be an imposition. By linking in a set of Condor libraries, system calls are caught and performed by Condor, instead of by the remote machine`s operating system. Condor sends the system call from the remote machine to the machine where the jobs was submitted. The system call`s function executes, and Condor sends the result back to the remote machine.