Page:CTSS programmer's guide.djvu/48

 command, the user receives a report containing: whether the job has finished or not; the time the job was submitted; the computer time used to date; the cutoff time; the current program level number; and the level populations in the scheduling algorithm.

Estimate of Computation Completion Time
When a user is present at his console operating a foreground program, he can easily determine the rate of computational progress by the use of the  command. However in the case of console-initiated background, estimation of completion time becomes a more difficult problem. For this purpose, an estimate command will be made available. Its properties are expected to be as follows:

The console user gives as command parameters the designation of the particular background job in question, and the total expected computation time required by the job. The estimate command can determine the position of the job in the scheduling algorithm, and it has available a cumulative history of the scheduling traffic on, for example, an hourly basis over a period of a week. For each hour, the traffic history consists of a histogram, for each level of the scheduling algorithm, of the number of job initiations versus the total computation time required (including time in subsequent levels). Knowing in addition the current job status and the scheduling algorithm itself, the estimate command is in a position to run a high-speed Monte Carlo simulation, into future time, of the expected system behavior. By running several such simulations, using different initial settings of the pseudo-random number generator, the estimate command can type out a message like: "Range of estimates over 3 trials = 131 min. to 237 min . Estimated Completion time between 3:16 pm July 1 and 5:02 pm July 1." (An alternative message might be "job already completed.")

If the estimated time is too long, the user will initially have no recourse except to cancel or stop the background job. Future systems may contain priority alternatives, with additional usage charges serving as restraints. 34