CoachSpeculative execution launches a second copy of a task that is running much longer than expected, on another machine; the first copy to finish is kept and the other is killed.
Voorbeelden
Example 13.9 (The sweep that finished on Saturday)
Longest first with backups ends at 10.02 hours, 5.5% above the lower bound of 9.50 hours. Without the slow node, but also without backups, it ends at 10.32: the backups recover more than the slow node costs, because they also rescue the tasks whose estimates were wrong and those that failed. First in, first out on the same cluster ends at 19.79 hours, twice as long, and holds 475 node-hours against 240. The cluster had been almost idle for three and a half hours: from 16.3 hours after submission, fewer than a tenth of its cores were busy.