BEGIN:VCALENDAR PRODID:-//Microsoft Corporation//Outlook MIMEDIR//EN VERSION:2.0 BEGIN:VEVENT DTSTART:20151119T223000Z DTEND:20151119T230000Z LOCATION:18AB DESCRIPTION;ENCODING=QUOTED-PRINTABLE:ABSTRACT: Recursive parallel programming models such as Cilk strive to simplify the task of parallel programming by enabling a simple divide-and-conquer model of programming. This model is effective in recursively partitioning work into smaller parts and combining their results. However, recursive work partitioning can impose additional constraints on concurrency than is implied by the true dependencies in a program. In this paper, we present a speculation-based approach to alleviate the concurrency constraints imposed by such recursive parallel programs. We design a runtime infrastructure that supports speculative execution and a predictor to accurately learn and identify opportunities to relax extraneous concurrency constraints. Experimental evaluation demonstrates that speculative relaxation of concurrency constraints can deliver gains of up to 1.6 times on 30 cores over baseline Cilk. SUMMARY:CilkSpec: Optimistic Concurrency for Cilk PRIORITY:3 END:VEVENT END:VCALENDAR