JICOS A Java-Centric Network Computing Service Peter Cappello & Christopher James Coakley Computer Science University of California, Santa Barbara

API Goals Application program is oblivious to: –Number of processors –Processor topology –Inter-process communication –Faulty compute servers

API Divide & Conquer (DAC) f(3)f(2) + f(1) f(0) + + f(1)f(0) + f(4)

API DAC Common environment –Input object –Shared object f(3)f(2) + f(1) f(0) + + f(1)f(0) + f(4)

Architectural Goals Scalable Heterogeneous processors & OS Mobile code Support adaptively parallel computation Tolerate faulty compute servers Reduce or hide communication latency

Architecture H H H H H H S H H H H H H

M C login setComputation getResult logout

Hiding Communication Latency Task Caching f(3)f(2) + f(1) f(0) + + f(1)f(0) + f(4)

Hiding Communication Latency Task Pre-fetching f(3)f(2) + f(1) f(0) + + f(1)f(0) + f(4)

Hiding Communication Latency Execute Task on Server f(3)f(2) + f(1) f(0) + + f(1)f(0) + f(4)

Tolerating Faulty Hosts Transactions kill performance

Tolerating Faulty Hosts Transactions kill performance

Tolerating Faulty Hosts ProxyH TASKS Proxy TASKS TASK H

Performance Experiments Problem: 200-city TSP –61,295 BranchAndBound Tasks (2.05s) –30,647 MinSolution Tasks (< 1ms) 120-processor experiments use 3 processor types (CX journal paper derives formula)

Fault Tolerance Experiments Problem: 200-city TSP Killed p processors after 1,500s, for p = 2, 6, 20, 24, 26, 30. % overhead: actual time / ideal time H H H H H H H H H H H H H H H H S 32 PROCESSORS

Fault Tolerance Experiments

Task Server Overhead H H H H H H H H H H H H H H H S/H H H H H H H H H H H H H H H H H S 22 PROCESSORS 11 HOSTS, 1 SERVER 12 MACHINES TIME: s 22 PROCESSORS 11 HOSTS, 1 SERVER 11 MACHINES TIME: s

Conclusions API = Cilk + Common Task Environment Architecture –network of servers, each serving many hosts. –Supports adaptive parallelism –Efficiently tolerates faulty hosts Excellent speedups –2 processors (1 Host): 9 hours and 32 minutes –120 processors: < 12 minutes (96.66 % ideal) –3 application-controlled latency-hiding directives Small Server overhead: Run Host on Server

THANK YOU! URL: cs.ucsb.edu/projects/jicos Download System Source Tutorial

A Distributed Computing Taxonomy NOT Application fixes processor topology a priori Adaptively parallelNOT Tolerates faulty computer serversNOT Divide & Conquer API NOT

Ancestry CilkLinda AtlasSatinJavelinCX JICOS Pirannha