Volunteer Computing and Large-Scale Simulation David P. Anderson U.C. Berkeley Space Sciences Lab February 3, 2007

Volunteer computing ● Distributed computing using volunteered computers (mostly privately owned) ● Early projects ( ) – GIMPS – distributed.net – – ● Different from “Peer-to-Peer computing”, “Grid computing”

Volunteer computing is hard ● Resources are anonymous, untrusted – overclockers – hackers ● Resources are very – heterogeneous – intermittent – high-churn ● Incentives are needed to attract, retain volunteers – most important one: credit for work done (Middleware can address all these issues)

Why is it interesting? ● More/cheaper computing power than other paradigms – Currently ~1 billion PCs – Consumer products have economy-of-scale advantage ● What determines how much a scientist gets? – public appeal of research – public relations activities – good web site, message boards, graphics ● Scientific education/outreach – Public learns about research – Scientists publicize their research

Computing power and cost ● ~450,000 active computers ● Hardware cost: ~ $1/GFLOP (save 1000x) ● Future: game consoles (e.g. Playstation 3) – ExaFLOP computing feasible

BOINC ● Software platform for volunteer computing – Open-source (LGPL), NSF-funded – Supports wide range of application characteristics – Encourages multi-project participation ● Goal: create a new computing paradigm (not just a static set of projects) Volunteers Projects (constantly changing)

Some BOINC-based projects ● Climateprediction.net – Oxford; global climate change study ● – LIGO; gravitational wave astronomy ● – U. Washington; protein study ● – U.C. Berkeley; SETI ● – CERN; accelerator simulation ● – STI, U. of Geneva; malaria epidemiology ●...and about 30 others

Attachment and resource share Projects Hosts 60 % 40 %

BOINC communication structure client scheduler I’m a Windows/x86 computer with 512 MB RAM and 20GB free disk. I do 2.5 GFLOPS and 4.2 MIPS. I’m running 35% of the time, and your project gets 50% of that. I need enough work to last for 3 days Queue of jobs: RAM/disk/FLOPS requirements, soft deadline OK, here are three jobs. Job 1 has application files A,B,C, input files C,D,E and output file F...

Replicated computing host project The answer is 42. It took me 10 GFLOPs to compute. What if the host is wrong (or lying)? host project 778, 10 GFLOPs 39.8, 10.1 GFLOPs 42.03, 11 GFLOPs

Simulations and replications ● Most simulations are unstable – wildly different answers on different platforms – “fuzzy comparison” doesn’t work ● Homogeneous replication: send replicas to numerically equivalent hosts, demand identical answers ● Check that answer is internally consistent and/or that it is consistent with ensemble results

Application types ● Standard – C/C++, slight mods for file I/O, checkpointing – graphics: supply OpenGL render function ● FORTRAN ● Legacy (no source code) – BOINC-supplied “wrapper” ● Compound applications – master, workers ● Scripted – actual program is contained in input file or command line

Work flow work generator (creates stream or batches of jobs) assimilator (handles correst result) validator (compares replicas, selects “correct” result) BOINC

What apps are good for volunteer computing? ● Needs a lot of computer time – 30 days: don’t bother – 10,000 years: no problem ● Lots of independent tasks (or sequence of batches of independent tasks) – Simulations: perturb initial conditions ● Data/compute ratio fairly low (< 1 GB per day of computing) ● Public appeal

Creating a BOINC-based project ● Port or develop application – always Windows; maybe Mac OS X; maybe Linux ● Get a server – hardware: lots of RAM, storage; ~$5K – software: Linux, MySQL, Apache, BOINC ● Develop work-flow components ● Develop web site ● Testing ● Publicity ● Message boards and customer support

Organizational alternatives ● Projects ● Meta-projects – World Community Grid – UC Berkeley? – NIH? science sys admin web design PR, support science sys admin web design PR, support science host

Conclusion ● Volunteer computing – cheap supercomputing – connect to the public ● Well-suited to large-scale simulation ● BOINC: open-source platform for volunteer computing –