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**Nadia Eghbal:** And for those unfamiliar, what is Lawrence Livermore? |
**Todd Gamblin:** Lawrence Livermore is one of three labs in the National Nuclear Security Agency. It's part of the DOE, and we're responsible for a whole lot of different national security missions. That includes things like nuclear non-proliferation, making sure that people don't sell nuclear materials... We're also ... |
\[03:55\] I think all sorts of missions at the Laboratory are based on computing and our Livermore Computing Center, which is where all the different clusters are that we run. I work both with the research organization and with the computing center, and also with the code teams, who are from all different parts of the ... |
**Nadia Eghbal:** So you play with nuclear weapons all day? |
**Todd Gamblin:** I do not play with nuclear weapons all day. \[laughter\] What I do is mostly in a support role. We're working with the simulation team... One of the things that we simulate is nuclear weapons, that's true. We also have a whole lot of open science codes; we work with all those different teams to help t... |
In the research role, what I do is I work with a lot of students in academia, I have post-docs who work for me, and we'll usually talk to the code teams, try to figure out what their problems are, what kind of things are they having issues with in terms of making sure that their simulations run fast, and then we try to... |
**Nadia Eghbal:** Cool. |
**Mikeal Rogers:** \[05:52\] So in terms of like your team and everything... Is this a bunch of people in the same physical location? I think when people hear of a lab, they're thinking like some place with a giant hadron collider, or something... Is this institution slightly virtualized, as well? You mentioned you're ... |
**Todd Gamblin:** I would say it's both. Livermore itself is a one square mile laboratory in Livermore, California; it's like an hour from San Francisco. We do have a giant laser here... We have the National Ignition Facility, which is the world's largest and highest energy laser; basically, that's like 192 beams that ... |
So that's more like on-site stuff... We would go and visit the code team, or they would come to our office, we have meetings, like a normal company... I sit in a building with the big computers, so basically I have an office building and there's essentially like a 48,000 square foot data center attached to it. But yeah... |
We also collaborate across the DOE and with a whole lot of universities. I have telecons all the time, I have collaborators at the University of Delaware, University of Arizona, University of Illinois and other places, with students, and then we also collaborate with people across the DOE. The Exascale project that I t... |
To some extent they're similar, because they have large physics experiments on their sites too, and all those big labs have big computing centers, but... We travel around the different labs and also to conferences and do things like present papers... So it's a fairly diverse job, working for the DOE. |
\[08:10\] I like it a lot because I'm not always working with programmers or computer scientists, I also get to talk to people who are doing physical sciences and other stuff. It's a pretty cool environment from that perspective. |
**Nadia Eghbal:** Can you talk a little bit about your lab's history with open source? I think you've mentioned in previous conversations that your lab has open sourced a bunch of other types of projects before, and I was wondering also how did you personally get into open source in your current role? |
**Todd Gamblin:** If you look at Livermore's history, I think from the Lab's founding in 1952, we've deployed fast computers; building software for them has been a long part of the lab's history. We built this thing called the Livermore Time Sharing System - I say "we", but this was way before my time... And that was o... |
We also used to build compilers here. Apparently, we had a compiler team, there was something called "the Pastel Compiler." I think Richard Stallman actually wanted to base the original version of GCC on that, but I believe the memory requirements for it were way too high for ordinary computers... It wasn't gonna run o... |
Then as the machines evolved, we've deployed more and more fast machines, and in the '90s they started looking more like clusters. We were one of the first labs to look at deploying Linux on our machines and maintaining our own Linux distribution for HPC (high performance computing) machines. So we did that... |
We have a developer here who ported ZFS to Linux from Solaris, and he maintains that port, that's pretty popular... And I think in general in the research community people have done open source a lot. I don't think that necessarily means that they've taken steps to popularize or necessarily build really large communiti... |
ZFS I think is one of the major ones now, and then Slurm is used all over the place, and that was invented at Livermore. That's a resource manager... It's basically like a batch system for submitting jobs to clusters and managing the nodes and the memory allocating time to users. |
**Mikeal Rogers:** These are pretty high-end use cases... Who are the other users of these open source projects, other than Lawrence Livermore? |
**Todd Gamblin:** Other labs deploy Slurm, and actually a lot of university computing centers will run that. Our Linux clusters all run Slurm; even our IBM Blue Gene machine - which is like a million and a half cores - runs Slurm, and other national labs also run Slurm on their systems. |
**Nadia Eghbal:** \[11:09\] The name makes me laugh every time. |
**Todd Gamblin:** Yeah, I think it's actually from Futurama... So yeah, we have lots of interestingly named tools. And then ZFS I think is used in the industry. I'm not a file systems expert, but I know that a lot of companies have started using ZFS on Linux; it's fairly widely used all over the place. |
We ported ZFS because our interest is in -- so we also have developers who work on a parallel file system called Lustre, and that's what we run on our clusters. Lustre is a parallel file system where there's a local file system that it's based on. Lustre runs on top of ZFS in our current configuration, and we're pretty... |
**Nadia Eghbal:** Was Spack the first project that you had open sourced at Lawrence Livermore yourself? |
**Todd Gamblin:** \[12:03\] It wasn't, actually. In addition to Spack, I've had a bunch of different research projects. For my PhD I worked on a scalable clustering algorithm. That's open source, it's called Muster and it's on GitHub, too. That was sort of for finding nodes in a parallel application that very similar p... |
I don't think that really caught on... It was sort of a research project; it wasn't generally useful, like a package manager is. We also had a project here called -- well, originally I wanted to call it ClownCar, but that was deemed not serious enough, so we renamed it to CRAM, which stands for ClownCar Renamed to Appe... |
**Nadia Eghbal:** Oh, government... |
**Todd Gamblin:** So that dealt with a real problem that we had here. When we deployed the Sequoia machine, which is the big IBM Blue Gene/Q system, originally people anticipated running maybe like 200, maybe 400 jobs at a time on that thing, and they were thinking that each job would be maybe 10,000 cores, or somethin... |
Now the mission has sort of changed, and one of the things that we're very interested in is uncertainty quantification, so trying to figure out what inputs is the simulation sensitive to? We decided that we wanted to run lots and lots of small jobs on the machine; we had people who really wanted to run a million and a ... |
CRAM basically takes one job and splits it into lots of them, and manages that sort of on the cluster, as opposed to on the front-end. So it's kind of a stopgap until we get a more scalable resource manager. |
Those are just some examples, but I would say in the research world there's lots of open source software. That's kind of the default for people who are doing research, publishing papers about it... We have a compiler project here called ROSE - it's a source-to-source compiler; that's been open source for a very long ti... |
**Mikeal Rogers:** Do you have a sense of how long it's been the default? Because it hasn't always been the default to do everything open source. Do you know when that shift happened? Or just like as long as you've been in it, you've been able to do everything open source? |
**Todd Gamblin:** As long as I've been in it, yes. I started here at the lab in 2008, and I know that it goes back further than that. Our early efforts with TOSS, which our Linux distribution (based on Red Hat) - that was in '99 or the early 2000s. Actually, there's a policy document from the DOE from 2004, and it basi... |
An open source nuclear weapon simulation sounds like a really bad idea, but some of the other software that we develop to make our systems run - that's pure computer science; we can put it out there, and other people can use it and benefit from it... And they do. |
So yeah, there's a DOE document that says we should make this software open source from like 2004, and it's interesting because -- you know, that's something we're struggling with now... We do have an IP organization as part of the Laboratory. Livermore has had some successful commercial software come out of some of ou... |
\[16:20\] But other projects, like Spack or a lot of this infrastructure stuff - I don't think we're gonna be able to sell that, and I don't necessarily think that we should, because we're in sort of a niche here. There aren't that many sites that do large-scale high-performance computing, and I think we have the same ... |
**Nadia Eghbal:** So what's it like when you think you have something that you might wanna open source? What does that process look like for your Lab? Do you have to talk to the IP Office? |
**Todd Gamblin:** Well, yeah... So the IP Office wants to make sure that the thing that you're putting out there as open source is not something that we could potentially get royalties off of. That's kind of interesting, because the government in general, technically -- I don't think we're actually allowed to have inte... |
But yeah, so we have to go through the IP organization when we put things out there. For most of my stuff, getting the approval isn't actually that hard; it's the actual process that's kind of tedious. Livermore's software release process involves burning two CDs and carrying them to three buildings throughout the Labo... |
The thing that I would really like to do here is start thinking about open source a little more carefully in terms of like "What is our open source strategy with this thing?" Look at open source as a potential software sustainability strategy for DOE projects. That's kind of like what we're doing in Spack; we've active... |
Depending on what it is, maybe that's a good strategy, maybe it's not. There's some things that we wanna develop internally that we wanna keep a well-staffed team on, and there's other things that we can probably share effort with other laboratories on and that we would wanna build like a larger community maybe, even o... |
I was on a working group here that was trying to come up with -- I guess it started out as like a software engineering working group, and I think by the end of it we had changed the name of the working group to Software Sustainability. I think everyone thought we were gonna come back and say "Okay, everyone should do w... |
**Adam Stacoviak:** After the break, Nadia and Mikeal talk with Todd about the back-story of Spack and where it's going. We talked about Spack's growing community, how they're finding contributors, especially in a government context. We also talked through the details of Spack becoming a NumFOCUS affiliated project and... |
**Break:** \[20:15\] |
**Nadia Eghbal:** Todd, you've mentioned Spack a couple of times as an open source project that you've created while at Lawrence Livermore... Could you explain a little bit about what Spack is for people that are not high performance computing people, and what inspired you to create it. |
**Todd Gamblin:**\[21:47\] I have an easier time explaining Spack to people who are not high-performance computing people than to people who are high-performance computing people, in the sense that like I think people who are not high-performance computing people are familiar with package managers... Spack is a package... |
I think the reason that I built my own package manager is because the way that we distribute software in HPC is kind of different from what you would expect from most software products. People actually build their code from source on the supercomputers, typically because they wanna optimize it for hardware, but also be... |
If you look at the climate community, they have just a whole bunch of Fortran models that are tied together in different ways. Our codes tend to be like C++, some C and maybe some Fortran down in the numerical libraries, but primarily they're C and C++. We have Python drivers for some of those things; I think recently ... |
But yeah, so one simulation could be 47, 70, maybe 100 libraries in C, C++, Fortran and Python. So building that and linking it all together and getting fast native libraries there is kind of hard. |
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