In episode 30, we interviewed Todd Gamblin from the Lawrence Livermore National Laboratory about the Spack project. We discussed his current research project along with his involvement in Spack. We widely discussed the philosophy of Spack, some usage patterns, its capabilities for managing package management in HPC clusters as well as standalone computers and which operating systems it supports at the moment. Todd shared with us his opinion on the trend for containerized workloads to achieve reproducible science and why it may not be the goal we need to set. He highlighted for us the similarities and differences between EasyBuild and Spack as well as the origin of those differences. We finished the interview with our usual quick questions.

00:00:00 Intro music00:00:17 Introduction00:00:36 Introducing Todd Gamblin00:00:58 His current research topics00:01:23 Spack as official duties00:01:43 Spack usage at Lawrence Livermore National Laboratory00:02:01 Other research projects00:02:47 Profiling in HPC00:04:24 His role as leader of software packaging technology for the exascale computing project00:04:58 One-minute elevator pitch for Spack00:05:34 Spack's usage philosophy compared to other package managers00:06:59 Installation from source code or binary?00:07:28 Spack's usage in the top500 super computers00:07:49 Geographical distribution of users00:08:18 Number of packages in the repo and some examples00:09:05 Managing computer clusters with Spack's automation capabilities00:11:04 Module files in Spack00:12:32 Syntax of a Spack package file00:13:43 Configuration of compiler flags00:15:00 Importing python libraries in the Spack files00:15:48 The procedure to submit a package00:16:27 Review process for new packages00:17:34 Reasons for rejection of Spack packages00:18:01 Operating systems supported by Spack00:18:23 WSL and Spack00:18:58 Restricting packages to certain hardware and software configurations00:20:04 Build testing and nightly builds00:21:28 Working with containers in a Spack environment00:22:25 Deploying prebuilt containers00:23:05 About the "universality" of containers00:24:16 His opinion on containerized applications for reproducible science00:26:17 Spack's log file to document reproducibility00:27:13 Reproducing older results00:28:10 Specifying requirements on compilers00:30:39 Post-installation verification test00:31:10 Using Spack on a standalone computer instead of HPC systems00:32:56 Differences between EasyBuild and Spack00:34:24 EasyBuild in the top50000:34:49 Transitionning between EasyBuild and Spack00:35:38 Other alternatives00:36:23 Using EasyBuild and Spack on the same system00:38:36 When did the project start?00:39:53 External contributions to Spack00:40:53 How many core developpers?00:41:30 Organization of the community and governance model00:43:06 Who decides which package is accepted in the repo?00:44:38 Spack's choice of software license00:47:09 Todd's vision about the importance of FLOSS for the openness of science00:48:13 Possible negative impacts of FLOSS00:48:58 Most notable recent scientific discovery00:49:14 Favourite text processing tool00:49:25 A topic in science about which he recently changed his mind about00:49:58 Anything else we forgot to ask?00:50:09 How to contact Todd00:50:46 Conclusion