amadio

Joined 10 years ago

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Feb 14

[ my public key: https://keybase.io/amadio; my proof: https://keybase.io/amadio/sigs/DbXHsryhLP8Aaw3USBvgYsUF5apVtLoKiqlcVA8uHzg ]

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Comment · 2 months ago

Most software at CERN is open source. But you are right, for things which are quite specific to CERN, like the control systems of the accelerator, there's also some proprietary code. Same for hardware actually, CERN develops open hardware too.

https://opensource.web.cern.ch/

Comment · 2 months ago

I'm a Gentoo dev and work at CERN since a while. Of course I jokingly suggested that to my colleagues. I think it could actually work pretty well, though. Many physicists use Gentoo.

We run most things on Alma Linux, but there's also RedHat in the mix.

A good intersection of CERN and Gentoo is EESSI. They use CVMFS, which is a FUSE filesystem used for software distribution from CERN, and Gentoo as part of their software stack. See links below for more info:

- https://www.eessi.io/docs/filesystem_layer/

- https://www.eessi.io/docs/compatibility_layer/

Comment · 9 months ago

These da Vinci style drawings were likely created using the SketchUp models from sometime ago, which you can download from the page below to play with:

https://twiki.cern.ch/twiki/bin/view/CMSPublic/SketchUpCMS

Comment · 11 months ago

If you would like to know more details about the physics case for FCC, there was an academic training recently at CERN:

https://indico.cern.ch/event/1582427/

Comment · 11 months ago

For those of you using CMake, have a look at the module below:

https://github.com/xrootd/xrootd/blob/master/cmake/XRootDVer...

and also the genversion.sh script at the top of the repo.

I use these plus #cmakedefine and git tags to manage the project version without having to do it via commits.

Comment · 1 year ago

At CERN, software stacks are created centrally and software distribution for experiments is done with CVMFS (https://cernvm.cern.ch/fs/), an HTTP-based read-only FUSE filesystem.

EESSI (https://eessi.io) has taken this model further by using CVMFS, Gentoo Prefix (https://prefix.gentoo.org), and EasyBuild to create full HPC environments for various architectures.

CVMFS also has a docker driver to allow only used parts of a container image to be fetched on demand, which is very good for cases in which only a small part of a fat image is used in a job. EESSI has some documentation about it here: https://www.eessi.io/docs/tutorial/containers/

Comment · 1 year ago

For those interested, there's more information here: https://home.cern/science/computing/birth-web

If you come to CERN, you can also see the NeXT machine that was the first web server.

Comment · 1 year ago

CERN is a heavy user of ceph, with about 100PB of data across cephfs, object stores (used as backend for S3), and block storage (mostly for storage for VMs). CVMFS (https://cernvm.cern.ch/fs/) is used to distribute the software stacks used by LHC experiments across the WLCG (Worldwide LHC Computing Grid), and is back by S3 with ceph for its storage needs. Physics data, however, is stored on EOS (https://eos.web.cern.ch) and CERN just recently crossed the 1EB mark of raw disk storage managed by EOS. EOS is also used as the storage solution for CERNBox (https://cernbox.web.cern.ch/), which holds user data. Data analyses use ROOT and read the data remotely from EOS using XRootD (https://github.com/xrootd/xrootd), as EOS is itself based on XRootD. XRootD is very efficient to read data across the network compared to other solutions. It is also used by other experiments beyond high energy physics, for example by LSST in its clustered database called Qserv (https://qserv.lsst.io).

Comment · 1 year ago

I think this is good advice overall. I wrote a CMake script that does most of the heavy lifting for XRootD (see https://news.ycombinator.com/item?id=39657703). The CI is then a couple of lines, one to install the dependencies using the packaging tools, and another one calling that script. So don't underestimate the convenience that packaging can give you when installing dependencies.

Comment · 1 year ago

Since you left this "optimize me" comment here:

https://github.com/RandyGaul/cute_headers/blob/755849fc2819d...

See an optimized quaternion multiplication implementation in SSE by me here:

https://stackoverflow.com/questions/18542894/how-to-multiply...

Comment · 1 year ago

I was just taking a look and couldn't help but notice the switch statement for your operator[], which likely causes a lot of unnecessary bad speculation at runtime:

https://github.com/RandyGaul/cute_headers/blob/755849fc2819d...

I fixed this exact problem in a highly used library in high energy physics:

https://gitlab.cern.ch/CLHEP/CLHEP/-/commit/5f20daf0cae91179...

Many believe the C++ compiler will magically optimize the switch away, but in some cases, like the example above for CLHEP, it doesn't happen, so you end up with bad performance.

Comment · 2 years ago

Unfortunately this is no longer maintained, but it's interesting nonetheless: https://abi-laboratory.pro/?view=timeline&l=curl