1) Message boards : LHC@home Science : Ready to restart! (Message 47245)
Posted 12 Sep 2022 by Henry Nebrensky
Post:
It looks like they are indeed training the magnets these days, there are magnet quenches with no beam.
Possibly, but given the potential side-effects of a quench - remember those magnets scattered around the tunnel after the first startup - I know I would be wary of trying to train to 14TeV current settings before getting 13TeV data in the can. I'm intrigued by the cryptic references to UFOs in that blog post - sounds suspiciously like someone's dropping their spanners on the machine. (Unless that's a dated baguette reference?)
2) Message boards : LHC@home Science : Ready to restart! (Message 47195)
Posted 27 Aug 2022 by Henry Nebrensky
Post:
Meanwhile the LHC magnets remain at 2K, allowing more time to train the magnets.
What does that involve?
3) Message boards : LHC@home Science : Proton Physics : Stable Beams (Message 47054)
Posted 30 Jul 2022 by Henry Nebrensky
Post:
Why does the luminosity at an experiment's IP vary relative to the circulating beam? (e.g. what happened at Alice before/after 20:00-ish?)

Does this mean that the LHC dynamically alters the lattice even within a fill?
4) Message boards : Theory Application : Sherpa tasks run okay for long time, then they fail (Message 47024)
Posted 15 Jul 2022 by Henry Nebrensky
Post:
7.100 events (8d 17h) atm.
But isn't that going to take more like 14 days to complete, rather than 10?
5) Message boards : Number crunching : CentOS9 squid Win11pro (Message 46857)
Posted 8 Jun 2022 by Henry Nebrensky
Post:
CentOS8 have no Mirror, out of support since 2022/01.
As announced a couple of years ago, CentOS became "CentOS Stream". Conversion instructions for CentOS8 to CentOS Stream8 are at https://www.centos.org/centos-stream/.
(I've not tried them; I've been reverting to C7 instead).
6) Questions and Answers : Getting started : How To Setup VirtualBox With LHC@HOME On Command Line Only Server? (Message 46645)
Posted 15 Apr 2022 by Henry Nebrensky
Post:
I got some cloud VMs and want to contribute to the project, but the native applications always fail, and I couldn't fix it. I am wondering how can I setup VirtualBox with LHC.
As these are already VMs, I doubt Virtualbox will run correctly inside them. Never tried it though.

I did simply `sudo apt install virtualbox -y`, is that all?

Answering the subject line, my old notes for CentOS7/8 (Minimal install) say:

    VBox needs gcc, make, elfutils-libelf-devel, kernel-devel and kernel-headers; not a dependency in the RPM. May also need: setools-libs libsemanage-python
    yum install gcc make elfutils-libelf-devel kernel-devel  kernel-headers setools-libs libsemanage-python libseccomp

    Install the downloaded VirtualBox RPM:
    yum localinstall VBox-version.RPM

    user running BOINCmust be in VBox group:
    usermod --append --groups vboxusers boinc

    Rebuild the kernel modules:
    vboxconfig

    Start VBox services:
    service vboxautostart-service start
service vboxdrv restart

    Optional:
    VBoxManage extpack install /tmp/Oracle_VM_VirtualBox_Extension_Pack-version.vbox-extpack


All as root, via SSH. That should should give a working VirtualBox testable by restarting the BOINC client.
If working, remember to chkconfig the services on before rebooting.
When updating the kernel, remember to re-run vboxconfig to build the new modules before rebooting.

Other useful bits:

VBoxManage list extpacks

VBoxManage list vms
VBoxManage showvminfo 1e6cf289-3176-476f-b80c-6fa3fbe42922
VBoxManage unregistervm 1e6cf289-3176-476f-b80c-6fa3fbe42922 --delete


Distro-specific and SysV-to-systemd translation left as an exercise for the reader.

Note that I've not tested this in a couple of years as I don't have any suitable machine at the moment. Any problems see Yeti's Checklist
7) Message boards : Number crunching : CentOS9 (Message 46488)
Posted 20 Mar 2022 by Henry Nebrensky
Post:
Mirror for CentOS8 is out of Service since 22/01/31.
Isn't that part of the change from CentOS to CentOS Stream? This has caused some "discussion" in the community, including proposals for LHC to move away from CentOS to some other distro. I don't know if there's any clear route on this yet.

CVMFS is not supported for CentOS9 (only CentOS7 and CentOS8).
May well be low-priority due to above.
8) Message boards : ATLAS application : Atlas task slowing right down near the end but still using all cores - continue? (Message 46414)
Posted 3 Mar 2022 by Henry Nebrensky
Post:
I would vote for 240.
Actually, I'd vote for 360 - them Babylonians knew what they were doing ...
Are they the ones responsible for clocks?
... and angles, (which is where clock faces came from?).
But, actually computezrmle was right: 240 also gets you a division by 16, for future expansion.
9) Message boards : ATLAS application : Atlas task slowing right down near the end but still using all cores - continue? (Message 46403)
Posted 2 Mar 2022 by Henry Nebrensky
Post:
I would vote for 240.
Actually, I'd vote for 360 - them Babylonians knew what they were doing - but if people are already struggling with compute times then it would be better to stick to low hanging fruit. :(
10) Message boards : ATLAS application : Atlas task slowing right down near the end but still using all cores - continue? (Message 46402)
Posted 2 Mar 2022 by Henry Nebrensky
Post:
Even within a task, as the number of threads is reduced then each thread must run more events, and it's more likely - but not guaranteed - that they will average out across the threads.
Even with the full 8 cores, that's 25 events per thread, which is more than enough to average things out.
Doesn't that depend on the variance, which I've never studied? In any case, the aim is that the averaging overcomes the variance, which is why divisibility is important for avoiding a small number of events left over.

Also, do you have a figure for how much time is wasted? Since it's 200 in the pool, the wasted cores at the end are probably a fraction of a percent of inefficiency.
IIRC, back when I was running 8-core native Atlas I would generally see the active threads reduce over usually 1-2 minutes, 5 if slow, for tasks of about 4 hrs total wall-clock. (There might be numbers in some ancient post here, but the laptop's tired tonight :( )
A few minutes in 4 hours is nothing.
Thank you - I did put some effort into setting those machines up...
11) Message boards : ATLAS application : Atlas task slowing right down near the end but still using all cores - continue? (Message 46399)
Posted 2 Mar 2022 by Henry Nebrensky
Post:
... they are random sizes.
You are looking on just 1 task but you would have to look at the long term averages.
Really huge numbers!
... I'm surprised there's a difference though, considering the wide variance in event times.
Even within a task, as the number of threads is reduced then each thread must run more events, and it's more likely - but not guaranteed - that they will average out across the threads.

Was the wide variance I saw unusual?
I've no idea.

Also, do you have a figure for how much time is wasted? Since it's 200 in the pool, the wasted cores at the end are probably a fraction of a percent of inefficiency.
IIRC, back when I was running 8-core native Atlas I would generally see the active threads reduce over usually 1-2 minutes, 5 if slow, for tasks of about 4 hrs total wall-clock. (There might be numbers in some ancient post here, but the laptop's tired tonight :( )
12) Message boards : ATLAS application : Atlas task slowing right down near the end but still using all cores - continue? (Message 46390)
Posted 1 Mar 2022 by Henry Nebrensky
Post:
As CP mentioned each ATLAS task processes 200 events from a pool.
It has struck me before, that changing the task's pool size to 180 or 240 events would give better divisibility.
13) Message boards : Sixtrack Application : Sixtrack BOINC application on track to be ported to GPUs? (Message 46205)
Posted 9 Feb 2022 by Henry Nebrensky
Post:
... and now SQUID. That is a lot to ask of volunteer crunchers.
Set up once, runs for months...
More to the point, you don't even need to start worrying about Squid until after you've been through the VirtualBox/CVMFS palaver at least once (to create useful traffic for a Squid to cache), and then only for the larger scale crunchers.
If Sixtrack becomes as painful to get running as, say, Atlas, then surely this will be a big turn-off when trying to encourage new, casual volunteers to join the project.
14) Message boards : Sixtrack Application : Sixtrack BOINC application on track to be ported to GPUs? (Message 46202)
Posted 9 Feb 2022 by Henry Nebrensky
Post:
I'm intrigued as to how the run-time compilation of C by a python app (p. 54 on) would translate to running on an arbitrary BOINC client, especially a Windows one.
Mmmmm, virtual machine?
But the big selling point of Sixtrack as a BOINC project is precisely that it Just Works, without all the shenanigans of VirtualBox or CVMFS or whatever...
15) Message boards : Sixtrack Application : Sixtrack BOINC application on track to be ported to GPUs? (Message 46188)
Posted 7 Feb 2022 by Henry Nebrensky
Post:
Just curious for XTrack (a part of the new XSuite) i find this pdf and the project seems to be ambitious (see page 15)...
I'm intrigued as to how the run-time compilation of C by a python app (p. 54 on) would translate to running on an arbitrary Boinc client, especially a Windows one.
16) Message boards : Theory Application : How to tell if a Theory native task is stuck (Message 44849)
Posted 1 May 2021 by Henry Nebrensky
Post:
How can i check if a native task is still doing what it's magic or if it's stalled?
https://lhcathome.cern.ch/lhcathome/forum_thread.php?id=5576&postid=44055

If it stopped updating the log file for a couple of hours I just killed it and moved on to the next. Look at one of the "Looooooong runners..." threads.
17) Message boards : ATLAS application : Use existing Tier-2 cvmfs squid for boinc ATLAS@home hosts (Message 44333)
Posted 17 Feb 2021 by Henry Nebrensky
Post:
A separate squid instance on each worker box will reduce efficiency and increase maintenance effort.

As the OP claims to be close to a WLCG Tier2 site I figured network bandwidth wouldn't be an issue, and if there's enough machines that maintenance issues are significant then you want to be using a configuration management system anyway in which case I found keeping machines identical made things simpler! And on a corporate/enterprise network, a separate squid is likely to result in questions from network admins about what it's doing there, who can connect through it, and to where...

For CVMFS the biggest single gain is in maintaining the cache across successive VM initialisations; the local squid route gets that without affecting any other activity on the machine, and without exposing new services on the network.
If I was in the OP's situation - and I've been close - I'd start there. Once the OP has some experience and a track record with their networking team they can always take another step, whether that's the standalone BOINC squid or fudgerating the local squids to use the Tier2 one or whatever else. (It'll also depend on what else the machine is used for - the OP mentioned a separate batch system in another post.)
18) Message boards : ATLAS application : Use existing Tier-2 cvmfs squid for boinc ATLAS@home hosts (Message 44328)
Posted 17 Feb 2021 by Henry Nebrensky
Post:
We do already have a cvmfs squid for our local WLCG Tier2 cluster and the obvious plan is to make our boinc hosts connect to it.
Does anybody have a working configuration for this scenario and could share it?

Years ago, for Atlas-native I simply used the same basic configuration of CVMFS on the boinc nodes as on the Grid cluster nodes.
As you're going with VirtualBox I have no idea how it will work out: defining a proxy in BOINC will route all web traffic through it, including the VM's Frontier traffic as well as BOINC job requests. Also, AIUI the Atlas VMs here have the CVMFS preconfigured to use the Cloudflare stratum one server instead of the CERN ones in which case I don't think you'll get the expected efficiency either, as the squid would end up having to hold two copies of each file. My inclination would be to just run a BOINC-specific squid on each machine to hold the local CVMFS cache across successive VM instances.
19) Message boards : Theory Application : WUs stuck at 100% (Message 44055)
Posted 3 Jan 2021 by Henry Nebrensky
Post:
When my WUs reach 100% ...
Don't take BOINC's "percentages" too seriously. For native Theory you can see what the project code is up to with something like:
tail -n 20 /var/lib/boinc/slots/?/cernvm/shared/runRivet.log
Most Theory apps will report progress as number of events processed, which you can compare with the total number of events requested (second to last number on the very first line).
As long as there's a steady rate of progress the task is fine. If the log file is stale (timestamp more than two hours ago) then I (personally) assume the code is stuck in an infinite loop, and abort the task.

(Unfortunately my computers have all had to be moved to the great datacentre in the sky, so I've written this down where I might stand a chance of finding it if I ever get to pick this up again!)
20) Message boards : Number crunching : Cupboard is bare? (Message 44033)
Posted 31 Dec 2020 by Henry Nebrensky
Post:
Atlas is back, thank you.
Embarrassingly that caught me by surprise as I wasn't expecting things to be fixed until next week - I'm having to shut my cluster down tonight as it must relocate to the great data-centre in the sky :(, and having spent ages aborting CMS tasks so the work finishes at a sensible time a load of Atlas tasks suddenly appears!


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