A proper introduction

-So who are you guys?
– I beg your pardon? – Paper man almost spit out all the beer he drunk while grinning at Pamela a minute ago.

– You heard me. Maybe you didn’t understand what I mean. I just don’t have your names. Or I didn’t get them, I’m sorry? Did you tell them to me?
– I think we didn’t. – Pasta Glasses said. – Sorry…I’m Paul. – Not sure of what to do with his beer, finally he leaves it over the table and offered me his palm. I decide to correspond and grab it. We shake hands.

– Paul, nice to meet you. I’m Miguel, but everybody calls me here Doctor Chalk.

– Doctor Chalk? – Paul seems to be freed after introducing himself. – I may be able to guess why they call you this way. It was a pleasure to meet you Miguel.

– And I’m Luc. – Paper man. He seems to regret not having introduced himself first. He doesn’t offer me his hand but looks instead inside his big glass beer mug, like if it had something else inside apart from beer. We both look at him slurping one third of it with his eyes looking far away from us. – Yes, I know, we should have introduced ourselves, but I was scared, what can I say. You are not everyday piped down some kind of rabbit hole just to appear to a place that, although familiar, it is alien to you. – He is referring to his Fall. Mine was not like that, it was more like a smooth transition. One moment you are here, the next there. Meaning here, on Yellow Earth. Maybe we are moving away from Earth, I mean our own original Earth. I make a mental note on the idea and get ready to hear Luc’s story.



– Ahai my friends. Do you buy or sell?
– Ahai, Pamela. I will buy a pack of Marlboro and a big beer. And what do you want, guys? – I remembered that we were not properly introduced. Paper man and Pasta glasses were still looking lost, like if they were still a little chiral.  – Beer also? – They nod, at the same time, like two good puppies. – So three beers then. – We were sitting around my favourite table, close to one of the doors of the Hedgehogs’ but not in the middle, isolated but sheltered by the other visitors. I realised our waitress was still waiting. Right. Time for a deal. Usually I get what I want because they know me, but I understand three people can’t be left out of the business so easily.

–  Love, here you have two young mathematicians, still having their brains fresh but not soaked, looking forward to help you on any future plan you want to calculate. Does it work as an open ticket for the rest of the night? – I give her my biggest smile. She looks at Pasta Glasses and Paper man. Paper man, that is obviously not stupid, produces out of his chest pocket a little paper notebook and what it looks like a silver pen, and waves them in front of her. She bows slowly to look at his eyes… and I see him flushing. Yes, Pamela is a very attractive woman, and she likes to dress with relaxed clothes, so that if she lifts her hand in the air, you may see most of her breast from the right angle. And she does that quite frequently. Now that she bowed, I guess Paper man is looking at a very nice portion of them.

– Right. – Pamela says. – They look like the real thing. Where did you find them?

– They are my new neighbours. Do you think they can compete with me? – Now it’s time she bows to me, but with picaresque. We did exchange more than services one. Her breast seem to be still as firm as the last time, maybe firmer.

– Nobody can compete with you, Doctor Chalk. – She is not flirting, I know that when she calls me Doctor it’s going to be a professional matter. She starts to leave. – We will see. We were said it’s time to estimate what we’re going to need for the next month. Probably you can help us there. I have no mind for the numbers, but I know how many people pass by here each night, and what they usually want. Will that work for you guys? – My puppies nod simultaneously. Pamela laughs. – Then we have a deal! Beers coming !!! – And she leaves our table half floating, half dancing, while we all three admire her ass.

Hedgehogs’ corner

I don’t go far away from my place. In this world we are now it is dangerous to wander around without a specific destination. It’s first thing you learn here: if you go 5 steps to the left, then 5 again to the left, and again and again and again until completing a 360 turn, you may not end up in the place you started, but somewhere else. The only way I have to describe it is, given my education, as an additional dimension that I tentatively call the chiral direction. Using directly the chiral, you can travel very fast from A to B, but its dimensionality  is somehow sticky to the others, so it could be that if you turn in the right way to the left by 30 degrees, when you move straight, you will move much faster than usual. Like as we did to reach the Hedgehogs’ corner. This way of travelling has an inconvenience also: you need to know how to get rid of the chiral stickiness.

Let me try to explain it with what I call the z analogy: you can go up if there’s a slope to climb until the top of the hill. Once at the top, you can only go down, except if there’s another, higher hill that starts close to where you stand. When you go chiral, it’s like that. Or as Galileo Galilei pointed out, what goes up must come down.

Hedgehogs’ corner must be high on chiral: everybody is ending up here. There’s a huge market here that is almost always open in some way (maybe there are only a few shops open instead of the full market) and the bars are great. Amongst the bars and restaurant that fill this neighbourhood, the most charismatic one and the biggest by far is the one giving the name to this place, that, against the logic of his name, is not located in a corner. Maybe it was, at the very beginning, but I never asked about the nature of the name to the owners, the heterogeneous group of people that seem to operate, with more or less success, this fantastic place that I learned to love. And the beer is great here.

Slurm update on CentOS 7

We have a big disconnection time (finally!) and everybody is happily taking coffee and discussing about what to do during the holidays while I’m alone running around updating hardware and software.  I have updated the NVIDIA drivers, the kernel, the GPFS system, and now slurm. I download the latest version from here.  Now instead of only compiling it I’m going to make rpm packages on the node that runs the controller and distribute them around. Like this:

rpmbuild -ta slurm-17.11.5.tar.bz2

My rpms appear on /root/rpmbuild/RPMS/x86_64/, since I built them as root. I copy them to my network location and simply install them using my installation script. My installation script is a “one liner” with the packages in the right order:

yum --nogpgcheck localinstall \
slurm-17.11.5-1.el7.centos.x86_64.rpm \
slurm-devel-17.11.5-1.el7.centos.x86_64.rpm \
slurm-munge-17.11.5-1.el7.centos.x86_64.rpm \
slurm-openlava-17.11.5-1.el7.centos.x86_64.rpm \
slurm-pam_slurm-17.11.5-1.el7.centos.x86_64.rpm \
slurm-perlapi-17.11.5-1.el7.centos.x86_64.rpm \
slurm-plugins-17.11.5-1.el7.centos.x86_64.rpm \
slurm-seff-17.11.5-1.el7.centos.x86_64.rpm \
slurm-sjobexit-17.11.5-1.el7.centos.x86_64.rpm \
slurm-sjstat-17.11.5-1.el7.centos.x86_64.rpm \
slurm-slurmdbd-17.11.5-1.el7.centos.x86_64.rpm \
slurm-slurmdb-direct-17.11.5-1.el7.centos.x86_64.rpm \
slurm-sql-17.11.5-1.el7.centos.x86_64.rpm \

Note that I made the rpms by compiling the tarball (rpmbuild) so if you managed to run the command, your rpms will work on your systems. We will see… now I need to wait until “the others” have “the other pieces” ready to be assembled…my job can’t go beyond this point. This is how it is, and this is how I like it 🙂

EDIT: in addition to the yum command above, I was forced to do an additional yum install slurm-slurmctld-17.11.5-1.el7.centos.x86_64.rpm (for the login node) and yum install  slurm-slurmd-17.11.5-1.el7.centos.x86_64.rpm (for the computing nodes). Otherwise the services (slurmctld and slurmd) don’t seem to be installed.  

Going down

The problem with this part of the city is the slopes. You need to be familiar with them or you will always end up going up instead of down, or down instead of up. And it very annoying, of course, specially if you are completely wasted.

The guys didn’t complain at all, they followed me out of our building to the street while mumbling something about the decoration of the flat. I was actually concentrated on going down properly and getting quickly the main stream to Hedgehogs’ corner. First steps were always crucial: if one diverges just 5 meters to the left, one can end up climbing a crazy mountain instead of softly sliding down away, enjoying the gravity of your own weights. I told the brothers.

– Hear me out, please – they immediately stopped discussing what I assumed was the decoration they wanted for the flat – probably as you previously observed the space-time geometry locally has a “z” instability. You can deduce the consequences of it, if you didn’t experience before. If you’re so kind to follow me, we’re going to use the minimum energy path to go all the way down to Hedgehogs’ corner.

– Thanks for guiding us man. You know how difficult it is for newcomers to work out how to move here. – Paper man was definitely the leader of the couple. By the way, I need to remember to find the right moment to ask them for their names. Or did they already told me? – I really miss my handy. And the social networks. And the internet, all together.

– You don’t miss that. – I stop going down and turn back, to look into their eyes. – We were slaves, you know? We were working for the profit of an oligarchy that only wanted to show up to be adored, to be said how cool they were that they had 500 billions more than the other guy. That they had enough money to buy a school for this or that, an university, of for all that matters, a country. They were, all together, owning the fucking planet. – I take one of my precious cigarettes and I light it. –  So yeah, don’t miss it. Here in the city we value you for what you’re able to do, not for what you own, or for who are you related with. You can get a reward corresponding to your abilities, not to the economy you happen to be embroiled in. – They now stare at me with a weird face. I give a puff and throw the smoke to them, despectively, forcing an answer.

– What the hell are you talking about? – Pasta Glasses is trying to be friendly and he looks genuinely shocked due to my little speech. – After the war, nobody was even able to say he was owning a fucking potato… because there were no potatoes! – Pasta Glasses was not angry, just obviously enjoying a lot lecturing me. – That was like a hundred years ago. – I throw my burning butt, maybe a little bit more violently that I should have. The war. When I left, there was no war. The menace was there, right, but nobody thought that as a real possibility. – I see. – Now Paper Man is back with the leading voice. – Sorry sensei, but you’re outdated. The System may not be the best form of government, but we were getting close to achieve something new. We were. Now we’re here. And with no easy way back, as far as I understood. So let’s assume it and be a part of it, be the best on it.

– A pragmatic approach. But it’s OK, provided you know where you stand.- I manage to add.- This way, please. – I point the on direction of the speed line to the Hedgehogs’. We walk in silence until reaching it. Then, to the left, until we’re in. The road looks curved around us, like a water channel or a half pipe. I start walking.  The building move out of my sight at a constant speed that I estimate of around 30 Km/h while I’m just walking… so in a couple of minutes we’re there. Hedgehogs’ corner.  I step out of the speed way, to reach the small square. – Now guys, time to test your mathematical abilities.

A very complex integral

– Could you please help us solving this integral?
I could’t believe my ears. I opened the door because they looked innocuous thought the sight glass. There they were, two nerd-looking teenagers, one of them practically rubbing in my face a paper with a complicated triple integral. The second one adjusted his glasses over his nose, while trying not to drop his pile of books. Some of the titles were readable from my vantage point of view.  Advanced Calculus. Numerical Recipes. Numerical Methods. All the classics. As for instinct, I reached my pocket, but my mobile phone was missing. Of course it was. Why should not be?

– Guys, calm down. Please elaborate. What’s going on?
– We were asked to to this …math …to be allowed to stay in. Aren’t you the famous physicist? – I’m flattered, but I try not to show it. I am just good visualising the solution to the problems. – We were thinking… that you will teach us. – The one with the glasses finished the sentence his friend with the paper started. So cute.

– Right. Don’t panic. Let me see. – I have a look. Damn, it’s not easy: maybe it requires a double substitution. It’s far, far more difficult than the ones I was asked to solve up to now. I wonder for what is going to be used… – Sorry to disappoint you, but it has no easy solution. Are you in hurry?
– Yes we are! – Paper Man practically shouted. On the other hand, Pasta Glasses was trying to make a sad face. – We really want to stay here. We’re no artists, neither entertainers, this is definitely our building. Of course we could try to go to a lower level… maybe school’s level will be better for us? – I look into the eyes of my future neighbours, trying to evaluate if they’re just playing with me.

– OK, ok. Don’t worry. I will speak to the building manager to delay your payment. – I realised I was feeling pity for the couple, but this is me, I’m a piteous person. I see a stray cat, I give him milk. I find a problem, I try to solve it. It’s the Curse of the Physicist. – Let me see those books. Yes, leave your calculations over the table. – They smile to me. I wonder how old are they, twenty, thirty? Here we don’t age, so they can be sixty as far as I know. But it’s OK, no stress allowed. We’re living the American Dream.  – Are you familiar with the neighbourhood already? – They nod. I look out, dusk is coming, and I’m a little bit hungry. Or I will say thirsty. – How good are you on basic calculus?

– We passed the basic education… -Paper Man seems to be the leader of the pack. Pasta Glasses continues. – We just started Math at the University before… arriving here… so we thought we could apply for a flat on this building…
– Boys, calm down. Of course you did right. This is the best place to challenge your mind. Why are we here? What is this city? Where is the rest of the world? – They look at me like if they were drinking my words. – We can speak about the future of mankind as we know it, and similar issues, at the Hedgehogs’ corner. But you probably will need to perform some basic math there before getting your drinks. Are you ready? Will you join me?

– Of course we will! – They both smile. What are those two? Brothers? I take my dusty raincoat, a pack of cigarettes, I check that I have my lighter and I push them downstairs.
– Then let’s go!

OSX su versus sudo

I had this weird problem. I need to run some commands with sudo. But I have a root password, why should I sudo something? The answer is simple: the SU password is not the same than the sudo one. So, as real root, supposing you have the root account enabled, you have more control than the sudo user. And you can give sudo rights to a local Admin account (sudo su will be work with that user’s password) without compromising your root account password. Now the problem will be to teach the user so that he doesn’t mess up with the system functions 😛 …I can’t help you there. Or can I?