izard: (Default)
2019-05-31 10:08 am

This blog

I'm writing the blog in English because I type twice as fast this way than in Russian (yes I am improving...), and 90% of my friends and friends read English any way. I answer comments in the same language they are posted.

I am trying not to post anything related to my employer, but if I do so, this expresses only my own views and does not represent official position of my employer.

When I post about some technical topic which seems non trivial and is related to my employer's product, don't expect it to be inside information. If I post about it, it means that this info is already public. Usually I do not post any personal information or anything that is related to my family.

All photos are mine, and I allow anyone to copy, change, do anything you please with them. I don't post "friends only".

Useful tags are: http://izard.livejournal.com/tag/software , http://izard.livejournal.com/tag/readlog , http://izard.livejournal.com/tag/idea , http://izard.livejournal.com/tag/deutschland and http://izard.livejournal.com/tag/trip_report
izard: (Default)
2017-07-24 09:26 am

Second first impressions.

I am back from Russia. I don't come there often, so each time I notice a visual difference.
For example, advertisements change a lot between my visits. 2 years ago, there were many
grafitti tags "dial 8-9xxxx to buy cheap viagra/cialis". Now the very first ad I've seen upon
arriving to Sheremetievo airport was "buy pills ZZZ, to make your male orgasm brighter and
more colorful.". I hope those in double blind controlled clinical trials for this substance had some fun.
And I wonder how they measured. Oh, I guess there was no clinical trials.. The pills are made in Nizhny Novgorod,
it was written in the ad btw. Also this time I seen more tags like "dial 8-9xxxx to buy salt/pepper/nutmeg" (for those who don't know, they don't mean salt/pepper). Sad.
izard: (Default)
2017-07-17 09:46 am

Jacob in Russia

It is his second time in Russia, but now he is old enough to understand a bit more.
- Mama, Papa, what is it? - pointing at a hole on an asphalt pavement.
- It is a hole.
- A hole? Who makes such holes? Why they make them? How they make them? May I touch it?
At 3 years and 1 month old, it is a first time he discovered a hole in asphalt that is not a part of a fenced construction area :)
izard: (Default)
2017-07-12 03:18 pm

Мы строили, и наконец построили.

Finally, live feed from Skylake-SP launch. Yes, it does not have SHA-NI, but it is the biggest improvement in u-arch since Nehalem.
izard: (Default)
2017-07-11 12:20 pm

Bugz

The worst kind of bugs - 3rd party libs dependencies..
On a fresh Fedora 26 install on one of my test servers, one of the tools I needed wanted to install some gtk and gdk dev libs.
# yum install ...
"you are about to install a ton of deps, tolal 100Mb" Y/n
Y
"done"
A tool works.
Now I need to install a kernel src package:
# yum install ...
File "/bin/yum", line 57, in
from dnf.yum import main
...
ImportError: /usr/lib64/python3.6/site-packages/rpm/_rpm.cpython-36m-x86_64-linux-gnu.so: undefined symbol: PySlice_AdjustIndices
Previous installs broke yum!

Very cool: I can't even google PySlice_AdjustIndices, and PySlice library simply does not have AdjustIndice method in 3.6.0, only SetIndices...

Of course I don't care to debug deeper (or file bugs with Fedora), it is just easier to re-install.
izard: (Default)
2017-07-06 03:43 pm

roofline model

I have to admit that I was wrong - when I first read about roofline model several years ago I thought it is too abstract to be used in a real s/w performance work.

It is not, and Intel Advisor tool that visualizes loops in roofline model actually more makes sense than I thought.
izard: (Default)
2017-06-23 10:06 am

Jacob speaks, 3.0 y.o

- Пусть мама сродит мне братика!
- Почему не сестренку?
- Девочки лучше, но с ними сложнее, а у мамы сил нет.
- А с братиком придется делиться ресурсами?
- Игрушками? Я старше, так что он у меня отнять не сможет, а я у него смогу. Но я своими буду делиться, иногда, ненадолго. А ему ты будешь тоже игрушки покупать, а я у него брать.
izard: (Default)
2017-06-16 01:51 pm

New mesh architecture announced for Xeon CPUs

Yesterday Akhilesh Kumar, the Skylake-SP CPU architect announced mesh architecture for future Xeon CPU,

that replaces ring. The ring was there in Xeon for 6 generations, and once the server CPU has grown from 4 to 20+ cores, latency of the ring became an important factor to consider in software performance work. In last 4 architectures, there were even sub-rings (Cluster-on-Die) to address this. Some folks were reverse-engineering a secret (though simple) hash function that directed different cache lines to different chunks of last level cache.

No need any more. That is just one of great features in the upcoming CPU.
izard: (Default)
2017-06-05 02:03 pm

The circle

After [profile] blau_krahe suggestion, I just read it during this long weekend. The narrative style in Russian is very similar to "Холодная зона" by the way.

It is fun to read, but unlike "Холодная зона", everything in this book seems just trivial. First 20% or so is absolutely realistic, then as the plot becomes somewhat darker in the following 10% of the book, the rest 70% becomes obvious. So I guessed all the remaining plot after I read the first 30%, just thinking: "What would an american author write to make absurdity grow until a possible maximum is reached." I think if the author would have been european, it would not be that easy.

So in a hindsight, I would recommend reading the first 30% of this book, skipping all the rest but last 5 pages or so.
izard: (Default)
2017-06-04 09:08 am

Aphids

Ants can't reach young leaves of a beech next to our home, so all the sugar aphids produce just crystallises on leaves.

Very tasty :)
izard: (Default)
2017-05-23 09:55 pm

What would a German do?

I got a weird problem with a neighbour, that demonstrates a typical German way of communication. My wife needed some room in a trunk of our car for shopping, so she removed a folding stroller from the trunk, and left it at our parking lot. (The parking place at our building's underground parking that belongs to us). In couple of hours Yulia came back, and did not find a stroller. She looked around and found it ~20 meters away, at some other neighbor's parking lot.

In the evening, I found a letter (with date, name and signature) under my car's wiper:

"Hi, I accidentally rolled over a stroller that was lying at your parking lot. Now I have some scratches on my car, if the stroller belongs to you, please call me +49NNN to discuss the compensation."

I wonder what I do next, obviously my German is not good enough to discuss these matters over phone, and Yulia would not stay calm during the conversation (though even if it turns out to be our fault, we still have an insurance for that).

I am also very curious, what would happen in US and Russia in the same circumstances?
izard: (Default)
2017-05-22 04:19 pm

work stuff

1. Looks like openvswitch constantly monitors PMUs, so it is difficult to monitor it's performance externally :(
2. I was asked to explain why sharing workload to 2 cores with 80% utilization was equivalent to sharing it to 6 cores with 40% utilization. Kinda funny, shouldn't it be obvious?
izard: (Default)
2017-05-20 10:25 am

Jacob speaks, мастер спорта майор чингачгук (с) анекдот

2 years 11 months old, riding on my neck:
- Я всадник! Я - полицейская конная стюардесса!
(перечислил все любимые профессии)
izard: (Default)
2017-05-11 04:29 pm

algorythm for kickstarter

As a backer of few dozens of kickstarter projects (that is the only way of shopping that I like), I noticed a pattern..

Many projects that I backed were very similar:

There is a product/gadget/tool (I'll call it bells and whistles, or B&W for short). One can buy B&W at one dollar shop for 10$, made in China, and the quality will be awful. You could probably use it once or even less, and it will break. In a supermarket, B&W will cost 50$, and you may use it 1-20 times before it breaks, if you are careful enough. Sometimes there is a high end variation available online, you may buy it for 100$, and it will last almost forever in non-professional use. Very often there is also a luxury/professional version that costs 500$, which is perfect but too expensive for an occasional user.

All above is likely manufactured in China, with BOMs of 1$, 10$, 20$ and 80$ respectively. Retail, marketing, brand/revenue combined makes up the rest of the price.

So at kickstarter, there are plenty of successful campaigns that have many nice words about R&D, but in fact it is just a procurement of B&W from a Chinise manufacturer at $60 BOM, selling it for 120$. For the end user, B&W from kickstarter at 120$ is often as good as a professional thing for 500$.

I guess this pattern is not fulfilling original kickstarter's mission to fund new R&D, but that is how it is.
izard: (Default)
2017-04-21 10:22 am

В третью стражу

Russian popadancy/althistory that does not suck. 1933-1937, 0% technical progress, nobody warns "tovarisch Koba et al". Group of "popadancy" just try to make WW2 into a series of smaller scale conflicts by clever espionage plots.
izard: (Default)
2017-04-20 09:59 am

O(n^3)!

Here is the code for the previous post

I should have wrote this code in the first place, took me only 5 minutes anyway. [personal profile] spamsink was right: apparently in runs in slightly below O(n^2).

But my proof of O(n^3) still stands, and I found a German university computer science textbook that also proves it should be O(n^3) in the worst case... Riddles!
izard: (Default)
2017-04-19 08:08 pm

O(n^3) or O(n^2)?

Those interview questions... I am not fond of computer science riddles, but some are.

I am reasoning about Welzel's algorithm complexity:
(to find a minimal bounding circle over set of points P, there is a recursive algorithm:
circle mbcr(P[n], R)
if |P| = 0 or |R| = 3
return get_circle(R)
if (P[0] in mbcr(P-P[0], R))
return mbcr(P-P[0], R)
return mbcr(P-P[0], R+P[0])

In a textbook, they say complexity is ϴ(n) for average case and O(n^2) in worst case..

I am getting different values. Lets assume worst case, when "if (P[0] in mbcr(P-P[0], R))" is always false.
mbcr(n, |R|=3) = O(1) - obviously.
mbcr(n, |R|=2) = O(n) - n * first recursion point, and each time it gets only once to second recursion point (which is mbcr(n, |R|=3) case).
mbcr(n, |R|=1) = O(n^2) - T(mbcr(n, |R|=1)) = O(n) + (n-1) * T(n-1, |R|=2)) = O(n + n^2) = O(n^2)
mbcr(n) = O(n^3) - T(mbcr(n)) = O(n) + (n-1) * (T(mbcr(n-1,|R|=1)) = O(n) + O(n^3) = O(n^3)

What am I missing?? Everything above seems very clear for me, can't stop thinking about this simple problem.
izard: (Default)
2017-04-03 12:41 pm

on new GitS

Watched it yesterday, and I like it more than original.

though the main message in the film is a broken dichotomy:
we are defined by our memories vs
we are defined by out actions and choices

Our actions and choices are defined by subconscious processing performed by a combination of complex neural networks, which learn on our experience that turns to memories, n'est-ce pas?
izard: (Default)
2017-03-28 12:40 pm

Lufthansa vs Aeroflot vs Turkish Airlines

I can share some personal statistics on these 3 airlines I use the most in last ~10 years.

It is about economy, I never flown business with Aeroflot or Turkish.
10 years ago:
Food: 1. LH, 2. Turkish, 3. Aeroflot
Service: 1. LH, 2. Turkish, 3. Aeroflot
5 years ago:
Food: 1. Turkish, 2. Aeroflot, 3. LH
Service: 1. LH, 2. Turkish, 3. Aeroflot
now:
Food: 1. Aeroflot, 2. Turkish, LH (Still big plus for Turkish - they have Ayran!)
Service: 1. LH, 2. Aeroflot, 3. Turkish

Its a pity Turkish airline's food is now just good, not fabulous as it was just a few years ago..
izard: (Default)
2017-03-27 10:48 am

You don't exist, go away!

I think today was the first time I seen this message in a terminal:
# ssh $IP
do_ypcall: clnt_cal: RPC: Time out
You don't exist, go away!
#

Good sense of humor, guys!