dennisgorelik: (Default)
In "Double.NaN != Double.NaN" discussion, [personal profile] ppk_ptichkin linked to Ariane 5 investigation.

My conclusions based on that investigation:
1) Delete unused code from the solution.
2) Make sure that the application is still functional, even in case when an exception happens.
3) Do integration tests.

e) At 36.7 seconds after H0 (approx. 30 seconds after lift-off) the computer within the back-up inertial reference system, which was working on stand-by for guidance and attitude control, became inoperative. This was caused by an internal variable related to the horizontal velocity of the launcher exceeding a limit which existed in the software of this computer.

f) Approx. 0.05 seconds later the active inertial reference system, identical to the back-up system in hardware and software, failed for the same reason. Since the back-up inertial system was already inoperative, correct guidance and attitude information could no longer be obtained and loss of the mission was inevitable.

g) As a result of its failure, the active inertial reference system transmitted essentially diagnostic information to the launcher's main computer, where it was interpreted as flight data and used for flight control calculations.

h) On the basis of those calculations the main computer commanded the booster nozzles, and somewhat later the main engine nozzle also, to make a large correction for an attitude deviation that had not occurred.

i) A rapid change of attitude occurred which caused the launcher to disintegrate at 39 seconds after H0 due to aerodynamic forces.


m) The inertial reference system of Ariane 5 is essentially common to a system which is presently flying on Ariane 4. The part of the software which caused the interruption in the inertial system computers is used before launch to align the inertial reference system and, in Ariane 4, also to enable a rapid realignment of the system in case of a late hold in the countdown. This realignment function, which does not serve any purpose on Ariane 5, was nevertheless retained for commonality reasons and allowed, as in Ariane 4, to operate for approx. 40 seconds after lift-off.

n) During design of the software of the inertial reference system used for Ariane 4 and Ariane 5, a decision was taken that it was not necessary to protect the inertial system computer from being made inoperative by an excessive value of the variable related to the horizontal velocity, a protection which was provided for several other variables of the alignment software. When taking this design decision, it was not analysed or fully understood which values this particular variable might assume when the alignment software was allowed to operate after lift-off.

o) In Ariane 4 flights using the same type of inertial reference system there has been no such failure because the trajectory during the first 40 seconds of flight is such that the particular variable related to horizontal velocity cannot reach, with an adequate operational margin, a value beyond the limit present in the software.

p) Ariane 5 has a high initial acceleration and a trajectory which leads to a build-up of horizontal velocity which is five times more rapid than for Ariane 4. The higher horizontal velocity of Ariane 5 generated, within the 40-second timeframe, the excessive value which caused the inertial system computers to cease operation.



On the basis of its analyses and conclusions, the Board makes the following recommendations.

R1 Switch off the alignment function of the inertial reference system immediately after lift-off. More generally, no software function should run during flight unless it is needed.

R2 Prepare a test facility including as much real equipment as technically feasible, inject realistic input data, and perform complete, closed-loop, system testing. Complete simulations must take place before any mission. A high test coverage has to be obtained.

R3 Do not allow any sensor, such as the inertial reference system, to stop sending best effort data.
dennisgorelik: (Default)
ElasticSearch team defends the bloat in ElasticSearch Percolator 5.4
If you're not interested in ranking you can easily turn it off, by wrapping the percolate query in a constant_score query.
The percolator tries to tag the queries automatically based on the containing query terms. However it can't do this for all percolator queries, because the percolator doesn't know how to extract meaningful information during indexing for all queries. This is a work in progress and will get better over time. It already has shown a significant performance improvement for cases where the percolator was able to analyze the percolator query correctly at index time.

1) Funny how in order to turn off unneeded feature, application developers have to create an extra wrapper around their query.

2) "work in progress" did not stop ElasticSearch team from breaking backward compatibility and forcing their users to rewrite their legacy code in favor of "work in progress" ElasticSearch 5.4.

3) "a significant performance improvement" is not quantified, and the cases where that improvement happened -
not described.

See also: ElasticSearch Percolator Bloat - part 1
dennisgorelik: (Default)
I bought NUC7i3BNH.
Then I tried to install Windows Server 2016 Standard on that NUC.
Windows Server installation itself was successful, but several drivers, including Network Adapters(!) and "Multimedia Audio Controller" - did not install.

Search for drivers brought me to:
where to my amazement I discovered that most of NUCs do NOT support Windows Server OS.

Further research pointed me to a hack that allows to manually use Windows 10 drivers on Windows Server 2016.
It goes like this:
1) Open C:\install\LAN_Server2016_64_22\PRO1000\Winx64\NDIS65\e1d65x64.inf
2) From this section:

copy these 3 lines:
%E15D8NC.DeviceDesc% = E15D8.10.0.1, PCI\VEN_8086&DEV_15D8
%E15D8NC.DeviceDesc% = E15D8.10.0.1, PCI\VEN_8086&DEV_15D8&SUBSYS_00008086
%E15D8NC.DeviceDesc% = E15D8.10.0.1, PCI\VEN_8086&DEV_15D8&SUBSYS_00011179

into this section:

3) Then turn off drivers checks:
bcdedit /set TESTSIGNING OFF

4) And finally install the driver:
pnputil.exe -i -a C:\install\LAN_Server2016_64_22\PRO1000\Winx64\NDIS65\e1d65x64.inf

After that Network (and Internet) started working on my new NUC.

But I do not understand - why Intel does not allow these drivers under Windows Server 2016 by default?

Update: Windows Server 2016 on NUC7i3BNH struggles - part 2.
dennisgorelik: (Default)
By juan-gandhi:
1) Мутабельные ключи в "хашмапе".
2) Стек для регистрации данных для последующей проверки, что мусора не осталось. Т.к. указатель на стек глобальный, а бегают несколько ниток, то чистый абсурд.
3) Класс на 183 метода, 0 тестов.
4) Регулярно, случайным образом, рушащиеся тесты, и святая вера, что "за последние несколько лет у нас ничего не ломалось".
5) Вера в то, что у нас все очень "эффективно" - и регулярные жалобы юзеров, что наш код очень медленный, в отличие от скального конкурента (!)
6) "Оптимистический мерж" - "это не мой тест упал, я тут не при чем, нам нужно релизить.

1) Интересно, зачем кому-то понадобилось делать мутабельные ключи в хашмапе?
2) Мне лично не встечалось, хотя при работе в multithread environment каких только ляпов не сделаешь...
3), 4), 5), 6) - мне в том или ином виде встречалось.
dennisgorelik: (2009)
Lots of applications need to load and convert document files of different formats into other formats or into text.
You would have think that there would be a good solution to it.
Unfortunately it's not the case.
Existing solutions are either for desktop only, or buggy or extremely expensive (~$10K/year).

I thought I found a solution - DevExpress Document Server library for $599.99

Unfortunately, after running for couple of weeks it crashed my service with StackOverflowException exception:
To my regret, there is no simple workaround to avoid this exception with your document. Regarding the time frame for fixing this issue, it is difficult to provide any estimate in such cases.

So now I need to find a way to prevent my service from dying in case if some random document is fed into it.



dennisgorelik: (Default)
Dennis Gorelik

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