**
I am pretty sure a set of sequential commands with same input cant
change it's output every time you run it
It might sound stupid . For example while installing an application or bulding using Cmake , atleast for me , i would encounter different bugs each time i run the installer using the same system.
I guess i might have changed the cmake setting or the system settings but it feels so strange and i am totally paranoid about it.
**.
you never initialize arr but you use it to do M=M-arr[i]; the behavior is undefined
out of that to use an array with a dynamic size is not recommended (ISO C++ forbids variable length array), allocate it in the heap
Related
i am using windows and i want to Set the maximum number of simultaneously existing ports to 65536. in Erlang docs it says:
ERLAG doc here , visit for syntax
+Q Number|legacy
Sets the maximum number of simultaneously existing ports for this system if a Number is passed as value. Valid range for
Number is [1024-134217727]
On Windows the default value is set to 8196 because the normal OS
limitations are set higher than most machines can handle.
If legacy is passed as value, the legacy algorithm for allocation of
port identifiers will be used. Using the legacy algorithm, identifiers
will be allocated in a strictly increasing fashion until largest
possible identifier has been reached. Note that this algorithm suffers
from performance issues and can under certain circumstances be
extremely expensive. The legacy algoritm is deprecated, and the legacy
option is scheduled for removal in OTP-R18.
i used below syntax but it gives me syntax error, whats wrong ?
Since my reputation doesnt allow me to just comment, I'll just answer...
If you dont like to start the erlang VM through a batch script or the command window, you can create a link to the werl.exe and edit the Command it executes by right clicking and changing the Properties of said link. For example:
Default link Target: "C:\Program Files (x86)\erl5.10.4\bin\werl.exe"
Would become: "C:\Program Files (x86)\erl5.10.4\bin\werl.exe" +Q 65536
This also allows for different configurations for different projects/applications.
Another way would be, to use .bat scripts instead of a link.
I am an avid csh/tcsh user.
But the current environment I have to work on has all ksh scripts. The team works on k-shell.
So, if I select a seed and run a test in k-shell and c-shell, would the outcome be the same?
Seed is just one example, I want to know whether using alternate shell would create any divergence of end result?
The whole point of a seeding mechanism for random number generators is to be able to reproduce results regardless of other factors. This means that as long as you're running the same compiled code for the simulator (same version, basically) you're going to get the same results when passing in a seed, regardless of what machine you're running on, what shell you use, etc.
Also, the shell you use has no end effect on the executable being started, other than setting environment variables that the program might use. You're going to have to make sure that you don't diverge in this point.
I am preparing LaTex/Tex fragments with lua programs getting information from SQL request to a database (LuaSQL).
I wish I could see intermediate states of expansion for debugging purpose but also to control what has been brought from SQL requests and lua processings.
My dream would be for instance to see the code of my Latex page as if I had typed it myself manually with all the information given by the SQL requests and the lua processing.
I would then have a first processing with my lua programs and SQL request to build a valid and readable luaLatex code I could amend if necessary ; then I would compile again that file to obtain the wanted pdf document.
Today, I use a lua development environment, ZeroBrane Studio, to execute and test the lua chunk before I integrate it in my luaLatex code. For instance:
my lua chunk :
for k,v in pairs(data.param) do
print('\\def\\'..k..'{'..data.param[k]..'}')
end
lua print out:
\gdef\pB{0.7}
\gdef\pAinterB{0.5}
\gdef\pA{0.4}
\gdef\pAuB{0.6}
luaLaTex code :
nothing visible ! except that now I can use \pA for instance in the code
my dream would be to have, in the luaLatex code :
\gdef\pB{0.7}
\gdef\pAinterB{0.5}
\gdef\pA{0.4}
\gdef\pAuB{0.6}
May be a solution would stand in the use of the expl3 extension ? But since I am not familiar with it nor with the precise Tex expansion process, I prefer to ask you experts before I invest heavily in the understanding of this module.
Addition :
Pushing forward the reflection, a consequence would be that from a Latex code I get a Latex code instead of a pdf file for instance. This implies that we use only the first steps of the four TeX processors as described by Veijkhout in "TeX by Topic" : the input processor, the expansion processor (but with a controlled depth of expansion), not the execution processor nor the visual processor. Moreover, there would be need to show the intermediate state, that means a new processor able to show tokens back into readable strings and correct Tex/Latex code that can be processed later.
Unless somebody has already done or seen something like that, I feel that my wish may be unfeasible in the short and middle terms. What is your feeling, should I abandon any hope ?
I have a relatively simple bash script that reads from a set of static input files, stores the input in bash variables and then does a bunch of processing over said input by calling out to external scripts (e.g. written in Python, Go, other bash scripts etc.) and using the intermediate results.
Lately I have been experiencing an intermittent problem where a single character seems to be getting altered somewhere during the processing which then causes subsequent errors. Specifically, a lot of the processing I'm doing involves slicing up a list of comma-separated records, and one of the values on each line is a unix timestamp, e.g. 1354245000.
What seems to be happening is that occasionally one of these values will get altered slightly, so I end up with a timestamp like 13542458=2 or 13542458>2 or 13542458;2 coming out of one of the intermediate scripts. This then subsequently gets fed into another script, which throws an exception when it tries to parse the value to an integer.
In the title of this question, I've suggested that this might be a potential CPU/RAM error. I know the general folly in thinking errors are caused by low level things like hardware/compilers etcetera, but the nature of this particular error makes me think it may be possible, for the following reasons:
The input files are the same on each invocation of the script, and the script only fails on some invocations.
I cannot think of any sources of randomness in the source code prior to where the script is breaking. It's basically just slicing and dicing csv input.
I cannot think of any sources of concurrency in the source code -- even the Go scripts aren't actually written to run anything concurrently.
This problem has only arisen in the last week or so. Prior to this time, this error would never occur.
While I haven't documented every erroneous character, they seem to often be quite close in the ASCII table to numeric values (=, >, ; etc). That said, I guess the Hamming distance between two characters quite far apart can be small also with changes to a high order bit.
The script often breaks at a different stage on different runs. i.e. I have a number of separate Python scripts, and sometimes it'll make it past one script and then the error will be induced in another. Other times it'll be induced on an earlier script.
What I'd like to know is, is there any methodical way to either confirm or rule out a hardware error for this problem? Or if it is a hardware problem, is it possibly undetectable by the operating system?
A bit of further info on the machine:
Linux 64-bit, Ubuntu 12.04
Intel i7 processor
16GB DDR3 RAM
I'm hoping someone can either point me to a reliable way to verify whether the hardware is to blame or otherwise a sound reason as to what else might be the cause.
Try booting into Memtest to check your memory.
While it is highly unlikely that it will be hardware, if you have exhausted you standard software debug as suggested by #OliCharlesworth, here is an outline of hardware error investigation:
(1) check your log area for any `MCE` logs (machine check exceptions).
If you find any in either your log area (syslog) or sometimes in
the present working dir or /dir -- you have a hardware failure.
(2) check your log area for disk errors. e.g:
smartd[3963]: Device: /dev/sda [SAT], 34 Currently unreadable (pending) sectors
(3) check your drive integrity, e.g.: (as root) # `smartctl -a /dev/sda` if any abnormality, run:
smartctl -t short /dev/sda (change drive as required)
(4) download/install/boot to [memtest86](http://www.memtest86.com/download.htm)
(run the complete test)
If your cpu/motherboard has thrown no mce's, you have no disk error, your drive tests OK with smartctl and you have no memory errors with memtest86, then recheck the software debugging. While additional hardware errors can still be present (bad capacitors, etc..) the likelihood at this point is software. Good luck.
I am using FFTW for FFTs, it's all working well but the optimisation takes a long time with the FFTW_PATIENT flag. However, according to the FFTW docs, I can improve on this by reusing wisdom between runs, which I can import and export to file. (I am using the floating point fftw routines, hence the fftwf_ prefix below instead of fftw_)
So, at the start of my main(), I have :
char wisdom_file[] = "optimise.fft";
fftwf_import_wisdom_from_filename(wisdom_file);
and at the end, I have:
fftwf_export_wisdom_to_filename(wisdom_file);
(I've also got error-checking to check the return is non-zero, omitted for simplicity above, so I know the files are reading and writing correctly)
After one run I get a file optimise.fft with what looks like ASCII wisdom. However, subsequent runs do not get any faster, and if I create my plans with the FFTW_WISDOM_ONLY flag, I get a null plan, showing that it doesn't see any wisdom there.
I am using 3 different FFTs (2 real to complex and 1 inverse complex to real), so have also tried import/export in each FFT, and to separate files, but that doesn't help.
I am using FFTW-3.3.3, I can see that FFTW-2 seemed to need more setting up to reuse wisdom, but the above seems sufficient now- what am I doing wrong?