I got this warning after adding a long string generated programmatically as an Azure Pipelines variable (as a quick and easy way to test changes instead of pushing a file to my repo):
##[warning]Environment variable 'INPUT_SCRIPT' exceeds the maximum supported length. Environment variable length: 40384 , Maximum supported length: 32766
The warning is pretty clear to understand and seems appropriate given a regular environment variable, but the task that used this new pipelines variable works as expected (assuming the entire string is there). Is this warning relevant? Will it bite me in the back later if I just ... leave it in?
The theoretical maximum length of an environment variable is around 32,760 characters. All environment variables must live together in a single environment block, which itself has a limit of 32767 characters.In practice, you have to share the environment block with all the other variables in the block, so your random call to SetEnvironmentVariable with a 32,760-character string is unlikely to succeed.It also depends on how you’re setting the variable; i.e., the code that your environment-variable-setting technique passes through before it gets to the SetEnvironmentVariable call. For details ,please refer to this link.
Here are two cases with the same warning for reference: 1 and 2
Is this warning relevant? Will it bite me in the back later if I just
... leave it in?
For this issue, I have not found the errors caused by this warning. Since you have already paid attention to this issue, if you encounter errors, you can share them here. Let us investigate them further.
Related
I want to get different solution every time I run minisat on the same problem. I can do that with using "rnd-seed" parameter of minisat. It simply randomize the variable selection so each time I can get different solution. Even though this parameter works perfectly on my machine (Ubuntu16) it does not work on gcloud (Google Cloud) running on Ubuntu machine.
I think I am missing a small part but I can not figure out what that is.
Note: I do not want to feed negotation of a solution to minisat to get different solution. I actually need to randomize the variable selection.
Edit: Let me explain why I need randomized solution. I solve lots of SAT problems and usually these SAT problems look like each other a lot. So, if I can not randomized variable selection, I get most of the time very similar solutions which I do not want. Therefore, I actually do not run minisat on the same problem.
Edit-2: #sascha wanted me to explain what I mean by "works" and "not works". When I run a cnf file on my PC, each time I get different solution. However, when I run the same cnf file on gcloud machine, I get always same solution.
The option -rnd-seed doesn't randomize branch variable selection. Rather, it allows you to set a seed for the pseudo-random number generator that Minisat uses.
Variable selection for branching does not involve randomness unless the -rnd-freq option is used. Pass in a floating point value between 0 and 1. 0 means no randomness, 1 means try to use a random variable every branch. The code only makes one attempt to choose a variable randomly, presumably because searching for an unset variable in an arbitrarily large priority queue can get pretty expensive. If that one attempt fails, Minisat branches using the normal priority queue.
has anyone experience the following issue?
A stack variable getting changed/corrupted after calling ne10 assembly function such as ne10_len_vec2f_neon?
e.g
float gain = 8.0;
ne10_len_vec2f_neon(src, dst, len);
after the call to ne10_len_vec2f_neon, the value of gain changes as its memory is getting corrupted.
1. Note this only happens when the project is compiled in release build but not debug build.
2. Does Ne10 assembly functions preserve registers?
3. Replacing the assembly function call to c equivalent such as ne10_len_vec2f_c and both release and debug build seem to work OK.
thanks for any help on this. Not sure if there's an inherent issue within the program or it is really the call to ne10_len_vec2f_neon causing the corruption with release build.enter code here
I had a quick rummage through the master NEON code here:
https://github.com/projectNe10/Ne10/blob/master/modules/math/NE10_len.neon.s
... and it doesn't really touch address-based stack at all, so not sure it's a stack problem in memory.
However based on what I remember of the NEON procedure call standard q4-q7 (alias d8-d15 or s16-s31) should be preserved by the callee, and as far as I can tell that code is clobbering q4-6 without the necessary save/restore, so it does indeed look like it's clobbering the stack in registers.
In the failed case do you know if gain is still stored in FPU registers, and if yes which ones? If it's stored in any of s16/17/18/19 then this looks like the problem. It also seems plausible that a compiler would choose to use s16 upwards for things it needs to keep across a function call, as it avoids the need to touch in-RAM stack memory.
In terms of a fix, if you perform the following replacements:
s/q4/q8/
s/q5/q9/
s/q6/q10/
in that file, then I think it should work; no means to test here, but those higher register blocks are not callee saved.
I need to increment an integer value each time the PLC program is updated to track changes.
There are system events like online_change and before_download, but I have no idea how to implement their functions.
Also I need to save value between updates. I think the tracking variable should be created as RETAIN but not sure.
The variable declaration type should be VAR RETAIN PERSISTENT in your case. Variables declared under RETAIN only will lose their values (intentionally) with a program change.
I believe the builtin Codesys library SysLibProjectInfo.lib has what you are looking for with the function SysGetProjectID. If you store SysGetProjectID as a RETAIN PERSISTENT and then compare against it, you can track changes (or, this unique value may be exactly what you wanted in the first place, without manually creating an ID).
Note: Depending on how you declare your variables, changing the I/O configuration can have unexpected changes even on VAR RETAIN PERSISTENT variables (as all dynamically allocated addresses are shifted and may not point where they used to).
If I understand you you only want to know like what version is running on the PLC and you want to track changes that you make? You can do it two ways:
Since it's a constant each time you make a change external to the PLC you roll the rev of a variable that is declared like SoftwareVersion :WORD := 100; and keep it in a Revision global list that you can add your notes to and change the version before downloading to PLC.
You can also use the PLC summary area that has fields to enter the values and then you can read them through CoDeSys without software upload.
And of course the suggestion above can work.
I was asked question about what would happen if I try to retrieve a reference value and then try to change it within the same line of code. My answer was that nothing will happen because as I tried to do this before I did not encounter any compiler errors (at least in C# or Java).
What is the real answer to this?
This is example with the pseudo code:
Module main()
Call changeNumber(10)
End Module
Module changeNumber(Integer Ref number)
Set number = number * number
Display number
End Module
(PS. Sorry for not formatting/creting this post correctly. I'm having bit of an issue here.)
There would be no unusual side effects, if that's what you're asking. The language specifications dictate a specific order of execution (number * number is evaluated, then set to number), which prevents any issues from occurring.
Nothing would happen, in your particular pseudo code.
In reference to a question you asked after this question -
Actually there could be issues in some rare instance, but it would depend on how you are allocating space for the number and your coding language. Consider this. you are explicitly naming the data type as an int, well what if the accepted input is a larger number than an int can handle (or a negative number), that ends up being x integers long and then you multiply it by that same number, your allocated space (which usually has padding with integer) could also have insufficient space that is too small for this particular instance, which would cause a segmentation fault in C. depending on which language you're using, whether it's higher level than C, it may have compilation checks for this case, but not always.
For example, if I implement some simple object caching, which method is faster?
1. return isset($cache[$cls]) ? $cache[$cls] : $cache[$cls] = new $cls;
2. return #$cache[$cls] ?: $cache[$cls] = new $cls;
I read somewhere # takes significant time to execute (and I wonder why), especially when warnings/notices are actually being issued and suppressed. isset() on the other hand means an extra hash lookup. So which is better and why?
I do want to keep E_NOTICE on globally, both on dev and production servers.
I wouldn't worry about which method is FASTER. That is a micro-optimization. I would worry more about which is more readable code and better coding practice.
I would certainly prefer your first option over the second, as your intent is much clearer. Also, best to keep away edge condition problems by always explicitly testing variables to make sure you are getting what you are expecting to get. For example, what if the class stored in $cache[$cls] is not of type $cls?
Personally, if I typically would not expect the index on $cache to be unset, then I would also put error handling in there rather than using ternary operations. If I could reasonably expect that that index would be unset on a regular basis, then I would make class $cls behave as a singleton and have your code be something like
return $cls::get_instance();
The isset() approach is better. It is code that explicitly states the index may be undefined. Suppressing the error is sloppy coding.
According to this article 10 Performance Tips to Speed Up PHP, warnings take additional execution time and also claims the # operator is "expensive."
Cleaning up warnings and errors beforehand can also keep you from
using # error suppression, which is expensive.
Additionally, the # will not suppress the errors with respect to custom error handlers:
http://www.php.net/manual/en/language.operators.errorcontrol.php
If you have set a custom error handler function with
set_error_handler() then it will still get called, but this custom
error handler can (and should) call error_reporting() which will
return 0 when the call that triggered the error was preceded by an #.
If the track_errors feature is enabled, any error message generated by
the expression will be saved in the variable $php_errormsg. This
variable will be overwritten on each error, so check early if you want
to use it.
# temporarily changes the error_reporting state, that's why it is said to take time.
If you expect a certain value, the first thing to do to validate it, is to check that it is defined. If you have notices, it's probably because you're missing something. Using isset() is, in my opinion, a good practice.
I ran timing tests for both cases, using hash keys of various lengths, also using various hit/miss ratios for the hash table, plus with and without E_NOTICE.
The results were: with error_reporting(E_ALL) the isset() variant was faster than the # by some 20-30%. Platform used: command line PHP 5.4.7 on OS X 10.8.
However, with error_reporting(E_ALL & ~E_NOTICE) the difference was within 1-2% for short hash keys, and up 10% for longer ones (16 chars).
Note that the first variant executes 2 hash table lookups, whereas the variant with # does only one lookup.
Thus, # is inferior in all scenarios and I wonder if there are any plans to optimize it.
I think you have your priorities a little mixed up here.
First of all, if you want to get a real world test of which is faster - load test them. As stated though suppressing will probably be slower.
The problem here is if you have performance issues with regular code, you should be upgrading your hardware, or optimize the grand logic of your code rather than preventing proper execution and error checking.
Suppressing errors to steal the tiniest fraction of a speed gain won't do you any favours in the long run. Especially if you think that this error may keep happening time and time again, and cause your app to run more slowly than if the error was caught and fixed.