I am new to StackOverflow so please correct me if there is a better way to post a question which is a specific case of an existing question.
Alberto Barrera answered
How does one seed the random number generator in Swift?
with
let time = UInt32(NSDate().timeIntervalSinceReferenceDate)
srand(time)
print("Random number: \(rand()%10)")
which is perfect generally, but when I try it in The IBM Swift Sandbox it gives the same number sequence every run, at least in the space of a half hour.
import Foundation
import CoreFoundation
let time = UInt32(NSDate().timeIntervalSinceReferenceDate)
srand(time)
print("Random number: \(rand()%10)")
At the moment, every Run prints 5.
Has anyone found a way to do this in the IBM Sandbox? I have found that random() and srandom() produce a different number sequence but similarly are the same each Run. I haven't found arc4random() in Foundation, CoreFoundation, Darwin, or Glibc.
As an aside, I humbly suggest someone with reputation above 1500 creates a tag IBM-Swift-Sandbox.
This was an issue with the way we implemented server-side caching in the Sandbox; non-deterministic code would continually return the same answer even though it should not have. We've disabled it for now, and you should be getting different results with each run. We're currently working on better mechanisms to ensure the scalability of the Sandbox.
I'll see about that tag, as well!
srand is working as expected. If you change value each time in let time = UInt32(NSDate().timeIntervalSinceReferenceDate) instead of NSDate().timeIntervalSinceReferenceDate with any number, it will output random numbers.
Maybe this is a caching issue, it just doesn't see any changes in code and doesn't send it for recompilation :)
I don't know what is going on but today it is totally working. So I guess the question is answered:
srand(UInt32(NSDate().timeIntervalSinceReferenceDate))
works fine.
(I think something must have changed. It was behaving the same way (generating the same number with repeated attempts) on two different computers for about 10 days... Bizarre.)
Related
I decided to mess around with asynchronous counters and tried to create an asynchronous down counter using FF-JK which counts from 13 to 1 and wraps around. However, I ran into various problems.
My RESET signal expression: Q0.Q1.Q2.Q3 + (Q1.Q2.Q3)' where Q0 is LSB and Q3 is MSB
My circuit is as follows:
However, when I simulated the circuit, it gave me the wrong results.
I hope I described my problem detailedly, and if there was anything I missed, please correct me. Thank you very much, and have a wonderful day.
I tried reconnecting my reset signal from PRN to CLRN and vice versa, I have also tried using T-FF, SR-FF, D-FF (the implementations were different).
I found a workaround for this problem, though, I would not consider it an optimal solution. However, it does the job now, and I look forward to receiving insights on the issues I faced.
Instead of designing the RESET signal and having the circuit loop in some undefined state, I designed a MOD-13 counter which goes through all 13 states from 0000 to 1100 and maps the output to the desired values (13 to 1 respectively).
MOD-13 counters are easier to design, as they prevent undefined states from being reached so easily, and the circuit responsible for mapping the states with the desired values are simple combinatorial circuits which are also easy to design.
Of course, there exists a much better way to do this, but I am not able to implement it at the moment. With that being said, I am always open for discussions, and I look forward to seeing what kind of error I had accumulated during implementation. Have a wonderful day!
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.
I've recently become interested in trying to adapt my Rock-Paper-Scissors game into a multiplayer-friendly program, so today I decided I'd look up a tutorial on servers. It seems I'm following it precisely (aside from using a different IDE). However, something is going wrong and I'm not sure exactly what it is, and it works fine for the tutorial maker. I've looked up EOFException but it didn't exactly help me out.
The tutorial on Youtube
My screenshot of the issue.
[Documentation on EOFException](I had a link here, but I need at least 10 reputation to post more than two links)
"Signals that an end of file or end of stream has been reached unexpectedly during input.
This exception is mainly used by data input streams to signal end of stream. Note that many other input operations return a special value on end of stream rather than throwing an exception."
[A similar but apparently unresolved question asked here](I had a link here too]
By the way, if you look up exactly what I've posted here, you'll also find that I've asked it at DaniWeb. I'm just posting in multiple places in case it isn't resolved at one or the other. If it is, well... the more knowledge, the better.
EOFException during readUTF() just means it's reached the end of the stream, like it says on the tin. Note that this method doesn't return null at end of stream, unlike readLine() (but like all other readXXX() methods).
It can also mean that your sending and receiving is out of sync, e.g. you are trying to read some ridiculously large number of bytes because you left out a readInt() or similar, or you wrote something extra at the peer that you shouldn't have, so you're trying to read the next bytes in the stream as the result of writeUTF() when it isn't. This is an application protocol error.
How this happened in the code you posted is another question, but your code doesn't close the sockets, which doesn't help. Add an out.close() to your server code, and in.close() to the client code. However I cannot reproduce your problem with or without these closes. Are you sure this is the real code?
I am very very new to matlab, actually I only just got the program to run one code. A good friend of mine wrote a code for me however it doesn't seem to work, I have provided the link to the code and data files required, can anyone tell me what's wrong or fix it for me? Much thanks!
The error I am getting is:
Warning: No such number of days in the future exist for a 30/360 day-count basis. > In daysadd at 141 In CDS_PD at 35
https://www.dropbox.com/s/jtjk187rpu0fhv5/cds.zip
It appears that it is only a warning and is an inherent limitation of the "30/360 day-count basis" as used by the daycount function. As far as I can tell it just means that the calculated day is not unique in this basis. So it doesn't necessarily mean that the program is functioning incorrectly.
See:
http://www.mathworks.com.au/help/finance/daysadd.html
http://www.mathworks.com.au/help/finance/_f0-6010.html#bsuk32t-1
http://www.google.com.au/search?q=30%2F360+day-count+basis
I'm fairly new to using Google Docs, but I have come to really appreciate it. The scripting is pretty easy to accomplish simple tasks, but I have come to realize a potential speed issue that is a little frustrating.
I've got a sheet that I use for my business to calculate the cost of certain materials on a jobsite. It works great, but was a little tedious to clear between jobs so I wrote a simple script to clear the ranges (defined by me and referenced by name) that I needed emptied.
Once again, worked great. The only problem with it is that clearing a few ranges (seven) ends up taking about ten full seconds. I -believe- that this is because the spreadsheet is being saved after each range is cleared, which becomes time intensive.
What I'd like to do is test this theory by disabling autosave in the script, and then re enabling it after the ranges have been cleared. I don't know if this is even possible because I haven't seen a function in the API to do it, but if it is I'd love to know about it.
Edit: this is the function I'm using as it stands. I've tried rewriting it a couple of times to be more concise and less API call intensive, but so far I haven't had any luck in reducing the time it takes to process the calls.
function clearSheet() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getActiveSheet();
sheet.getRange("client").clear();
sheet.getRange("lm_group_1").clear({contentsOnly:true});
sheet.getRange("lm_group_2").clear({contentsOnly:true});
sheet.getRange("dr_group_1").clear({contentsOnly:true});
sheet.getRange("dr_group_2").clear({contentsOnly:true});
sheet.getRange("fr_group_1").clear({contentsOnly:true});
sheet.getRange("fr_group_2").clear({contentsOnly:true});
sheet.getRange("gr_group_1").clear({contentsOnly:true});
sheet.getRange("client_name").activate();
}
That is not possible, and will probably never be. It's not "the nature" for Google Docs.
But depending on how you wrote your script, it's probable that all changes are already being wrote at once, in the end. There's some API calls that may be forcing a flush of your writings to the spreadsheet (like trying to read after you wrote something), but we'd need to see your code to check that.
Anyway, you can always check the spreadsheet revision history to verify if it's being done at once or in multiple steps.
About the performance, Apps Scripts have a natural delay that is unavoidable, but it's not 10s, so there's probably room to improve on your script, using fewer API calls and preferring batch calls like setValues over setValue and so on. But then again, we'd have to see your code to assert that and give more helpful tips.