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  • regular expression for bit strings with even number of 1s

    - by equilibrium
    Let L= { w in (0+1)* | w has even number of 1s}, i.e. L is the set of all bit strings with even number of 1s. Which one of the regular expressions below represents L? A) (0*10*1)* B) 0*(10*10*)* C) 0*(10*1)* 0* D) 0*1(10*1)* 10* According to me option D is never correct because it does not represent the bit string with zero 1s. But what about the other options? We are concerned about the number of 1s(even or not) not the number of zeros doesn't matter. Then which is the correct option and why?

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  • Check if NSString "000001XX"is a number with intValue

    - by Kenny
    Now I am trying to add a front end check on my app to detect if user input only number in the textfield. I use: - (IBAction)checkID:(UITextField *)sender { if ([sender.text isEqualToString:@""]) { sender.text = @"This information is required"; sender.backgroundColor =[UIColor redColor]; }else if (![sender.text intValue]) { sender.text = [sender.text stringByAppendingString:@" is not valid number"]; sender.backgroundColor =[UIColor redColor]; } NSLog(@"send.text is %@, intValue is %d",sender.text,[sender.text intValue]); } But I found it text begins with number and ends with string, its intValue is still the number. In my text, text is "00001aa", but the intValue is 1. Is there any other way to filter out this "00001aa" text? Thanks in advance.

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  • Write a recursive function in C that converts a number into a string

    - by user3501779
    I'm studying software engineering, and came across this exercise: it asks to write a recursive function in C language that receives a positive integer and an empty string, and "translates" the number into a string. Meaning that after calling the function, the string we sent would contain the number but as a string of its digits. I wrote this function, but when I tried printing the string, it did print the number I sent, but in reverse. This is the function: void strnum(int n, char *str) { if(n) { strnum(n/10, str+1); *str = n%10 + '0'; } } For example, I sent the number 123 on function call, and the output was 321 instead of 123. I also tried exchanging the two lines within the if statement, and it still does the same. I can't figure out what I did wrong. Can someone help please? NOTE: Use of while and for loop statements is not allowed for the exercise.

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  • only return random number when it is unique

    - by phil
    My brain is melting today and i cannot think how to do this simple bit of code. numberList is a string of numbers seperated by commas like '2, 34, 10' etc.. when i request a random number i need to check if the string has the number, if it does i want to keep requesting a random number until the random number is definitely not in the string. i cant think what kind of loop i would do to get this to work: Random r = new Random(); public int RandomPos(int max) { int i; do { i = r.Next(max) + 1; } while (!numberList.Contains(i.ToString())); return i; }

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  • ActionScript Negating a Number

    - by TheDarkIn1978
    i'd like to negate a number and would like to know if there's a built in method that will convert a negative number to a positive OR a positive into a negative, depending on the number. i know about Math.abs(), but that only seems to convert negative into positive. is there a method that will do both?

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  • Randomly choose value between 1 and 10 with equal number of instances

    - by user1723765
    I would like to generate 2000 random numbers between 1 and 10 such that for each random number I have the same number of instances. In this case 200 for each number. What should be random is the order in which it is generated. I have the following problem: I have an array with 2000 entries but not each with unique values, for example it starts like this: 11112233333333344445667777777777 and consists of 2000 entries. I would like to generate random numbers and assign each UNIQUE value a separate random number but have an entry for each value So my intended result would look like this: original array: 11112233333333344445667777777777 random numbers: 33334466666666699991778888888888

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  • Retrieving the first digit of a number

    - by Michoel
    Hi, I am just learning Java and am trying to get my program to retrieve the first digit of a number - for example 543 should return 5, etc. I thought to convert to a string, but I am not sure how I can convert it back? Thanks for any help. int number = 534; String numberString = Integer.toString(number); char firstLetterChar = numberString.charAt(0); int firstDigit = ????

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  • What this number means?

    - by FinalDestiny
    I have one number that has something related to the currentdate : 634101448539930000 634101448627430000 (this information was took 9 seconds later than the first one) I have many codes like this and I need to know what those number means. It's something related to the current time, because the new information has always a bigger number than the older ones. Please if anybody could help me, thanks

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  • Write a JavaScript that accepts a number from the user using the “prompt” function

    - by A sw A
    Write a JavaScript that accepts a number from the user using the “prompt” function. Then it draws a table in the HTML document that has the user specified number of rows and columns. In each table data, it displays the result of the math operation (row raised to the power of column). For example, if the user enters the number 3, the JavaScript should draw the following table: 1 1 1 2 4 8 3 9 27

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  • Good Form for Random Number Generator?

    - by JackCJR
    I wanted to get a few opinions on doing a random number generator. I read through a couple different ways to do it and this is the way that I created after doing a little reading. Is it acceptable form? Any foreseeable issues? function master(){ function generate(){ var pickFrom= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; var j = pickFrom.length; var i = Math.floor(Math.random()*j+1); //Generates a random number var code = pickFrom.charAt(i) //Picks a number based on what number was picked. document.write(code) } x = 1; while(x){ generate(); x--; } } master();

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  • "Possible SYN flooding" in log despite low number of SYN_RECV connections

    - by al4
    Recently we had an apache server which was responding very slowly due to SYN flooding. The workaround for this was to enable tcp_syncookies (net.ipv4.tcp_syncookies=1 in /etc/sysctl.conf). I posted a question about this here if you want more background. After enabling syncookies we started seeing the following message in /var/log/messages approximately every 60 seconds: [84440.731929] possible SYN flooding on port 80. Sending cookies. Vinko Vrsalovic informed me that this means the syn backlog is getting full, so I raised tcp_max_syn_backlog to 4096. At some point I also lowered tcp_synack_retries to 3 (down from the default of 5) by issuing sysctl -w net.ipv4.tcp_synack_retries=3. After doing this, the frequency seemed to drop, with the interval of the messages varying between roughly 60 and 180 seconds. Next I issued sysctl -w net.ipv4.tcp_max_syn_backlog=65536, but am still getting the message in the log. Throughout all this I've been watching the number of connections in SYN_RECV state (by running watch --interval=5 'netstat -tuna |grep "SYN_RECV"|wc -l'), and it never goes higher than about 240, much much lower than the size of the backlog. Yet I have a Red Hat server which hovers around 512 (limit on this server is the default of 1024). Are there any other tcp settings which would limit the size of the backlog or am I barking up the wrong tree? Should the number of SYN_RECV connections in netstat -tuna correlate to the size of the backlog? Update As best I can tell I'm dealing with legitimate connections here, netstat -tuna|wc -l hovers around 5000. I've been researching this today and found this post from a last.fm employee, which has been rather useful. I've also discovered that the tcp_max_syn_backlog has no effect when syncookies are enabled (as per this link) So as a next step I set the following in sysctl.conf: net.ipv4.tcp_syn_retries = 3 # default=5 net.ipv4.tcp_synack_retries = 3 # default=5 net.ipv4.tcp_max_syn_backlog = 65536 # default=1024 net.core.wmem_max = 8388608 # default=124928 net.core.rmem_max = 8388608 # default=131071 net.core.somaxconn = 512 # default = 128 net.core.optmem_max = 81920 # default = 20480 I then setup my response time test, ran sysctl -p and disabled syncookies by sysctl -w net.ipv4.tcp_syncookies=0. After doing this the number of connections in the SYN_RECV state still remained around 220-250, but connections were starting to delay again. Once I noticed these delays I re-enabled syncookies and the delays stopped. I believe what I was seeing was still an improvement from the initial state, however some requests were still delayed which is much worse than having syncookies enabled. So it looks like I'm stuck with them enabled until we can get some more servers online to cope with the load. Even then, I'm not sure I see a valid reason to disable them again as they're only sent (apparently) when the server's buffers get full. But the syn backlog doesn't appear to be full with only ~250 connections in the SYN_RECV state! Is it possible that the SYN flooding message is a red herring and it's something other than the syn_backlog that's filling up? If anyone has any other tuning options I haven't tried yet I'd be more than happy to try them out, but I'm starting to wonder if the syn_backlog setting isn't being applied properly for some reason.

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  • Sun Solaris - Find out number of processors and cores

    - by Adrian
    Our SPARC server is running Sun Solaris 10; I would like to find out the actual number of processors and the number of cores for each processor. The output of psrinfo and prtdiag is ambiguous: $psrinfo -v Status of virtual processor 0 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. Status of virtual processor 1 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. Status of virtual processor 2 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. Status of virtual processor 3 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. _ $prtdiag -v System Configuration: Sun Microsystems sun4u Sun Fire V445 System clock frequency: 199 MHZ Memory size: 32GB ==================================== CPUs ==================================== E$ CPU CPU CPU Freq Size Implementation Mask Status Location --- -------- ---------- --------------------- ----- ------ -------- 0 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C0/P0 1 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C1/P0 2 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C2/P0 3 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C3/P0 _ $more /etc/release Solaris 10 8/07 s10s_u4wos_12b SPARC Copyright 2007 Sun Microsystems, Inc. All Rights Reserved. Use is subject to license terms. Assembled 16 August 2007 Patch Cluster - EIS 29/01/08(v3.1.5) What other methods can I use? EDITED: It looks like we have a 4 processor system with one core each: $psrinfo -p 4 _ $psrinfo -pv The physical processor has 1 virtual processor (0) UltraSPARC-IIIi (portid 0 impl 0x16 ver 0x34 clock 1592 MHz) The physical processor has 1 virtual processor (1) UltraSPARC-IIIi (portid 1 impl 0x16 ver 0x34 clock 1592 MHz) The physical processor has 1 virtual processor (2) UltraSPARC-IIIi (portid 2 impl 0x16 ver 0x34 clock 1592 MHz) The physical processor has 1 virtual processor (3) UltraSPARC-IIIi (portid 3 impl 0x16 ver 0x34 clock 1592 MHz)

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  • another "SSH connect to host github.com port 22: Bad file number"

    - by Mariusz
    Hello. I have a problem with my first-time ssh connection. Yes, I've already done yours guides, already tried your "Dealing with firewalls and proxies" article and the problem is still occuring. I am using Win7 32bit, Windows Firewall is disabled, haven't any third-party firewalls, ESET Nod32 Antivirus is not blocking any ports, I am not using any PROXY (neither local proxy) . Here goes the logs: Ordinary SSH connection try C:\Users\Mariusz>ssh -vvv [email protected] OpenSSH_4.6p1, OpenSSL 0.9.8e 23 Feb 2007 debug2: ssh_connect: needpriv 0 debug1: Connecting to github.com [207.97.227.239] port 22. debug1: connect to address 207.97.227.239 port 22: Not owner ssh: connect to host github.com port 22: Bad file number NCAT connection try C:\Users\Mariusz>ncat github.com 22 Strange connect error from 207.97.227.239 (10013): No error 10013 = WSAEACCES I think that method called "smart-http-support" won't be usable for me because I haven't created repo yet. I have just GIT INIT locally, and finished at step GIT PUSH, which returns the same: ssh: connect to host github.com port 22: Bad file number fatal: The remote end hung up unexpectedly corkscrew method (first article from yours guide) . While PUTTYing (with pageant in bg), after inputing login - an error is occuring (MessageBox): Disconnected: No supported authentication methods available And in terminal such message is printing out: Server refused our key Key I have generated correctly, using ssh-keygen. I tried not method by editing ~/.ssh/config yet because I had thought that because I haven't PUSHed anything to my remote repo so I won't be able to CLONE anything. Method called ssh-forwarding is not for my, cause it "requires access to an external ssh server" and I haven't any at this time. What else could I do? Thanks in advance for any help. Mariusz.

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  • Small maximum number of connections on a Linux router

    - by Eugene
    I have a Linux box acting as a router with no iptables or other firewall and no networking applications running on it, just pure router. I've put it in a test environment that generates many TCP connections, each having unique source and destination IP, and those connections go through this router. I'm observing that number of connections successfully created rise to approximately 500 and then no more connections can be created for several minutes, then another 100 connections can be created and there is another pause, and so on. If 10 connections for each source-destination pair are created, then maximum numbers go about 10 times up, so the problem is probably with many connections from different IPs. As traffic is simply routed, it doesn't have to do with number of file descriptors, iptables connection tracking and other things often proposed to check in similar cases. The box has plenty of free RAM and CPU, both NICs are gigabit. The kernel is 2.6.32. I've already tried increasing net.core.*mem_max, net.core.netdev_max_backlog and txqueuelen on both NICs, with completely no effect. What else should I check ? Is there some rate-limit in the kernel itself ?

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  • file read performance degrades as number of files increases

    - by bfallik-bamboom
    We're observing poor file read IO results that we'd like to better understand. We can use fio to write 100 files with a sustained aggregate throughput of ~700MB/s. When we switch the test to read instead of write, the aggregate throughput is only ~55MB/s. The drop seems related to the number of files since the throughput for read and write are comparable for a single file then diverge proportionally as we increase the number of files. The test server has 24 CPU cores, 48GB of memory, and is running CentOS 6.0. The disk hardware is a RAID 6 array with 12 disks and a Dell H800 controller. This device is partitioned with ext4 using the default settings. Increasing the readahead (using blockdev) improves the read throughput significantly but it still doesn't match write speed. For instance, increasing the readahead from 128KB to 1M improved the read throughput to ~145MB/s. Is this a known performance issue in our OS/disk/filesystem configuration? If so, how can we tell? If not, what tools or tests can we use to further isolate the issue? Thanks.

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  • How can I check cells for number series?

    - by Stephen Younger
    I have a bit of a problem evaluating an excel cell. Example: M M M M M M M M M 1 2 3 4 5 6 7 8 9 2;5;7 1;9 3;5;7;9 I have a number of excel cells which contain numbers (months). In the first column I have a series of numbers. I want to use conditional formatting to color the corresponding cells in the right columns. If correctly colored I would get something like this: M M M M M M M M M 1 2 3 4 5 6 7 8 9 2;5;7 X X X 1;9 X X 3;5;7;9 X X X X The formula I have now is this: IF(ISNUMBER(FIND(L$22;$K23));$H23;"") but the problem is that cells are colored too which contain part of a number. If I enter 10;15 as input I get this: M M M M M M M M M M M M M M M 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 10;15 X X X X because 1 and 5 are found too. I only want column 10 and 15 to be marked. How can I change the formula or the input?

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  • mysqld - master to slave replication using rsync innodb, sequence number issues

    - by Luis
    I've read several of the related topics posted here, but I have not been able to avoid this innodb error. The steps I've taken to replicate data from a Slackware server - 5.5.27-log (S) to a FreeBSD slave - 5.5.21-log (F) were these: (S) flush tables with read lock; (S) in another terminal show master status; (S) stop mysqld via command line in third terminal; (F) while both servers are stopped, rsync mysql datadir from (S), excluding master.info, mysql-bin and relay-* files; (F) start mysqld (skip-slave) 121018 12:03:29 InnoDB: Error: page 7 log sequence number 456388912904 InnoDB: is in the future! Current system log sequence number 453905468629. InnoDB: Your database may be corrupt or you may have copied the InnoDB InnoDB: tablespace but not the InnoDB log files. See InnoDB: http://dev.mysql.com/doc/refman/5.5/en/forcing-innodb-recovery.html InnoDB: for more information. This kind of error happens for a lot of tables. I know I can use dump, but the database is large, ca. 70GB and the systems are slow (old), so would like to get this replication to work with data transfer. What should I try to solve this issue?

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