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  • how to export VARs from a subshell to a parent shell?

    - by webwesen
    I have a Korn shell script #!/bin/ksh # set the right ENV case $INPUT in abc) export BIN=${ABC_BIN} ;; def) export BIN=${DEF_BIN} ;; *) export BIN=${BASE_BIN} ;; esac # exit 0 <- bad idea for sourcing the file now these VARs are export'ed only in a subshell, but I want them to be set in my parent shell as well, so when I am at the prompt those vars are still set correctly. I know about . .myscript.sh but is there a way to do it without 'sourcing'? as my users often forget to 'source'. EDIT1: removing the "exit 0" part - this was just me typing without thinking first EDIT2: to add more detail on why do i need this: my developers write code for (for simplicity sake) 2 apps : ABC & DEF. every app is run in production by separate users usrabc and usrdef, hence have setup their $BIN, $CFG, $ORA_HOME, whatever - specific to their apps. so ABC's $BIN = /opt/abc/bin # $ABC_BIN in the above script DEF's $BIN = /opt/def/bin # $DEF_BIN etc. now, on the dev box developers can develop both ABC and DEF at the same time under their own user account 'justin_case', and I make them source the file (above) so that they can switch their ENV var settings back and forth. ($BIN should point to $ABC_BIN at one time and then I need to switch to $BIN=$DEF_BIN) now, the script should also create new sandboxes for parallel development of the same app, etc. this makes me to do it interactively, asking for sandbox name, etc. /home/justin_case/sandbox_abc_beta2 /home/justin_case/sandbox_abc_r1 /home/justin_case/sandbox_def_r1 the other option i have considered is writing aliases and add them to every users' profile alias 'setup_env=. .myscript.sh' and run it with setup_env parameter1 ... parameterX this makes more sense to me now

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  • Shrink Windows OS partition with unmovable files

    - by Tim
    I am trying to shink Windows 7 OS partition C: but cannot shrink as much as I plan due to unmovable files. I have tried Windows own defrag tool before but it does not move files that are unmovable. Here are some ideas I have learned from previous posts, and I hope at least one of them will work and wish to know the detail how to do: Inspired by this post, which suggests backup C:, then delete C: , create a smaller partition, and then copy the backup to the smaller partition. I was wondering if anyone here can confirm that Windows 7 will still work in this way? What reliable tools can be used for backuping the system, and deleting and creating partition, and then copying back the backup in this method? I am actually trying another way suggested in this post. I have identified what unmovable file currently stop further shrinking: \ProgramData\Microsoft\Search\Data\Applications\Windows\Projects\SystemIndex\Indexer\CiFiles\00010015.wid::$DATA If I understand correctly, the file belongs to Windows Search. Can I set up somewhere in Windows system settings to temperately eliminate the file and similar ones (because there are many similar files under the same directory which I guess will also stand in the way of shrinking and unmovable by defrag)? Any other idea that might work will also be appreciated. Thanks and regards!

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  • Some websites hosted on my server cant be reached from some places.

    - by valter
    Hello. I have a bloblem that is causing me headaches to solve. I have a webserver at 100tb.com, running CentOS. I also have these nameservers setted up: 67.213.220.170 ns1.maisturismo.net 67.213.220.171 ns2.maisturismo.net My domain is at Godaddy. I added two Host Summary pointig to the nameserver ips... NS1 to the first IP, and NS2 to the second... Than I changed the nameservers of maisturismo.net to ns1.maisturismo.net and ns2.maisturismo.net http://img20.imageshack.us/i/dnswm.jpg/ Bellow the image showing my dns records to maisturismo.net http://img137.imageshack.us/i/nameservers.jpg/ Its strange... Everythink looks fine, but the webiste is not reachable from [zend2.com][1] proxy, and from some other places, like a friend's house, that dont use the same web provider that I use. I have another nameserver setted up on my server, that have the same problem, All websites that use it cant be reached from zend2.com and from my friends house, except a ".com.br"(Brazillian Domain). Do you have same idea about, what is causing this? I really cant imagine what is the problem... Thanks. [1]: http:// zend2.com

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  • Windows 7 "freezes" (chills?), and then "unfreezes" for about 1 minute.

    - by gbc001
    Hi, I have an Acer Timeline 1810T netbook (4GB RAM) with Windows 7 x64. About once or twice a day, it "freezes" - the reason i put this in quotation marks is that it does not really freeze, as in you cant move mouse, etc. I can move my mouse and jump between different applications, but I cant use the applications for anything. So I can jump between notepad and Firefox, but I cant browse to a new web page. I have been trying to determine the source of this misery for a while now, and I suspect it has something to do with the hard drive - indirectly if not directly. Here are some screen shots of the resource monitor during a "freeze" and during normal operation: Freeze: http://imgur.com/Gcgq1.jpg Normal operation: imgur.com/mlHaI.jpg As you can see, CPU is fine during freeze, but the disk is going bananas.. Does anyone have an idea of what these reading mean, or about the problem in general? There seems to be no specific activity that sets this off - it can be during browsing, or during media playback with nothing else open. Very appreciative of any help!

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  • How can I change the file name of the Program Files (x86) folder?

    - by Madrauk
    Let me stop you before the "you shouldn't do that" and "you will corrupt your file paths". I know what I'm doing, but I'll give you the story to convince you. Basically, my hard drive is failing to the point where programs installed on it are not responding consistently. So, in preparation for my replacement, I'm moving as many files as possible to my secondary because the new drive will be smaller (it's an emergency I can't buy a fancy expensive new drive) and so I can actually use my computer until the new drive comes in. The basic idea behind what I'm doing is I've copied the contents of the Program Files x86 folder to another spot on my other drive, and I want to replace the original folder in the C drive with a symbolic link that points to the other drive, so the programs can run from that drive and be fine but it will save space on my C drive and simplify the moving process when the new one comes in. To do that, I need to rename the program files folder, make the symbolic link, hopefully delete the program files folder, then restart my computer so all the programs are running properly and I can confirm it works. Now that I've told you why, can anyone help me out?

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  • How do I remove a printer connection without the user's intervention?

    - by 1.618
    Here's the situation: We're replacing 11 printers with newer models, and we'll be installing them on our print server and sharing them out. The plan is to share the new printers under different names than the ones they're replacing, and un-share the old ones. So I need to come up with a way to remove the client connections to old printers automatically. Clients are mostly Windows 7 with a few XP. My first idea was to call prnmngr.vbs from the login script to remove each old printer explicitly by name. The problem is that some users don't log out when they're done for the day, so I can't count on their login script running before they next need to print. I could remotely run prnmngr.vbs using SCCM, but if it's not 'impersonating' the user, I don't think it will remove their printers. Any ideas? Could I lookup how to access WMI using c# code and write a "trojan" to remove specific printers without requiring the user to do anything? (I'm only half joking). I'm open to any suggestion! Thanks!

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  • Growing a small hosting company [closed]

    - by user2353007
    We currently have a few servers, 1 WHM VPS (2GB), 1 MS SQL VPS (2 GB), and 1 IIS VPS (2GB). The VPS servers are doing fine as far as uptime and response times but we would like to add the following features. 1) monitoring with load statistics 2) failover I have looked a Zabbix, Zenoss, Nagios, and a couple of other cloud solutions like monitor.us and watchdog from Zerigo. Ideally for the monitoring solution. Our current hosting company suggested we get a dedicated server or VPS and install load balancing software (not sure I like that idea). I've looked into Rackspace and Amazon load balancers which seem like the most feasible solutions for load balancers. Does anybody have any input on the monitoring and load balancing products I'm looking into? Monitoring should monitor uptime as well as give reports on memory usage, disk usage, processor usage, and which processes/websites/users are responsible for the load. It would be ideal if the load balancer worked with any IP. Not sure if either Rackspace or Amazon load balancers would allow load balancing with servers outside their datacenter. Thank you.

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  • How to copy a large LVM volume (14TB) from one server to another?

    - by bruce
    I have to copy a very large LVM volume from server A to server B. Below is the filesystem of server A and server B Server A [root@AVDVD-Filer ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_avdvdfiler-lv_root 16T 14T 1.5T 91% / tmpfs 3.0G 0 3.0G 0% /dev/shm /dev/cciss/c0d0p1 194M 23M 162M 13% /boot /dev/mapper/vg_avdvdfiler-test 2.3T 201M 2.1T 1% /test /dev/sr0 3.3G 3.3G 0 100% /mnt server B [root@localhost ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup-LogVol00 20G 2.5G 16G 14% / tmpfs 3.0G 0 3.0G 0% /dev/shm /dev/cciss/c0d0p1 194M 23M 162M 13% /boot /dev/mapper/VolGroup00-LogVol00 16T 133M 15T 1% /xiangao/lv1 /dev/mapper/VolGroup00-LogVol01 4.7T 190M 4.5T 1% /xiangao/lv2 I want to copy the LVM volume /dev/mapper/vg_avdvdfiler-lv_root on server A to LVM volume /dev/mapper/VolGroup00-LogVol00 on server B. Server A and server B are in the same IP segment. In the LVM volume on server A, there is all average 500M avi wmv mp4 etc. I tried mounting /dev/mapper/vg_avdvdfiler-lv_root on server A to server B through NFS, then use cp to copy. It is clear I failed. Because the LVM volume is too big, I do not have good idea why. I hope a good solution here.

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  • How to provide users with isolated drive letters in Windows 2008 R2 (Terminal Server) [migrated]

    - by Pierre
    I need to be able to host several RDP sessions on a Terminal Server, where users of group A see a drive X: mapped to a given folder of the server and another group B see the same drive letter X: mapped to another folder. For instance : User 1, Group A X: --> C:\data\A User 2, Group A X: --> C:\data\A User 3, Group B X: --> C:\data\B User 4, Group C X: --> C:\data\C Is this possible. If so, how do I configure the virtual drive mapping so that the user has nothing special to do; i.e. I want the letter X: to be available to Remote Apps launched by the user, or if the user logs in to the remote desktop. Can I somehow use subst to get this to work? I would like to avoid, if possible, mounting drive letters on local shares (i.e. I don't like the idea of having to go through \\localhost\data-A to reach the user's data).

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  • cygwin fork error

    - by Techie Help
    I have set up a new PC and installed cygwin on it. Its windows 7 pro. Whenever I try to build our application on it, I get the following error: 0 [main] sh 3472 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 /bin/sh: fork: retry: Resource temporarily unavailable 0 [main] sh 3220 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 /bin/sh: fork: retry: Resource temporarily unavailable 0 [main] sh 4896 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 /bin/sh: fork: retry: Resource temporarily unavailable 0 [main] sh 4884 child_info_fork::abort: can't commit memory for stack 0x28A000(90112), Win32 error 487 It prints this few times and then dies. I have already done a lot of research on this problem. I have already uninstalled and installed cygwin more than 5 times. Done rebaseall everytime I installed it. Checked for possible BLODA, I had notron antivirus, which I have removed. As an aside, I tried posting this question to cygwin mailing list after subscribing to it. But my mail does not appear on the list. I suppose they want address to be munged and I have no clue how to do it. supposedly, they are treating it as a spam. Any idea how I can post to the mailing list there.

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  • Slow Routing Over LAN (Wired)

    - by reverendj1
    I'm having issues with my router acting very slow (Adtran Netvanta 3458). We have two networks, let's call them A and B. When I run netperf from two servers on network A (no routing) I get speeds along the lines of 900 Mbps. Which makes sense, since we have all 1Gbps switches. When testing A to B (or vice-versa) I get speeds along the lines of 22Mbps. I have also tested connecting my laptop to the switchports on the router, and testing two servers on network A (no routing) and got speeds around 90 Mbps. Which makes sense since the switchports on the router are 100Mbps. Does anyone have any idea why routing would be so slow? We bought the router over a year ago, and we think it has been doing this since then, but we never actually tested it before. (network B isn't really used much, so we didn't notice much) We were implementing a site-to-site VPN and noticed it was ridiculously slow, so we started testing basic routing performance. I have ruled out cabling and router CPU/memory utilization. Adtran looked at my config, but didn't see anything wrong with it.

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  • Is it possible to automate a driver change on Windows for a plug&play peripheral ?

    - by Gnoupi
    Is it possible to automate a change of driver for a same peripheral, under Windows ? Typically to switch between two ones. (I'm talking about the kind of driver which doesn't require the computer to reboot, typically). I have a peripheral for which I use the constructor's driver in some cases, but also a modified driver in other cases. Not that the changing driver is really annoying, but I would like to know if it would be possible to make it easier, like for example in a shortcut. I know the name of the driver, even which files involved. For more details, the concerned peripheral is a "Xbox360 Gamepad for Windows" (or something like this). The base driver is good for new games, but it doesn't handle correctly older ones (some issues with axes, and vibrations). The modified driver makes it behave like a classic controller, but then it doesn't work correctly on new games (typically using the new version of dxinput linked to the "Games for Windows"). However, this is not a question specific to this gamepad, I'm asking in general about automating this change of drivers. I currently use Windows XP, so my question is mostly about it, but I'm also interested in the same issue for later versions (Windows 7, most likely). I'm not really sure if this is even possible, but in case someone has an idea, I'm asking.

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  • Integrating external computer into a domain - some recommendations please

    - by TomTom
    Given: * A multi loation company. Every office has local routers that connect to a central VPN capable rouer in a data center. All fine so far. We now need to move a computer off site into a hosting center across the globe, to get it closer to some supplier computers we work for. it will run limited logic but latency is important, and our latency so far is too large. This computer will be in a data center and does no require incoming connections except for adminsitrative purposes, although it needs outgoing connetions. I have no real chance to put one of my VPN routers there, sadly - otherwise I would have no problem. Usage of RRAs is not recommended (we had various probblems there over time). I could deal with it. The computer MUSt integrate into the corporate structure via VPN and join the domain and be fully "tracked" (controlled for performance). What is the best suggestion? So far it looks like my best bets woudl be to log in via RRAS and deal with whatever issues arise there plus uise the local firewall the limit incoming connections to this computer to what is needed (which runs down to an emergency RDP connection allowance). Anyone a better idea?

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  • Debian 7 and PHP 5.4.4 error reporting

    - by milovan
    I use default php.ini and then in my PHP script (local.settings.php in Drupal) I simply set ini_set('error_reporting', 'E_ALL & ~E_NOTICE & ~E_STRICT'); According to documentation this means "show all messages minus notice and strict warnings". But in my case it still shows strict warnings! I have no idea why, because I clearly stated "~E_STRICT". If I comment it out then I see strict warnings. So it means that default from php.ini "E_ALL & ~E_DEPRECATED & ~E_STRICT" didn't do its job as it also has "~E_STRICT" but I still see strict warnings. On Debian 6 there was Suhoshin patch which was controlling usage of php_ini in PHP scripts. Especially when you try to get more memory than defined cap. Now on debian 7 there is no Suhoshin nor any other security element that might control php_ini. So what might cause php_ini not to be executed? Is there some new variable / setup / other that needs to be checked?

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  • What could possibly cause my computer to power down at random times?

    - by geoffreydv
    I have recently bought a new Power Supply and a new graphics card. My PC ran smoothly for a few months now but since a couple of days I'm having a strange problem. I am trying to isolate the problem to a specific piece of hardware (because if it's either the Power Supply or the Graphics card they are still under warranty). The problem started when I was playing a game (diablo 3). My PC suddenly powered down. I was unable to turn it on again by pressing the power button. I unplugged the power cable for a few seconds and plugged it back in. This time the pc powered on but the indication light turned orange instead of white as it normally does. The fans were not spinning and I did not see anything on my screen. After trying a couple of times I gave up. Two days later I tried again and this time the PC did boot up as usual. Everything looked okay until I tested if the problem was resolved by starting Diablo again. After about two minutes it powered down again as it did the first time. If I don't run any games my PC does power down after about 3-5 hours. Another fact that might be relevant: One time the PC did not shut down immediatly, instead first my graphics "powered down" but the music I was playing kept on playing. After about 20 seconds the pc powered down completely as usual. What I also noticed is that when I boot instantly after a power down, the chance of another power down occuring is much higher. Does anyone have an idea what could be causing this kind of behaviour or has a certain tool to diagnose the specific hardware parts? Thanks Specs: Memory: 6GB Processor: Intel i5 OS: Windows 7 64 bit The PC is a Dell Studio XPS 8100 with a replaced PSU and Graphics card: PSU: Corsair CX500 (500 watt) Graphics card: AMD Radeon 6850

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  • cannot connect to my nginx server from remote machine

    - by margincall
    I thought that it's iptables problem.. but it seems not. I really have no idea about this situation. I'm getting a server hosting(CentOS). I installed Nginx + Django and nginx uses 8080 port. A domain is connected to the server. When I executed "wget [domain]:8080/[app name]/" in the server, it worked. Of course, "wget 127.0.0.1:8080/[app name]/" has no problem. (wget [server ip]:8080/[app name]/, either) However, from other computers, connecting was failed. (message says, no route) I checked my firewall setting. I excuted these commands. iptables -I INPUT -p tcp --dport 8080 -j ACCEPT iptables -I OUTPUT -p tcp --sport 8080 -j ACCEPT iptables -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 8080 -j ACCEPT /etc/init.d/iptables restart I don't really understand all options of commands and I think there were useless commands, but I just tried all googled iptables settings. But still I cannot connect to my server. What should I check, first? I don't know this is important, but add to this post. On 80 port, an apache server is running. It works fine, I can connect to apache from other computers. There is DB connecting issue, (PHP to MySQL) but I think that it is just PHP coding bug. please excuse my low-level English. I'm not native English speaker.. but I tried to explane well as far as possible. Thank you for reading this question.

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  • I'm having trouble getting my server to appear online.

    - by JMRboosties
    Total newb question I'm sure. First I had installed WAMP (http://www.wampserver.com), and I was able to access my pages from other computers in my router network, and the virtual device used to debug Android programs (the purpose of my having a server). This functionality failed, however, at some point over these past few days. While my own browser displays the pages just fine, other computers, my Android phone (on our room's wifi), and my virtual device are no longer able to connect to my pages. I had not made any changes in the settings. I uninstalled WAMP and installed EasyPHP. However, the problem was not resolved. I know this is rather vague, but does anyone here have an idea of what may have happened? I forwarded both port 80 (I know its the default HTTP port, I did it just to be safe), and now port 8888 which EasyPHP uses. I turned my firewall on my hosting computer off for good measure. I cannot access my pages from neither remote computers or computers using my router. Any ideas you may have on how to resolve this would be awesome, thanks a lot. And if you need anymore info please tell me.

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  • Configuring two subnets with two NICS. Access from a NAS to the internet

    - by archipestre
    I am having trouble configuring my NAS. I have a DSL router with WIFI (192.168.1.1) in my flatmates room. In my room I have a server with two NICS: 1) wlan0 (192.168.1.2) that connects to the DSL router via wireless 2) em1 (192.168.0.1) that connects to the NAS (192.168.0.20) with a crossover cable. I have Fedora 17 and I have enable packet forwarding. My IP configuration is as follows: WLAN0 inet 192.168.0.1 netmask 255.255.255.0 broadcast 192.168.0.255 EM1 inet 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.1.255 My routing table looks like: Destination Gateway G enmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 wlan0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 em1 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0 I have enable a static route in the DSL server: Status Network Destination Subnet Mask Interface Gateway Remove Edit Active 192.168.0.0 255.255.255.0 LAN 192.168.1.2 From my server I can ping the DSL router and the NAS. From the NAS I can ping both NICS of the server. However the NAS is unable to ping the DSL router or any address in the Internet. Any idea of what is wrong. Thank you in advance

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  • Looking for a nice and handy bandwidth limiter

    - by Spirit
    Here's the thing. My ISP are f*gs. Most of the time the network is realy good, but then again there are times when it sucks. They say we have 20mbp/s. Me and my brother are usually playing dota and it's fine. One of us plays the other's watching streaming or both of us are playing or something like that. But sometimes like one of these days one is lagging even if the other is watching youtube at 360p quality. So I do know that there are many bandwidth limiters out there. But what could you recommend given my situation. I like both of us to be able to install it and it would be good idea to have something like ON/OFF switch. When he is not here I would like to turn that thing off. But when one of us plays I would like to turn it ON and whatever I do, to be limited to 10 or 8mbps. That way we will not interrupt each other. Thanks guys :)

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  • schroot build environment setup how to avoid bind-mount home

    - by minghua
    The recent linux distributions such as Fedora and Ubuntu all use chroot environment to make the build. Because when making the build often it needs to install some special tools, and to install to the existing system. Using chroot avoids making any changes to the host system. To set up such a build environment, the first step is to make a chroot. I'm following the setup guide at https://wiki.debian.org/Schroot [wheezy-test] description=Contains the SPICE program aliases=test type=directory directory=/srv/chroot/test users=jsmith root-groups=root script-config=desktop/config personality=linux preserve-environment=true In the host on my setup the /home is on /dev/mapper. When schroot is entered, the same home is bind-mounted. Is there a way to avoid this? I prefer to use a different /home inside chroot. When changing the type from directory to plain, the binding is not performed. However that also loses /proc, /sys, etc. You'd have to manually bind-mount them. That does not seem to be a good solution. If a simple configuration change is unavailable, any idea where the script is for type=directory? Probably I'll manually modify the script. Thanks in advance for any answers or hints!

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  • Is there a way to measure wifi traffic on a network from a client?

    - by millimoose
    Is there some way (preferrably one that comes with an existing tool) to measure the traffic going through the whole WiFi network from a computer connected to it? (That is, not from the AP or something between the modem and AP.) My situation is this: a few months back, the internet connection at my parent's place got really sluggish and laggy. (Lag spikes that cause page loads to time out etc, connections plain getting lost and dropping packets forever.) It's impossible to get mom's husband to do anything about this because he brushes this off with something like "just tell your sister to turn off torrents". Unfortunately the WiFi router's firmware doesn't do traffic logging. I'm not going to risk bricking it to put WRT on it; nor am I keen on rewiring the network to add a proxy to analyse the traffic. (I'm one of those people that make computers break just by looking at them, except machines I own.) I'd like to be able to find out roughly how much data is going over the air here while all the LAN wires are out of the router, all the computers accused of torrenting are off, etc. The idea is to either show that: Even if everything but my macbook is turned off, something is congesting the network. The husband is a systems developer and has a whole lot of mysterious hardware that's not to be touched around, one of them might be culprit. There is barely any traffic on the network, but the internet is still sluggish. Meaning this is likely a problem the ISP should solve. (Some hardware of theirs being glitchy, someone on an aggregated line hogging it constantly...) The network is encrypted, but I can temporarily set it to open for the sake of finding this out. So, in conclusion? Can this be done? Or is there some alternative way I could try to diagnose the problem?

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  • Cannot open /dev/rfcomm1 : Host is down

    - by srj0408
    I am working on raspberry PI and on Bluetooth. I am using old raspberry pi kernel as the new one has got some bugs that were not resolved with respect to the bluez daemon. At present my kernel version is 3.6.11. I am using a USB bluetooth dongle and my sole purpose is to auto connect the bluetooth dongle when ever it is in range. For that i think i have to run a script in the backend on RPI that will keep on checking the existence of usb bluetooth dongle. I started from the very scratch. I installed bluez daemon using apt-get install bluetooth bluez utils blueman and then i used hciconfig which gives me that my bluetooth usb dongle is working fine. But when i did hcitool scan , it give me no device in range even though my Serial bluetooth Device was on. I wasn't able to find any device in vicinity. Also when i unplugged and plug the USB dongle again, i was able to scan the serial device , but when i repeat the process, i find the earlier condition of not finding any deice. I had find another useful link, but that need address of the bluetooth device that need to be connected. I want to automate this using hcitool scan, storing the output to the a file and then comparing it with already paired devices and their name. For that i need to figure out why hcitool scan is sometime working and sometime not. ? Can some one help me in figuring out why this is happening. Is there any problem on hardware side i.e Bluetooth dongle is buggy or i had some problem in bluez utils. Edit 1: While as of now, hcitool scan is giving me my remote device address but still i am getting the same issue of HOUST IS DOWN, '/dev/rfcomm1'. I am really not getting any idea of what to be done.

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  • Can't get a display albums function to work... php [closed]

    - by Zhenia
    need your help with the code, please. I am trying to display an album from the database, but i just get some strange signs having no idea why... the signs are Albums Help me out if you know how to solve this problem. how can i maKe the code to display name of the album and amount of images in it? i am sure all is fine with the db. this is the function: function get_albums() { $albums = array(); // not always have got to put brackets $albums_query = "SELECT albums.album_id, albums.timestamp, albums.name, LEFT(albums.description, 50) as description, COUNT(images.image_id) as image_count FROM albums LEFT JOIN images ON albums.album_id = images.album_id WHERE albums.user_id = '{$_SESSION['user_id']}' GROUP BY albums.album_id"; $res = mysql_query($albums_query) or die(mysql_error().'<br>'.$albums_query); while($albums_row = mysql_fetch_assoc($res)){ $albums = array ( 'id' => $albums_row['album_id'], 'timestamp'=> $albums_row['timestamp'], 'name' => $albums_row['name'], 'description' => $albums_row['description'], 'count' =>$albums_row['image_count'] ); } return $albums; } and the other half of the code: <?php $albums = get_albums(); if(empty($albums)) { echo'<p>You don\'t have any albums</p>'; }else{ foreach($albums as $album){ echo'<p><a href="view_album.php?album_id=',$album['id'],'">',$album['name'],'</a>(',$album['count'],'images)<br /></p>'; } } ?>

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  • How to optimize dynamic programming?

    - by Chan
    Problem A number is called lucky if the sum of its digits, as well as the sum of the squares of its digits is a prime number. How many numbers between A and B are lucky? Input: The first line contains the number of test cases T. Each of the next T lines contains two integers, A and B. Output: Output T lines, one for each case containing the required answer for the corresponding case. Constraints: 1 <= T <= 10000 1 <= A <= B <= 10^18 Sample Input: 2 1 20 120 130 Sample Output: 4 1 Explanation: For the first case, the lucky numbers are 11, 12, 14, 16. For the second case, the only lucky number is 120. The problem is quite simple if we use brute force, however the running time is so critical that my program failed most test cases. My current idea is to use dynamic programming by storing the previous sum in a temporary array, so for example: sum_digits(10) = 1 -> sum_digits(11) = sum_digits(10) + 1 The same idea is applied for sum square but with counter equals to odd numbers. Unfortunately, it still failed 9 of 10 test cases which makes me think there must be a better way to solve it. Any idea would be greatly appreciated. #include <iostream> #include <vector> #include <string> #include <algorithm> #include <unordered_map> #include <unordered_set> #include <cmath> #include <cassert> #include <bitset> using namespace std; bool prime_table[1540] = { 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0 }; unsigned num_digits(long long i) { return i > 0 ? (long) log10 ((double) i) + 1 : 1; } void get_sum_and_sum_square_digits(long long n, int& sum, int& sum_square) { sum = 0; sum_square = 0; int digit; while (n) { digit = n % 10; sum += digit; sum_square += digit * digit; n /= 10; } } void init_digits(long long n, long long previous_sum[], const int size = 18) { int current_no_digits = num_digits(n); int digit; for (int i = 0; i < current_no_digits; ++i) { digit = n % 10; previous_sum[i] = digit; n /= 10; } for (int i = current_no_digits; i <= size; ++i) { previous_sum[i] = 0; } } void display_previous(long long previous[]) { for (int i = 0; i < 18; ++i) { cout << previous[i] << ","; } } int count_lucky_number(long long A, long long B) { long long n = A; long long end = B; int sum = 0; int sum_square = 0; int lucky_counter = 0; get_sum_and_sum_square_digits(n, sum, sum_square); long long sum_counter = sum; long long sum_square_counter = sum_square; if (prime_table[sum_counter] && prime_table[sum_square_counter]) { lucky_counter++; } long long previous_sum[19] = {1}; init_digits(n, previous_sum); while (n < end) { n++; if (n % 100000000000000000 == 0) { previous_sum[17]++; sum_counter = previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[16] = 0; previous_sum[15] = 0; previous_sum[14] = 0; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000000000000 == 0) { previous_sum[16]++; sum_counter = previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[15] = 0; previous_sum[14] = 0; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000000000000 == 0) { previous_sum[15]++; sum_counter = previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[14] = 0; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000000000000 == 0) { previous_sum[14]++; sum_counter = previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[13] = 0; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000000000 == 0) { previous_sum[13]++; sum_counter = previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[12] = 0; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000000000 == 0) { previous_sum[12]++; sum_counter = previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[11] = 0; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000000000 == 0) { previous_sum[11]++; sum_counter = previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[10] = 0; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000000 == 0) { previous_sum[10]++; sum_counter = previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[9] = 0; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000000 == 0) { previous_sum[9]++; sum_counter = previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[8] = 0; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000000 == 0) { previous_sum[8]++; sum_counter = previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[7] = 0; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000000 == 0) { previous_sum[7]++; sum_counter = previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[6] = 0; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000000 == 0) { previous_sum[6]++; sum_counter = previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[5] = 0; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100000 == 0) { previous_sum[5]++; sum_counter = previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[4] = 0; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10000 == 0) { previous_sum[4]++; sum_counter = previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[3] = 0; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 1000 == 0) { previous_sum[3]++; sum_counter = previous_sum[3] + previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[3] * previous_sum[3] + previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[2] = 0; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 100 == 0) { previous_sum[2]++; sum_counter = previous_sum[2] + previous_sum[3] + previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[2] * previous_sum[2] + previous_sum[3] * previous_sum[3] + previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[1] = 0; previous_sum[0] = 0; } else if (n % 10 == 0) { previous_sum[1]++; sum_counter = previous_sum[1] + previous_sum[2] + previous_sum[3] + previous_sum[4] + previous_sum[5] + previous_sum[6] + previous_sum[7] + previous_sum[8] + previous_sum[9] + previous_sum[10] + previous_sum[11] + previous_sum[12] + previous_sum[13] + previous_sum[14] + previous_sum[15] + previous_sum[16] + previous_sum[17] + previous_sum[18]; sum_square_counter = previous_sum[1] * previous_sum[1] + previous_sum[2] * previous_sum[2] + previous_sum[3] * previous_sum[3] + previous_sum[4] * previous_sum[4] + previous_sum[5] * previous_sum[5] + previous_sum[6] * previous_sum[6] + previous_sum[7] * previous_sum[7] + previous_sum[8] * previous_sum[8] + previous_sum[9] * previous_sum[9] + previous_sum[10] * previous_sum[10] + previous_sum[11] * previous_sum[11] + previous_sum[12] * previous_sum[12] + previous_sum[13] * previous_sum[13] + previous_sum[14] * previous_sum[14] + previous_sum[15] * previous_sum[15] + previous_sum[16] * previous_sum[16] + previous_sum[17] * previous_sum[17] + previous_sum[18] * previous_sum[18]; previous_sum[0] = 0; } else { sum_counter++; sum_square_counter += ((n - 1) % 10) * 2 + 1; } // get_sum_and_sum_square_digits(n, sum, sum_square); // assert(sum == sum_counter && sum_square == sum_square_counter); if (prime_table[sum_counter] && prime_table[sum_square_counter]) { lucky_counter++; } } return lucky_counter; } void inout_lucky_numbers() { int n; cin >> n; long long a; long long b; while (n--) { cin >> a >> b; cout << count_lucky_number(a, b) << endl; } } int main() { inout_lucky_numbers(); return 0; }

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  • A way of doing real-world test-driven development (and some thoughts about it)

    - by Thomas Weller
    Lately, I exchanged some arguments with Derick Bailey about some details of the red-green-refactor cycle of the Test-driven development process. In short, the issue revolved around the fact that it’s not enough to have a test red or green, but it’s also important to have it red or green for the right reasons. While for me, it’s sufficient to initially have a NotImplementedException in place, Derick argues that this is not totally correct (see these two posts: Red/Green/Refactor, For The Right Reasons and Red For The Right Reason: Fail By Assertion, Not By Anything Else). And he’s right. But on the other hand, I had no idea how his insights could have any practical consequence for my own individual interpretation of the red-green-refactor cycle (which is not really red-green-refactor, at least not in its pure sense, see the rest of this article). This made me think deeply for some days now. In the end I found out that the ‘right reason’ changes in my understanding depending on what development phase I’m in. To make this clear (at least I hope it becomes clear…) I started to describe my way of working in some detail, and then something strange happened: The scope of the article slightly shifted from focusing ‘only’ on the ‘right reason’ issue to something more general, which you might describe as something like  'Doing real-world TDD in .NET , with massive use of third-party add-ins’. This is because I feel that there is a more general statement about Test-driven development to make:  It’s high time to speak about the ‘How’ of TDD, not always only the ‘Why’. Much has been said about this, and me myself also contributed to that (see here: TDD is not about testing, it's about how we develop software). But always justifying what you do is very unsatisfying in the long run, it is inherently defensive, and it costs time and effort that could be used for better and more important things. And frankly: I’m somewhat sick and tired of repeating time and again that the test-driven way of software development is highly preferable for many reasons - I don’t want to spent my time exclusively on stating the obvious… So, again, let’s say it clearly: TDD is programming, and programming is TDD. Other ways of programming (code-first, sometimes called cowboy-coding) are exceptional and need justification. – I know that there are many people out there who will disagree with this radical statement, and I also know that it’s not a description of the real world but more of a mission statement or something. But nevertheless I’m absolutely sure that in some years this statement will be nothing but a platitude. Side note: Some parts of this post read as if I were paid by Jetbrains (the manufacturer of the ReSharper add-in – R#), but I swear I’m not. Rather I think that Visual Studio is just not production-complete without it, and I wouldn’t even consider to do professional work without having this add-in installed... The three parts of a software component Before I go into some details, I first should describe my understanding of what belongs to a software component (assembly, type, or method) during the production process (i.e. the coding phase). Roughly, I come up with the three parts shown below:   First, we need to have some initial sort of requirement. This can be a multi-page formal document, a vague idea in some programmer’s brain of what might be needed, or anything in between. In either way, there has to be some sort of requirement, be it explicit or not. – At the C# micro-level, the best way that I found to formulate that is to define interfaces for just about everything, even for internal classes, and to provide them with exhaustive xml comments. The next step then is to re-formulate these requirements in an executable form. This is specific to the respective programming language. - For C#/.NET, the Gallio framework (which includes MbUnit) in conjunction with the ReSharper add-in for Visual Studio is my toolset of choice. The third part then finally is the production code itself. It’s development is entirely driven by the requirements and their executable formulation. This is the delivery, the two other parts are ‘only’ there to make its production possible, to give it a decent quality and reliability, and to significantly reduce related costs down the maintenance timeline. So while the first two parts are not really relevant for the customer, they are very important for the developer. The customer (or in Scrum terms: the Product Owner) is not interested at all in how  the product is developed, he is only interested in the fact that it is developed as cost-effective as possible, and that it meets his functional and non-functional requirements. The rest is solely a matter of the developer’s craftsmanship, and this is what I want to talk about during the remainder of this article… An example To demonstrate my way of doing real-world TDD, I decided to show the development of a (very) simple Calculator component. The example is deliberately trivial and silly, as examples always are. I am totally aware of the fact that real life is never that simple, but I only want to show some development principles here… The requirement As already said above, I start with writing down some words on the initial requirement, and I normally use interfaces for that, even for internal classes - the typical question “intf or not” doesn’t even come to mind. I need them for my usual workflow and using them automatically produces high componentized and testable code anyway. To think about their usage in every single situation would slow down the production process unnecessarily. So this is what I begin with: namespace Calculator {     /// <summary>     /// Defines a very simple calculator component for demo purposes.     /// </summary>     public interface ICalculator     {         /// <summary>         /// Gets the result of the last successful operation.         /// </summary>         /// <value>The last result.</value>         /// <remarks>         /// Will be <see langword="null" /> before the first successful operation.         /// </remarks>         double? LastResult { get; }       } // interface ICalculator   } // namespace Calculator So, I’m not beginning with a test, but with a sort of code declaration - and still I insist on being 100% test-driven. There are three important things here: Starting this way gives me a method signature, which allows to use IntelliSense and AutoCompletion and thus eliminates the danger of typos - one of the most regular, annoying, time-consuming, and therefore expensive sources of error in the development process. In my understanding, the interface definition as a whole is more of a readable requirement document and technical documentation than anything else. So this is at least as much about documentation than about coding. The documentation must completely describe the behavior of the documented element. I normally use an IoC container or some sort of self-written provider-like model in my architecture. In either case, I need my components defined via service interfaces anyway. - I will use the LinFu IoC framework here, for no other reason as that is is very simple to use. The ‘Red’ (pt. 1)   First I create a folder for the project’s third-party libraries and put the LinFu.Core dll there. Then I set up a test project (via a Gallio project template), and add references to the Calculator project and the LinFu dll. Finally I’m ready to write the first test, which will look like the following: namespace Calculator.Test {     [TestFixture]     public class CalculatorTest     {         private readonly ServiceContainer container = new ServiceContainer();           [Test]         public void CalculatorLastResultIsInitiallyNull()         {             ICalculator calculator = container.GetService<ICalculator>();               Assert.IsNull(calculator.LastResult);         }       } // class CalculatorTest   } // namespace Calculator.Test       This is basically the executable formulation of what the interface definition states (part of). Side note: There’s one principle of TDD that is just plain wrong in my eyes: I’m talking about the Red is 'does not compile' thing. How could a compiler error ever be interpreted as a valid test outcome? I never understood that, it just makes no sense to me. (Or, in Derick’s terms: this reason is as wrong as a reason ever could be…) A compiler error tells me: Your code is incorrect, but nothing more.  Instead, the ‘Red’ part of the red-green-refactor cycle has a clearly defined meaning to me: It means that the test works as intended and fails only if its assumptions are not met for some reason. Back to our Calculator. When I execute the above test with R#, the Gallio plugin will give me this output: So this tells me that the test is red for the wrong reason: There’s no implementation that the IoC-container could load, of course. So let’s fix that. With R#, this is very easy: First, create an ICalculator - derived type:        Next, implement the interface members: And finally, move the new class to its own file: So far my ‘work’ was six mouse clicks long, the only thing that’s left to do manually here, is to add the Ioc-specific wiring-declaration and also to make the respective class non-public, which I regularly do to force my components to communicate exclusively via interfaces: This is what my Calculator class looks like as of now: using System; using LinFu.IoC.Configuration;   namespace Calculator {     [Implements(typeof(ICalculator))]     internal class Calculator : ICalculator     {         public double? LastResult         {             get             {                 throw new NotImplementedException();             }         }     } } Back to the test fixture, we have to put our IoC container to work: [TestFixture] public class CalculatorTest {     #region Fields       private readonly ServiceContainer container = new ServiceContainer();       #endregion // Fields       #region Setup/TearDown       [FixtureSetUp]     public void FixtureSetUp()     {        container.LoadFrom(AppDomain.CurrentDomain.BaseDirectory, "Calculator.dll");     }       ... Because I have a R# live template defined for the setup/teardown method skeleton as well, the only manual coding here again is the IoC-specific stuff: two lines, not more… The ‘Red’ (pt. 2) Now, the execution of the above test gives the following result: This time, the test outcome tells me that the method under test is called. And this is the point, where Derick and I seem to have somewhat different views on the subject: Of course, the test still is worthless regarding the red/green outcome (or: it’s still red for the wrong reasons, in that it gives a false negative). But as far as I am concerned, I’m not really interested in the test outcome at this point of the red-green-refactor cycle. Rather, I only want to assert that my test actually calls the right method. If that’s the case, I will happily go on to the ‘Green’ part… The ‘Green’ Making the test green is quite trivial. Just make LastResult an automatic property:     [Implements(typeof(ICalculator))]     internal class Calculator : ICalculator     {         public double? LastResult { get; private set; }     }         One more round… Now on to something slightly more demanding (cough…). Let’s state that our Calculator exposes an Add() method:         ...   /// <summary>         /// Adds the specified operands.         /// </summary>         /// <param name="operand1">The operand1.</param>         /// <param name="operand2">The operand2.</param>         /// <returns>The result of the additon.</returns>         /// <exception cref="ArgumentException">         /// Argument <paramref name="operand1"/> is &lt; 0.<br/>         /// -- or --<br/>         /// Argument <paramref name="operand2"/> is &lt; 0.         /// </exception>         double Add(double operand1, double operand2);       } // interface ICalculator A remark: I sometimes hear the complaint that xml comment stuff like the above is hard to read. That’s certainly true, but irrelevant to me, because I read xml code comments with the CR_Documentor tool window. And using that, it looks like this:   Apart from that, I’m heavily using xml code comments (see e.g. here for a detailed guide) because there is the possibility of automating help generation with nightly CI builds (using MS Sandcastle and the Sandcastle Help File Builder), and then publishing the results to some intranet location.  This way, a team always has first class, up-to-date technical documentation at hand about the current codebase. (And, also very important for speeding up things and avoiding typos: You have IntelliSense/AutoCompletion and R# support, and the comments are subject to compiler checking…).     Back to our Calculator again: Two more R# – clicks implement the Add() skeleton:         ...           public double Add(double operand1, double operand2)         {             throw new NotImplementedException();         }       } // class Calculator As we have stated in the interface definition (which actually serves as our requirement document!), the operands are not allowed to be negative. So let’s start implementing that. Here’s the test: [Test] [Row(-0.5, 2)] public void AddThrowsOnNegativeOperands(double operand1, double operand2) {     ICalculator calculator = container.GetService<ICalculator>();       Assert.Throws<ArgumentException>(() => calculator.Add(operand1, operand2)); } As you can see, I’m using a data-driven unit test method here, mainly for these two reasons: Because I know that I will have to do the same test for the second operand in a few seconds, I save myself from implementing another test method for this purpose. Rather, I only will have to add another Row attribute to the existing one. From the test report below, you can see that the argument values are explicitly printed out. This can be a valuable documentation feature even when everything is green: One can quickly review what values were tested exactly - the complete Gallio HTML-report (as it will be produced by the Continuous Integration runs) shows these values in a quite clear format (see below for an example). Back to our Calculator development again, this is what the test result tells us at the moment: So we’re red again, because there is not yet an implementation… Next we go on and implement the necessary parameter verification to become green again, and then we do the same thing for the second operand. To make a long story short, here’s the test and the method implementation at the end of the second cycle: // in CalculatorTest:   [Test] [Row(-0.5, 2)] [Row(295, -123)] public void AddThrowsOnNegativeOperands(double operand1, double operand2) {     ICalculator calculator = container.GetService<ICalculator>();       Assert.Throws<ArgumentException>(() => calculator.Add(operand1, operand2)); }   // in Calculator: public double Add(double operand1, double operand2) {     if (operand1 < 0.0)     {         throw new ArgumentException("Value must not be negative.", "operand1");     }     if (operand2 < 0.0)     {         throw new ArgumentException("Value must not be negative.", "operand2");     }     throw new NotImplementedException(); } So far, we have sheltered our method from unwanted input, and now we can safely operate on the parameters without further caring about their validity (this is my interpretation of the Fail Fast principle, which is regarded here in more detail). Now we can think about the method’s successful outcomes. First let’s write another test for that: [Test] [Row(1, 1, 2)] public void TestAdd(double operand1, double operand2, double expectedResult) {     ICalculator calculator = container.GetService<ICalculator>();       double result = calculator.Add(operand1, operand2);       Assert.AreEqual(expectedResult, result); } Again, I’m regularly using row based test methods for these kinds of unit tests. The above shown pattern proved to be extremely helpful for my development work, I call it the Defined-Input/Expected-Output test idiom: You define your input arguments together with the expected method result. There are two major benefits from that way of testing: In the course of refining a method, it’s very likely to come up with additional test cases. In our case, we might add tests for some edge cases like ‘one of the operands is zero’ or ‘the sum of the two operands causes an overflow’, or maybe there’s an external test protocol that has to be fulfilled (e.g. an ISO norm for medical software), and this results in the need of testing against additional values. In all these scenarios we only have to add another Row attribute to the test. Remember that the argument values are written to the test report, so as a side-effect this produces valuable documentation. (This can become especially important if the fulfillment of some sort of external requirements has to be proven). So your test method might look something like that in the end: [Test, Description("Arguments: operand1, operand2, expectedResult")] [Row(1, 1, 2)] [Row(0, 999999999, 999999999)] [Row(0, 0, 0)] [Row(0, double.MaxValue, double.MaxValue)] [Row(4, double.MaxValue - 2.5, double.MaxValue)] public void TestAdd(double operand1, double operand2, double expectedResult) {     ICalculator calculator = container.GetService<ICalculator>();       double result = calculator.Add(operand1, operand2);       Assert.AreEqual(expectedResult, result); } And this will produce the following HTML report (with Gallio):   Not bad for the amount of work we invested in it, huh? - There might be scenarios where reports like that can be useful for demonstration purposes during a Scrum sprint review… The last requirement to fulfill is that the LastResult property is expected to store the result of the last operation. I don’t show this here, it’s trivial enough and brings nothing new… And finally: Refactor (for the right reasons) To demonstrate my way of going through the refactoring portion of the red-green-refactor cycle, I added another method to our Calculator component, namely Subtract(). Here’s the code (tests and production): // CalculatorTest.cs:   [Test, Description("Arguments: operand1, operand2, expectedResult")] [Row(1, 1, 0)] [Row(0, 999999999, -999999999)] [Row(0, 0, 0)] [Row(0, double.MaxValue, -double.MaxValue)] [Row(4, double.MaxValue - 2.5, -double.MaxValue)] public void TestSubtract(double operand1, double operand2, double expectedResult) {     ICalculator calculator = container.GetService<ICalculator>();       double result = calculator.Subtract(operand1, operand2);       Assert.AreEqual(expectedResult, result); }   [Test, Description("Arguments: operand1, operand2, expectedResult")] [Row(1, 1, 0)] [Row(0, 999999999, -999999999)] [Row(0, 0, 0)] [Row(0, double.MaxValue, -double.MaxValue)] [Row(4, double.MaxValue - 2.5, -double.MaxValue)] public void TestSubtractGivesExpectedLastResult(double operand1, double operand2, double expectedResult) {     ICalculator calculator = container.GetService<ICalculator>();       calculator.Subtract(operand1, operand2);       Assert.AreEqual(expectedResult, calculator.LastResult); }   ...   // ICalculator.cs: /// <summary> /// Subtracts the specified operands. /// </summary> /// <param name="operand1">The operand1.</param> /// <param name="operand2">The operand2.</param> /// <returns>The result of the subtraction.</returns> /// <exception cref="ArgumentException"> /// Argument <paramref name="operand1"/> is &lt; 0.<br/> /// -- or --<br/> /// Argument <paramref name="operand2"/> is &lt; 0. /// </exception> double Subtract(double operand1, double operand2);   ...   // Calculator.cs:   public double Subtract(double operand1, double operand2) {     if (operand1 < 0.0)     {         throw new ArgumentException("Value must not be negative.", "operand1");     }       if (operand2 < 0.0)     {         throw new ArgumentException("Value must not be negative.", "operand2");     }       return (this.LastResult = operand1 - operand2).Value; }   Obviously, the argument validation stuff that was produced during the red-green part of our cycle duplicates the code from the previous Add() method. So, to avoid code duplication and minimize the number of code lines of the production code, we do an Extract Method refactoring. One more time, this is only a matter of a few mouse clicks (and giving the new method a name) with R#: Having done that, our production code finally looks like that: using System; using LinFu.IoC.Configuration;   namespace Calculator {     [Implements(typeof(ICalculator))]     internal class Calculator : ICalculator     {         #region ICalculator           public double? LastResult { get; private set; }           public double Add(double operand1, double operand2)         {             ThrowIfOneOperandIsInvalid(operand1, operand2);               return (this.LastResult = operand1 + operand2).Value;         }           public double Subtract(double operand1, double operand2)         {             ThrowIfOneOperandIsInvalid(operand1, operand2);               return (this.LastResult = operand1 - operand2).Value;         }           #endregion // ICalculator           #region Implementation (Helper)           private static void ThrowIfOneOperandIsInvalid(double operand1, double operand2)         {             if (operand1 < 0.0)             {                 throw new ArgumentException("Value must not be negative.", "operand1");             }               if (operand2 < 0.0)             {                 throw new ArgumentException("Value must not be negative.", "operand2");             }         }           #endregion // Implementation (Helper)       } // class Calculator   } // namespace Calculator But is the above worth the effort at all? It’s obviously trivial and not very impressive. All our tests were green (for the right reasons), and refactoring the code did not change anything. It’s not immediately clear how this refactoring work adds value to the project. Derick puts it like this: STOP! Hold on a second… before you go any further and before you even think about refactoring what you just wrote to make your test pass, you need to understand something: if your done with your requirements after making the test green, you are not required to refactor the code. I know… I’m speaking heresy, here. Toss me to the wolves, I’ve gone over to the dark side! Seriously, though… if your test is passing for the right reasons, and you do not need to write any test or any more code for you class at this point, what value does refactoring add? Derick immediately answers his own question: So why should you follow the refactor portion of red/green/refactor? When you have added code that makes the system less readable, less understandable, less expressive of the domain or concern’s intentions, less architecturally sound, less DRY, etc, then you should refactor it. I couldn’t state it more precise. From my personal perspective, I’d add the following: You have to keep in mind that real-world software systems are usually quite large and there are dozens or even hundreds of occasions where micro-refactorings like the above can be applied. It’s the sum of them all that counts. And to have a good overall quality of the system (e.g. in terms of the Code Duplication Percentage metric) you have to be pedantic on the individual, seemingly trivial cases. My job regularly requires the reading and understanding of ‘foreign’ code. So code quality/readability really makes a HUGE difference for me – sometimes it can be even the difference between project success and failure… Conclusions The above described development process emerged over the years, and there were mainly two things that guided its evolution (you might call it eternal principles, personal beliefs, or anything in between): Test-driven development is the normal, natural way of writing software, code-first is exceptional. So ‘doing TDD or not’ is not a question. And good, stable code can only reliably be produced by doing TDD (yes, I know: many will strongly disagree here again, but I’ve never seen high-quality code – and high-quality code is code that stood the test of time and causes low maintenance costs – that was produced code-first…) It’s the production code that pays our bills in the end. (Though I have seen customers these days who demand an acceptance test battery as part of the final delivery. Things seem to go into the right direction…). The test code serves ‘only’ to make the production code work. But it’s the number of delivered features which solely counts at the end of the day - no matter how much test code you wrote or how good it is. With these two things in mind, I tried to optimize my coding process for coding speed – or, in business terms: productivity - without sacrificing the principles of TDD (more than I’d do either way…).  As a result, I consider a ratio of about 3-5/1 for test code vs. production code as normal and desirable. In other words: roughly 60-80% of my code is test code (This might sound heavy, but that is mainly due to the fact that software development standards only begin to evolve. The entire software development profession is very young, historically seen; only at the very beginning, and there are no viable standards yet. If you think about software development as a kind of casting process, where the test code is the mold and the resulting production code is the final product, then the above ratio sounds no longer extraordinary…) Although the above might look like very much unnecessary work at first sight, it’s not. With the aid of the mentioned add-ins, doing all the above is a matter of minutes, sometimes seconds (while writing this post took hours and days…). The most important thing is to have the right tools at hand. Slow developer machines or the lack of a tool or something like that - for ‘saving’ a few 100 bucks -  is just not acceptable and a very bad decision in business terms (though I quite some times have seen and heard that…). Production of high-quality products needs the usage of high-quality tools. This is a platitude that every craftsman knows… The here described round-trip will take me about five to ten minutes in my real-world development practice. I guess it’s about 30% more time compared to developing the ‘traditional’ (code-first) way. But the so manufactured ‘product’ is of much higher quality and massively reduces maintenance costs, which is by far the single biggest cost factor, as I showed in this previous post: It's the maintenance, stupid! (or: Something is rotten in developerland.). In the end, this is a highly cost-effective way of software development… But on the other hand, there clearly is a trade-off here: coding speed vs. code quality/later maintenance costs. The here described development method might be a perfect fit for the overwhelming majority of software projects, but there certainly are some scenarios where it’s not - e.g. if time-to-market is crucial for a software project. So this is a business decision in the end. It’s just that you have to know what you’re doing and what consequences this might have… Some last words First, I’d like to thank Derick Bailey again. His two aforementioned posts (which I strongly recommend for reading) inspired me to think deeply about my own personal way of doing TDD and to clarify my thoughts about it. I wouldn’t have done that without this inspiration. I really enjoy that kind of discussions… I agree with him in all respects. But I don’t know (yet?) how to bring his insights into the described production process without slowing things down. The above described method proved to be very “good enough” in my practical experience. But of course, I’m open to suggestions here… My rationale for now is: If the test is initially red during the red-green-refactor cycle, the ‘right reason’ is: it actually calls the right method, but this method is not yet operational. Later on, when the cycle is finished and the tests become part of the regular, automated Continuous Integration process, ‘red’ certainly must occur for the ‘right reason’: in this phase, ‘red’ MUST mean nothing but an unfulfilled assertion - Fail By Assertion, Not By Anything Else!

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