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  • DHCP server not starting

    - by Bruce
    I'm trying to set a DHCP server on 12.04. I installed: sudo apt-get install isc-dhcp-server My configuration files look like this: /etc/default/isc-dhcp-server INTERFACES="eth0" /etc/network/interfaces auto lo iface lo inet loopback /etc/dhcp/dhcpd.conf ddns-update-style none; default-lease-time 600; max-lease-time 7200; authoritative; log-facility local7; subnet 192.168.1.0 netmask 255.255.255.0 { range 192.168.1.235 192.168.1.240; option subnet-mask 255.255.255.0; option broadcast-address 192.168.1.255; option routers 192.168.1.1; default-lease-time 100000; max-lease-time 100000; } When I run sudo service isc-dhcp-server restart I get: stop: Unknown instance: isc-dhcp-server start/running, process 15384 After this if I run sudo service isc-dhcp-server status it shows that its stopped: isc-dhcp-server stop/waiting What am I doing wrong here?

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  • Solving Combinatory Problems with LINQ /.NET4

    - by slf
    I saw this article pop-up in my MSDN RSS feed, and after reading through it, and the sourced article here I began to wonder about the solution. The rules are simple: Find a number consisting of 9 digits in which each of the digits from 1 to 9 appears only once. This number must also satisfy these divisibility requirements: The number should be divisible by 9. If the rightmost digit is removed, the remaining number should be divisible by 8. If the rightmost digit of the new number is removed, the remaining number should be divisible by 7. And so on, until there's only one digit (which will necessarily be divisible by 1). This is his proposed monster LINQ query: // C# and LINQ solution to the numeric problem presented in: // http://software.intel.com/en-us/blogs/2009/12/07/intel-parallel-studio-great-for-serial-code-too-episode-1/ int[] oneToNine = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; // the query var query = from i1 in oneToNine from i2 in oneToNine where i2 != i1 && (i1 * 10 + i2) % 2 == 0 from i3 in oneToNine where i3 != i2 && i3 != i1 && (i1 * 100 + i2 * 10 + i3) % 3 == 0 from i4 in oneToNine where i4 != i3 && i4 != i2 && i4 != i1 && (i1 * 1000 + i2 * 100 + i3 * 10 + i4) % 4 == 0 from i5 in oneToNine where i5 != i4 && i5 != i3 && i5 != i2 && i5 != i1 && (i1 * 10000 + i2 * 1000 + i3 * 100 + i4 * 10 + i5) % 5 == 0 from i6 in oneToNine where i6 != i5 && i6 != i4 && i6 != i3 && i6 != i2 && i6 != i1 && (i1 * 100000 + i2 * 10000 + i3 * 1000 + i4 * 100 + i5 * 10 + i6) % 6 == 0 from i7 in oneToNine where i7 != i6 && i7 != i5 && i7 != i4 && i7 != i3 && i7 != i2 && i7 != i1 && (i1 * 1000000 + i2 * 100000 + i3 * 10000 + i4 * 1000 + i5 * 100 + i6 * 10 + i7) % 7 == 0 from i8 in oneToNine where i8 != i7 && i8 != i6 && i8 != i5 && i8 != i4 && i8 != i3 && i8 != i2 && i8 != i1 && (i1 * 10000000 + i2 * 1000000 + i3 * 100000 + i4 * 10000 + i5 * 1000 + i6 * 100 + i7 * 10 + i8) % 8 == 0 from i9 in oneToNine where i9 != i8 && i9 != i7 && i9 != i6 && i9 != i5 && i9 != i4 && i9 != i3 && i9 != i2 && i9 != i1 let number = i1 * 100000000 + i2 * 10000000 + i3 * 1000000 + i4 * 100000 + i5 * 10000 + i6 * 1000 + i7 * 100 + i8 * 10 + i9 * 1 where number % 9 == 0 select number; // run it! foreach (int n in query) Console.WriteLine(n); Octavio states "Note that no attempt at all has been made to optimize the code", what I'd like to know is what if we DID attempt to optimize this code. Is this really the best this code can get? I'd like to know how we can do this best with .NET4, in particular doing as much in parallel as we possibly can. I'm not necessarily looking for an answer in pure LINQ, assume .NET4 in any form (managed c++, c#, etc all acceptable).

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  • Product Search SEO

    - by dana
    I am a wondering if there is a recommended "best practice" for a product search SEO. I know to create a dynamic sitemap file that lists links to all products in the site. However, I want to implement a a bookmark-able "advanced search". Should I let search engines index any of the results? Take the following parameters for a search on a make believe used car website: minprice (minimum price in dollars) maxprice (maximum price in dollars) make (honda, audi, volvo) model (accord, A4, S40) minyear (minimum model year) maxyear (maximum model year) minmileage (minimum mileage) maxmileage (maximum mileage) Given these parameters, there could be an infinite number of search combinations: Price Between $10,000 and $20,000 /search?minprice=10000&maxprice&20000 Audis with less than 50k miles /search?model=audi&maxmileage=50000 More than 100,000 miles and less than $5,000 /search?minmileage=100000&maxprice=5000 etc. Over time, there may be inbound links to a variety of these types of searches, yet they are all slices of the same data. Should I allow for all of these searches to be indexed?

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  • SEO for a list of products with filters

    - by dana
    I am a wondering if there is a recommended "best practice" for a product search SEO. I know to create a dynamic sitemap file that lists links to all products in the site. However, I want to implement a a bookmark-able "advanced search". Should I let search engines index any of the results? Take the following parameters for a search on a make believe used car website: minprice (minimum price in dollars) maxprice (maximum price in dollars) make (honda, audi, volvo) model (accord, A4, S40) minyear (minimum model year) maxyear (maximum model year) minmileage (minimum mileage) maxmileage (maximum mileage) Given these parameters, there could be an infinite number of search combinations: Price Between $10,000 and $20,000 /search?minprice=10000&maxprice&20000 Audis with less than 50k miles /search?model=audi&maxmileage=50000 More than 100,000 miles and less than $5,000 /search?minmileage=100000&maxprice=5000 etc. Over time, there may be inbound links to a variety of these types of searches, yet they are all slices of the same data. Should I allow for all of these searches to be indexed?

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  • Algorithm to calculate a page importance based on its views / comments

    - by stacker
    I need an algorithm that allows me to determine an appropriate <priority> field for my website's sitemap based on the page's views and comments count. For those of you unfamiliar with sitemaps, the priority field is used to signal the importance of a page relative to the others on the same website. It must be a decimal number between 0 and 1. The algorithm will accept two parameters, viewCount and commentCount, and will return the priority value. For example: GetPriority(100000, 100000); // Damn, a lot of views/comments! The returned value will be very close to 1, for example 0.995 GetPriority(3, 2); // Ok not many users are interested in this page, so for example it will return 0.082

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  • playing only part of a sound using FMOD

    - by carneades
    I'm trying to play only part of a sound using FMOD, say frames 50000-100000 of a 200000 frame file. I have found a couple of ways to seek forward (i.e. to start playback at frame 50000) but I have not found a way to make sure the sound stops playing at 100000. Is there any way FMOD can natively do this without having to add lbsndfile or the like into the picture? I should also mention that I am using the streaming option. I have to assume that these sounds are arbitrarily large and cannot be comfortably/quickly loaded into memory.

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  • How to get "all" (or the MAIN/LAUNCHER) android intent

    - by Christoph Jerolimov
    Hey, i want receive all start app intents (i think MAIN/LAUNCHER, see below) to log how often i used the application. So i do not want create an activity... I tried several receiver blocks, but for now nothing works: with, without priority, only the action, both, only the category and so on.. <receiver android:name=".Receiver" android:enabled="true" android:process=".e"> <intent-filter priority="100000" android:priority="100000"> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </receiver> Have anyone an idea? Thanks

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  • mysql way to make a lock in a php page

    - by Cris
    Hello, i have the following mysql table: myTable: id int auto_increment voucher int not null id_user int null I've populated voucher field with values from 1 to 100000 so i've got 100000 records; when a user clicks a button in a PHP page, i need to allocate a record for the user so i make something similar like: update myTable set id_user=XXX where voucher=(SELECT * FROM (SELECT MIN(voucher) FROM myTable WHERE id_user is null) v); The problem is that I don't use locks and i should use them because if two users click in the same moment i risk to assign the same voucher to different persons (2 updates in the same record so i lose 1 user) ... I think there must be a correct way to do this, can you help me please? Thanks ! cris

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  • If statement structure in php

    - by user305859
    Please help - i keep getting an error with this bit of code - it is probibly some thing small but dont seem to see what is wrong - while($row = mysql_fetch_array($result)) { $varp = $row['ustk_retail']; if ($varp<80000) { $o1 = 1; } if (($varp=80000) && ($varp<100000)) { $o2 = "1"; } if (($varp=100000) && ($varp<120000)) { $o3 = "1"; } if (($varp=120000) && ($varp<140000)) { $o4 = "1"; } if (($varp=140000) && ($varp<160000)) { $o5 = "1"; } if (($varp=160000) && ($varp<180000)) { $o6 = "1"; } if (($varp=180000) && ($varp<200000)) { $o7 = "1"; } if (($varp=200000) && ($varp<220000)) { $o8 = "1"; } if (($varp=220000) && ($varp<240000)) { $o9 = "1"; } if (($varp=240000) && ($varp<260000)) { $o10 = "1"; } if (($varp=260000) && ($varp<280000)) { $o11 = "1"; } if (($varp=280000) && ($varp<300000)) { $o12 = "1"; } if ($varp=300000) { $o13 = "1"; } } Any ideas would help

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  • How to do call function after client finishes download from tornado web server?

    - by Shabbyrobe
    I would like to be able to run some cleanup functions if and only if the client successfully completes the download of a file I'm serving using Tornado. I installed the firefox throttle tool and had it slow the connection down to dialup speed and installed this handler to generate a bunch of rubbish random text: class CrapHandler(BaseHandler): def get(self, token): crap = ''.join(random.choice(string.ascii_uppercase + string.digits) for x in range(100000)) self.write(crap) print "done" I get the following output from tornado immediately after making the request: done I 100524 19:45:45 web:772] 200 GET /123 (192.168.45.108) 195.10ms The client then plods along downloading for about 20 seconds. I expected that it would print "done" after the client was done. Also, if I do the following I get pretty much the same result: class CrapHandler(BaseHandler): @tornado.web.asynchronous def get(self, token): crap = ''.join(random.choice(string.ascii_uppercase + string.digits) for x in range(100000)) self.write(crap) self.finish() print "done" Am I missing something fundamental here? Can tornado even support what I'm trying to do? If not, is there an alternative that does?

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  • Interesting interview question. .Net

    - by rahul
    Coding Problem NumTrans There is an integer K. You are allowed to add to K any of its divisors not equal to 1and K. The same operation can be applied to the resulting number and so on. Notice that starting from the number 4, we can reach any composite number by applying several such operations. For example, the number 24 can be reached starting from 4 using 5 operations: 468121824 You will solve a more general problem. Given integers n and m, return the minimal number of the described operations necessary to transform n into m. Return -1 if m can't be obtained from n. Definition Method signature: int GetLeastCount (int n, int m) Constraints N will be between 4 and 100000, inclusive. M will be between N and 100000, inclusive. Examples 1) 4 576 Returns: 14 The shortest order of operations is: 468121827365481108162243324432576 2) 8748 83462 Returns: 10 The shortest order of operations is: 874813122196832624439366590497873283106834488346083462 3) 4 99991 Returns: -1 The number 99991 can't be obtained because it’s prime!

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  • JDOM Parser and Namespace how to get clean Content

    - by senzacionale
    MY xml: <?xml version="1.0"?> <company xmlns="http://www.xx.com/xx"> <staff> <firstname>yong</firstname> <lastname>mook kim</lastname> <nickname>mkyong</nickname> <salary>100000</salary> </staff> <staff> <firstname>low</firstname> <lastname>yin fong</lastname> <nickname>fong fong</nickname> <salary>200000</salary> </staff> </company> Reader in = new StringReader(message); Document document = (Document)saxBuilder.build(in); Element rootNode = document.getRootElement(); List<?> list = rootNode.getChildren("staff", Namespace.getNamespace("xmlns="http://www.infonova.com/MediationFeed"")); XMLOutputter outp = new XMLOutputter(); outp.setFormat(Format.getCompactFormat()); for (int ii = 0; ii < list.size(); ii++) { Element node = (Element)list.get(ii); StringWriter sw = new StringWriter(); outp.output(node.getContent(), sw); StringBuffer sb = sw.getBuffer(); String xml = sb.toString(); } but my xml object looks like this <firstname xmlns="http://www.xx.com/xx">yong</firstname> <lastname xmlns="http://www.xx.com/xx">mook kim</lastname> <nickname xmlns="http://www.xx.com/xx">mkyong</nickname> <salary xmlns="http://www.xx.com/xx">100000</salary> every elemnt has namespace. why this? i don't want namespace... I want the same output as is in xml example like <firstname>yong</firstname> <lastname>mook kim</lastname> <nickname>mkyong</nickname> <salary>100000</salary>

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  • Grails - How to format a value in a textfield into comma style such that it can be easily read?

    - by WaZ
    Hi there, I want to allow users enter numbers in textfield and once the textbox loses focus. The number is formatted with commas. e.g. User enters 100000 textfield looses focus value displayed: 100,000 How can I achieve this in Grails. I have looked at <g:formatNumber number="${myNumber}" format="\\$###,##0" /> But it doesnt solve my problem as the number is from a textfield. thanks Much appreciated.

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  • SQL conditional Pivot

    - by Coov
    Yes, this is another Pivot question... I've read through nearly all the previous questions and I can't seem to hack together a query that does what I need. Here is what my table looks like: FirmName Account Balance Pmt Revolving Installment Mortgage Amex 12345 10000 2000 1 0 0 Discover 54321 20000 4000 1 0 0 Chase 13579 100000 1500 0 0 1 Wells Fargo 2468 40000 900 0 1 0 The last three bit columns (Revolving, Installment, & Mortgage) dictate how the columns should be rolled up into a type. Each result requires three columns based on the type and its row count. The outcome should be one row with many columns. Here is what the result should look like: Revolving1_Firm Revolving1_Balance Revolving1_Pmt Revolving2_Firm Revolving2_Balance Revolving2_Pmt Realestate1_Firm Realestate1_Balance Realestate1_Pmt Vehicle1_Firm Vehicle1_Balance Vehicle1_Pmt Amex 10000 2000 Discover 20000 4000 Chase 100000 1500 Wells Fargo 40000 900 How do you pivot based on the bit fields (Revolving, Installment, & Mortgage) and retain the proper count so that that each column gets count # appended to it?

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  • map is not showing correct location in my blackberry applications

    - by Ali
    I am calling blackberry map by converting the real coordinates as you can see public static void showMap(String latitude,String longatude){ try{ int specailLatitude=(int)(Double.parseDouble(latitude))*100000; int specailLongatude=(int)(Double.parseDouble(longatude))*100000; MapView mapView=new MapView(); mapView.setLatitude(specailLatitude); mapView.setLongitude(specailLongatude); mapView.setZoom(07); MapsArguments arg=new MapsArguments(mapView); Invoke.invokeApplication(Invoke.APP_TYPE_MAPS, arg); }catch(Exception e){ CustomUtility.showToast("Map is not available "+e.getMessage()); } }// end of the showMap but problem is this its now showing correct location , it always shows same location in UAE , please help that i am converting correctly ?

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  • Errors with large data sources

    - by The Sheek Geek
    I'm doing some benchmarking on large data sources and binding/exporting data for reporting. I started with using a data set, filling it with 100000 rows and then attempting to open a crystal report with the retrieved data. I noticed that the data set filled just fine (took about 779 milliseconds) however, when attempting to export the data to the report or even bind to a gridview the application would fail with an OutOfMemoryException. Does anyone experienced this before or have an idea of how to get around it? It is very possible that clients will run reports for years worth of data and 100000 rows are not inconceivable. The application and the benchmark code are written in C# using ORACLE and SQL Server databases. I still have some data sources to test, but would like to know how to get around this just in case I don't find a better solution.

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  • R: Cut and labels/breaks length conflict

    - by AkselO
    I am working with the cut function to prep data for a barplot histogram but keep running into a seeming inconsistency between my labels and breaks: Error in cut.default(sample(1:1e+05, 500, T), breaks = sq, labels = sprintf("$%.0f", : labels/breaks length conflict Here is an example. I pretend that it is income data, using a sequence of 0 to $100,000 in bins of $10,000. I use the same variable to generate both breaks and labels, with minor formating on the label side. I thought they might for some reason have different lengths when comparing to a character vector, but they appear to have the same length, still. > sq<-seq(0,100000,10000) > cut(sample(1:100000, 500, T),breaks=sq,labels=sprintf("$%.0f",sq)) > length(sprintf("$%.0f",sq)) [1] [11] > length(sq) [1] [11]

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  • GeoIP and Nginx

    - by JavierMartinez
    I have a nginx with geoip, but it is not working rightly. The issue is the next: Nginx are getting geodata from $_SERVER['REMOTE_ADDR'] instead of $_SERVER['HTTP_X_HAPROXY_IP'], which have the real client ip. So, the reported geodata belongs to my server ip instead of client ip. Does anybody where could be the error to fix it? Nginx version and compiled modules: nginx -V nginx version: nginx/1.2.3 TLS SNI support enabled configure arguments: --prefix=/etc/nginx --conf-path=/etc/nginx/nginx.conf --error-log- path=/var/log/nginx/error.log --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-log-path=/var/log/nginx/access.log --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --lock-path=/var/lock/nginx.lock --pid-path=/var/run/nginx.pid --with-pcre-jit --with-debug --with-file-aio --with-http_addition_module --with-http_dav_module --with-http_geoip_module --with-http_gzip_static_module --with-http_image_filter_module --with-http_realip_module --with-http_secure_link_module --with-http_stub_status_module --with-http_ssl_module --with-http_sub_module --with-http_xslt_module --with-ipv6 --with-sha1=/usr/include/openssl --with-md5=/usr/include/openssl --with-mail --with-mail_ssl_module --add-module=/usr/src/nginx/source/nginx-1.2.3/debian/modules/nginx-auth-pam --add-module=/usr/src/nginx/source/nginx-1.2.3/debian/modules/nginx-echo --add-module=/usr/src/nginx/source/nginx-1.2.3/debian/modules/nginx-upstream-fair --add-module=/usr/src/nginx/source/nginx-1.2.3/debian/modules/nginx-dav-ext-module --add-module=/usr/src/nginx/source/nginx-1.2.3/debian/modules/nginx-syslog --add-module=/usr/src/nginx/source/nginx-1.2.3/debian/modules/nginx-cache-purge nginx site conf (frontend machine) server { root /var/www/storage; server_name ~^.*(\.)?mydomain.com$; if ($host ~ ^(.*)\.mydomain\.com$) { set $new_host $1.mydomain.com; } if ($host !~ ^(.*)\.mydomain\.com$) { set $new_host www.mydomain.com; } add_header Staging true; real_ip_header X-HAProxy-IP; set_real_ip_from 10.5.0.10/32; location /files { expires 30d; if ($uri !~ ^/files/([a-fA-F0-9]+)_(220|45)\.jpg$) { return 403; } rewrite ^/files/([a-fA-F0-9][a-fA-F0-9])([a-fA-F0-9][a-fA-F0-9])([a-fA-F0-9][a-fA-F0-9])([a-fA-F0-9][a-fA-F0-9])([a-fA-F0-9]+)_(220|45)\.jpg$ /files/$1/$2/$3/$4/$1$2$3$4$5_$6.jpg break; try_files $uri @to_backend; } location /assets { if ($uri ~ ^/assets/r([a-zA-Z0-9]+[^/])(/(css|js|fonts)/.*)) { rewrite ^/assets/r([a-zA-Z0-9]+[^/])/(css|js|fonts)/(.*)$ /assets/$2/$3 break; } try_files $uri @to_backend; } location / { proxy_set_header Host $new_host; proxy_set_header X-HAProxy-IP $remote_addr; proxy_pass http://10.5.0.10:8080; } location @to_backend { proxy_set_header Host $new_host; proxy_pass http://10.5.0.10:8080; } } nginx.conf (backend machine) http{ ... ## # GeoIP Config ## geoip_country /etc/nginx/geoip/GeoIP.dat; # the country IP database geoip_city /etc/nginx/geoip/GeoLiteCity.dat; # the city IP database ... } fastcgi_params (backend machine) ### SET GEOIP Variables ### fastcgi_param GEOIP_COUNTRY_CODE $geoip_country_code; fastcgi_param GEOIP_COUNTRY_CODE3 $geoip_country_code3; fastcgi_param GEOIP_COUNTRY_NAME $geoip_country_name; fastcgi_param GEOIP_CITY_COUNTRY_CODE $geoip_city_country_code; fastcgi_param GEOIP_CITY_COUNTRY_CODE3 $geoip_city_country_code3; fastcgi_param GEOIP_CITY_COUNTRY_NAME $geoip_city_country_name; fastcgi_param GEOIP_REGION $geoip_region; fastcgi_param GEOIP_CITY $geoip_city; fastcgi_param GEOIP_POSTAL_CODE $geoip_postal_code; fastcgi_param GEOIP_CITY_CONTINENT_CODE $geoip_city_continent_code; fastcgi_param GEOIP_LATITUDE $geoip_latitude; fastcgi_param GEOIP_LONGITUDE $geoip_longitude; haproxy.conf (frontend machine) defaults log global option forwardfor option httpclose mode http retries 3 option redispatch maxconn 4096 contimeout 100000 clitimeout 100000 srvtimeout 100000 listen cluster_webs *:8080 mode http option tcpka option httpchk option httpclose option forwardfor balance roundrobin server backend-stage 10.5.0.11:80 weight 1 $_SERVER dump: http://paste.laravel.com/7dy Where 10.5.0.10 is frontend private ip and 10.5.0.11 backend private ip

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  • Google I/O 2011: JavaScript Programming in the Large with Closure Tools

    Google I/O 2011: JavaScript Programming in the Large with Closure Tools Michael Bolin Most developers who have tinkered with JavaScript could not imagine writing 1000 lines of code in such a language, let alone 100000. Yet that is exactly what Google engineers have done using a suite of JavaScript tools named "Closure" to produce many of the most popular and sophisticated applications on the Web, such as Gmail and Google Maps. From: GoogleDevelopers Views: 4915 35 ratings Time: 57:07 More in Science & Technology

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  • C#: LINQ vs foreach - Round 1.

    - by James Michael Hare
    So I was reading Peter Kellner's blog entry on Resharper 5.0 and its LINQ refactoring and thought that was very cool.  But that raised a point I had always been curious about in my head -- which is a better choice: manual foreach loops or LINQ?    The answer is not really clear-cut.  There are two sides to any code cost arguments: performance and maintainability.  The first of these is obvious and quantifiable.  Given any two pieces of code that perform the same function, you can run them side-by-side and see which piece of code performs better.   Unfortunately, this is not always a good measure.  Well written assembly language outperforms well written C++ code, but you lose a lot in maintainability which creates a big techncial debt load that is hard to offset as the application ages.  In contrast, higher level constructs make the code more brief and easier to understand, hence reducing technical cost.   Now, obviously in this case we're not talking two separate languages, we're comparing doing something manually in the language versus using a higher-order set of IEnumerable extensions that are in the System.Linq library.   Well, before we discuss any further, let's look at some sample code and the numbers.  First, let's take a look at the for loop and the LINQ expression.  This is just a simple find comparison:       // find implemented via LINQ     public static bool FindViaLinq(IEnumerable<int> list, int target)     {         return list.Any(item => item == target);     }         // find implemented via standard iteration     public static bool FindViaIteration(IEnumerable<int> list, int target)     {         foreach (var i in list)         {             if (i == target)             {                 return true;             }         }           return false;     }   Okay, looking at this from a maintainability point of view, the Linq expression is definitely more concise (8 lines down to 1) and is very readable in intention.  You don't have to actually analyze the behavior of the loop to determine what it's doing.   So let's take a look at performance metrics from 100,000 iterations of these methods on a List<int> of varying sizes filled with random data.  For this test, we fill a target array with 100,000 random integers and then run the exact same pseudo-random targets through both searches.                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     Any         10       26          0.00046             30.00%     Iteration   10       20          0.00023             -     Any         100      116         0.00201             18.37%     Iteration   100      98          0.00118             -     Any         1000     1058        0.01853             16.78%     Iteration   1000     906         0.01155             -     Any         10,000   10,383      0.18189             17.41%     Iteration   10,000   8843        0.11362             -     Any         100,000  104,004     1.8297              18.27%     Iteration   100,000  87,941      1.13163             -   The LINQ expression is running about 17% slower for average size collections and worse for smaller collections.  Presumably, this is due to the overhead of the state machine used to track the iterators for the yield returns in the LINQ expressions, which seems about right in a tight loop such as this.   So what about other LINQ expressions?  After all, Any() is one of the more trivial ones.  I decided to try the TakeWhile() algorithm using a Count() to get the position stopped like the sample Pete was using in his blog that Resharper refactored for him into LINQ:       // Linq form     public static int GetTargetPosition1(IEnumerable<int> list, int target)     {         return list.TakeWhile(item => item != target).Count();     }       // traditionally iterative form     public static int GetTargetPosition2(IEnumerable<int> list, int target)     {         int count = 0;           foreach (var i in list)         {             if(i == target)             {                 break;             }               ++count;         }           return count;     }   Once again, the LINQ expression is much shorter, easier to read, and should be easier to maintain over time, reducing the cost of technical debt.  So I ran these through the same test data:                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile   10       41          0.00041             128%     Iteration   10       18          0.00018             -     TakeWhile   100      171         0.00171             88%     Iteration   100      91          0.00091             -     TakeWhile   1000     1604        0.01604             94%     Iteration   1000     825         0.00825             -     TakeWhile   10,000   15765       0.15765             92%     Iteration   10,000   8204        0.08204             -     TakeWhile   100,000  156950      1.5695              92%     Iteration   100,000  81635       0.81635             -     Wow!  I expected some overhead due to the state machines iterators produce, but 90% slower?  That seems a little heavy to me.  So then I thought, well, what if TakeWhile() is not the right tool for the job?  The problem is TakeWhile returns each item for processing using yield return, whereas our for-loop really doesn't care about the item beyond using it as a stop condition to evaluate. So what if that back and forth with the iterator state machine is the problem?  Well, we can quickly create an (albeit ugly) lambda that uses the Any() along with a count in a closure (if a LINQ guru knows a better way PLEASE let me know!), after all , this is more consistent with what we're trying to do, we're trying to find the first occurence of an item and halt once we find it, we just happen to be counting on the way.  This mostly matches Any().       // a new method that uses linq but evaluates the count in a closure.     public static int TakeWhileViaLinq2(IEnumerable<int> list, int target)     {         int count = 0;         list.Any(item =>             {                 if(item == target)                 {                     return true;                 }                   ++count;                 return false;             });         return count;     }     Now how does this one compare?                         List<T> On 100,000 Iterations     Method         Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile      10       41          0.00041             128%     Any w/Closure  10       23          0.00023             28%     Iteration      10       18          0.00018             -     TakeWhile      100      171         0.00171             88%     Any w/Closure  100      116         0.00116             27%     Iteration      100      91          0.00091             -     TakeWhile      1000     1604        0.01604             94%     Any w/Closure  1000     1101        0.01101             33%     Iteration      1000     825         0.00825             -     TakeWhile      10,000   15765       0.15765             92%     Any w/Closure  10,000   10802       0.10802             32%     Iteration      10,000   8204        0.08204             -     TakeWhile      100,000  156950      1.5695              92%     Any w/Closure  100,000  108378      1.08378             33%     Iteration      100,000  81635       0.81635             -     Much better!  It seems that the overhead of TakeAny() returning each item and updating the state in the state machine is drastically reduced by using Any() since Any() iterates forward until it finds the value we're looking for -- for the task we're attempting to do.   So the lesson there is, make sure when you use a LINQ expression you're choosing the best expression for the job, because if you're doing more work than you really need, you'll have a slower algorithm.  But this is true of any choice of algorithm or collection in general.     Even with the Any() with the count in the closure it is still about 30% slower, but let's consider that angle carefully.  For a list of 100,000 items, it was the difference between 1.01 ms and 0.82 ms roughly in a List<T>.  That's really not that bad at all in the grand scheme of things.  Even running at 90% slower with TakeWhile(), for the vast majority of my projects, an extra millisecond to save potential errors in the long term and improve maintainability is a small price to pay.  And if your typical list is 1000 items or less we're talking only microseconds worth of difference.   It's like they say: 90% of your performance bottlenecks are in 2% of your code, so over-optimizing almost never pays off.  So personally, I'll take the LINQ expression wherever I can because they will be easier to read and maintain (thus reducing technical debt) and I can rely on Microsoft's development to have coded and unit tested those algorithm fully for me instead of relying on a developer to code the loop logic correctly.   If something's 90% slower, yes, it's worth keeping in mind, but it's really not until you start get magnitudes-of-order slower (10x, 100x, 1000x) that alarm bells should really go off.  And if I ever do need that last millisecond of performance?  Well then I'll optimize JUST THAT problem spot.  To me it's worth it for the readability, speed-to-market, and maintainability.

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  • Insert Or update (aka Replace or Upsert)

    - by Davide Mauri
    The topic is really not new but since it’s the second time in few days that I had to explain it different customers, I think it’s worth to make a post out of it. Many times developers would like to insert a new row in a table or, if the row already exists, update it with new data. MySQL has a specific statement for this action, called REPLACE: http://dev.mysql.com/doc/refman/5.0/en/replace.html or the INSERT …. ON DUPLICATE KEY UPDATE option: http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html With SQL Server you can do the very same using a more standard way, using the MERGE statement, with the support of Row Constructors. Let’s say that you have this table: CREATE TABLE dbo.MyTargetTable (     id INT NOT NULL PRIMARY KEY IDENTITY,     alternate_key VARCHAR(50) UNIQUE,     col_1 INT,     col_2 INT,     col_3 INT,     col_4 INT,     col_5 INT ) GO INSERT [dbo].[MyTargetTable] VALUES ('GUQNH', 10, 100, 1000, 10000, 100000), ('UJAHL', 20, 200, 2000, 20000, 200000), ('YKXVW', 30, 300, 3000, 30000, 300000), ('SXMOJ', 40, 400, 4000, 40000, 400000), ('JTPGM', 50, 500, 5000, 50000, 500000), ('ZITKS', 60, 600, 6000, 60000, 600000), ('GGEYD', 70, 700, 7000, 70000, 700000), ('UFXMS', 80, 800, 8000, 80000, 800000), ('BNGGP', 90, 900, 9000, 90000, 900000), ('AMUKO', 100, 1000, 10000, 100000, 1000000) GO If you want to insert or update a row, you can just do that: MERGE INTO     dbo.MyTargetTable T USING     (SELECT * FROM (VALUES ('ZITKS', 61, 601, 6001, 60001, 600001)) Dummy(alternate_key, col_1, col_2, col_3, col_4, col_5)) S ON     T.alternate_key = S.alternate_key WHEN     NOT MATCHED THEN     INSERT VALUES (alternate_key, col_1, col_2, col_3, col_4, col_5) WHEN     MATCHED AND T.col_1 != S.col_1 THEN     UPDATE SET         T.col_1 = S.col_1,         T.col_2 = S.col_2,         T.col_3 = S.col_3,         T.col_4 = S.col_4,         T.col_5 = S.col_5 ; If you want to insert/update more than one row at once, you can super-charge the idea using Table-Value Parameters, that you can just send from your .NET application. Easy, powerful and effective

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  • NFS: Server says "authenticated mount request", but client sees "access denied"

    - by zigdon
    I have two machine, an NFS server (RHEL) and a client (Debian). The server has NFS set up, exporting a particular directory: server:~$ sudo /usr/sbin/rpcinfo -p localhost program vers proto port 100000 2 tcp 111 portmapper 100000 2 udp 111 portmapper 100024 1 udp 910 status 100024 1 tcp 913 status 100021 1 udp 53391 nlockmgr 100021 3 udp 53391 nlockmgr 100021 4 udp 53391 nlockmgr 100021 1 tcp 32774 nlockmgr 100021 3 tcp 32774 nlockmgr 100021 4 tcp 32774 nlockmgr 100007 2 udp 830 ypbind 100007 1 udp 830 ypbind 100007 2 tcp 833 ypbind 100007 1 tcp 833 ypbind 100011 1 udp 999 rquotad 100011 2 udp 999 rquotad 100011 1 tcp 1002 rquotad 100011 2 tcp 1002 rquotad 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 4 udp 2049 nfs 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100003 4 tcp 2049 nfs 100005 1 udp 1013 mountd 100005 1 tcp 1016 mountd 100005 2 udp 1013 mountd 100005 2 tcp 1016 mountd 100005 3 udp 1013 mountd 100005 3 tcp 1016 mountd server$ cat /etc/exports /dir *.my.domain.com(ro) client$ grep dir /etc/fstab server.my.domain.com:/dir /dir nfs tcp,soft,bg,noauto,ro 0 0 All seems well, but when I try to mount, I see the following: client$ sudo mount /dir mount.nfs: access denied by server while mounting server.my.domain.com:/dir And on the server I see: server$ tail /var/log/messages Mar 15 13:46:23 server mountd[413]: authenticated mount request from client.my.domain.com:723 for /dir (/dir) What am I missing here? How should I be debugging this?

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  • Solaris: detect hotswap SATA disk insert

    - by growse
    What's the method used on Solaris to get the system to rescan for new disks that have been hot-plugged on a SATA controller? I've got an HP X1600 NAS which had 9 drives configred in a ZFS pool. I've added 3 disks, but the format command still only shows the original 9. When I plugged them in, I saw this: cpqary3: [ID 823470 kern.notice] NOTICE: Smart Array P212 Controller cpqary3: [ID 823470 kern.notice] Hot-plug drive inserted, Port=1I Box=1 Bay=12 cpqary3: [ID 479030 kern.notice] Configured Drive ? ....... NO cpqary3: [ID 100000 kern.notice] cpqary3: [ID 823470 kern.notice] NOTICE: Smart Array P212 Controller cpqary3: [ID 823470 kern.notice] Hot-plug drive inserted, Port=1I Box=1 Bay=11 cpqary3: [ID 479030 kern.notice] Configured Drive ? ....... NO cpqary3: [ID 100000 kern.notice] cpqary3: [ID 823470 kern.notice] NOTICE: Smart Array P212 Controller cpqary3: [ID 823470 kern.notice] Hot-plug drive inserted, Port=1I Box=1 Bay=10 cpqary3: [ID 479030 kern.notice] Configured Drive ? ....... NO But can't figure out how to get the format command to see them so I know they've been detected by the system.

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  • NFS: Server says "authenticated mount request", but client sees "access denied"

    - by zigdon
    I have two machine, an NFS server (RHEL) and a client (Debian). The server has NFS set up, exporting a particular directory: server:~$ sudo /usr/sbin/rpcinfo -p localhost program vers proto port 100000 2 tcp 111 portmapper 100000 2 udp 111 portmapper 100024 1 udp 910 status 100024 1 tcp 913 status 100021 1 udp 53391 nlockmgr 100021 3 udp 53391 nlockmgr 100021 4 udp 53391 nlockmgr 100021 1 tcp 32774 nlockmgr 100021 3 tcp 32774 nlockmgr 100021 4 tcp 32774 nlockmgr 100007 2 udp 830 ypbind 100007 1 udp 830 ypbind 100007 2 tcp 833 ypbind 100007 1 tcp 833 ypbind 100011 1 udp 999 rquotad 100011 2 udp 999 rquotad 100011 1 tcp 1002 rquotad 100011 2 tcp 1002 rquotad 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 4 udp 2049 nfs 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100003 4 tcp 2049 nfs 100005 1 udp 1013 mountd 100005 1 tcp 1016 mountd 100005 2 udp 1013 mountd 100005 2 tcp 1016 mountd 100005 3 udp 1013 mountd 100005 3 tcp 1016 mountd server$ cat /etc/exports /dir *.my.domain.com(ro) client$ grep dir /etc/fstab server.my.domain.com:/dir /dir nfs tcp,soft,bg,noauto,ro 0 0 All seems well, but when I try to mount, I see the following: client$ sudo mount /dir mount.nfs: access denied by server while mounting server.my.domain.com:/dir And on the server I see: server$ tail /var/log/messages Mar 15 13:46:23 server mountd[413]: authenticated mount request from client.my.domain.com:723 for /dir (/dir) What am I missing here? How should I be debugging this?

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  • Large keepalive_requests values are severely slowing-down Nginx

    - by Gil
    When running a bacon (43-byte transparent pixel) load test on Nginx, we have tried several keepalive_requests values (from 10 to 100,000) and the optimal value seems to be 10. Here are the server HTTP headers of this tiny reply: HTTP/1.1 200 OK Server: nginx/1.5.6 Date: Wed, 23 Oct 2013 12:39:45 GMT Content-Type: image/gif Content-Length: 43 Last-Modified: Mon, 28 Sep 1970 06:00:00 GMT Connection: keep-alive Nginx is twice slower with keepalive_requests 100000 than with keepalive_requests 10. Can you help understanding that result? Or tell what we do wrong? For reference, here is the nginx.conf file.

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