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  • Using SSLv3 - Enabling Strong Ciphers Server 2008

    - by Igor K
    I've disabled SSLv2 and SSLv3 is on. However I cannot connect to a remote server which fails with The client and server cannot communicate, because they do not possess a common algorithm Ran an SSL check (http://www.serversniff.net/sslcheck.php) on the remote server and ours, and noticed none of the ciphers they accept we have on our server. How can this be configured? (Windows Web Server 2008) Remote Server Accepted SSL ciphers: DHE-RSA-AES256-SHA AES256-SHA EDH-RSA-DES-CBC3-SHA DES-CBC3-SHA DHE-RSA-AES128-SHA AES128-SHA Our server by default accepts: DES-CBC3-SHA RC4-SHA RC4-MD5

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  • CentOS Vs Windows Server 2008

    - by Steve
    Hi, Apologies if the question appears ambiguous, I have little experience in this area and was after some informed opinions. I am deploying a test scenario of a server/client network and need to make some choices for Server. The client will be a Windows system as it meets the requirements for the client, the server choice has more room for selection. From my experience with Linux in general and the appealing nature of open source for low cost, security etc and the availability and performance of database and web server programs I have been considering CentOS as a server choice. I have the ability to make most of the choices of what software / server packages I wish to install. This includes Active Directory (something I have no experience with). How well does this operate with Windows clients? Am I being too selective and creating unnecessary complication by setting out not to use a Windows Server OS?

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  • SQL SERVER 2005 with Windows 7 Problems

    - by azamsharp
    First of all I restored the database from other server and now all the stored procedures are named as [azamsharp].[usp_getlatestposts]. I think [azamsharp] is prefixed since it was the user on the original server. Now, on my local machine this does not run. I don't want the [azamsharp] prefix with all the stored procedures. Also, when I right click on the Sproc I cannot even see the properties option. I am running the SQL SERVER 2005 on Windows 7. UPDATE: The weird thing is that if I access the production database from my machine I can see the properties option. So, there is really something wrong with Windows 7 security. UPDATE 2: When I ran the orphan users stored procedure it showed two users "azamsharp" and "dbo1". I fixed the "azamsharp" user but "dbo1" is not getting fixed. When I run the following script: exec sp_change_users_login 'update_one', 'dbo1', 'dbo1' I get the following error: Msg 15291, Level 16, State 1, Procedure sp_change_users_login, Line 131 Terminating this procedure. The Login name 'dbo1' is absent or invalid.

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  • How can I get a Windows 2008 print server to deploy to child domains?

    - by Tyler Benson
    I am setting up a print server for our company that has a parent domain and 2 child domains. The print server is on the parent domain and I have no problems getting the print server to deploy printers through group policy to users on its own domain. The problem I am having is that it isn't deploying the printers to users that are in it's child domains. Some other info that may help: I am not sharing or listing printers in the directory I have added pushprinterconnections.exe to the group policy login script Does anything come to mind?

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  • How to allow an internal server accept remote connections not through RD Gateway

    - by Matt Ahrens
    So, I help administrate a collection of servers running various windows server environments. We have a RD Gateway server, properly configured, to gatekeep for us. It does not have the other servers listed in it's server farm category, though. I just added a refurbished server for a non-profit development environment that is sharing the rack space and port. I would like this server to be accessible via remote connection, but not require RD gateway certification (I cannot add the users for this development server to our gateway since they do not work for the organization hosting the rack.) Is there any way for me to add this dev. server as an exception to which servers should require RD Gateway clearance, or otherwise let users bypass RD gateway credentials for this one machine? Thanks, and let me know if I am misinformed on how RD gateway works or anything. I am still learning.

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  • SQL2005 reporting server: intense security activity

    - by David Wimbush
    On my reporting server the Security log shows large numbers of Logon/Logoff events, often 10 or more, when you run pretty much any report in the Report Manager. Is this normal or is it a classic sign of having the wrong setup? Some system details: Windows Server 2003 R2 SP2, virtual server running under VMWare). SQL Server 2005 SP3 Standard Edition, running databases, Report Manager, and Ananlysis Services cubes. No other major services on the machine (i.e. it's not a domain controller, Exchange server or anything like that). Any ideas, please, guys?

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  • Windows Server Backup 2008 - Language Incompatibilities?

    - by Chris Walters
    I have 2 Windows 2008 Server R2 machines - one is Japanese language based and the other English. When I try to connect from the English language server using Windows Server Backup (snap-in) I get the following message: "An internal error has occurred in the backup engine or the computer that you are connected to remotely is running a version of backup application that is not compatible with the version on your local computer" Both claim to be running Version 1 of Windows Server Backup. Is remote connection to non-identical language server OSs a known problem? Specifically this is seen when attempting the "Connect To Another Server" in the action pane of Windows Server Backup.

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  • Ubuntu (desktop) server needed for school

    - by Dave Moody
    I need to build an ubuntu server for school, but I hate with a passion command line interfaces. I need a server with a desktop, like the current win server 2003 (which has crashed, ugh). This server needs to host the school lan domain, have an active directory, and handle the roaming profiles that the students and staff access through WinXP workstations. It also needs to work as a file server, maybe a print server. Can anyone advise me on how to create an Ubuntu server starting with Ubuntu Desktop edition? Much thanks if you respond... Dave.

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  • Micrsoft fax server not seeing new modem

    - by Tim Meers
    I recently added a new modem (a plain ol consumer grade one) to a fax server thats been up and running for years running on Microsoft Server 2003 fax services. The server currently has two modems, the new one is identical to one of the existing. After installing the new modem it showed up in the Fax Server Manager as a device but was not doing outbound faxes. (The server by default does not handle incoming.) So after a reboot the server no loger sees the modem in the Fax Server Manager but is listed as a device in device manager. I've attempted to restart just the fax service and even the whole box again but to no avail. Any one have any ideas on this one? Or any one with good links to resources for the fax service?

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  • Server 2008 Hyper-V User Accounts to access each other

    - by asn1981
    Hi, I have a windows server 2008 r2 with 3 hyper-v vm's IIS server Sql server 3 - Mail server I'm new to networking/server configuration. I have created a Virtual Network and can see each of the 3 VMs as well as the host on the network. I can connect from each VM to the host using the admin account. However, what would be the best (secure) way to create connections/accounts between the VMs, presumabely this shouldn't be done with an admin account but one with lesser priveledges. For example, to be able to access the SQL Server VM from the IIS server VM?

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  • Should we use Visual Studio 2010 for all SQL Server Database Development?

    - by Luke
    Our company currently has seven dedicated SQL Server 2008 servers each running an average of 10 databases. All databases have many stored procedures and UDFs that commonly reference other databases both on the same server and also across linked servers. We currently use SSMS for all database related administration and development but we have recently purchased Visual Studio 2010 primarily for ongoing C# WinForms and ASP.NET development. I have used VS2010 to perform schema comparisons when rolling out changes from a development server into production and I'm finding it great for this task. We would like to consider using VS2010 for all database development going forward but as far as I understand, we would have to set up ALL databases as projects because of the dependencies on linked servers etc. My question is, do you have any experience using VS2010 for database development in a similar environment? Is it easy to use in tandem with SSMS or is it a one way street once VS2010 projects have been set up for all databases? Can you make any recommendations/impart any experience with a similar scenario? Thanks, Luke

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  • simple document server built over Apache HTTP server

    - by abhinav
    Hi, I want to build a simple document server. The requirement for now is : provide a hierarchical directory structure for placing documents (like pdfs, doc files) that is accessible through a browser, and provide the facility to search for documents by name and then be able to download them from server. Right now, placing documents can be done manually (directly place the files into some designated directory). I can do the hierarchical structure part of the problem by adding some configs to Apache's httpd.conf file. Basically I create a root directory for documents and then give an alias to this directory in httpd.conf file. That way, I can browse the directory structure in my browser and also download files placed there. I can provide more detail on this if needed. However, it is the searching documents by name part that I am not able to get to a clear solution yet. I have a few ideas like integrating Lucene with Apache server, or maybe using CouchDb, but I am not very sure of all the details to solve this problem. Could anyone suggest some clear approach as to how to solve this part ?

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  • SQL Server Command Timeouts Timeout expired. The timeout period elapsed prior to completion of the o

    - by user104295
    Hi there, we've had a ASP.NET web application deployed for a number of years now.... last week we migrated to a slightly slower server to save some money. Now we're frequently getting command timeouts: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding This is understandable in that a slower server will take longer to produce results; take longer time and produce a timeout. Is there any system-wide way to get SqlClient to set a longer timeout? We cannot change the code, as it's everywhere... we're using multiple data access technologies as well. Maybe there's a default command timeout setting on a connection string? We just need to increase it by 30 seconds; we're happy to wait a bit longer for queries to return. thanks

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  • I'm asked to tune a long starting app into a short time period

    - by Jason
    Hi, I'm asked to shorten the startup period of a long starting app, however I have also to obligate to my managers to the amount of time i will reduce the startup - something like 10-20 seconds. As i'm new in my company I said I can obligate with timeframe of months (its a big server and I'm new and i plan to do lazy load + performance tuning). that answer was not accepted I was required to do some kind of a cache to hold important data in another server and then when my server starts up it would reach all its data from that cache - I find it a kind of a workaround and i don't really like it. do you like it? what do you think I should do? any suggestions? PS when i profiled the app i saw many small issues that make the startup long (like 2 minutes) it would not be a short process to fix all and to make lazy load. Any kind of suggestions would help. language - java. Thanks

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  • SQL Server 2008. Allow Remote Connections?

    - by George
    I have SQL Server 2000 and 2008 installed on a Windows XP Pro box. I can connect to both db instances locally. From another box, a Windows 7 box, I can connect to the SQL 2000 instance on the first box but I cannot connect to the 2008 instance using the same SQL Server authentication credentials that worked locally. Allow Remote Connections is set to TRUE for both the 2000 and 2008 database instances. What else can I look for to be able to connect to the remote 2008 instance from the Windows 7 box? I am trying to connect using Mgt Studio 2008.

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  • AdventureWorks2012 now available for all on SQL Azure

    - by jamiet
    Three days ago I tweeted this: Idea. MSFT could host read-only copies of all the [AdventureWorks] DBs up on #sqlazure for the SQL community to use. RT if agree #sqlfamily — Jamie Thomson (@jamiet) March 24, 2012 Evidently I wasn't the only one that thought this was a good idea because as you can see from the screenshot that tweet has, so far, been retweeted more than fifty times. Clearly there is a desire to see the AdventureWorks databases made available for the community to noodle around on so I am pleased to announce that as of today you can do just that - [AdventureWorks2012] now resides on SQL Azure and is available for anyone, absolutely anyone, to connect to and use* for their own means. *By use I mean "issue some SELECT statements". You don't have permission to issue INSERTs, UPDATEs, DELETEs or EXECUTEs I'm afraid - if you want to do that then you can get the bits and host it yourself. This database is free for you to use but SQL Azure is of course not free so before I give you the credentials please lend me your ears eyes for a short while longer. AdventureWorks on Azure is being provided for the SQL Server community to use and so I am hoping that that same community will rally around to support this effort by making a voluntary donation to support the upkeep which, going on current pricing, is going to be $119.88 per year. If you would like to contribute to keep AdventureWorks on Azure up and running for that full year please donate via PayPal to [email protected]: Any amount, no matter how small, will help. If those 50+ people that retweeted me beforehand all contributed $2 then that would just about be enough to keep this up for a year. If the community contributes more that we need then there are a number of additional things that could be done: Host additional databases (Northwind anyone??) Host in more datacentres (this first one is in Western Europe) Make a charitable donation That last one, a charitable donation, is something I would really like to do. The SQL Community have proved before that they can make a significant contribution to charitable orgnisations through purchasing the SQL Server MVP Deep Dives book and I harbour hopes that AdventureWorks on Azure can continue in that vein. So please, if you think AdventureWorks on Azure is something that is worth supporting please make a contribution. OK, with the prickly subject of begging for cash out of the way let me share the details that you need to connect to [AdventureWorks2012] on SQL Azure: Server mhknbn2kdz.database.windows.net  Database AdventureWorks2012 User sqlfamily Password sqlf@m1ly That user sqlfamily has all the permissions required to enable you to query away to your heart's content. Here is the code that I used to set it up: CREATE USER sqlfamily FOR LOGIN sqlfamily;CREATE ROLE sqlfamilyrole;EXEC sp_addrolemember 'sqlfamilyrole','sqlfamily';GRANT VIEW DEFINITION ON Database::AdventureWorks2012 TO sqlfamilyrole;GRANT VIEW DATABASE STATE ON Database::AdventureWorks2012 TO sqlfamilyrole;GRANT SHOWPLAN TO sqlfamilyrole;EXEC sp_addrolemember 'db_datareader','sqlfamilyrole'; You can connect to the database using SQL Server Management Studio (instructions to do that are provided at Walkthrough: Connecting to SQL Azure via the SSMS) or you can use the web interface at https://mhknbn2kdz.database.windows.net: Lastly, just for a bit of fun I created a table up there called [dbo].[SqlFamily] into which you can leave a small calling card. Simply execute the following SQL statement (changing the values of course): INSERT [dbo].[SqlFamily]([Name],[Message],[TwitterHandle],[BlogURI])VALUES ('Your name here','Some Message','your twitter handle (optional)','Blog URI (optional)'); [Id] is an IDENTITY field and there is a default constraint on [DT] hence there is no need to supply a value for those. Note that you only have INSERT permissions, not UPDATE or DELETE so make sure you get it right first time! Any offensive or distasteful remarks will of course be deleted :) Thank you for reading this far and have fun using AdventureWorks on Azure. I hope it proves to be useful for some of you. @jamiet AdventureWorks on Azure - Provided by the SQL Server community, for the SQL Server community!

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  • WebLogic Server?????????????·??·???????????????????????????????

    - by ???02
    WebLogic Server?????????????·??·???????????????????????????????WebLogic Server??????????????????·??·???????????????????????????????????????????????¦?????!? WebLogic Server??????????~ WebLogic Server??? ??????????????????!! ~¦???????????????????? ?????? ??????¦ WebLogic Server 10.3.5 ¦ Database 11g????????¦ Oracle WebLogic Server - ??   - WebLogic Server???  - WebLogic Server 10gR3 ?????Update  - ????????????????????????WebLogic Server?????  - WebLogic Server 11gR1 Update  - ?????????/Oracle????????  - ???¦ WebLogic Server - ???????   - ????/???????????????/?????/????????/JRF????/?????????????/???????/JDBC/RAC????¦ WebLogic Server - JDBC??????  - WebLogic Server?JDBC????????????????(?????????11gR1(10.3.3))  - ????:JDBC????????/??/??/????/??·????/??????  - ??????????GridLink for RAC????????????????¦ WebLogic Server - GridLink for RAC  - GridLink???·???? Oracle RAC?????????????????????????·???????·??????¦ WebLogic Server - Enterprise Grid Messaging  - Enterprise Grid Messaging???Oracle WebLogic Server??????????????????????Java Messaging Service (JMS)???????  - Oracle Advanced Queuing???Oracle RAC???????????Oracle????????????????¦ WebLogic Server - Web????  - Web??????/????/??  - WebLogic Server 10.3.x?Web???????  - JAX-WS Stack ???/JAX-RPC Stack ???  - JAX-WS??/JAX-WS?JAX-PRC???  - JAX-WS???WebLogic Web ?????????¦ WebLogic Server - ?????????????  - Java EE??/Java EE????????/Java EE????/WebLogic Server/JVM??????????·???????¦ WebLogic Server - ????????/????  -  ????????:??????????????????????????????????????/?????????????????/?????????EJB??????????????  - ???????·?????????????????????/HTTP????????/??????????????/???????????????

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  • How to improve WinForms MSChart performance?

    - by Marcel
    Hi all, I have created some simple charts (of type FastLine) with MSChart and update them with live data, like below: . To do so, I bind an observable collection of a custom type to the chart like so: // set chart data source this._Chart.DataSource = value; //is of type ObservableCollection<SpectrumLevels> //define x and y value members for each series this._Chart.Series[0].XValueMember = "Index"; this._Chart.Series[1].XValueMember = "Index"; this._Chart.Series[0].YValueMembers = "Channel0Level"; this._Chart.Series[1].YValueMembers = "Channel1Level"; // bind data to chart this._Chart.DataBind(); //lasts 1.5 seconds for 8000 points per series At each refresh, the dataset completely changes, it is not a scrolling update! With a profiler I have found that the DataBind() call takes about 1.5 seconds. The other calls are negligible. How can I make this faster? Should I use another type than ObservableCollection? An array probably? Should I use another form of data binding? Is there some tweak for the MSChart that I may have missed? Should I use a sparsed set of date, having one value per pixel only? Have I simply reached the performance limit of MSCharts? From the type of the application to keep it "fluent", we should have multiple refreshes per second. Thanks for any hints!

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  • Books and resources for Java Performance tuning - when working with databases, huge lists

    - by Arvind
    Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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  • Silverlight combobox performance issue

    - by Vinzz
    Hi, I'm facing a performance issue with a crowded combobox (5000 items). Rendering of the drop down list is really slow (as if it was computing all items before showing any). Do you have any trick to make this dropdown display lazy? Xaml code: <Grid x:Name="LayoutRoot"> <StackPanel Orientation="Horizontal" Width="200" Height="20"> <TextBlock>Test Combo </TextBlock> <ComboBox x:Name="fooCombo" Margin="5,0,0,0"></ComboBox> </StackPanel> </Grid> code behind: public MainPage() { InitializeComponent(); List<string> li = new List<string>(); int Max = 5000; for (int i = 0; i < Max; ++i) li.Add("Item - " + i); fooCombo.ItemsSource = li; }

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  • Increase performance on iphone at pdf rendering

    - by burki
    Hi! I have a UITableView, and in every cell there's displayed a UIImage created from a pdf. But now the performance is very bad. Here's my code I use to generate the UIImage from the PDF. Creating CGPDFDocumentRef and UIImageView (in cellForRowAtIndexPath method): ... CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), (CFStringRef)formula.icon, NULL, NULL); CGPDFDocumentRef documentRef = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL); CFRelease(pdfURL); UIImageView *imageView = [[UIImageView alloc] initWithImage:[self imageFromPDFWithDocumentRef:documentRef]]; ... Generate UIImage: - (UIImage *)imageFromPDFWithDocumentRef:(CGPDFDocumentRef)documentRef { CGPDFPageRef pageRef = CGPDFDocumentGetPage(documentRef, 1); CGRect pageRect = CGPDFPageGetBoxRect(pageRef, kCGPDFCropBox); UIGraphicsBeginImageContext(pageRect.size); CGContextRef context = UIGraphicsGetCurrentContext(); CGContextTranslateCTM(context, CGRectGetMinX(pageRect),CGRectGetMaxY(pageRect)); CGContextScaleCTM(context, 1, -1); CGContextTranslateCTM(context, -(pageRect.origin.x), -(pageRect.origin.y)); CGContextDrawPDFPage(context, pageRef); UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return finalImage; } What can I do to increas the speed and keep the memory low?

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  • Iterator performance contract (and use on non-collections)

    - by polygenelubricants
    If all that you're doing is a simple one-pass iteration (i.e. only hasNext() and next(), no remove()), are you guaranteed linear time performance and/or amortized constant cost per operation? Is this specified in the Iterator contract anywhere? Are there data structures/Java Collection which cannot be iterated in linear time? java.util.Scanner implements Iterator<String>. A Scanner is hardly a data structure (e.g. remove() makes absolutely no sense). Is this considered a design blunder? Is something like PrimeGenerator implements Iterator<Integer> considered bad design, or is this exactly what Iterator is for? (hasNext() always returns true, next() computes the next number on demand, remove() makes no sense). Similarly, would it have made sense for java.util.Random implements Iterator<Double>? Should a type really implement Iterator if it's effectively only using one-third of its API? (i.e. no remove(), always hasNext())

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  • Varying performance of MSVC release exe

    - by Andrew
    Hello everyone, I am curious what could be the reason for highly varying performance of the same executable. Sometimes, I run it and it takes 20 seconds and sometimes it is 110. Source is compiled with MSVC in Release mode with standard options. The code is here: vector<double> Un; vector<double> Ucur; double *pUn, *pUcur; ... // time marching for (old_time=time-logfreq, time+=dt; time <= end_time; time+=dt) { for (i=1, j=Un.size()-1, pUn=&Un[1], pUcur=&Ucur[1]; i < j; ++i, ++pUn, ++pUcur) { *pUcur = (*pUn)*(1.0-0.5*alpha*( *(pUn+1) - *(pUn-1) )); } Ucur[0] = (Un[0])*(1.0-0.5*alpha*( Un[1] - Un[j] )); Ucur[j] = (Un[j])*(1.0-0.5*alpha*( Un[0] - Un[j-1] )); Un = Ucur; }

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  • Python performance improvement request for winkler

    - by Martlark
    I'm a python n00b and I'd like some suggestions on how to improve the algorithm to improve the performance of this method to compute the Jaro-Winkler distance of two names. def winklerCompareP(str1, str2): """Return approximate string comparator measure (between 0.0 and 1.0) USAGE: score = winkler(str1, str2) ARGUMENTS: str1 The first string str2 The second string DESCRIPTION: As described in 'An Application of the Fellegi-Sunter Model of Record Linkage to the 1990 U.S. Decennial Census' by William E. Winkler and Yves Thibaudeau. Based on the 'jaro' string comparator, but modifies it according to whether the first few characters are the same or not. """ # Quick check if the strings are the same - - - - - - - - - - - - - - - - - - # jaro_winkler_marker_char = chr(1) if (str1 == str2): return 1.0 len1 = len(str1) len2 = len(str2) halflen = max(len1,len2) / 2 - 1 ass1 = '' # Characters assigned in str1 ass2 = '' # Characters assigned in str2 #ass1 = '' #ass2 = '' workstr1 = str1 workstr2 = str2 common1 = 0 # Number of common characters common2 = 0 #print "'len1', str1[i], start, end, index, ass1, workstr2, common1" # Analyse the first string - - - - - - - - - - - - - - - - - - - - - - - - - # for i in range(len1): start = max(0,i-halflen) end = min(i+halflen+1,len2) index = workstr2.find(str1[i],start,end) #print 'len1', str1[i], start, end, index, ass1, workstr2, common1 if (index > -1): # Found common character common1 += 1 #ass1 += str1[i] ass1 = ass1 + str1[i] workstr2 = workstr2[:index]+jaro_winkler_marker_char+workstr2[index+1:] #print "str1 analyse result", ass1, common1 #print "str1 analyse result", ass1, common1 # Analyse the second string - - - - - - - - - - - - - - - - - - - - - - - - - # for i in range(len2): start = max(0,i-halflen) end = min(i+halflen+1,len1) index = workstr1.find(str2[i],start,end) #print 'len2', str2[i], start, end, index, ass1, workstr1, common2 if (index > -1): # Found common character common2 += 1 #ass2 += str2[i] ass2 = ass2 + str2[i] workstr1 = workstr1[:index]+jaro_winkler_marker_char+workstr1[index+1:] if (common1 != common2): print('Winkler: Wrong common values for strings "%s" and "%s"' % \ (str1, str2) + ', common1: %i, common2: %i' % (common1, common2) + \ ', common should be the same.') common1 = float(common1+common2) / 2.0 ##### This is just a fix ##### if (common1 == 0): return 0.0 # Compute number of transpositions - - - - - - - - - - - - - - - - - - - - - # transposition = 0 for i in range(len(ass1)): if (ass1[i] != ass2[i]): transposition += 1 transposition = transposition / 2.0 # Now compute how many characters are common at beginning - - - - - - - - - - # minlen = min(len1,len2) for same in range(minlen+1): if (str1[:same] != str2[:same]): break same -= 1 if (same > 4): same = 4 common1 = float(common1) w = 1./3.*(common1 / float(len1) + common1 / float(len2) + (common1-transposition) / common1) wn = w + same*0.1 * (1.0 - w) return wn

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  • Haskell math performance

    - by Travis Brown
    I'm in the middle of porting David Blei's original C implementation of Latent Dirichlet Allocation to Haskell, and I'm trying to decide whether to leave some of the low-level stuff in C. The following function is one example—it's an approximation of the second derivative of lgamma: double trigamma(double x) { double p; int i; x=x+6; p=1/(x*x); p=(((((0.075757575757576*p-0.033333333333333)*p+0.0238095238095238) *p-0.033333333333333)*p+0.166666666666667)*p+1)/x+0.5*p; for (i=0; i<6 ;i++) { x=x-1; p=1/(x*x)+p; } return(p); } I've translated this into more or less idiomatic Haskell as follows: trigamma :: Double -> Double trigamma x = snd $ last $ take 7 $ iterate next (x' - 1, p') where x' = x + 6 p = 1 / x' ^ 2 p' = p / 2 + c / x' c = foldr1 (\a b -> (a + b * p)) [1, 1/6, -1/30, 1/42, -1/30, 5/66] next (x, p) = (x - 1, 1 / x ^ 2 + p) The problem is that when I run both through Criterion, my Haskell version is six or seven times slower (I'm compiling with -O2 on GHC 6.12.1). Some similar functions are even worse. I know practically nothing about Haskell performance, and I'm not terribly interested in digging through Core or anything like that, since I can always just call the handful of math-intensive C functions through FFI. But I'm curious about whether there's low-hanging fruit that I'm missing—some kind of extension or library or annotation that I could use to speed up this numeric stuff without making it too ugly.

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