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• ColdFusion static key/value list?

  - by richardtallent

  I have a database table that is a dictionary of defined terms -- key, value. I want to load the dictionary in the application scope from the database, and keep it there for performance (it doesn't change). I gather this is probably some sort of "struct," but I'm extremely new to ColdFusion (helping out another team). Then, I'd like to do some simple string replacement on some strings being output to the browser, looping through the defined terms and replacing the terms with some HTML to define the terms (a hover or a link, details to be worked out later, not important). Can anyone point me in the right direction of: How to define the stucture (if that is what I need for a key/value pair list) How to query at the application start-up and reuse the list properly The best way to do the string replacement

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• C#: When should I use TryParse?

  - by zxcvbnm

  I understand it doesn't throw an Exception and because of that it might be sightly faster, but also, you're most likely using it to convert input to data you can use, so I don't think it's used so often to make that much of difference in terms of performance. Anyway, the examples I saw are all along the lines of an if/else block with TryParse, the else returning an error message. And to me, that's basically the same thing as using a try/catch block with the catch returning an error message. So, am I missing something? Is there a situation when this is actually useful?

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• Restoring Sharepoint content database

  - by jude

  Hi, My WSS_Content database had got corrupt. And my pc was infected by virus. I had no backup of my WSS_Content database. So, I copied the corrupt database to a separete disk, formatted and reinstalled Sharepoint, with SQL Server 2005 as before (I'm using sharepoint 2007 ). I used Sytools Sharepoint Recovery tool, that i found on the net, which helped me restore my corrupt WSS_Content database. Now i want to set this content database as my "The content database" for my newly installed sharepoint. I tried the steps that i found in the link :- http://www.stationcomputing.com/scblogspace/Lists/Posts/Post.aspx?ID=40 I get stuck at step 3. Can anybody help me. I am really in a big mess. Would appreciate any help. Thanks, Jude Aloysius

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• Cannot play a recorded sound on device.

  - by B_

  I'm using the exact code from the iPhone Application Programming Guide Multimedia Support to use AVAudioRecorder to record a file to the disk and then AVAudioPlayer to load and play that file. This is working fine in the simulator but is not working on the device. The file gets loaded (we can see the NSTimeInterval) but does not play (play returns false). After it didn't work with the sample code from the website, we tried changing to a bunch of different codecs with no success. And of course, the sound is on. Thanks a bunch.

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• How do I use compiler intrinsic __fmul_?

  - by Eric Thoma

  I am writing a massively parallel GPU application. I have been optimizing it by hand. I received a 20% performance increase with _fdividef(x, y), and according to The Cuda C Programming Guide (section C.2.1), using similar functions for multiplication and adding is also beneficial. The function is stated as this: "_fmulrn,rz,ru,rd". __fdividef(x,y) was not stated with the arguments in brackets. I was wondering, what are those brackets? If I run the simple code: int t = __fmul_(5,4); I a compiler error about how _fmul is undefined. I have the CUDA runtime included, so I don't think it is a setup thing; rather it is something to do with those square brackets. How do I correctly use this function? Thank you.

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• Caching instances in a jee web app

  - by SibzTer

  Hi, Consider the scenario of a typical webapp with JSFs on the front and ejb3, with Hibernate as JPA provider, talking to backend database such as mysql, etc. The main user actions are login and mostly CRUD operations (minus any D(elete) operations). And the App Server is GlassFish of course. Given this scenario, how and where all would one go about providing caching to improve performance? From what I have googled, I have seen that hibernate provides some sort of caching through different cache providers. Is there any sort of caching that can be provided for the jsf pages? How about session beans or entity beans on the ejb side of things? Also, I just read about memcached and was wondering if this was something to consider?

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• "Out of Memory" error in Lotus Notes automation from VBA

  - by PowerUser

  This VBA function sporadically fails with a Notes automation error "Run-Time Error '7' Out of Memory". Naturally, when I try to manually reproduce it, everything runs fine. Function ToGMT(ByVal X As Date) As Date Static NtSession As NotesSession If NtSession Is Nothing Then Set NtSession = New NotesSession NtSession.Initialize End If (do stuff) End function To put this in context, this VBA function is being called by an Access query, 3-4 times per record, with 20,000 records. For performance reasons, the NotesSession has been made static. Any ideas why it is sporadically giving an out-of-memory error? (Also, I'm initiating the NotesSession just so I can convert a datetime to GMT using Lotus's rules. If you know a better way, I'm listening).

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• Images to video - converting to IplImage makes video blue

  - by user891908

  I want to create a video from images using opencv. The strange problem is that if i will write image (bmp) to disk and then load (cv.LoadImage) it it renders fine, but when i try to load image from StringIO and convert it to IplImage, it turns video to blue. Heres the code: import StringIO output = StringIO.StringIO() FOREGROUND = (0, 0, 0) TEXT = 'MY TEXT' font_path = 'arial.ttf' font = ImageFont.truetype(font_path, 18, encoding='unic') text = TEXT.decode('utf-8') (width, height) = font.getsize(text) # Create with background with place for text w,h=(600,600) contentimage=Image.open('0.jpg') background=Image.open('background.bmp') x, y = contentimage.size # put content onto background background.paste(contentimage,(((w-x)/2),0)) draw = ImageDraw.Draw(background) draw.text((0,0), text, font=font, fill=FOREGROUND) pi = background pi.save(output, "bmp") #pi.show() #shows image in full color output.seek(0) pi= Image.open(output) print pi, pi.format, "%dx%d" % pi.size, pi.mode cv_im = cv.CreateImageHeader(pi.size, cv.IPL_DEPTH_8U, 3) cv.SetData(cv_im, pi.tostring()) print pi.size, cv.GetSize(cv_im) w = cv.CreateVideoWriter("2.avi", cv.CV_FOURCC('M','J','P','G'), 1,(cv.GetSize(cv_im)[0],cv.GetSize(cv_im)[1]), is_color=1) for i in range(1,5): cv.WriteFrame(w, cv_im) del w

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• Is there such a thing as too many tables?

  - by Stacey

  I've been searching stackoverflow for about an hour now and couldn't find any topics related, so I apologize if this is a duplicate question. My inquery is this. Is there a point at which there are too many tables in a database? Even if the structure is well organized, thought out, and perfectly facilitates the design intent? I have a database that is quickly approaching 40 tables - about 10 main ones, and over 30 ancillary tables (junction tables, 'enumeration' tables, etc). Am I just a bad developer - or should I be trying something different? It seems like so many to me, I'm really afraid at how it will impact the performance of the project. I have done a lot of condensing where possible, grouped similar things where possible, etc. The database is built in MS-SQL 2008.

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• Copying data from STDOUT to a remote machine using SFTP

  - by freddie

  In order to backup large database partitions to a remote machine using SFTP, I'd like to use the databases dump command and send it directly over using SFTP to a remote location. This is useful when needing to dump large data sets when you don't have enough local disk space to create the backup file, and then copy it to a remote location. I've tried using python + paramiko which provides this functionality, but the performance much worse than using the native openssh/sftp binary to transfer files. Does anyone have any idea on how to do this either with the native sftp client on linux, or some library like paramiko? (but one that performs close to the native sftp client)?

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• Download and write .tar.gz files without corruption.

  - by arbales

  I've tried numerous ways of downloading files, specifically .zip and .tar.gz, with Ruby and write them to the disk. I've found that the file appears to be the same as the reference (in size), but the archives refuse to extract. What I'm attempting now is: Thanks! def download_request(url, filePath:path, progressIndicator:progressBar) file = File.open(path, "w+") begin Net::HTTP.get_response URI.parse(url) do |response| if response['Location']!=nil puts 'Direct to: ' + response['Location'] return download_request(response['Location'], filePath:path, progressIndicator:progressBar) end # some stuff response.read_body do |segment| file.write(segment) # some progress stuff. end end ensure file.close end end download_request("http://github.com/jashkenas/coffee-script/tarball/master", filePath:"tarball.tar.gz", progressIndicator:nil)

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• Decoupling into DAL and BLL - my concerns.

  - by novice_man

  Hi, In many posts concerning this topic I come across very simple examples that do not answer my question. Let's say a have a document table and user table. In DAL written in ADO.NET i have a method to retries all documents for some criteria. Now I the UI I have a case where I need to show this list along with the names of the creator. Up to know I have it done with one method in DAL containig JOIN statement. However eveytime I have such a complex method i have to do custom mapping to some object that doesn't mark 1:1 to DB. Should it be put into another layer ? If so then I will have to resing from join query for iteration through results and querying each document author. . . which doen't make sense... (performance) what is the best approach for such scenarios ?

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• NSMutableSet addObject question

  - by Jacob Relkin

  I've got a class that wraps around an NSMutableSet object, and I have an instance method that adds objects (using the addObject: method) to the NSMutableSet. This works well, but I'm smelling a performance hitch because inside the method i'm explicitly calling containsObject: before adding the object to the set. Three part question: Do I need to be calling containsObject: before I add an object to the set? If so, then what actual method should I be using, containsObject or containsObjectIdenticalTo:? If that is not so, what contains method gets invoked under the hood of addObject:? This is important to me because if I pass an object to containsObject: it would return true, but if I pass it to containsObjectIdenticalTo: it would return false.

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• Algorithms for modern hardware?

  - by Jurily

  Once again, I find myself with a set of broken assumptions. The article itself is about a 10x performance gain by modifying a proven-optimal algorithm to account for virtual memory: What good is an O(log2(n)) algorithm if those operations cause page faults and slow disk operations? For most relevant datasets an O(n) or even an O(n^2) algorithm, which avoids page faults, will run circles around it. Are there more such algorithms around? Should we re-examine all those fundamental building blocks of our education? What else do I need to watch out for when writing my own?

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• For what purpose does java have a float primitive type?

  - by Roman

  I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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• Threading vs single thread

  - by user177883

  Is it always guaranteed that a multi-threaded application would run faster than a single threaded application? I have two threads that populates data from a data source but different entities (eg: database, from two different tables), seems like single threaded version of the application is running faster than the version with two threads. Why would the reason be? when i look at the performance monitor, both cpu s are very spikey ? is this due to context switching? what are the best practices to jack the CPU and fully utilize it? I hope this is not ambiguous.

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• Which data structure for List of objects + datagrid wiev

  - by Martin

  Hi, I have to develop a code which will store a list of objects, as example below 101, value 11, value 12, value 13 ...etc 102, value 21, value 22, value 23 ...etc 103, value 31, value 32, value 33 ...etc 104, value 41, value 42, value 43 ...etc Now, the difficulty is, that first column is an identifier, and whole table should always be sorted by it. Easy access to each element is required. Additionally, list should be easily updated, and extended by adding element at the end as well as in front and still keep being sorted by first column. Finally, I would like to be able to display values of the above in datagridview. What is most important is a performance of the implementation, as rows will be updated many times per second, and datagridview should be able to display all changes immediately. I was thinking about creating class for the values, and then a Dictionary but encountered a problem with displaying values in gridview. What would be the most optimal way of implementing the code? Thanks in advance Martin

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• mounting without -o loop

  - by jumpinjoe

  Hi, I have written a dummy (ram disk) block device driver for linux kernel. When the driver is loaded, I can see it as /dev/mybd. I can successfully transfer data onto it using dd command, compare the copied data successfully. The problem is that when I create ext2/3 filesystem on it, I have to use -o loop option with the mount command. Otherwise mount fails with following result: mount: wrong fs type, bad option, bad superblock on mybd, missing codepage or helper program, or other error What could be the problem? Please help. Thanks.

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• Why are gettimeofday() intervals occasionally negative?

  - by Andres Jaan Tack

  I have an experimental library whose performance I'm trying to measure. To do this, I've written the following: struct timeval begin; gettimeofday(&begin, NULL); { // Experiment! } struct timeval end; gettimeofday(&end, NULL); // Print the time it took! std::cout << "Time: " << 100000 * (end.tv_sec - begin.tv_sec) + (end.tv_usec - begin.tv_usec) << std::endl; Occasionally, my results include negative timings, some of which are nonsensical. For instance: Time: 226762 Time: 220222 Time: 210883 Time: -688976 What's going on?

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• How to pull a RANDOM and UNIQUE record from SQL via LINQ.

  - by Jeremy H

  Okay, I found lots of posts on SO about how to pull a RANDOM item from the database when using LINQ. There seems to be a couple of differnet ways to handle this. What I need to do though is pull a RANDOM item from the database that the user has not seen before. The data I am pulling from the database is very small. Is there any way I can just hit the database once for 1000 records and then randomly scroll through those? Should I put a cookie on the users system recording the IDs of which items they have seen, pull a random record, check to see if it is seen and if so, pull from the database again? That seems like performance issues just waiting to happen. I don't expect anyone to code it for me, I am just looking for concepts and pointing in the right direction of how I should go about this. Need more details? Just let me know!

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• How to roll my own index in c#?

  - by bill seacham

  I need a faster way to create an index file. The application generates pairs of items to be indexed. I currently add each pair as it is generated to a sorted dictionary and then write it out to a disk file. This works well until the number of items added exceeds one million, at which time it slows to the point that is unacceptable. There can be as many as three million data items to be indexed. I prefer to avoid a database because I do not want to significantly increase the size of the deployment package, which is now less than one-half of one megabyte. I tried Access but it is even slower than the sorted dictionary -if it had an efficient bulk load utility then that might work, but I do not find such a tool for Access. Is there a better way to roll my own index?

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• How bad is opening and closing a SQL connection for several times? What is the exact effect?

  - by Eren

  For example, I need to fill lots of DataTables with SQLDataAdapter's Fill() method: DataAdapter1.Fill(DataTable1); DataAdapter2.Fill(DataTable2); DataAdapter3.Fill(DataTable3); DataAdapter4.Fill(DataTable4); DataAdapter5.Fill(DataTable5); .... .... Even all the dataadapter objects use the same SQLConnection, each Fill method will open and close the connection unless the connection state is already open before the method call. What I want to know is how does unnecessarily opening and closing SQLConnections affect the performance of the application. How much does it need to scale to see the bad effects of this problem (100,000s of concurrent users?). In a mid-size website (daily 50000 users) does it worth bothering and searching for all the Fill() calls, keeping them together in the code and opening the connection before any Fill() call and closing afterwards?

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• Using Rails and Rspec, how do you test that the database is not touched by a method

  - by Will Tomlins

  So I'm writing a test for a method which for performance reasons should achieve what it needs to achieve without using SQL queries. I'm thinking all I need to know is what to stub: describe SomeModel do describe 'a_getter_method' do it 'should not touch the database' do thing = SomeModel.create something_inside_rails.should_not_receive(:a_method_querying_the_database) thing.a_getter_method end end end EDIT: to provide a more specific example: class Publication << ActiveRecord::Base end class Book << Publication end class Magazine << Publication end class Student << ActiveRecord::Base has_many :publications def publications_of_type(type) #this is the method I am trying to test. #The test should show that when I do the following, the database is queried. self.publications.find_all_by_type(type) end end describe Student do describe "publications_of_type" do it 'should not touch the database' do Student.create() student = Student.first(:include => :publications) #the publications relationship is already loaded, so no need to touch the DB lambda { student.publications_of_type(:magazine) }.should_not touch_the_database end end end So the test should fail in this example, because the rails 'find_all_by' method relies on SQL.

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• Sharing [config] data across modules,functions

  - by williamstw

  I have some configuration data in a config file that I read off disk when the app starts. I need to make that configuration data available to other functions/modules in the application. I started down the path of looking into ets/mnesia to store the data on startup to make it shared among all processes, but then my inner voice cautioned me that there must be a more functional, erlang-y way to do this. The only alternate approach I've come up with so far is setting up a module that has an actor loop that reads the data on startup and responds to messages like {Key, From} and responds by From ! {ok,Value}. Then, I gave up and decided to ask... Thanks, --tim

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• Best way to store chat messages and files

  - by Stnaire

  I would like to know what do you think about storing chat messages in a database? I need to be able to bind other stuff to them (like files, or contacts) and using a database is the best way I see for now. The same question comes for files, because they can be bound to chat messages, I have to store them in the database too.. With thousands of messages and files I wonder about performance drops and database size. What do you think considering I'm using PHP with MySQL/Doctrine?

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