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• How can a Delphi TPersistent object calculate its own deserialization time?

  - by mjustin

  For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": start of the deserialization process after the deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event So the log for TMyForm.Create(nil) could look like: - 00.000 instance created - 00.010 before deserialization - 01.823 after deserialization - 02.340 before OnFormCreate Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions.

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• Are there Adaptive Replacement Cache patent-free alternatives?

  - by aleccolocco

  An open source high-performance project I'm working on needs to keep a cache of parsed/compiled files. A plain LRU or a plain LFU wouldn't fit. Plain LRU wouldn't work as there will be remote batch/spider processes hitting the service regularly. Plain LFU wouldn't work because content will age. ARC seems like the perfect solution but since IBM holds patents to it at least one open source project dropped it. Are there any (good enough) alternatives? EDIT: I'm not looking for exactly the same thing, just something that could handle those two situations. Perhaps some simple strategy with timestamps and sources. There have to be many programmers who faced this situation before. That's why the "good enough" bit.

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• Reading ResultSet from multiple threads

  - by superdario

  Hello, In the database, I have a definition table that is read from the application once upon starting. This definition table rarely changes, so it makes sense to read it once and restart the application every time it changes. However, after the table is read (put into a ResultSet), it will be read by multiple handlers running in their own threads. How do you suggest to accomplish this? My idea was to populate a CachedRowSet, and then create a copy of this set (through the createCopy() method) for each handler every time a new request comes. Do you think this is wise? Does this offer a good performance? Thanks.

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• MySQL: Get unique values across multiple columns in alphabetical order

  - by RuCh

  Hey everyone, If my table looks like this: id | colA | colB | colC =========================== 1 | red | blue | yellow 2 | orange | red | red 3 | orange | blue | cyan What SELECT query do I run such that the results returned are: blue, cyan, orange, red, yellow Basically, I want to extract a collective list of distinct values across multiple columns and return them in alphabetical order. I am not concerned with performance optimization, because the results are being parsed to an XML file that will serve as a cache (database is hardly updated). So even a dirty solution would be fine. Thanks for any help!

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• Mysql query taking too much time

  - by aditya

  I have problem related to mysql database. i am linux webserver admin and i am facing a problem with a mysql query. The database is very small. I tried to track in logs and found that a query is taking minimum 5 sec to respond . The first page of site is coming from the database. Client are using cms. when the server gets some number of hits database server starts to give response very slowly and wait time increases from 5 sec to several seconds. I checked slow query logs { Query_time: 11.480138 Lock_time: 0.003837 Rows_sent: 921 Rows_examined: 3333 SET timestamp=1346656767; SELECT `Tender`.`id`, `Tender`.`department_id`, `Tender`.`title_english`, `Tender`.`content_english`, `Tender`.`title_hindi`, `Tender`.`content_hindi`, `Tender`.`file_name`, `Tender`.`start_publish`, `Tender`.`end_publish`, `Tender`.`publish`, `Tender`.`status`, `Tender`.`createdBy`, `Tender`.`created`, `Tender`.`modifyBy`, `Tender`.`modified` FROM `mcms_tenders` AS `Tender` WHERE `Tender`.`department_id` IN ( 31, 33, 32, 30 ); } Every line in the log is same only there is diff in Query time. Is there any way tweak the performance?

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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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• 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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• How to correct this glitch

  - by Rebol Tutorial

  I removed background: url(none); in my stylesheet because of load performance http://stackoverflow.com/questions/2577422/why-firebug-pretends-that-my-stylesheet-is-calling-my-xmlrpc The problem is that it now causes some glitch on css list. Any idea how to fix this ? Thanks. Update: picture below Tried to put background: none as suggested but didn't solve the problem/ ul.sidebar_list li ul li ul { margin: 0px; padding: 0px!important; float: left; width: 100%; list-style-type: none; background: none; }

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• Oracle SQL Update query takes days to update

  - by B Senthil Kumar

  I am trying to update a record in the target table based on the record coming in from source. For instance, if the incoming record is present in the target table I would update them in the target else I would simply insert. I have over one million records in my source while my target has 46 million records. The target table is partitioned based on calendar key. I implement this whole logic using Informatica. I find that the Informatica code is perfectly fine looking at the Informatica session log but its in the update it takes long time (more than 5 days to update one million records). Any suggestions as to what can be done on the scenario to improve the performance?

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• MySQL Many to Many with Unique keys and Update/Select if Exists otherwise Insert

  - by Jayrox

  In my goal to have a Many-to-Many relationship in my MySQL database I have arrived at another bridge to build. Current Tables: Users (id, name) Tags (id, name) User_Tags (user_id, tag_id) Here is the goal: I would like to have the ability to take a tag i.e: #fb and insert it into my Tags database which has a unique constraint on name and if the tag exists I would like to return it's id I would like to insert the tag.id and the current user's user.id into User_Tags. I do not have any unique constraints on the User_Tags table because I would like to be able to track the user's most commonly used tags and present them in a list ordered by frequency of use. I am currently developing this project in PHP using prepared statements. Additionally, performance is not currently an issue as my user count is still fairly small, but it is steadily growing and may be an issue in the future.

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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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• C++ Urban Myths

  - by Neil Butterworth

  I'm starting to write an article on what I'm calling "C++ Urban Myths" - that is, ideas and conceptions about C++ that are common but have no actual roots in reality. Some that I've come up with so far are: TR1 is part of standard C++ TR1 (technical Report #1) proposed a whole bunch of changes to C++. Unfortunately, it was never accepted. It is faster to use iterators to access a vector than operator[] Or vice versa. All tests I've carried out indicate the two are nearly identical in performance. The C++ Standard contains something called the STL It doesn't - neither "STL" nor "Standard Template Library" appear in the Standard. I'm wondering if the SO C++ community can come up with any better ones? Ideally, they should be expressible in a single sentence, and not involve any code. Edit: I guess I didn't make it clear enough that I was interested in myths believed by C++ developers, not misconceptions held by non-C++users. Oh well...

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• SDL versus GLFW?

  - by user697111

  What are the pros and cons to each? It seems they serve the same purpose. I have a few demos with each and they seem about the same. Performance or cross platform wise, is one better than the other? The only thing I notice is that SDL seems to have more "helper" libraries (fonts, images, mixer, built in sound support, etc). On its site, GLFW claims to be more "OpenGL" focused, but still have to use a GLEW to get any newer OpenGL features (same with SDL). I guess I'm leaning towards using SDL now (more mature, more features, more community). Are there any reasons I've missed why GLFW stands out and I should use it instead of SDL?

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• What are block expressions actually good for?

  - by Helper Method

  I just solved the first problem from Project Euler in JavaFX for the fun of it and wondered what block expressions are actually good for? Why are they superior to functions? Is it the because of the narrowed scope? Less to write? Performance? Here's the Euler example. I used a block here but I don't know if it actually makes sense // sums up all number from low to high exclusive which are divisible by a or b function sumDivisibleBy(a: Integer, b: Integer, high: Integer) { def low = if (a <= b) a else b; def sum = { var result = 0; for (i in [low .. <high] where i mod 3 == 0 or i mod 5 == 0) { result += i } result } } Does a block makes sense here?

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• Seeking tutorial: introduction to ODBC with Delphi

  - by mawg

  I have a lot of embedded C/C++/Ada experience and an outdated smattering of Delphi plus some database stuff. Now I have to implement an app in Delphi which can manipulate MySql, Oracle, maybe MS Access. In short, I need ODBC. I need to programmatically created a database, define its structure and populate its contents, then later query its existence and programmatically search. I would prefer not to use 3rd party components, unless there is a compelling reason to do so (performance ought not to be an issue for the app, it won't have much data or be run often, at least not in v1.0) . Can anyone point me at a tutorial which can get me up to speed? Thanks

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• Why don't scripting languages output Unicode to the Windows console?

  - by hippietrail

  The Windows console has been Unicode aware for at least a decade and perhaps as far back as Windows NT. However for some reason the major cross-platform scripting languages including Perl and Python only ever output various 8-bit encodings, requiring much trouble to work around. Perl gives a "wide character in print" warning, Pythong gives a charmap error and quits. Why on earth after all these years do they not just simply call the Win32 -W APIs that output UTF-16 Unicode instead of forcing everything through the ANSI/codepage bottleneck? Is it just that cross-platform performance is low priority? Is it that the languages use UTF-8 internally and find it too much bother to output UTF-16? Or are the -W APIs inherently broken to such a degree that they can't be used as-is?

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• How to implement Voting for Grails Domain Classes?

  - by userWebMobile

  I have a Book class and need to implement a yes/no voting functionality. My domain classes look like this: class Book { String title static hasMany = [votes: Vote] } class User { String name static hasMany = [votes: Vote] } class Vote { boolean yesVote static belongsTo = [user: User, book: Book] } What is the best way to implement a voting for the book class. I need the following informations: What is the average yesVote for a book over all votes (either yes or no)? How to check if a specific user has done a vote? What is the best way to implement the computation of the average yesVote such that the performance does not drop?

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• How to implement square root and exponentiation on arbitrary length numbers?

  - by tomp

  I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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• page control in flex(like php)

  - by Mahedi

  Hi, I'm new in flex. I have a design like this in one page have two option like this Hard & soft when i click hard(option) there will show three option(in php got to another page) like standard, square & pocket and in the page below BACK(when click this option it will back previous state(page)) option will be show When mouse over on any option's this will show its properties in any side of page when select any one of them it will go next step(page) for more performance. Soft option will work like hard option. Please help me with code example or tutorials. Best regard mahedi

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• Should we use a CSS frame work ? Are they worth it ?

  - by Gaurav M

  CSS frameworks have nice styles inbuilt and ask you to focuses on the grids but still there is a bit of dependency and lack of freedom it provide.. If I need to generate a webpage by looking on a PSD based mockup screen ..either i will use the classes provided by the framework but if that actual measurements does not exist I need to again specify my own rules that will add upto my CSS filesize and if performance is a constraint as always it is...you need not a big size file..though its in kb but every drop counts. Any comments and suggestions to use the framework in a best possible way.

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• ContextSwitchDeadlock Was Detected error in C#

  - by assassin

  Hi, I am running a C# application, and during run-time I get the following error: The CLR has been unable to transition from COM context 0x20e480 to COM context 0x20e5f0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Can anyone please help me out with the problem here? Thanks a lot.

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• A linq join combined with a regex

  - by Geert Beckx

  Is it possible to combine these 2 queries or would this make my code too complex? Also I think there should be a performance gain by combining these queries since I think in the near future my source table could be over 11000 records. This is what i came up with so far : Dim lit As LiteralControl ' check characters not in alphabet Dim r As New Regex("^[^a-zA-Z]+") Dim query = From o In source.ToTable _ Where r.IsMatch(o.Field(Of String)("nam")) lit = New LiteralControl(String.Format("letter: {0}, count: {1}<br />", "0-9", query.Count)) plhAlpabetLinks.Controls.Add(lit) Dim q = From l In "ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToLower.ToCharArray _ Group Join o In source.ToTable _ On l Equals o.Field(Of String)("nam").ToLowerInvariant(0) Into g = Group _ Select l, g.Count ' iterate the alphabet to generate all the links. For Each letter In q.AsEnumerable lit = New LiteralControl(String.Format("letter: {0}, count: {1}<br />", letter.l, letter.Count)) plhAlpabetLinks.Controls.Add(lit) Next Kind regards, G.

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• mod_perl memory leak

  - by marghi

  Hello, I recently discovered that one of our sites has a memory leak in it, it's very strange because it happened all of the sudden. I've used GTop to measure the memory size per process and it tells me that the real value is somewhere around 65 MB (on the server) per request and and additional 5 MB shared. I tried preloading the modules in the startup.pl file a indicated in the performance tuning article for mod_perl. Nothing happened if fact the shared memory decreased down to 3.7 MB, in this situation I thought that my application is leaking memory do before any line of code got executed I measured the memory just to find out that the total value is in fact 64 MB, my questions are: Is there a default preallocation of memory for each process? Is there a configuration issue? Is mod_perl leaking memory ? Thank you very much.

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• Filtering with joined tables

  - by viraptor

  I'm trying to get some query performance improved, but the generated query does not look the way I expect it to. The results are retrieved using: query = session.query(SomeModel). options(joinedload_all('foo.bar')). options(joinedload_all('foo.baz')). options(joinedload('quux.other')) What I want to do is filter on the table joined via 'first', but this way doesn't work: query = query.filter(FooModel.address == '1.2.3.4') It results in a clause like this attached to the query: WHERE foos.address = '1.2.3.4' Which doesn't do the filtering in a proper way, since the generated joins attach tables foos_1 and foos_2. If I try that query manually but change the filtering clause to: WHERE foos_1.address = '1.2.3.4' AND foos_2.address = '1.2.3.4' It works fine. The question is of course - how can I achieve this with sqlalchemy itself?

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• entity framework and dirty reads

  - by bryanjonker

  I have Entity Framework (.NET 4.0) going against SQL Server 2008. The database is (theoretically) getting updated during business hours -- delete, then insert, all through a transaction. Practically, it's not going to happen that often. But, I need to make sure I can always read data in the database. The application I'm writing will never do any types of writes to the data -- read-only. If I do a dirty read, I can always access the data; the worst that happens is I get old data (which is acceptable). However, can I tell Entity Framework to always use dirty reads? Are there performance or data integrity issues I need to worry about if I set up EF this way? Or should I take a step back and see about rewriting the process that's doing the delete/insert process?

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