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• immutable strings vs std::string

  - by Caspin

  I've recent been reading about immutable strings, here and here as well some stuff about why D chose immutable strings. There seem to be many advantages. trivially thread safe more secure more memory efficient in most use cases. cheap substrings (tokenizing and slicing) Not to mention most new languages have immutable strings, D2.0, Java, C#, Python, Ruby, etc. Would C++ benefit from immutable strings? Is it possible to implement an immutable string class in c++ (or c++0x) that would have all of these advantages?

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• Media Foundation: another way to call IMFActivate::ShutdownObject?

  - by KenC

  Hi, Here is a question about IMFActivate::ActivateObject and IMFActivate::ShutdownObject in Media Foundation. According to MSDN, the component that calls ActivateObject is responsible for calling ShutdownObject. But there are two examples not following this rule: http://msdn.microsoft.com/en-us/library/dd388503%28VS.85%29.aspx and http://msdn.microsoft.com/en-us/library/dd317912%28VS.85%29.aspx In these two examples, they call ActivateObject and then release IMFActivate interface without calling ShutdownObject method. This is going to lead to memory leaking, right? Or there is another way to release the resource occupied by the object? (Can I use IMFMediaSource::Shutdown to release the object instead of using IMFActivate::ShutdownObject) Thanks in advance.

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• Delphi VirtualStringTree - Check for Duplicates?

  - by Jeff

  Hello S.O! Yeah, I know I post a lot of questions, but thats because I either need assurance that I am doing it right, what I am doing wrong, or if I am totally clueless, and cant find anything in the documentation. Anyways, I am trying to check for duplicate nodes. Here is how I would want to do it: Loop thru my nodes, and compare each single node's text (record), but if I got many nodes, wouldnt that be too time and memory consuming? Would there be a better approach for this? Thanks! - Jeff.

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• render HTML (convert to bitmap)

  - by MK

  Can somebody recommend the best (and preferably portable) way to render HTML documents onto a bitmap? As far as I understand my main 2 options are WebKit and Gecko, but I wasn't able to find a good starting point on how to do it. When I last tried doing this 5 years ago, I ended up using Gecko to send the document to a printer, which is not really what I need. I need rendering to a in-memory bitmap. To clarify: server side, no Java, no .NET, batch processing, performance, not interactive, no Javascript.

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• Estimate serialization size of objects?

  - by Stefan K.

  In my thesis, I woud like to enhance messaging in a cluster. It's important to log runtime information about how big a message is (should I prefer processing local or remote). I could just find frameoworks about estimating the object memory size based on java instrumentation. I've tested classmexer, which didn't come close to the serialization size and sourceforge SizeOf. In a small testcase, SizeOf was around 10% wrong and 10x faster than serialization. (Still transient breaks the estimation completely and since e.g. ArrayList is transient but is serialized as an Array, it's not easy to patch SizeOf. But I could live with that) On the other hand, 10x faster with 10% error doesn't seem very good. Any ideas how I could do better?

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• How to stop a curl while requesting or stop the running php script?

  - by Chris

  I using url to request remote urls that sometimes may very slow or just down. In this case, my php scripts still waiting for the response, it makes apache has to many requests stay in memory and then overload. I need a way to stop curl requesting or stop running php script when specified time passed. I'd tried declare(), it makes no sense for curl. Can someone know how to solve it? BTW: what is the effect of CURLOPT_CONNECTTIMEOUT and CURLOPT_TIMEOUT? They don't work like what I think.

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• What's the best way to count unique visitors with Hadoop?

  - by beagleguy

  hey all, just getting started on hadoop and curious what the best way in mapreduce would be to count unique visitors if your logfiles looked like this... DATE siteID action username 05-05-2010 siteA pageview jim 05-05-2010 siteB pageview tom 05-05-2010 siteA pageview jim 05-05-2010 siteB pageview bob 05-05-2010 siteA pageview mike and for each site you wanted to find out the unique visitors for each site? I was thinking the mapper would emit siteID \t username and the reducer would keep a set() of the unique usersnames per key and then emit the length of that set. However that would be potentially storing millions of usernames in memory which doesn't seem right. Anyone have a better way? I'm using python streaming by the way thanks

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• plist vs static array

  - by morticae

  Generally, I use static arrays and dictionaries for containing lookup tables in my classes. However, with the number of classes creeping quickly into the hundreds, I'm hesitant to continue using this pattern. Even if these static collections are initialized lazily, I've essentially got a bounded memory leak going on as someone uses my app. Most of these are arrays of strings so I can convert strings into NSInteger constants that can be used with switch statements, etc. I could just recreate the array/dictionary on every call, but many of these functions are used heavily and/or in tight loops. So I'm trying to come up with a pattern that is both performant and not persistent. If I store the information in a plist, does the iphoneOS do anything intelligent about caching those when loaded? Do you have another method that might be related?

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• When getting substring in .Net, does the new string reference the same original string data or does

  - by Elan

  Assuming I have the following strings: string str1 = "Hello World!"; string str2 = str1.SubString(6, 5); // "World" I am hoping that in the above example str2 does not copy "World", but simply ends up being a new string that points to the same memory space only that it starts with an offset of 6 and a length of 5. In actuality I am dealing with some potentially very long strings and am interested in how this works behind the scenes for performance reasons. I am not familiar enaugh with IL to look into this.

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• Disk-based caching of dynamic images in IIS 7

  - by Daniel Schierbeck

  I'm writing an image server which needs to handle a relatively large number of concurrent requests (~5,000). The images being served are dynamically scaled down and cropped based on per-image specifications, which are queried from a database. The number of images is rather large, so an in-memory cache isn't viable (thrashing would most definitely occur). I'm using native caching in IIS 7 to avoid hitting the ASP.NET app which generates the images on-the-fly. I've looked around, but I couldn't find a simple way to configure IIS to store the cache on-disk -- is there such an option, or would I need to roll my own? I'd rather avoid placing the generated images in a public folder, so they can be served statically, since I would prefer to invalidate the cache entries using a query parameter (last-edit time from the database,) which doesn't seem possible to reconcile with static caching. I would love to get some feedback on this!

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• Groovy Grails, How do you stream or buffer a large file in a Controller's response?

  - by Julian Noye

  Hi Guys I have a controller that makes a connection to a url to retrieve a csv file. I am able to send the file in the response using the following code, this works fine. def fileURL = "www.mysite.com/input.csv" def thisUrl = new URL(fileURL); def connection = thisUrl.openConnection(); def output = connection.content.text; response.setHeader "Content-disposition", "attachment; filename=${'output.csv'}" response.contentType = 'text/csv' response.outputStream << output response.outputStream.flush() However I don't think this method is inappropriate for a large file, as the whole file is loaded into the controllers memory. I want to be able to read the file chunk by chunk and write the file to the response chunk by chunk. Any ideas?

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• How to use a dialog in an Excel shared addin

  - by user169867

  I'm writing a shared addin for Excel. It adds a CommandBarButton that when clicked opens a WPF window to collect some information from the user. I wanted to keep the same WPF dialog in memory and reuse it so that if the user clicks the CommandBarButton again their previous values would still be there. So I made a reference to my WPD as a private member of my addin object that implements Extensibility.IDTExtensibility2. I created the window during OnStartupComplete(), but for some reason when I run Excel the window immediately opens even though I never called ShowDialog() and when I do call ShowDialog() when the CommandBarButton is clicked to reOpen the window it fails to load. Does anyone know why this happens and what the correct way to handle this is? Thanks very much for any help.

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• Writing out BMP files with DataBuffer.TYPE_FLOAT or DataBuffer.TYPE_DOUBLE in java

  - by Basil Dsouza

  Hi Guys, I had a problem working with the image classes in java. I am creating a buffered image with DataBuffer.TYPE_DOUBLE. This all works fine in memory (I think). But the problem starts when I try to write it using ImageIO.write. Initially I was getting no exception at all and instead was only getting an empty output file for my troubles.. After a bit of poking around in the code, i found out that the bmp writer doesnt support writing type_double type of files. From: BMPImageWriterSpi.canEncodeImage: if (dataType < DataBuffer.TYPE_BYTE || dataType > DataBuffer.TYPE_INT) return false; So my question is, does anyone have a way of writing out those kind of images to disk? any documentation or tutorial, or link would be helpful. Thanks, Basil Dsouza

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• SQLAlchemy automatically converts str to unicode on commit

  - by Victor Stanciu

  Hello, When inserting an object into a database with SQLAlchemy, all it's properties that correspond to String() columns are automatically transformed from <type 'str'> to <type 'unicode'>. Is there a way to prevent this behavior? Here is the code: from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData from sqlalchemy.orm import mapper, sessionmaker engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() table = Table('projects', metadata, Column('id', Integer, primary_key=True), Column('name', String(50)) ) class Project(object): def __init__(self, name): self.name = name mapper(Project, table) metadata.create_all(engine) session = sessionmaker(bind=engine)() project = Project("Lorem ipsum") print(type(project.name)) session.add(project) session.commit() print(type(project.name)) And here is the output: <type 'str'> <type 'unicode'> I know I should probably just work with unicode, but this would involve digging through some third-party code and I don't have the Python skills for that yet :)

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• .NET Regular expressions on bytes instead of chars

  - by brickner

  Hi, I'm trying to do some parsing that will be easier using regular expressions. The input is an array (or enumeration) of bytes. I don't want to convert the bytes to chars for the following reasons: Computation efficiency Memory consumption efficiency Some non-printable bytes might be complex to convert to chars. Not all the bytes are printable. So I can't use Regex. The only solution I know, is using Boost.Regex (which works on bytes - C chars), but this is a C++ library that wrapping using C++/CLI will take considerable work. How can I use regular expressions on bytes in .NET directly, without working with .NET strings and chars? Thank you.

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• Partition of tables in MySQL

  - by Joel

  Hello, I have read that in a case where a table has many columns, but most of the time only one of them is used (say a title column in a forum post), a way to increase performance would be a partition to two tables, where one will contain only the title and the other one will contain the other columns (such as the forum post body). However, in case I use select ForumTitle from Forum; won't that be good enough to prevent the load of all columns (such as the forum post's body) to the memory, and eliminate the need of partition? Thanks, Joel

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• MySqlDataAdapter or MySqlDataReader for bulk transfer?

  - by Jeff Meatball Yang

  I'm using the MySql connector for .NET to copy data from MySql servers to SQL Server 2008. Has anyone experienced better performance using one of the following, versus the other? DataAdapter and calling Fill to a DataTable in chunks of 500 DataReader.Read to a DataTable in a loop of 500 I am then using SqlBulkCopy to load the 500 DataTable rows, then continue looping until the MySql record set is completely transferred. I am primarily concerned with using a reasonable amount of memory and completing in a short amount of time. Any help would be appreciated!

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• ASP.NET MVC Session usage

  - by Ben

  Currently I am using ViewData or TempData for object persistance in my ASP.NET MVC application. However in a few cases where I am storing objects into ViewData through my base controller class, I am hitting the database on every request (when ViewData["whatever"] == null). It would be good to persist these into something with a longer lifespan, namely session. Similarly in an order processing pipeline, I don't want things like Order to be saved to the database on creation. I would rather populate the object in memory and then when the order gets to a certain state, save it. So it would seem that session is the best place for this? Or would you recommend that in the case of order, to retrieve the order from the database on each request, rather than using session? Thoughts, suggestions appreciated. Thanks Ben

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• Lightweight web browser for testing

  - by Ghostrider

  I have e very specific test setup in mind. I would like to start a web-browser that understands Javascript and can use HTTP proxy, point it to a URL (ideally by specifying it in the command line along with the proxy config), wait for the page to load while listening (in the proxy) requests are generated as web-page is rendered and Javascript is executed, then kill the whole thing and restart. I don't care about how the page renders graphically at all. Which browser or tool should I use for this? Ideally it should be something self-contained that doesn't require installation (just an EXE file that runs from command line). Lynx would have been ideal but for the fact that it doesn't support JS. It should have as small memory footprint as possible.

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• Using memtables in sql. When is it reasonable and is it safe?

  - by Spiros

  I was just reading an update from a friend's project, mentioning the use of memtables to store data temporatily and then flush to a table on disk. Up to now, I have never faced a situation where I would use a memtable, or a situation where I would think the use of a mem table would be beneficial; so I wonder, when would someone use mem tables? what makes a memtable (appart from access speed) a reasonable choice? and how safe is it, even for temp data? there is always the limitation of available physical memory.

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• actionscript 3.0 garbage collection with casalib ?

  - by algro

  I would love to see an actual example how to use the casalib-garbage-collection. I used the destroy method like in the description: casa-lib description If I have a Loader in a Subclass, do I also have to use the CasaLibLoader? Do I have still to care about all Instances/Eventlisteners to do proper garbage collection? If yes, whats the advantage of casalib-garbage-collection? I assumed to call destroy on a Casalib-Sprite and then it would destroy all its subclasses and references, and therefore safe memory. It would be awesome to get an easy instruction. Thanks in advance

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• Silverlight error-handling conventions: There is no relationship between onSilverlightError and Repo

  - by rasx

  When I see the call System.Windows.Browser.HtmlPage.Window.Eval (which is evil) in ReportErrorToDOM (in App.xaml.cs) this shows me that it has no relationship to onSilverlightError. So what kind of JavaScript-based scenario calls onSilverlightError? When will onSilverlightError definitely be needed? What are Silverlight error-handling conventions in general? This is a very important comment by Erik Monk but needs more detail: There are 2 kinds of terminal errors in Silverlight. 1) Managed errors (hit the managed Application_UnhandledException method). Note that some errors may not even get to this point. If the managed infrastructure can't be loaded for some reason (out of memory error maybe...), you won't get this kind of error. Still, if you can get it, you can use a web service (or the CLOG project) to communicate it back to the server. 2) Javascript errors.

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• Flex Dataprovider caching issue.

  - by prashanth

  I have two combobox controls. If i change combobox A then I am reading from xml and populating combobox B. The xml is loaded into memory in Application's creationComplete method. When I select values in combobox A and then open combobox B, I am seeing the values correctly, but when I deploy it on the server in a different machine (which is in a different subdomain), then my combobox B values are not cleared and are retained by old selection, when I select the combobox B, then it is getting refreshed. I am making the dataprovider = null for combobox b, and when I am assigning new collection then i am refreshing the arraycollection as well. But still the problem is not solved.

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• Does MATLAB perform tail call optimization?

  - by Shea Levy

  I've recently learned Haskell, and am trying to carry the pure functional style over to my other code when possible. An important aspect of this is treating all variables as immutable, i.e. constants. In order to do so, many computations that would be implemented using loops in an imperative style have to be performed using recursion, which typically incurs a memory penalty due to the allocation a new stack frame for each function call. In the special case of a tail call (where the return value of a called function is immediately returned to the callee's caller), however, this penalty can be bypassed by a process called tail call optimization (in one method, this can be done by essentially replacing a call with a jmp after setting up the stack properly). Does MATLAB perform TCO by default, or is there a way to tell it to?

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• iPad crashes that aren't happening on iPhone or iPod Touch

  - by alyoshak

  Has anyone had difficulty getting what has otherwise been a solid iPhone app working on the iPad? I was under the impression that iPhone apps would run without problems on the iPad. We are are experiencing crashes (not intermittent - same place, at same time) that we've never gotten on the iPhone or iPod Touch. I have become suspicious that the crashes are memory-management related, but even if so, why only on the iPad? 2010-05-17 10:19:06.474 ASSIST[82:207] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UISectionRowData 0x6041480> valueForUndefinedKey:]: this class is not key value coding-compliant for the key deliveryDate.' 2010-05-17 10:19:06.481 ASSIST[82:207] Stack: ( 852041337, 861292157, 852040861, 850755255, 850750995, 850758945, 81279, 123007, 126693, 149141, 851599725, 827486573, 827486477, 827486431, 827485745, 827487359, 827454123, 851903137, 851590065, 851588321, 819339483, 819339655, 827151561, 827144691, 9461, 9324 ) terminate called after throwing an instance of 'NSException' Program received signal: “SIGABRT”.

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