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• Is it possible to give a python dict an initial capacity (and is it usefull)

  - by Peter Smit

  I am filling a python dict with around 10,000,000 items. My understanding of dict (or hashtables) is that when too much elements get in them, the need to resize, an operation that cost quite some time. Is there a way to say to a python dict that you will be storing at least n items in it, so that it can allocate memory from the start? Or will this optimization not do any good to my running speed? (And no, I have not checked that the slowness of my small script is because of this, I actually wouldn't now how to do that. This is however something I would do in Java, set the initial capacity of the HashSet right)

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• Best way to deallocate an array of array in javascript

  - by andre.dias

  What is the best way to deallocate an array of array in javascript to make sure no memory leaks will happen? var foo = new Array(); foo[0] = new Array(); foo[0][0] = 'bar0'; foo[0][1] = 'bar1'; foo[1] = new Array(); ... delete(foo)? iterate through foo, delete(foo[index]) and delete(foo)? 1 and 2 give me the same result? none?

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• How to solve this problem with lists?

  - by osabri

  what i don't understand in my task here what kind of list i can use, and if it should have 2 attributes key and value ? or only value? with pointers to another node ofc the task: "design a function which create a list using input from the keyboard _ the prefered solution. Assume that some magic stops the input; so the length of a list is not known in advance.(alternative solution: a function which creates explicitly a fixed list. However, all other function can not assume any knowledge about the length of lists). Necessary utilities( additional functions to be created): a function which deallocates the memory used for lists and a function which prints the content of the list. let the element of lists contain a letter. Design a function which create a copy of such list. can't also understand the list line !!!!!???

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• Is there any significant benefit to reading string directly from control instead of moving it into a

  - by Kevin

  sqlInsertFrame.Parameters.AddWithValue("@UserName", txtUserName.txt); Given the code above...if I don't have any need to move the textbox data into a string variable, is it best to read the data directly from the control? In terms of performance, it would seem smartest to not create any unnecessary variables which use up memory if its not needed. Or is this a situation where its technically true but doesn't yield any real world results due to the size of the data in question. Forgive me, I know this is a very basic question.

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• Upload File to Database in ColdFusion

  - by George Johnston

  I simply would like to upload a file to my database using ColdFusion. I understand how to upload an image to a directory, but I would like to place it directly in the database. I have set a database field to varbinary(MAX) to accept the image and have the stored procedure to insert it. Currently my code for uploading the image to my file system is: <cfif isdefined("form.FileUploadImage")> <cffile action="upload" filefield="FileUploadImage" destination="#uploadfolder#" nameconflict="overwrite" accept="image/*" > </cfif> I've obviously left some of the supporting code out, but really all I need to do is get a binary representation of the file stored in memory, instead of the file system. Any experts out there that can help? Thanks, George

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• How are a session identifiers generated?

  - by Asaf R

  Most web applications depend on some kind of session with the user (for instance, to retain login status). The session id is kept as a cookie in the user's browser and sent with every request. To make it hard to guess the next user's session these session-ids need to be sparse and somewhat random. The also have to be unique. The question is - how to efficiently generate session ids that are sparse and unique? This question has a good answer for unique random numbers, but it seems not scalable for a large range of numbers, simply because the array will end up taking a lot of memory.

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• how to read httpWebRequest's request stream in c#, i got error" the stream is not readable" ?

  - by sam

  hi i want to read request stream from a custom httpWebRequest class that inherits from httpWebRequest and i have tried to read the request stream in different stages but sitll not sure how to archieve that in the class,thanks very much for any help. This custom httpWebRequest is used to serilize soap message and i want to know what request has been sent in string format. I also implemented custom HttpRequestCreator,HttpWebResponse but till cant find a place/stage i can read the request stream. If i output everything in a memory stream then copy the content to request stream, anyone knows which stage i can do it in the constructor, BeginGetRequestStream,EndGetRequestStream or GetRequestStream?

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• Implications of Fulltext Search over many columns

  - by Alex

  Hello, I have a really wide table which includes separate columns for billing address, shipping address, primary address, names, aliases etc. (I can't normalize this table further, and that's not the question here anyways). I'm implementing SQL Server fulltext search, and I'm wondering whether I should limit the search ability to just the primary fields (primary address and names for example), or if I can extend the search ability across all columns without occurring too much of a performance or memory penalty. I've done some basic testing with 10,000 sample rows and it's quite fast but I don't have much experience with fulltext indexing, especially its dictionary internals, so I don't know if the index is going to grow over time, or if there is anything else to consider. Thoughts?

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• Connect two daemons in python

  - by Simon

  What is the best way to connect two daemons in Python? I have daemon A and B. I'd like to receive data generated by B in A's module (maybe bidirectional). Both daemons support plugins, so I'd like to shut communication in plugins. What's the best and cross-platform way to do that? I know few mechanisms from low-level solutions - shared memory (C/C++), linux pipe, sockets (TCP/UDP), etc. and few high-level - queue (JMS, Rabbit), RPC. Both daemons should run on the same host, but obviously better approach is to abstract from connection type. What are typical solutions/libraries in python? I'm looking for an elegant and lightweight solution. I don't need external server, just two processes talking with each other. What should I use in python to do that?

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• Garbage Collection Java

  - by simion

  On the slides i am revising from it says the following; Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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• In C, as free() knows an array size, why isn't there a function that gets the array size? [closed]

  - by user354959

  Possible Duplicate: If free() knows the length of my array, why can’t I ask for it in my own code? Searching around (including here at stackoverflow), I got that malloc() allocates an array and also creates a header to control the array info. In this header, there's also the array size. free() use such information to know how to deallocate that array. So, if the array size info is "there" (somewhere in the memory), why there isn't a function that returns an array size, looking for this at the array header? Or am I missing something?

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• Double indirection and structures passed into a function

  - by ZPS

  I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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• Has anybody used the WB B-tree library?

  - by Chris B

  I stumbled across the WB on-disk B-tree library: http://people.csail.mit.edu/jaffer/WB It seems like it could be useful for my purposes (swapping data to disk during very large statistical calculations that do not fit in memory), but I was wondering how stable it is. Reading the manual, it seems worringly 'researchy' - there are sections labelled [NOT IMPLEMENTED] etc. But maybe the manual is just out-of-date. So, is this library useable? Am I better off looking at Tokyo Cabinet, MemcacheDB, etc.? By the way I am working in Java.

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• Cilk or Cilk++ or OpenMP

  - by Aman Deep Gautam

  I'm creating a multi-threaded application in Linux. here is the scenario: Suppose I am having x instance of a class BloomFilter and I have some y GB of data(greater than memory available). I need to test membership for this y GB of data in each of the bloom filter instance. It is pretty much clear that parallel programming will help to speed up the task moreover since I am only reading the data so it can be shared across all processes or threads. Now I am confused about which one to use Cilk, Cilk++ or OpenMP(which one is better). Also I am confused about which one to go for Multithreading or Multiprocessing

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• How to create a NSAutoreleasePool without Objective-C?

  - by fbafelipe

  I have multiplatform game written in C++. In the mac version, even though I do not have any obj-c code, one of the libraries I use seems to be auto-releasing stuff, and I get memory leaks for that, since I did not create a NSAutoreleasePool. What I want is to be able to create (and destroy) a NSAutoreleasePool without using obj-c code, so I don't need to create a .m file, and change my build scripts just for that. Is that possible? How can that be done? OBS: Tagged C and C++, because a solution in any of those languages will do.

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• [Ruby] How can I randomly iterate through a large Range?

  - by void

  I would like to randomly iterate through a range. Each value will be visited only once and all values will eventually be visited. For example: (0..9).sort_by{rand}.map{|x| f(x)} where f(x) is some function that operates on each value. A Fisher-Yates shuffle could be used to increase efficiency, but this code is sufficient for many purposes. My problem is that sort_by will transform the range into an array, which is not cool because I am working with astronomically large numbers. Ruby will quickly consume a large amount of RAM trying to create a monstrous array. This is also why the following code will not work: tried = {} # store previous attempts bigint = 99**99 bigint.times { x = rand(bigint) redo if tried[x] tried[x] = true f(x) # some function } This code is very naive and quickly runs out of memory as tried obtains more entries. What sort of algorithm can accomplish what I am trying to do?

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• Memcachedb Versus MongoDB Versus CouchDB in terms of file based caching solution?

  - by Scott Faisal

  We need a caching solution that essentially caches data (text files) anywhere from 3 days up to a week based on user preferences and criteria. In this case memory based caching does not make sense to us. We were referred to MemcacheDB however I also thought of some NO SQL solutions. Our current application uses RDMS (MYSQL) and I guess it makes sense to use MemcacheDB however NOSQL does appeal as it is something more on the horizon. However we have not deployed a production level application under NOSQL and the beta stuff does not settle well with management/investors. Any how what are your thoughts and how would you address it? Thank You

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• linux's fork and system resources

  - by Dmitry Bespalov

  Suppose I have following code in linux: int main() { FILE* f = fopen("file.txt", "w"); fork(); fwrite("A", 1, 1, f); fclose(f); return 0; } What I know about fork from documentation, is that it makes the copy of current process. It copies state of the memory as well, so *f should be equal in both instances. But what happens with system resources, such as a file handle? In this example I open the file with write intentions, so only one instance can write into file, right? Which of the instances will actually write into file? Who should care further about the file handle, and call fclose() ?

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• NSArray vs. SQLite for Complex Queries on iPhone

  - by GingerBreadMane

  Developing for iPhone, I have a collection of points that I need to make complex queries on. For example: "How many points have a y-coordinate of 10" and "Return all points with an X-coordinate between 3 and 5 and a y-coordinate of 7". Currently, I am just cycling through each element of an NSArray and checking to see if each element matches my query. It's a pain to write the queries though. SQLite would be much nicer. I'm not sure which would be more efficient though since a SQLite database resides on disk and not in memory (to my understanding). Would SQLite be as efficient or more efficient here? Or is there a better way to do it other than these methods that I haven't thought of? I would need to perform the multiple queries with multiple sets of points thousands of times, so the best performance is important.

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• How do I view how many concurrent long polling requests there are on my server?

  - by Pascal

  My host is Joyent. My host says I have 15 process limit and prstat -J shows those processes but that doesn't tell me how many long polling requests are currently being served. I could record it myself but that would add alot of performance overhead. I need to know when the server is at its long polling limits. I know this limit occurs far before the memory or CPU is used up. From experimentation, I've already verified that the number of long polls open is NOT equivalant to the number of processes running, probably because each process has multiple threads, each serving a request. thanks.

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• Treating a fat webservice in .net 3.5 c#

  - by Chris M

  I'm dealing with an obese 3rd party webservice that returns about 3mb of data for a simple search results, about 50% of the data in that response is junk. Would it make sense then to remap this data to my own result object and ditch the response so I'm storing 1-2 mb in memory for filtering and sorting rather than using the web-responses own object and using 2-4 or am I missing a point? So far I've been accessing the webservice from a separate project and using a new class to provide the interaction and to handle the persistence so my project looks like this |- Web (mvc2 proj) |- DAL (database/storage fluent-nhibernate) |- SVCGateway (interaction layer + webservice related models) |- Services -------------- |- Tests |- Specs I'm trying to make the application behave fast and I also need to store the result set temporarily in case a customer goes to view the product and wants to go back to the results. (Service returns only 500 of possible 14K results). So basically I'm looking for confirmation that I'm doing the right thing in pushing the results into my own objects or if I'm breaking some rule or even if there's a better way of handling it. Thanks

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• OpenGL texture not showing up on some computers, problem with auxDIBImageLoad?

  - by CptanPanic

  I have a simple openGL GUI that has uses a bmp as a texture. The problem is on some computers the texture doesn't show up. But on ones with newer OpenGL drivers it works. How can I make it more compatible. I think the problem may be with auxDIBImageLoad. When I inspect the result, I see the x,y correct, but the data pointer points to memory bank with all zeros. What could be wrong?

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• Writing a PHP web crawler using cron

  - by Horse

  Hi all I have written myself a web crawler using simplehtmldom, and have got the crawl process working quite nicely. It crawls the start page, adds all links into a database table, sets a session pointer, and meta refreshes the page to carry onto the next page. That keeps going until it runs out of links That works fine however obviously the crawl time for larger websites is pretty tedious. I wanted to be able to speed things up a bit though, and possibly make it a cron job. Any ideas on making it as quick and efficient as possible other than setting the memory limit / execution time higher?

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• Is there a version of postActionEvent for KeyEvent (specifically for a JTextArea)?

  - by Brian Pelc

  I'm writing a program that contains multiple JTextFields and 2 JTextAreas within an input panel. I have a submit button on the bottom. I have it set up so when a user types something into each field (including the JTextAreas) and hits the Enter key, it updates a text file, and when they press the submit button it updates the file then outputs a new version of it in the local directory. If the user presses Enter in any of the fields, it validates their input, however, I want to re-validate all fields when they press the submit button. Each field (again, JTextAreas included) has it's own validation check within its ActionListener or KeyListener (for the JTextAreas). It's easy enough to use postActionEvent() for the JTextFields, but is there a similar method for the JTextAreas to force fire a KeyEvent? I don't want to duplicate code and consume memory by re-writing the validation for those 2 Components inside the ActionEvent for the JButton. Unfortunately, I can't provide a sample because I'm writing the program on a classified machine (PC).

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• Is it possible to find out what FlashBuilder is doing during compilation?

  - by justkevin

  I've found that Flash Builder 4 (formerly Flex Builder) has trouble working with large projects. After a certain point, builds seem to take longer and longer. I've tried many different ways of improving build time including: Moving embedded resources into externally linked projects. Using -incremental. Tweaking the .ini jvm settings including memory and -server. Turning off automatic build (I'd prefer not to have to do this, because one of the main reasons for using an IDE is to be told about errors as you make them). Deleting the project and re-checking out from the repository. While some of these may help a bit, the performance is still annoyingly slow. I feel if I knew what was taking so long I could refactor my projects to build faster. Is there some setting that tells FlashBuilder to let me see what parts of the build process take so much time?

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