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• Android Signal analysis + some filters.

  - by Profete162

  Hello, as the world cup is the main sport event and the Vuvuzelas are the most annoying sound in the world, I had an idea to remove them definitively by reading this new ( http://www.popsci.com/diy/article/2010-06/simple-software-can-filter-out-vuvuzela-whine) that told us that the sound has some frequencies at 233Hz + 466,932,1864Hz. I have already made a lot of Android application by myself but never touching the signal analysis and filtering part, so here are a few questions, I do not ask for precise answer but maybe links and tutorial to find something to work on. I guess that a new Android phone has the CPU and power to make real-time filtering. 1) How can I intercept the sound coming from the Jack microphone - Line-IN plug- ( I plan to link my TV to my phone with Jack to Jack plug). My question is totally software and coding, I have all the wires and adapters to plug a jack into my android phone Line IN. 2) Are there some Fourier analysis librairies, may I have a look to Java libraries on the web and import them to my Android project? I really apologize because my question seem not precise, but I think that would be something great. Thank you for your answers.

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• Socket Read In Multi-Threaded Application Returns Zero Bytes or EINTR (-1)

  - by user309670

  Hi. Am a c-coder for a while now - neither a newbie nor an expert. Now, I have a certain daemoned application in C on a PPC Linux. I use PHP's socket_connect as a client to connect to this service locally. The server uses epoll for concurrent connections via a Unix socket. A user submitted string is parsed for certain characters/words using strstr() and if found, spawns 4 joinable threads to different websites simultaneously. I use socket, connect, write and read, to interact with the said webservers via TCP on port 80 in each thread. All connections and writes seems successful. Reads to the webserver sockets fail however, with either (A) all 3 threads seem to hang, and only one thread returns -1 and errno is set to 104. The responding thread takes like 10 minutes - an eternity long:-(. *I read somewhere that the 104 (is EINTR) suggests that ...'the connection was reset by peer', or (B) 0 bytes from 3 threads, and only 1 of the 4 threads actually returns some data. Isn't the socket read/write thread-safe? Otherwise, use thread-safe (and reentrant) libc functions such as strtok_r, gethostbyname_r, etc. *I doubt that the said webhosts are actually resetting the connection, because when I run a single-threaded standalone (everything else equal) all things works perfectly right. There's a second problem too (oops), I can't write back to the client who connect to my epoll-ed Unix socket. My daemon application will hang and hog CPU 100% for ever. Yet nothing is written to the clients end. Am sure the client (a very typical PHP socket application) hasn't closed the connection whenever this is happening - no error(s) detected either. I cannot figure-out whatever is wrong even with Valgrind or GDB

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• Maven - 'all' or 'parent' project for aggregation?

  - by disown

  For educational purposes I have set up a project layout like so (flat in order to suite eclipse better): -product | |-parent |-core |-opt |-all Parent contains an aggregate project with core, opt and all. Core implements the mandatory part of the application. Opt is an optional part. All is supposed to combine core with opt, and has these two modules listed as dependencies. I am now trying to make the following artifacts: product-core.jar product-core-src.jar product-core-with-dependencies.jar product-opt.jar product-opt-src.jar product-opt-with-dependencies.jar product-all.jar product-all-src.jar product-all-with-dependencies.jar Most of them are fairly straightforward to produce. I do have some problem with the aggregating artifacts though. I have managed to make the product-all-src.jar with a custom assembly descriptor in the 'all' module which downloads the sources for all non-transitive deps, and this works fine. This technique also allows me to make the product-all-with-dependencies.jar. I however recently found out that you can use the source:aggregate goal in the source plugin to aggregate sources of the entire aggregate project. This is also true for the javadoc plugin, which also aggregates through the usage of the parent project. So I am torn between my 'all' module approach and ditching the 'all' module and just use the 'parent' module for all aggregation. It feels unclean to have some aggregate artifacts produced in 'parent', and others produced in 'all'. Is there a way of making an 'product-all' jar in the parent project, or to aggregate javadoc in the 'all' project? Or should I just keep both? Thanks

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• Endianness and C API's: Specifically OpenSSL.

  - by Hassan Syed

  I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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• How many users are sufficient to make a heavy load for web application

  - by galymzhan

  I have a web application, which has been suffering high load recent days. The application runs on single server which has 8-core Intel CPU and 4gb of RAM. Software: Drupal 5 (Apache 2, PHP5, MySQL5) running on Debian. After reaching 500 authenticated and 200 anonymous users (simultaneous), the application drastically decreases its performance up to total failure. The biggest load comes from authenticated users, who perform activities, causing insert/update/deletes on db. I think mysql is a bottleneck. Is it normal to slow down on such number of users? EDIT: I forgot to mention that I did some kind of profiling. I runned commands top, htop and they showed me that all memory was being used by MySQL! After some time MySQL starts to perform terribly slow, site goes down, and we have to restart/stop apache to reduce load. Administrators said that there was about 200 active mysql connections at that moment. The worst point is that we need to solve this ASAP, I can't do deep profiling analysis/code refactoring, so I'm considering 2 ways: my tables are MyIsam, I heard they use table-level locking which is very slow, is it right? could I change it to Innodb without worry? what if I take MySQL, and move it to dedicated machine with a lot of RAM?

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• Trying to not need two separate solutions for x86 and x64 program.

  - by Sean Anderson

  Hi all, I have a program which needs to function in both an x86 and an x64 environment. It is using Oracle's ODBC drivers. I have a reference to Oracle.DataAccess.DLL. This DLL is different depending on whether the system is x64 or x86, though. Currently, I have two separate solutions and I am maintaining the code on both. This is atrocious. I was wondering what the proper solution is? I have my platform set to "Any CPU." and it is my understanding that VS should compile the DLL to an intermediary language such that it should not matter if I use the x86 or x64 version. Yet, if I attempt to use the x64 DLL I receive the error "Could not load file or assembly 'Oracle.DataAccess, Version=2.102.3.2, Culture=neutral, PublicKeyToken=89b483f429c47342' or one of its dependencies. An attempt was made to load a program with an incorrect format." I am running on a 32 bit machine, so the error message makes sense, but it leaves me wondering how I am supposed to efficiently develop this program when it needs to work on x64. Thanks.

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• rails not recognizing project

  - by tipu

  I can create a new project using rails and I can use stuff like rails migration ... and i (correctly) get a error because the sqlite gem is missing. but when i try using rails migration ... with a project i checked out from github, it doesn't recognize that it is a rails project i get: Usage: rails new APP_PATH [options] Options: -d, [--database=DATABASE] # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db) # Default: sqlite3 -O, [--skip-active-record] # Skip Active Record files [--dev] # Setup the application with Gemfile pointing to your Rails checkout -J, [--skip-prototype] # Skip Prototype files -T, [--skip-test-unit] # Skip Test::Unit files -G, [--skip-git] # Skip Git ignores and keeps -b, [--builder=BUILDER] # Path to an application builder (can be a filesystem path or URL) [--edge] # Setup the application with Gemfile pointing to Rails repository -m, [--template=TEMPLATE] # Path to an application template (can be a filesystem path or URL) -r, [--ruby=PATH] # Path to the Ruby binary of your choice # Default: /usr/bin/ruby1.8 [--skip-gemfile] # Don't create a Gemfile and it goes on. any ideas? edit: it's probably an important detail that earlier my rails wasn't working at all. i had to cp /usr/bin/ruby to /usr/bin/local/ruby

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• Should I use IDisposable for purely managed resources?

  - by John Gietzen

  Here is the scenario: I have an object called a Transaction that needs to make sure that only one entity has permission to edit it at any given time. In order to facilitate a long-lived lock, I have the class generating a token object that can be used to make the edits. You would use it like this: var transaction = new Transaction(); using (var tlock = transaction.Lock()) { transaction.Update(data, tlock); } Now, I want the TransactionLock class to implement IDisposable so that its usage can be clear. But, I don't have any unmanaged resources to dispose. however, the TransctionLock object itself is a sort of "unmanaged resource" in the sense that the CLR doesn't know how to properly finalize it. All of this would be fine and dandy, I would just use IDisposable and be done with it. However, my issue comes when I try to do this in the finalizer: ~TransactionLock() { this.Dispose(false); } I want the finalizer to release the transaction from the lock, if possible. How, in the finalizer, do I detect if the parent transaction (this.transaction) has already been finalized? Is there a better pattern I should be using? The Transaction class looks something like this: public sealed class Transaction { private readonly object lockMutex = new object(); private TransactionLock currentLock; public TransactionLock Lock() { lock (this.lockMutex) { if (this.currentLock != null) throw new InvalidOperationException(/* ... */); this.currentLock = new TransactionLock(this); return this.currentLock; } } public void Update(object data, TransactionLock tlock) { lock (this.lockMutex) { this.ValidateLock(tlock); // ... } } internal void ValidateLock(TransactionLock tlock) { if (this.currentLock == null) throw new InvalidOperationException(/* ... */); if (this.currentLock != tlock) throw new InvalidOperationException(/* ... */); } internal void Unlock(TransactionLock tlock) { lock (this.lockMutex) { this.ValidateLock(tlock); this.currentLock = null; } } }

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• Calling Python app/script from C#

  - by Maxim Z.

  I'm building an ASP.NET MVC (C#) site where I want to implement STV (Single Transferable Vote) voting. I've used OpenSTV for voting scenarios before, with great success, but I've never used it programmatically. The OpenSTV Google Code project offers a Python script that allows usage of OpenSTV from other applications: import sys sys.path.append("path to openstv package") from openstv.ballots import Ballots from openstv.ReportPlugins.TextReport import TextReport from openstv.plugins import getMethodPlugins (ballotFname, method, reportFname) = sys.argv[1:] methods = getMethodPlugins("byName") f = open(reportFname, "w") try: b = Ballots() b.loadUnknown(ballotFname) except Exception, msg: print >> f, ("Unable to read ballots from %s" % ballotFname) print >> f, msg sys.exit(-1) try: e = methods[method](b) e.runElection() except Exception, msg: print >> f, ("Unable to count votes using %s" % method) print >> f, msg sys.exit(-1) try: r = TextReport(e, outputFile=f) r.generateReport(); except Exception, msg: print >> f, "Unable to write report" print >> f, msg sys.exit(-1) f.close() Is there a way for me to make such a Python call from my C# ASP.NET MVC site? If so, how? Thanks in advance!

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• When memory is actually freeded?

  - by zhyk

  Hello all. I'm trying to understand memory management stuff in Objective-C. If I see the memory usage listed by Activity Monitor, it looks like memory is not being freed (I mean column rsize). But in "Object Allocations" everything looks fine. Here is my simple code: #import <Foundation/Foundation.h> int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSInteger i, k=10000; while (k>0) { NSMutableArray *array = [[NSMutableArray alloc]init]; for (i=0;i<1000*k; i++) { NSString *srtring = [[NSString alloc] initWithString:@"string...."]; [array addObject:srtring]; [srtring release]; srtring = nil; } [array release]; array = nil; k-=500; } [NSThread sleepForTimeInterval:5]; [pool release]; return 0; } As for retain and release it's cool, everything is balanced. But rsize decreases only after quitting from this little program. Is it possible to "clean" memory somehow before quitting?

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• wordpress generating slow mysql queries - is it index problem?

  - by tash

  Hello Stack Overflow I've got very slow Mysql queries coming up from my wordpress site. It's making everything slow and I think this is eating up CPU usage. I've pasted the Explain results for the two most frequently problematic queries below. This is a typical result - although very occasionally teh queries do seem to be performed at a more normal speed. I have the usual wordpress indexes on the database tables. You will see that one of the queries is generated from wordpress core code, and not from anything specific - like the theme - for my site. I have a vague feeling that the database is not always using the indexes/is not using them properly... Is this right? Does anyone know how to fix it? Or is it a different problem entirely? Many thanks in advance for any help anyone can offer - it is hugely appreciated Query: [wp-blog-header.php(14): wp()] SELECT SQL_CALC_FOUND_ROWS wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') ORDER BY wp_posts.post_date DESC LIMIT 0, 6 id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE wp_posts ref type_status_date type_status_date 63 const 427 Using where; Using filesort Query time: 34.2829 (ms) 9) Query: [wp-content/themes/LMHR/index.php(40): query_posts()] SELECT SQL_CALC_FOUND_ROWS wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.ID NOT IN ( SELECT tr.object_id FROM wp_term_relationships AS tr INNER JOIN wp_term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy = 'category' AND tt.term_id IN ('217', '218', '223', '224') ) AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') ORDER BY wp_posts.post_date DESC LIMIT 0, 6 id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY wp_posts ref type_status_date type_status_date 63 const 427 Using where; Using filesort 2 DEPENDENT SUBQUERY tr ref PRIMARY,term_taxonomy_id PRIMARY 8 func 1 Using index 2 DEPENDENT SUBQUERY tt eq_ref PRIMARY,term_id_taxonomy,taxonomy PRIMARY 8 antin1_lovemusic2010.tr.term_taxonomy_id 1 Using where Query time: 70.3900 (ms)

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• Pump Messages During Long Operations + C#

  - by Newbie

  Hi I have a web service that is doing huge computation and is taking more than a minute. I have generated the proxy file of the web service and then from my client end I am using the dll(of course I generated the proxy dll). My client side code is TimeSeries3D t = new TimeSeries3D(); int portfolioId = 4387919; string[] str = new string[2]; str[0] = "MKT_CAP"; DateRange dr = new DateRange(); dr.mStartDate = DateTime.Today; dr.mEndDate = DateTime.Today; Service1 sc = new Service1(); t = sc.GetAttributesForPortfolio(portfolioId, true, str, dr); But since it is taking to much time for the server to compute, after 1 minute I am receiving an error message The CLR has been unable to transition from COM context 0x33caf30 to COM context 0x33cb0a0 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. Kindly guide me what to do? Thanks

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• What limits scaling in this simple OpenMP program?

  - by Douglas B. Staple

  I'm trying to understand limits to parallelization on a 48-core system (4xAMD Opteron 6348, 2.8 Ghz, 12 cores per CPU). I wrote this tiny OpenMP code to test the speedup in what I thought would be the best possible situation (the task is embarrassingly parallel): // Compile with: gcc scaling.c -std=c99 -fopenmp -O3 #include <stdio.h> #include <stdint.h> int main(){ const uint64_t umin=1; const uint64_t umax=10000000000LL; double sum=0.; #pragma omp parallel for reduction(+:sum) for(uint64_t u=umin; u<umax; u++) sum+=1./u/u; printf("%e\n", sum); } I was surprised to find that the scaling is highly nonlinear. It takes about 2.9s for the code to run with 48 threads, 3.1s with 36 threads, 3.7s with 24 threads, 4.9s with 12 threads, and 57s for the code to run with 1 thread. Unfortunately I have to say that there is one process running on the computer using 100% of one core, so that might be affecting it. It's not my process, so I can't end it to test the difference, but somehow I doubt that's making the difference between a 19~20x speedup and the ideal 48x speedup. To make sure it wasn't an OpenMP issue, I ran two copies of the program at the same time with 24 threads each (one with umin=1, umax=5000000000, and the other with umin=5000000000, umax=10000000000). In that case both copies of the program finish after 2.9s, so it's exactly the same as running 48 threads with a single instance of the program. What's preventing linear scaling with this simple program?

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• How to format the node_redis info function output?

  - by hh54188

  I want check the Redis info on my pc with node, so I use node_redis and run the info function: var redis = require("redis"), client = redis.createClient(); client.on("connect", function () { client.info(function (err, replay) { console.log(replay); }) }) but the response is un-format: `#Server\r\nredis_version:2.6.16\r\nredis_git_sha1:00000000\r\nredis_git_dirty:0\r\nredis_mode:standalone\r\nos:Linux 3.8.0-29-generic x86_64\r\narch_bits:64\r\nmultiplexing_api:epoll\r\ngcc_version:4.6.3\r\nprocess_id:2941\r\nrun_id:e60f261a6f4f6f081563a47961315eff6b1c005d\r\ntcp_port:6379\r\nuptime_in_seconds:1777\r\nuptime_in_days:0\r\nhz:10\r\nlru_clock:2040689\r\n\r\n# Clients\r\nconnected_clients:2\r\nclient_longest_output_list:0\r\nclient_biggest_input_buf:0\r\nblocked_clients:0\r\n\r\n# Memory\r\nused_memory:562584\r\nused_memory_human:549.40K\r\nused_memory_rss:2031616\r\nused_memory_peak:561784\r\nused_memory_peak_human:548.62K\r\nused_memory_lua:31744\r\nmem_fragmentation_ratio:3.61\r\nmem_allocator:jemalloc-3.2.0\r\n\r\n# Persistence\r\nloading:0\r\nrdb_changes_since_last_save:0\r\nrdb_bgsave_in_progress:0\r\nrdb_last_save_time:1383553917\r\nrdb_last_bgsave_status:ok\r\nrdb_last_bgsave_time_sec:-1\r\nrdb_current_bgsave_time_sec:-1\r\naof_enabled:0\r\naof_rewrite_in_progress:0\r\naof_rewrite_scheduled:0\r\naof_last_rewrite_time_sec:-1\r\naof_current_rewrite_time_sec:-1\r\naof_last_bgrewrite_status:ok\r\n\r\n# Stats\r\ntotal_connections_received:3\r\ntotal_commands_processed:5\r\ninstantaneous_ops_per_sec:0\r\nrejected_connections:0\r\nexpired_keys:0\r\nevicted_keys:0\r\nkeyspace_hits:0\r\nkeyspace_misses:0\r\npubsub_channels:0\r\npubsub_patterns:0\r\nlatest_fork_usec:0\r\n\r\n# Replication\r\nrole:master\r\nconnected_slaves:0\r\n\r\n# CPU\r\nused_cpu_sys:0.13\r\nused_cpu_user:0.19\r\nused_cpu_sys_children:0.00\r\nused_cpu_user_children:0.00\r\n\r\n# Keyspace\r\n' How can I turn it to an object? like: { redis_version:2.6.16, redis_git_sha1:00000000, redis_git_dirty:0, ...... } so that I can read each property's value, get information I need

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• Silverlight, Flash, or JavaScript for web app that runs client-side, or just stick with C#?

  - by Sootah

  Silverlight, Flash, and JavaScript, oh my.. I have a couple of applications that I need to develop for one of my business partners that will be distributed to dozens of people. These applications will need to be able to query information from the internet (query via Google, grab feeds from our other sites, just general web access) and save files to their computer. The reason I want to host the application is so that it all can be centrally managed, and any updates would be instantly deployed to everyone that uses the service. There always seems to be headaches with developing a pure desktop app in a language like C# with regards to making sure people use the latest version, don't have some odd problem with the installer, etc. Since we don't want to tie up our server's CPU I want effectively all of the processing done client-side. Meaning that they would log into their account, access the app, and then all the work done within the app is all handled by their machine. Only specific data would be sent back to the server. So - which language is best for this? Microsoft's Silverlight, Adobe's Flash, or Sun's JavaScript? I've heard a lot of good things about Silverlight and have wanted to try it for some time. I've only done extremely limited JavaScript programming, and absolutely none with Flash. Or, with my main requirement being that the client does all of its own processing should I just stick with C#? Also, is there any way to integrate a C# app into a webpage? I've never even considered it (or have any idea if it's even possible) until just now. Thanks in advance! -Sootah

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• Handling user interface in a multi-threaded application (or being forced to have a UI-only main thre

  - by Patrick

  In my application, I have a 'logging' window, which shows all the logging, warnings, errors of the application. Last year my application was still single-threaded so this worked [quite] good. Now I am introducing multithreading. I quickly noticed that it's not a good idea to update the logging window from different threads. Reading some articles on keeping the UI in the main thread, I made a communication buffer, in which the other threads are adding their logging messages, and from which the main thread takes the messages and shows them in the logging window (this is done in the message loop). Now, in a part of my application, the memory usage increases dramatically, because the separate threads are generating lots of logging messages, and the main thread cannot empty the communication buffer quickly enough. After the while the memory decreases again (if the other threads have finished their work and the main thread gradually empties the communication buffer). I solved this problem by having a maximum size on the communication buffer, but then I run into a problem in the following situation: the main thread has to perform a complex action the main thread takes some parts of the action and let's separate threads execute this while the seperate threads are executing their logic, the main thread processes the results from the other threads and continues with its work if the other threads are finished Problem is that in this situation, if the other threads perform logging, there is no UI-message loop, and so the communication buffer is filled, but not emptied. I see two solutions in solving this problem: require the main thread to do regular polling of the communication buffer only performing user interface logic in the main thread (no other logic) I think the second solution seems the best, but this may not that easy to introduce in a big application (in my case it performs mathematical simulations). Are there any other solutions or tips? Or is one of the two proposed the best, easiest, most-pragmatic solution? Thanks, Patrick

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• Compact data structure for storing a large set of integral values

  - by Odrade

  I'm working on an application that needs to pass around large sets of Int32 values. The sets are expected to contain ~1,000,000-50,000,000 items, where each item is a database key in the range 0-50,000,000. I expect distribution of ids in any given set to be effectively random over this range. The operations I need on the set are dirt simple: Add a new value Iterate over all of the values. There is a serious concern about the memory usage of these sets, so I'm looking for a data structure that can store the ids more efficiently than a simple List<int>or HashSet<int>. I've looked at BitArray, but that can be wasteful depending on how sparse the ids are. I've also considered a bitwise trie, but I'm unsure how to calculate the space efficiency of that solution for the expected data. A Bloom Filter would be great, if only I could tolerate the false negatives. I would appreciate any suggestions of data structures suitable for this purpose. I'm interested in both out-of-the-box and custom solutions. EDIT: To answer your questions: No, the items don't need to be sorted By "pass around" I mean both pass between methods and serialize and send over the wire. I clearly should have mentioned this. There could be a decent number of these sets in memory at once (~100).

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• Learning libraries without books or tutorials

  - by Kawili-wili

  While many ask questions about where to find good books or tutorials, I'd like to take the opposite tack. I consider myself to be an entry-level programmer ready to move up to mid-level. I have written code in c, c++, c#, perl, python, clojure, vb, and java, so I'm not completely clueless. Where I see a problem in moving to the next level is learning to make better use of the literally hundreds upon hundreds of libraries available out there. I seem paralyzed unless there is a specific example in a book or tutorial to hand-hold me, yet I often read in various forums where another programmer attempts to assist with a question. He/she will look through the docs or scan the available classes/methods in their favorite IDE and seem to grok what's going on in a relatively short period of time, even if they had no previous experience with that specific library or function. I yearn to break the umbilical chord of constantly spending hour upon hour searching and reading, searching and reading, searching and reading. Many times there is no book or tutorial, or if there is, the discussion glosses over my specific needs or the examples shown are too far off the path for the usage I had in mind or the information is outdated and makes use of deprecated components or the library itself has fallen out of mainstream, yet is still perfectly usable (but no docs, books, or tutorials to hand-hold). My question is: In the absence of books or tutorials, what is the best way to grok new or unfamiliar libraries? I yearn to slicken the grok path so I can get down to the business of doing what I love most -- coding.

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• SQL Server log backups "stalling"

  - by MattK

  I have interited a box running SQL Server 2008 and Windows 2003, and have had a few events where largeish (35GB) log backups "stall", both before and after the installation of SQL 2008 SP1. The server log ships to a standby, so regular log backups are taken at 15 minute intervals. However, after an index reorg causes the log to grow to about 35GB (on a DB with about 17GB of data), the next log backup runs to ~95% completion, then seems to stop. The process shows as suspended, with a wait state of BACKUPIO. CPU, read, and write activity on the SPID also does not change, and the process stays in this state for hours, when normally a backup of this size should complete in about 20 minutes. This server has a single RAID-1 volume, thus the source database files and destination backup files are on the same volume. However, I cannot determine if another process is blocking the backup. The backup SPID cannot be killed, and the only way to terminate the log backup and clear the lock on the backup file is to cycle the SQL Server service. There was one event where the backup terminated completely, with an error that another process had locked the backup file, but no details about what that process was. Can anyone suggest a cause or diagnostic process to this situation?

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• C#. How to pass message from unsafe callback to managed code?

  - by maxima120

  Is there a simple example of how to pass messages from unsafe callback to managed code? I have a proprietary dll which receives some messages packed in structs and all is coming to a callback function. The example of usage is as follows but it calls unsafe code too. I want to pass the messages into my application which is all managed code. *P.S. I have no experience in interop or unsafe code. I used to develop in C++ 8 yrs ago but remember very little from that nightmarish times :) P.P.S. The application is loaded as hell, the original devs claim it processes 2mil messages per sec.. I need a most efficient solution.* static unsafe int OnCoreCallback(IntPtr pSys, IntPtr pMsg) { // Alias structure pointers to the pointers passed in. CoreSystem* pCoreSys = (CoreSystem*)pSys; CoreMessage* pCoreMsg = (CoreMessage*)pMsg; // message handler function. if (pCoreMsg->MessageType == Core.MSG_STATUS) OnCoreStatus(pCoreSys, pCoreMsg); // Continue running return (int)Core.CALLBACKRETURN_CONTINUE; } Thank you.

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• response.redirect to classic asp failing

  - by jeff

  I have the following code pasted below. For some reason, the response.redirect seems to be failing and it is maxing out the cpu on my server and just doesn't do anything. The .net code uploads the file fine, but does not redirect to the asp page to do the processing. I know this is absolute rubbish why would you have .net code redirecting to classic asp, it is a legacy app. I have tried putting false or true etc. at the end of the redirect as I have read other people have had issues with this. Please help as it's driving me insane! It's so strange, it runs locally on my machine but won't run on my server! public void btnUploadTheFile_Click(object Source, EventArgs evArgs) { //need to check that the uploaded file is an xls file. string strFileNameOnServer = "PJI3.txt"; string strBaseLocation = ConfigurationSettings.AppSettings["str_file_location"]; if ("" == strFileNameOnServer) { txtOutput.InnerHtml = "Error - a file name must be specified."; return; } if (null != uplTheFile.PostedFile) { try { uplTheFile.PostedFile.SaveAs(strBaseLocation+strFileNameOnServer); txtOutput.InnerHtml = "File <b>" + strBaseLocation+strFileNameOnServer+"</b> uploaded successfully"; Response.Redirect ("/COBRA/pages/sap_import_pji3_prc.asp"); } catch (Exception e) { txtOutput.InnerHtml = "Error saving <b>" + strBaseLocation+strFileNameOnServer+"</b><br>"+ e.ToString(); } } }

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• cell and array in Matlab

  - by Tim

  Hi, I am a little confused about the usage of cell and array in Matlab. I would like to hear about your understandings. Here are my observations: (1). array can dynamically adjust its own memory to allow dynamic number of elements, while cell seems not act in the same way. a=[]; a=[a 1]; b={}; b={b 1}; (2). several elements can be retrieved from cell, while they seem not from array. a={'1' '2'}; figure, plot(...); hold on; plot(...) ; legend(a{1:2}); b=['1' '2']; figure, plot(...); hold on; plot(...) ; legend(b(1:2)); % b(1:2) is an array, not its elements, so it is wrong with legend. Are these correct? What are some other different usages between the cell and array? Thanks and regards!

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• Program structure in long running data processing python script

  - by fmark

  For my current job I am writing some long-running (think hours to days) scripts that do CPU intensive data-processing. The program flow is very simple - it proceeds into the main loop, completes the main loop, saves output and terminates: The basic structure of my programs tends to be like so: <import statements> <constant declarations> <misc function declarations> def main(): for blah in blahs(): <lots of local variables> <lots of tightly coupled computation> for something in somethings(): <lots more local variables> <lots more computation> <etc., etc.> <save results> if __name__ == "__main__": main() This gets unmanageable quickly, so I want to refactor it into something more manageable. I want to make this more maintainable, without sacrificing execution speed. Each chuck of code relies on a large number of variables however, so refactoring parts of the computation out to functions would make parameters list grow out of hand very quickly. Should I put this sort of code into a python class, and change the local variables into class variables? It doesn't make a great deal of sense tp me conceptually to turn the program into a class, as the class would never be reused, and only one instance would ever be created per instance. What is the best practice structure for this kind of program? I am using python but the question is relatively language-agnostic, assuming a modern object-oriented language features.

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• How to catch YouTube embed code and turn into URL

  - by Jonathan Vanasco

  I need to strip YouTube embed codes down to their URL only. This is the exact opposite of all but one question on StackOverflow. Most people want to turn the URL into an embed code. This question addresses the usage patttern I want, but is tied to a specific embed code's regex ( Strip YouTube Embed Code Down to URL Only ) I'm not familiar with how YouTube has offered embeds over the years - or how the sizes differ. According to their current site, there are 2 possible embed templates and a variety of options. If that's it, I can handle a regex myself -- but I was hoping someone had more knowledge they could share, so I could write a proper regex pattern that matches them all and not run into endless edge-cases. The full use case scenario : user enters content in web based wysiwig editor backend cleans out youtube & other embed codes; reformats approved embeds into an internal format as the text is all converted to markdown. on display, appropriate current template/code display for youtube or other 3rd party site is generated At a previous company, our tech-team devised a plan where YouTube videos were embedded by listing the URL only. That worked great , but it was in a CMS where everyone was trained. I'm trying to create a similar storage, but for user-generated-content.

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• Trusted Folder/Drive Picker in the Browser

  - by kylepfritz

  I'd like to write a Folder/Drive picker the runs in the browser and allows a user to select files to upload to a webservice. The primary usage would be selecting folders or a whole CD and uploading them to the web with their directory structure in tact. I'm imagining something akin to Jumploader but which automatically enumerates external drives and CDs. I remember a version of Facebook's picture uploader that could do this sort of enumeration and was java-based but it has since been replaced by a much slicker plugin-based architecture. Because the application needs to run at very high trust, I think I'm limited to old-school java applets. Is there another alternative? I'm hesitant to start down the plugin route because of the necessity of writing one for both IE and Mozilla at a minimum. Are there good places to get started there? On the applet front, I built a clunky prototype to demonstrate that I can enumerate devices and list files. It runs fine in the applet viewer but I don't think I have the security settings configured correctly for it to run in the browser at full trust. Currently I don't get any drives back when I run it in the browser. Applet Prototype: public class Loader extends javax.swing.JApplet { ... private void EnumerateDrives(java.awt.event.ActionEvent evt) { File[] roots = File.listRoots(); StringBuilder b = new StringBuilder(); for (File root : roots) { b.append(root.getAbsolutePath() + ", "); } jLabel.setText(b.toString()); } } Embed Html: <p>Loader:</p> <script src="http://www.java.com/js/deployJava.js" type="text/javascript" ></script> <script> var attributes = {code:'org.exampl.Loader.Loader.class', archive:'Loader/dist/Loader.jar', width:600, height:400} ; var parameters = {}; deployJava.runApplet(attributes, parameters, '1.6');

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