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  • How do I do nested transactions in NHibernate?

    - by Gavin Schultz-Ohkubo
    Can I do nested transactions in NHibernate, and how do I implement them? I'm using SQL Server 2008, so support is definitely in the DBMS. I find that if I try something like this: using (var outerTX = UnitOfWork.Current.BeginTransaction()) { using (var nestedTX = UnitOfWork.Current.BeginTransaction()) { ... do stuff nestedTX.Commit(); } outerTX.Commit(); } then by the time it comes to outerTX.Commit() the transaction has become inactive, and results in a ObjectDisposedException on the session AdoTransaction. Are we therefore supposed to create nested NHibernate sessions instead? Or is there some other class we should use to wrap around the transactions (I've heard of TransactionScope, but I'm not sure what that is)? I'm now using Ayende's UnitOfWork implementation (thanks Sneal). Forgive any naivety in this question, I'm still new to NHibernate. Thanks! EDIT: I've discovered that you can use TransactionScope, such as: using (var transactionScope = new TransactionScope()) { using (var tx = UnitOfWork.Current.BeginTransaction()) { ... do stuff tx.Commit(); } using (var tx = UnitOfWork.Current.BeginTransaction()) { ... do stuff tx.Commit(); } transactionScope.Commit(); } However I'm not all that excited about this, as it locks us in to using SQL Server, and also I've found that if the database is remote then you have to worry about having MSDTC enabled... one more component to go wrong. Nested transactions are so useful and easy to do in SQL that I kind of assumed NHibernate would have some way of emulating the same...

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  • fast algorithm implementation to sort very small set

    - by aaa
    hello. This is the problem I ran into long time ago. I thought I may ask your for your ideas. assume I have very small set of numbers (integers), 4 or 8 elements, that need to be sorted, fast. what would be the best approach/algorithm? my approach was to use the max/min functions. I guess my question pertains more to implementation, rather than type of algorithm. At this point it becomes somewhat hardware dependent , so let us assume Intel 64-bit processor with SSE3 . Thanks

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  • Why is numpy's einsum faster than numpy's built in functions?

    - by Ophion
    Lets start with three arrays of dtype=np.double. Timings are performed on a intel CPU using numpy 1.7.1 compiled with icc and linked to intel's mkl. A AMD cpu with numpy 1.6.1 compiled with gcc without mkl was also used to verify the timings. Please note the timings scale nearly linearly with system size and are not due to the small overhead incurred in the numpy functions if statements these difference will show up in microseconds not milliseconds: arr_1D=np.arange(500,dtype=np.double) large_arr_1D=np.arange(100000,dtype=np.double) arr_2D=np.arange(500**2,dtype=np.double).reshape(500,500) arr_3D=np.arange(500**3,dtype=np.double).reshape(500,500,500) First lets look at the np.sum function: np.all(np.sum(arr_3D)==np.einsum('ijk->',arr_3D)) True %timeit np.sum(arr_3D) 10 loops, best of 3: 142 ms per loop %timeit np.einsum('ijk->', arr_3D) 10 loops, best of 3: 70.2 ms per loop Powers: np.allclose(arr_3D*arr_3D*arr_3D,np.einsum('ijk,ijk,ijk->ijk',arr_3D,arr_3D,arr_3D)) True %timeit arr_3D*arr_3D*arr_3D 1 loops, best of 3: 1.32 s per loop %timeit np.einsum('ijk,ijk,ijk->ijk', arr_3D, arr_3D, arr_3D) 1 loops, best of 3: 694 ms per loop Outer product: np.all(np.outer(arr_1D,arr_1D)==np.einsum('i,k->ik',arr_1D,arr_1D)) True %timeit np.outer(arr_1D, arr_1D) 1000 loops, best of 3: 411 us per loop %timeit np.einsum('i,k->ik', arr_1D, arr_1D) 1000 loops, best of 3: 245 us per loop All of the above are twice as fast with np.einsum. These should be apples to apples comparisons as everything is specifically of dtype=np.double. I would expect the speed up in an operation like this: np.allclose(np.sum(arr_2D*arr_3D),np.einsum('ij,oij->',arr_2D,arr_3D)) True %timeit np.sum(arr_2D*arr_3D) 1 loops, best of 3: 813 ms per loop %timeit np.einsum('ij,oij->', arr_2D, arr_3D) 10 loops, best of 3: 85.1 ms per loop Einsum seems to be at least twice as fast for np.inner, np.outer, np.kron, and np.sum regardless of axes selection. The primary exception being np.dot as it calls DGEMM from a BLAS library. So why is np.einsum faster that other numpy functions that are equivalent? The DGEMM case for completeness: np.allclose(np.dot(arr_2D,arr_2D),np.einsum('ij,jk',arr_2D,arr_2D)) True %timeit np.einsum('ij,jk',arr_2D,arr_2D) 10 loops, best of 3: 56.1 ms per loop %timeit np.dot(arr_2D,arr_2D) 100 loops, best of 3: 5.17 ms per loop The leading theory is from @sebergs comment that np.einsum can make use of SSE2, but numpy's ufuncs will not until numpy 1.8 (see the change log). I believe this is the correct answer, but have not been able to confirm it. Some limited proof can be found by changing the dtype of input array and observing speed difference and the fact that not everyone observes the same trends in timings.

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  • High CPU usage when running several "java -version" in parallel

    - by Prateesh
    This is just out of curiosity to understand i have a small shell script for ((i = 0; i < 50; i++)) do java -version & done when i run this my CPU usage report by sar is as below 07:51:25 PM CPU %user %nice %system %iowait %steal %idle 07:51:30 PM all 6.98 0.00 1.75 1.00 0.00 90.27 07:51:31 PM all 43.00 0.00 12.00 0.00 0.00 45.00 07:51:32 PM all 86.28 0.00 13.72 0.00 0.00 0.00 07:51:33 PM all 5.25 0.00 1.75 0.50 0.00 92.50 As you can see, on the third line the CPU is at 100% My java version is 1.5.0_22-b03.

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  • Tuning MySQL to take advantage of a 4GB VPS

    - by alistair.mp
    Hello, We're running a large site at the moment which has a dedicated VPS for it's database server which is running MySQL and nothing else. At the moment all four CPU cores are running at close to 100% all of the time but the memory usage sticks at around 268MB out of an available 4096MB. I'm wondering what we can do to better utilise the memory and reduce the CPU load by tweaking MySQL's settings? Here is what we currently have in my.cnf: http://pastie.org/private/hxeji9o8n3u9up9mvtinbq Thanks

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  • Is there a fast way to jump to element using XMLReader?

    - by Derk
    I am using XMLReader to read a large XML file with about 1 million elements on the level I am reading from. However, I've calculated it will take over 10 seconds when I jump to -for instance- element 500.000 using XMLReader::next ([ string $localname ] ) or XMLReader::read ( void ) This is not very usable. Is there a faster way to do this?

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  • Good way to make animations with cocos2d?

    - by Johnny Oin
    Hi there, I'm making a little iphone game, and I would get some clues. Let's imagine: Two background sprites moving pretty fast from right to left, and moving up and down with accelerometer. I guess I can't use animations here, cause the movement of the background is recalculated at each frame. So I use a schedule with an interval of 0.025s and move my sprites at each clock with a : sprite.position = ccp(x, y); So here is my problem: the result is laggy, with only these two sprites. I tried both declaring sprites in the header, and getting them with CCNodes and Tags. It's quite the same. So if someone can give me a hint on what is the best way to do that, that would be so nice. I wonder if the problem can't be the fact that sprites are moving very fast, but i'm not sure. Anyway, thanks for your time. J.

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  • 2 approaches for tracking online users with Redis. Which one is faster?

    - by Stanislav
    Recently I found an nice blog post presenting 2 approaches for tracking online users of a web site with the help of Redis. 1) Smart-keys and setting their expiration http://techno-weenie.net/2010/2/3/where-s-waldo-track-user-locations-with-node-js-and-redis 2) Set-s and intersects http://www.lukemelia.com/blog/archives/2010/01/17/redis-in-practice-whos-online/ Can you judge which one should be faster and why?

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  • Image 8-connectivity without excessive branching?

    - by shoosh
    I'm writing a low level image processing algorithm which needs to do alot of 8-connectivity checks for pixels. For every pixel I often need to check the pixels above it, below it and on its sides and diagonals. On the edges of the image there are special cases where there are only 5 or 3 neighbors instead of 8 neighbors for a pixels. The naive way to do it is for every access to check if the coordinates are in the right range and if not, return some default value. I'm looking for a way to avoid all these checks since they introduce a large overhead to the algorithm. Are there any tricks to avoid it altogether?

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  • Slow SelectSingleNode

    - by Simon
    I have a simple structured XML file like this: <ttest ID="ttest00001", NickName="map00001"/> <ttest ID="ttest00002", NickName="map00002"/> <ttest ID="ttest00003", NickName="map00003"/> <ttest ID="ttest00004", NickName="map00004"/> ..... This xml file can be around 2.5MB. In my source code I will have a loop to get nicknames In each loop, I have something like this: nickNameLoopNum = MyXmlDoc.SelectSingleNode("//ttest[@ID=' + testloopNum + "']").Attributes["NickName"].Value This single line will cost me 30 to 40 millisecond. I searched some old articles (dated back to 2002) saying, use some sort of compiled "xpath" can help the situation, but that was 5 years ago. I wonder is there a mordern practice to make it faster? (I'm using .NET 3.5)

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  • My Zend Framework 'quoting' mess.

    - by tharkun
    I've got a probably very simple issue to which I can't find a satisfactory (subjectively seen) answer in the Zend Framework manual or elsewhere... There are so many ways how I can hand over my php variables to my sql queries that I lost the overview and probably I lack some understanding about quoting in general. Prepared Statements $sql = "SELECT this, that FROM table WHERE id = ? AND restriction = ?"; $stmt = $this->_db->query($sql, array($myId, $myValue)); $result = $stmt->fetchAll(); I understand that with this solution I don't need to quote anything because the db handles this for me. Querying Zend_Db_Table and _Row objects over the API $users = new Users(); a) $users->fetchRow('userID = ' . $userID); b) $users->fetchRow('userID = ' . $users->getAdapter()->quote($userID, 'INTEGER')); c) $users->fetchRow('userID = ?', $userID); d) $users->fetchRow('userID = ?', $users->getAdapter()->quote($userID, 'INTEGER')); Questions I understand that a) is not ok because it's not quoted at all. But what about the other versions, what's the best? Is c) being treated like a statement and automatically quoted or do I need to use d) when I use the ? identifier?

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  • Doing large updates against indexed view

    - by user217136
    We have an indexed view that runs across three large tables. Two of these tables (A & B) are constantly getting updated with user transactions and the other table (C) contains data product info that is needs to be updated once a week. This product table contains over 6 million records. We need this view across these three tables for our core business process and unfortunately we cannot change this aspect. We even had a sql server MVP come in to help test under load to make sure we have the most efficient configuration. There is one column in the product table that gets utilized in the view and has to be updated each week. The problem we are now encountering is that as volume is increasing on our transactions against tables A & B, the update to Table C is causing deadlocks. I have tried several different methods to no avail: 1) I was hoping that we could change the view so that table C could be a dirty read "WITH (NOLOCK)" but apparently that functionality is not available with indexes views. 2) I thought about updating a new column in Table C and then just renaming it when the process is done but you cannot do that due to the dependency in the view. 3) I also entertained the idea of writing this value to a temporary product table, and then running an ALTER statement against the view to have it point to my new table. however when i did that the indexes on my view were dropped and it took quite a bit of time to recreate them. 4) we tried to do the weekly update in small chunks (as small as 100 records at a time) but we still run into dead locks. questions: a) we are using sql server 2005. Does sql server 2008 have a new functionality with their indexed views that would help us? Is there now a way to do dirty reads w/ an indexed view? b) a better approach to altering an existing view to point to a new table? thanks!

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  • Perf4J Logging Config Help

    - by manyxcxi
    I currently have a long running process that I am trying to analyze with Perf4J. I currently have it writing results in CSV format to its own log file using the AsyncCoalescingStatisticsAppender and a StatisticsCsvLayout on the file appender. My question is; when I try and use the --graph option from the command line (using the perf4j jar) it isn't populating the data points- it isn't populating anything. Are my appenders set incorrectly? The log file contains hundreds (sometimes thousands) of data points of about 10 different tag names. <appender name="perfAppender" class="org.apache.log4j.FileAppender"> <param name="File" value="perfStats.log"/> <layout class="org.perf4j.log4j.StatisticsCsvLayout"> </layout> </appender> <appender name="CoalescingStatistics" class="org.perf4j.log4j.AsyncCoalescingStatisticsAppender"> <!-- The TimeSlice option is used to determine the time window for which all received StopWatch logs are aggregated to create a single GroupedTimingStatistics log. Here we set it to 10 seconds, overriding the default of 30000 ms --> <param name="TimeSlice" value="10000"/> <appender-ref ref="ConsoleAppender"/> <appender-ref ref="CompositeRollingFileAppender"/> <appender-ref ref="perfAppender"/> </appender>

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  • Loading animation Memory leak

    - by Ayaz Alavi
    Hi, I have written network class that is managing all network calls for my application. There are two methods showLoadingAnimationView and hideLoadingAnimationView that will show UIActivityIndicatorView in a view over my current viewcontroller with fade background. I am getting memory leaks somewhere on these two methods. Here is the code -(void)showLoadingAnimationView { textmeAppDelegate *textme = (textmeAppDelegate *)[[UIApplication sharedApplication] delegate]; [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES]; if(wrapperLoading != nil) { [wrapperLoading release]; } wrapperLoading = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 480.0)]; wrapperLoading.backgroundColor = [UIColor clearColor]; wrapperLoading.alpha = 0.8; UIView *_loadingBG = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 480.0)]; _loadingBG.backgroundColor = [UIColor blackColor]; _loadingBG.alpha = 0.4; circlingWheel = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge]; CGRect wheelFrame = circlingWheel.frame; circlingWheel.frame = CGRectMake(((320.0 - wheelFrame.size.width) / 2.0), ((480.0 - wheelFrame.size.height) / 2.0), wheelFrame.size.width, wheelFrame.size.height); [wrapperLoading addSubview:_loadingBG]; [wrapperLoading addSubview:circlingWheel]; [circlingWheel startAnimating]; [textme.window addSubview:wrapperLoading]; [_loadingBG release]; [circlingWheel release]; } -(void)hideLoadingAnimationView { [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO]; wrapperLoading.alpha = 0.0; [self.wrapperLoading removeFromSuperview]; //[NSTimer scheduledTimerWithTimeInterval:0.8 target:wrapperLoading selector:@selector(removeFromSuperview) userInfo:nil repeats:NO]; } Here is how I am calling these two methods [NSThread detachNewThreadSelector:@selector(showLoadingAnimationView) toTarget:self withObject:nil]; and then somewhere later in the code i am using following function call to hide animation. [self hideLoadingAnimationView]; I am getting memory leaks when I call showLoadingAnimationView function. Anything wrong in the code or is there any better technique to show loading animation when we do network calls?

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  • WPF Dragging causes renderer to stop

    - by Cameron MacFarland
    I'm having a problem with my WPF app, where any sort of drag operation stops the UI from updating. The issue seems periodic, as in, the item drags, stops, drags again, stops, etc. in 2 second intervals. It's affecting all controls, including scroll bars. If checked this question as well as this one, and it doesn't seem to be caused by window transparencies. I'm running Win7 x64 with .NET 3.5sp1. Does anyone know what might be causing this, or a way of figuring out what might be causing this?

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  • Bulk inserts into sqlite db on the iphone...

    - by akaii
    I'm inserting a batch of 100 records, each containing a dictonary containing arbitrarily long HTML strings, and by god, it's slow. On the iphone, the runloop is blocking for several seconds during this transaction. Is my only recourse to use another thread? I'm already using several for acquiring data from HTTP servers, and the sqlite documentation explicitly discourages threading with the database, even though it's supposed to be thread-safe... Is there something I'm doing extremely wrong that if fixed, would drastically reduce the time it takes to complete the whole operation? NSString* statement; statement = @"BEGIN EXCLUSIVE TRANSACTION"; sqlite3_stmt *beginStatement; if (sqlite3_prepare_v2(database, [statement UTF8String], -1, &beginStatement, NULL) != SQLITE_OK) { printf("db error: %s\n", sqlite3_errmsg(database)); return; } if (sqlite3_step(beginStatement) != SQLITE_DONE) { sqlite3_finalize(beginStatement); printf("db error: %s\n", sqlite3_errmsg(database)); return; } NSTimeInterval timestampB = [[NSDate date] timeIntervalSince1970]; statement = @"INSERT OR REPLACE INTO item (hash, tag, owner, timestamp, dictionary) VALUES (?, ?, ?, ?, ?)"; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(database, [statement UTF8String], -1, &compiledStatement, NULL) == SQLITE_OK) { for(int i = 0; i < [items count]; i++){ NSMutableDictionary* item = [items objectAtIndex:i]; NSString* tag = [item objectForKey:@"id"]; NSInteger hash = [[NSString stringWithFormat:@"%@%@", tag, ownerID] hash]; NSInteger timestamp = [[item objectForKey:@"updated"] intValue]; NSData *dictionary = [NSKeyedArchiver archivedDataWithRootObject:item]; sqlite3_bind_int( compiledStatement, 1, hash); sqlite3_bind_text( compiledStatement, 2, [tag UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text( compiledStatement, 3, [ownerID UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_int( compiledStatement, 4, timestamp); sqlite3_bind_blob( compiledStatement, 5, [dictionary bytes], [dictionary length], SQLITE_TRANSIENT); while(YES){ NSInteger result = sqlite3_step(compiledStatement); if(result == SQLITE_DONE){ break; } else if(result != SQLITE_BUSY){ printf("db error: %s\n", sqlite3_errmsg(database)); break; } } sqlite3_reset(compiledStatement); } timestampB = [[NSDate date] timeIntervalSince1970] - timestampB; NSLog(@"Insert Time Taken: %f",timestampB); // COMMIT statement = @"COMMIT TRANSACTION"; sqlite3_stmt *commitStatement; if (sqlite3_prepare_v2(database, [statement UTF8String], -1, &commitStatement, NULL) != SQLITE_OK) { printf("db error: %s\n", sqlite3_errmsg(database)); } if (sqlite3_step(commitStatement) != SQLITE_DONE) { printf("db error: %s\n", sqlite3_errmsg(database)); } sqlite3_finalize(beginStatement); sqlite3_finalize(compiledStatement); sqlite3_finalize(commitStatement);

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  • has anyone used simile timeline with large amounts of data

    - by oo
    i am using this simile timeline with large amounts of data and i keep getting firefox popping up saying "a script has appeared to no longer be running, do you want to kill it"? is there a limit to the amount of json you can send back to it. I have about 1000 different timeline points with dates, descriptions, etc.

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  • Javascript scope chain

    - by Geromey
    Hi, I am trying to optimize my program. I think I understand the basics of closure. I am confused about the scope chain though. I know that in general you want a low scope (to access variables quickly). Say I have the following object: var my_object = (function(){ //private variables var a_private = 0; return{ //public //public variables a_public : 1, //public methods some_public : function(){ debugger; alert(this.a_public); alert(a_private); }; }; })(); My understanding is that if I am in the some_public method I can access the private variables faster than the public ones. Is this correct? My confusion comes with the scope level of this. When the code is stopped at debugger, firebug shows the public variable inside the this keyword. The this word is not inside a scope level. How fast is accessing this? Right now I am storing any this.properties as another local variable to avoid accessing it multiple times. Thanks very much!

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  • MS Query Analyzer / Management Studio replacement?

    - by kprobst
    I've been using SQL Server since version 6.5 and I've always been a bit amazed at the fact that the tools seem to be targeted to DBAs rather than developers. I liked the simplicity and speed of the Query Analyzer for example, but hated the built-in editor, which was really no better than a syntax coloring-capable Notepad. Now that we have Management Studio the management part seems a bit better but from a developer standpoint the tools is even worse. Visual Studio's excellent text editor... without a way to customize keyboard bindings!? Don't get me started on how unusable is the tree-based management hierarchy. Why can't I re-root the tree on a list of stored procs for example the way the Enterprise Manager used to allow? Now I have a treeview that needs to be scrolled horizontally, which makes it eminently useless. The SQL server support in Visual Studio is fantastic for working with stored procedures and functions, but it's terrible as a general ad hoc data query tool. I've tried various tools over the years but invariably they seem to focus on the management side and shortchange the developer in me. I just want something with basic admin capabilities, good keyboard support and requisite DDL functionality (ideally something like the Query Analyzer). At this point I'm seriously thinking of using vim+sqlcmd and a console... I'm that desperate :) Those of you who work day in and day out with SQL Server and Visual Studio... do you find the tools to be adequate? Have you ever wished they were better and if you have found something better, could you share please? Thanks!

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  • Lucene search taking TOOO long.

    - by Josh Handel
    I;m using Lucene.net (2.9.2.2) on a (currently) 70Gig index.. I can do a fairly complicated search and get all the document IDs back in 1 ~ 2 seconds.. But to actually load up all the hits (about 700 thousand in my test queries) takes 5+ minutes. We aren't using lucene for UI, this is a datastore between processes where we have hundreds of millions of pre-cached data elements, and the part I am working on exports a few specific fields from each found document. (ergo, pagination doesn't make since as this is an export between processes). My question is what is the best way to get all of the documents in a search result? currently I am using a custom collector that does a get on the document (with a MapFieldSelector) as its collecting.. I've also tried iterating through the list after the collector has finished.. but that was even worse. I'm open to ideas :-). Thanks in advance.

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  • Make compiler copy characters using movsd

    - by Suma
    I would like to copy a relatively short sequence of memory (less than 1 KB, typically 2-200 bytes) in a time critical function. The best code for this on CPU side seems to be rep movsd. However I somehow cannot make my compiler to generate this code. I hoped (and I vaguely remember seeing so) using memcpy would do this using compiler built-in instrinsic, but based on disassembly and debugging it seems compiler is using call to memcpy/memmove library implementation instead. I also hoped the compiler might be smart enough to recognize following loop and use rep movsd on its own, but it seems it does not. char *dst; const char *src; // ... for (int r=size; --r>=0; ) *dst++ = *src++; Is there some way to make the Visual Studio compiler to generate rep movsd sequence other than using inline assembly?

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  • Practical approach to concurrency control

    - by Industrial
    Hi everyone, I'd read this article recently and are very interested on how to make a practical approach to Concurrency control on a web server. The server will run CentOS + PHP + mySQL with Memcached. How would you set it up to work? http://saasinterrupted.com/2010/02/05/high-availability-principle-concurrency-control/ Thanks!

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  • Pre-generating GUIDs for use in python?

    - by rjuiaa1
    I have a python program that needs to generate several guids and hand them back with some other data to a client over the network. It may be hit with a lot of requests in a short time period and I would like the latency to be as low as reasonably possible. Ideally, rather than generating new guids on the fly as the client waits for a response, I would rather be bulk-generating a list of guids in the background that is continually replenished so that I always have pre-generated ones ready to hand out. I am using the uuid module in python on linux. I understand that this is using the uuidd daemon to get uuids. Does uuidd already take care of pre-genreating uuids so that it always has some ready? From the documentation it appears that it does not. Is there some setting in python or with uuidd to get it to do this automatically? Is there a more elegant approach then manually creating a background thread in my program that maintains a list of uuids?

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