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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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• 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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• Would watching a file for changes or redundantly querying that file be more efficient?

  - by badpanda

  I am wondering whether watching a file/directory for changes using the FileSystemWatcher class is extremely memory intensive. I am developing a desktop application in C# that will be running behind the scenes continuously on low-performance computers, and I need some way of checking to see if various files have changed. I can think of a few solutions: Watch the directories using FileSystemWatcher. Run a timed thread on an interval that goes through and manually checks this. Check manually every time the actionhandler thread runs (the program will occasionally do something, on an action). Any suggestions? Thanks! badPanda

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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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• 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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• cant populate cells with an array when i have loaded a second UITableViewController

  - by richard Stephenson

  hi there, im very new to iphone programming, im creating my first app, (a world cup one) the first view is a table view. the cell text label is filled with an array, so it shows all the groups (group a, B, c,ect) then when you select a group, it pulls on another UITableViewcontroller, but whatever i do i cant set the text label of the cells (e.g france,mexico,south africa, etc. infact nothin i do to the cellForRowAtIndexPath makes a difference , could someone tell me what im doing wrong please Thanks `here is my code for the view controller #import "GroupADetailViewController.h" @implementation GroupADetailViewController @synthesize groupLabel = _groupLabel; @synthesize groupADetail = _groupADetail; @synthesize teamsInGroupA; #pragma mark Memory management - (void)dealloc { [_groupADetail release]; [_groupLabel release]; [super dealloc]; } #pragma mark View lifecycle - (void)viewDidLoad { [super viewDidLoad]; // Set the number label to show the number data teamsInGroupA = [[NSArray alloc]initWithObjects:@"France",@"Mexico",@"Uruguay",@"South Africa",nil]; NSLog(@"loaded"); // Set the title to also show the number data [[self navigationItem]setTitle:@"Group A"]; //[[self navigationItem]cell.textLabel.text:@"test"]; //[[self navigationItem] setTitle[NSString String } - (void)viewDidUnload { [self setgroupLabel:nil]; } #pragma mark Table view methods - (NSInteger)numberOfSectionsInTableView:(UITableView*)tableView { // Return the number of sections in the table view return 1; } - (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)section { // Return the number of rows in a specific section // Since we only have one section, just return the number of rows in the table return 4; NSLog:("count is %d",[teamsInGroupA count]); } - (UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath*)indexPath { static NSString *cellIdentifier2 = @"Cell2"; // Reuse an existing cell if one is available for reuse UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier2]; // If no cell was available, create a new one if (cell == nil) { NSLog(@"no cell, creating"); cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier2] autorelease]; [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator]; } NSLog(@"cell already there"); // Configure the cell to show the data for this row //[[cell textLabel]setText:[NSString string //[[cell textLabel]setText:[teamsInGroupA objectAtIndex:indexPath.row]]; //NSUInteger row = [indexPath row]; //[cell setText:[[teamsInGroupA objectAtIndex:indexPath:row]retain]]; //cell.textLabel.text:@"Test" [[cell textLabel]setText:[teamsInGroupA objectAtIndex:indexPath.row]]; return cell; } @end #import "GroupADetailViewController.h" @implementation GroupADetailViewController @synthesize groupLabel = _groupLabel; @synthesize groupADetail = _groupADetail; @synthesize teamsInGroupA; #pragma mark Memory management - (void)dealloc { [_groupADetail release]; [_groupLabel release]; [super dealloc]; } #pragma mark View lifecycle - (void)viewDidLoad { [super viewDidLoad]; // Set the number label to show the number data teamsInGroupA = [[NSArray alloc]initWithObjects:@"France",@"Mexico",@"Uruguay",@"South Africa",nil]; NSLog(@"loaded"); // Set the title to also show the number data [[self navigationItem]setTitle:@"Group A"]; //[[self navigationItem]cell.textLabel.text:@"test"]; //[[self navigationItem] setTitle[NSString String } - (void)viewDidUnload { [self setgroupLabel:nil]; } #pragma mark Table view methods - (NSInteger)numberOfSectionsInTableView:(UITableView*)tableView { // Return the number of sections in the table view return 1; } - (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)section { // Return the number of rows in a specific section // Since we only have one section, just return the number of rows in the table return 4; NSLog:("count is %d",[teamsInGroupA count]); } - (UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath*)indexPath { static NSString *cellIdentifier2 = @"Cell2"; // Reuse an existing cell if one is available for reuse UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier2]; // If no cell was available, create a new one if (cell == nil) { NSLog(@"no cell, creating"); cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier2] autorelease]; [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator]; } NSLog(@"cell already there"); // Configure the cell to show the data for this row //[[cell textLabel]setText:[NSString string //[[cell textLabel]setText:[teamsInGroupA objectAtIndex:indexPath.row]]; //NSUInteger row = [indexPath row]; //[cell setText:[[teamsInGroupA objectAtIndex:indexPath:row]retain]]; //cell.textLabel.text:@"Test" [[cell textLabel]setText:[teamsInGroupA objectAtIndex:indexPath.row]]; return cell; } @end

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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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• When does printf("%s", char*) stop printing?

  - by remagen

  In my class we are writing our own copy of C's malloc() function. To test my code (which can currently allocate space fine) I was using: char* ptr = my_malloc(6*sizeof(char)); memcpy(ptr, "Hello\n", 6*sizeof(char)); printf("%s", ptr); The output would typically be this: Hello Unprintable character Some debugging figured that my code wasn't causing this per say, as ptr's memory is as follows: [24 bytes of meta info][Number of requested bytes][Padding] So I figured that printf was reaching into the padding, which is just garbage. So I ran a test of: printf("%s", "test\nd"); and got: test d Which makes me wonder, when DOES printf("%s", char*) stop printing chars?

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• How can you tell the source of the data when using the Stream.BeginRead Method?

  - by xarzu

  When using the Stream.BeginRead Method, and you are reading from a stream into a memory, how is it determined where you are reading the data from? See: http://msdn.microsoft.com/en-us/library/system.io.stream.beginread.aspx In the list of parameters, I do not see one that tells where the data is being read from: Parameters buffer Type: System.Byte[] The buffer to read the data into. offset Type: System.Int32 The byte offset in buffer at which to begin writing data read from the stream. count Type: System.Int32 The maximum number of bytes to read. callback Type: System.AsyncCallback An optional asynchronous callback, to be called when the read is complete. state Type: System.Object A user-provided object that distinguishes this particular asynchronous read request from other requests.

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• Windbg pseudoregister expansion

  - by Giuseppe Guerrini

  Hi, I am trying to automate a device driver's debug session in Windows XP with Windbg. My device has an "index" register and a "data" register, both memory mapped. The index register must be filled with the internal register's index, and the value can be read from the data register. So, the followind Windbg command prints correctly the value of the internel register 0x4C: !ed [uc] 0xfa000000 0x4c; !dd [uc] 0xfa000004 L1 Now I would like to dump a range of internal registers, but it seems that the alias expansion doesn't work as expected in the !ed command. I am trying this cycle: .for (r $t0=0; @$t0<0x100; r $t0=@$t0+1) { !ed [uc] 0xfa000000 @$t0; !dd [uc] 0xfa000004 L1 } but it seems that the !ed command is ignored, as if @$t0 was expanded in an empty string. Tried "$t0", "@$t0", "${t0}" and "@${t0}", but without success. What am I doing wrong? Thank you in advance

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• ORM solutions (JPA; Hibernate) vs. JDBC

  - by Grasper

  I need to be able to insert/update objects at a consistent rate of at least 8000 objects every 5 seconds in an in-memory HSQL database. I have done some comparison performance testing between Spring/Hibernate/JPA and pure JDBC. I have found a significant difference in performance using HSQL.. With Spring/Hib/JPA, I can insert 3000-4000 of my 1.5 KB objects (with a One-Many and a Many-Many relationship) in 5 seconds, while with direct JDBC calls I can insert 10,000-12,000 of those same objects. I cannot figure out why there is such a huge discrepancy. I have tweaked the Spring/Hib/JPA settings a lot trying to get close in performance without luck. I want to use Spring/Hib/JPA for future purposes, expandability, and because the foreign key relationships (one-many and many-many) are difficult to maintain by hand; but the performance requirements seem to point towards using pure JDBC. Any ideas of why there would be such a huge discrepancy?

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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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• 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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• 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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• Why dont Android applications provide an "Exit" option?

  - by Howiecamp

  Is there something in the Android developer guidelines that disuadea developers from providing the option to "exit" (stop running) an application from within the application itself? I love multitasking and all but it's not clear to me why: the vast majority of apps don't have their own Exit functions and hence just keep running forever don't give you a choice about running when you turn on the phone - they just do by default Both of these things lead to memory usage constantly increasing and your device running with this performance burden all of the time despite the fact that you may only want certain apps to run some of the time. Am I missing something?

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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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• 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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• 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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• Cobol: science and fiction

  - by user847

  There are a few threads about the relevance of the Cobol programming language on this forum, e.g. this thread links to a collection of them. What I am interested in here is a frequently repeated claim based on a study by Gartner from 1997: that there were around 200 billion lines of code in active use at that time! I would like to ask some questions to verify or falsify a couple of related points. My goal is to understand if this statement has any truth to it or if it is totally unrealistic. I apologize in advance for being a little verbose in presenting my line of thought and my own opinion on the things I am not sure about, but I think it might help to put things in context and thus highlight any wrong assumptions and conclusions I have made. Sometimes, the "200 billion lines" number is accompanied by the added claim that this corresponded to 80% of all programming code in any language in active use. Other times, the 80% merely refer to so-called "business code" (or some other vague phrase hinting that the reader is not to count mainstream software, embedded systems or anything else where Cobol is practically non-existent). In the following I assume that the code does not include double-counting of multiple installations of the same software (since that is cheating!). In particular in the time prior to the y2k problem, it has been noted that a lot of Cobol code is already 20 to 30 years old. That would mean it was written in the late 60ies and 70ies. At that time, the market leader was IBM with the IBM/370 mainframe. IBM has put up a historical announcement on his website quoting prices and availability. According to the sheet, prices are about one million dollars for machines with up to half a megabyte of memory. Question 1: How many mainframes have actually been sold? I have not found any numbers for those times; the latest numbers are for the year 2000, again by Gartner. :^( I would guess that the actual number is in the hundreds or the low thousands; if the market size was 50 billion in 2000 and the market has grown exponentially like any other technology, it might have been merely a few billions back in 1970. Since the IBM/370 was sold for twenty years, twenty times a few thousand will result in a couple of ten-thousands of machines (and that is pretty optimistic)! Question 2: How large were the programs in lines of code? I don't know how many bytes of machine code result from one line of source code on that architecture. But since the IBM/370 was a 32-bit machine, any address access must have used 4 bytes plus instruction (2, maybe 3 bytes for that?). If you count in operating system and data for the program, how many lines of code would have fit into the main memory of half a megabyte? Question 3: Was there no standard software? Did every single machine sold run a unique hand-coded system without any standard software? Seriously, even if every machine was programmed from scratch without any reuse of legacy code (wait ... didn't that violate one of the claims we started from to begin with???) we might have O(50,000 l.o.c./machine) * O(20,000 machines) = O(1,000,000,000 l.o.c.). That is still far, far, far away from 200 billion! Am I missing something obvious here? Question 4: How many programmers did we need to write 200 billion lines of code? I am really not sure about this one, but if we take an average of 10 l.o.c. per day, we would need 55 million man-years to achieve this! In the time-frame of 20 to 30 years this would mean that there must have existed two to three million programmers constantly writing, testing, debugging and documenting code. That would be about as many programmers as we have in China today, wouldn't it? Question 5: What about the competition? So far, I have come up with two things here: 1) IBM had their own programming language, PL/I. Above I have assumed that the majority of code has been written exclusively using Cobol. However, all other things being equal I wonder if IBM marketing had really pushed their own development off the market in favor of Cobol on their machines. Was there really no relevant code base of PL/I? 2) Sometimes (also on this board in the thread quoted above) I come across the claim that the "200 billion lines of code" are simply invisible to anybody outside of "governments, banks ..." (and whatnot). Actually, the DoD had funded their own language in order to increase cost effectiveness and reduce the proliferation of programming language. This lead to their use of Ada. Would they really worry about having so many different programming languages if they had predominantly used Cobol? If there was any language running on "government and military" systems outside the perception of mainstream computing, wouldn't that language be Ada? I hope someone can point out any flaws in my assumptions and/or conclusions and shed some light on whether the above claim has any truth to it or not.

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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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• .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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• How can I modify objects inside frames with AS3 in a permanent way?

  - by curro

  I have a MovieClip symbol created with flash in a fla file library. There is a textfield in frame one of this movieclip's timeline . There is another frame in the movieclip timeline. There is a custon class definition for this symbol. It is a flipping card in a memory game. I access the textfield by going to frame 2 (gotoAndStop(2)) and setting the textfield's text property ( this.field.text = "hello" ). However if I go to frame 1 and then return to frame 2, the text becomes the original one in the library's symbol. I have to modify the text propery again in a showFace method I've written. Besides, I cannot pass parameters in the constructor because it is a symbol in the library and that would give errors. I find this behaviour of flash extremely weird. Is there a way I can set properties inside frames permanently? Thank you

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• Is there a distributed VCS that can manage large files?

  - by joelhardi

  Is there a distributed version control system (git, bazaar, mercurial, darcs etc.) that can handle files larger than available RAM? I need to be able to commit large binary files (i.e. datasets, source video/images, archives), but I don't need to be able to diff them, just be able to commit and then update when the file changes. I last looked at this about a year ago, and none of the obvious candidates allowed this, since they're all designed to diff in memory for speed. That left me with a VCS for managing code and something else ("asset management" software or just rsync and scripts) for large files, which is pretty ugly when the directory structures of the two overlap.

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• Why isn't Passenger respecting my custom log format?

  - by Millisami

  I need to change the log format of my rails app. I put this file in lib directory and required it in development.rb env file. require 'hodel_3000_compliant_logger' config.logger = Hodel3000CompliantLogger.new(config.log_path) and I should get the output of the development.log file as follows: Jun 28 03:05:13 millisami-notebook rails[18243]: Memory usage: 86888 | PID: 18243 I get this exact log when I start my app with script/server (Mongrel). But when I run the app via Passenger, the format being logged is Rails' default. Why doesn't Passenger write to the log file like Mongrel does?

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• Java multi-threading - what is the best way to monitor the activity of a number of threads?

  - by MalcomTucker

  I have a number of threads that are performing a long runing task. These threads themselves have child threads that do further subdivisions of work. What is the best way for me to track the following: How many total threads my process has created What the state of each thread currently is What part of my process each thread has currently got to I want to do it in as efficient a way as possible and once threads finish, I don't want any references to them hanging around becasuse I need to be freeing up memory as early as possible. Any advice?

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