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• Strange jQueryUI dialog error

  - by umpirsky

  I have dialog created like this $('#add_error').click(function(e) { $('<div>') .load('/someaction/format/html/') .dialog({ title: 'Some title', modal: true, width: 385, close: function() { $(this).remove(); } }); e.preventDefault(); }); It works ok, but every third (not really sure if its really third) time I click link to open dialog, it fails with error in firebug "$("").addClass("ui-widget-overlay") is undefined" In dialog.js that is piece of code: var $el = (this.oldInstances.length ? this.oldInstances.splice(0, 1)[0] : $('<div></div>').addClass('ui-widget-overlay')) .appendTo(document.body) .css({ width: this.width(), height: this.height() }); under create: function(dialog) method. Strange thing is that this error does not occur when I remove close: function() { $(this).remove(); } Any idea?

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• Dynamic Flex verticalaxisrenderers

  - by user276424

  Hi, I've created a linechart in flex using pure as3. I need now to convert it to a dynamic multi axis chart. What I mean by dynamic, is that I can programmatically add or remove axisrenderers from the verticalaxisrenderer array at runtime. It seems i can remove axisrenderers at runtime by simply doing this: verticalAxisRenderers = verticalAxisRenderers.splice(index,1); However, ADDING axisrenderers is not working. I am doing it by so: verticalAxisRenderers.push(ar2); verticalAxisRenderers = verticalAxisRenderers; Where am I going wrong? Please help! Thanks, Tone

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• C++ wrapper for posix and linux specific functions

  - by Libzajc

  Hi Do you know about any good library wrapping posix and linux functions and structures ( eg. sockets or file descriptors ) into C++ classes? For example I'm thinking about a base FileDescriptor class and some inheriting classes ( unix sockets etc ) with methods like write, read or even some syscalls ( sendfile, splice ) - all throwing exceptions instead of setting errno. Or some shared memory class etc. I can't seem to find anything like that and by now I consider writing it myself, as I often have to write a C++ app for linux and either use C functions ( painful error checking ), or wrap them myself every time.

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• Is this an F# quotations bug?

  - by ControlFlow

  [<ReflectedDefinition>] let rec x = (fun() -> x + "abc") () The sample code with the recursive value above produces the following F# compiler error: error FS0432: [<ReflectedDefinition>] terms cannot contain uses of the prefix splice operator '%' I can't see any slicing operator usage in the code above, looks like a bug... :) Looks like this is the problem with the quotation via ReflectedDefinitionAttribute only, normal quotation works well: let quotation = <@ let rec x = (fun() -> x + "abc") () in x @> produces expected result with the hidden Lazy.create and Lazy.force usages: val quotation : Quotations.Expr<string> = LetRecursive ([(x, Lambda (unitVar, Application (Lambda (unitVar0, Call (None, String op_Addition[String,String,String](String, String), [Call (None, String Force[String](Lazy`1[System.String]), [x]), Value ("abc")])), Value (<null>)))), (x, Call (None, Lazy`1[String] Create[String](FSharpFunc`2[Unit,String]), [x])), (x, Call (None, String Force[String](Lazy`1[String]), [x]))], x) So the question is: is this an F# compiler bug or not?

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• How to get javascript object references or reference count?

  - by Tauren

  How to get reference count for an object Is it possible to determine if a javascript object has multiple references to it? Or if it has references besides the one I'm accessing it with? Or even just to get the reference count itself? Can I find this information from javascript itself, or will I need to keep track of my own reference counters. Obviously, there must be at least one reference to it for my code access the object. But what I want to know is if there are any other references to it, or if my code is the only place it is accessed. I'd like to be able to delete the object if nothing else is referencing it. If you know the answer, there is no need to read the rest of this question. Below is just an example to make things more clear. Use Case In my application, I have a Repository object instance called contacts that contains an array of ALL my contacts. There are also multiple Collection object instances, such as friends collection and a coworkers collection. Each collection contains an array with a different set of items from the contacts Repository. Sample Code To make this concept more concrete, consider the code below. Each instance of the Repository object contains a list of all items of a particular type. You might have a repository of Contacts and a separate repository of Events. To keep it simple, you can just get, add, and remove items, and add many via the constructor. var Repository = function(items) { this.items = items || []; } Repository.prototype.get = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { return this.items[i]; } } } Repository.prototype.add = function(item) { if (toString.call(item) === "[object Array]") { this.items.concat(item); } else { this.items.push(item); } } Repository.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { this.removeIndex(i); } } } Repository.prototype.removeIndex = function(index) { if (items[index]) { if (/* items[i] has more than 1 reference to it */) { // Only remove item from repository if nothing else references it this.items.splice(index,1); return; } } } Note the line in remove with the comment. I only want to remove the item from my master repository of objects if no other objects have a reference to the item. Here's Collection: var Collection = function(repo,items) { this.repo = repo; this.items = items || []; } Collection.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { // Remove object from this collection this.items.splice(i,1); // Tell repo to remove it (only if no other references to it) repo.removeIndxe(i); return; } } } And then this code uses Repository and Collection: var contactRepo = new Repository([ {id: 1, name: "Joe"}, {id: 2, name: "Jane"}, {id: 3, name: "Tom"}, {id: 4, name: "Jack"}, {id: 5, name: "Sue"} ]); var friends = new Collection( contactRepo, [ contactRepo.get(2), contactRepo.get(4) ] ); var coworkers = new Collection( contactRepo, [ contactRepo.get(1), contactRepo.get(2), contactRepo.get(5) ] ); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 2, 5 coworkers.remove(2); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 5 friends.remove(4); contactRepo.items; // contains item ids 1, 2, 3, 5 friends.items; // contains item ids 2 coworkers.items; // contains item ids 1, 5 Notice how coworkers.remove(2) didn't remove id 2 from contactRepo? This is because it was still referenced from friends.items. However, friends.remove(4) causes id 4 to be removed from contactRepo, because no other collection is referring to it. Summary The above is what I want to do. I'm sure there are ways I can do this by keeping track of my own reference counters and such. But if there is a way to do it using javascript's built-in reference management, I'd like to hear about how to use it.

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• Why do I have to specify the -i switch with a backup extension when using ActivePerl?

  - by Zaid

  I cannot get in-place editing Perl one-liners running under ActivePerl to work unless I specify them with a backup extension: C:\> perl -i -ape "splice (@F, 2, 0, q(inserted text)); $_ = qq(@F\n);" file1.txt Can't do inplace edit without backup. The same command with -i.bak or -i.orig works a treat, but also creates an unwanted backup file in the process. Has anyone else faced similar issues? Is there a way around this?

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• what wrong in the program using tie and array

  - by SCNCN2010

  File : #comment1 #comment2 #comment3 #START HERE a: [email protected] b: [email protected] my perl program : use Data::Dumper; use Tie::File; tie my @array, 'Tie::File', 'ala.txt' or die $!; my $rec = 'p: [email protected]'; my $flag =1 ; my $add_flag = 0; for my $i (0..$#array) { next if ($array[$i] =~ /^\s*$/); if ( $flag == 1 ) { if ($array[$i] =~ /#START HERE/ ) { $flag = 0; } else { next ; } } if (($array[$i] cmp $rec) == 1) { splice @array, $i, 1, $rec; $add_flag = 1; last ; } } if ( $add_flag == 0 ) { my $index = $#array+1; $array[$index] = $rec ; } the recording adding end of file always . I am trying to add to middle or begin or end like aplphbetical order

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• Using a "vo" for joined data?

  - by keithjgrant

  I'm building a small financial system. Because of double-entry accounting, transactions always come in batches of two or more, so I've got a batch table and a transaction table. (The transaction table has batch_id, account_id, and amount fields, and shared data like date and description are relegated to the batch table). I've been using basic vo-type models for each table so far. Because of this table structure structure, though, transactions will almost always be selected with a join on the batch table. So should I take the selected records and splice them into two separate vo objects, or should I create a "shared" vo that contains both batch and transaction data? There are a few cases in which batch records and/or transaction records. Are there possible pitfalls down the road if I have "overlapping" vo classes?

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• Python - from file to data structure?

  - by Seafoid

  Hi, I have large file comprising ~100,000 lines. Each line corresponds to a cluster and each entry within each line is a reference i.d. for another file (protein structure in this case), e.g. 1hgn 1dju 3nmj 8kfn 9opu 7gfb 4bui I need to read in the file as a list of lists where each line is a sublist, thus preserving the integrity of the cluster, e.g. nested_list = [['1hgn', '1dju', '3nmj', '8kfn'], ['9opu', '7gfb'], ['4bui']] My current code creates a nested list but the entries within each list are a single string and not comma separated. Therefore, I cannot splice the list with indices so easily. Any help greatly appreciated. Thanks, S :-)

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• How do I map a macro across a list in Scheme?

  - by josh

  I have a Scheme macro and a long list, and I'd like to map the macro across the list, just as if it were a function. How can I do that using R5RS? The macro accepts several arguments: (mac a b c d) The list has (define my-list ((a1 b1 c1 d1) (a2 b2 c2 d2) ... (an bn cn dn))) And I'd like to have this: (begin (mac a1 b1 c1 d2) (mac a2 b2 c2 d2) ... (mac an bn cn dn)) (By the way, as you can see I'd like to splice the list of arguments too)

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• Issues with shooting in a HTML5 platformer game

  - by fnx

  I'm coding a 2D sidescroller using only JavaScript and HTML5 canvas, and in my game I have two problems with shooting: 1) Player shoots continous stream of bullets. I want that player can shoot only a single bullet even though the shoot-button is being held down. 2) Also, I get an error "Uncaught TypeError: Cannot call method 'draw' of undefined" when all the bullets are removed. My shooting code goes like this: When player shoots, I do game.bullets.push(new Bullet(this, this.scale)); and after that: function Bullet(source, dir) { this.id = "bullet"; this.width = 10; this.height = 3; this.dir = dir; if (this.dir == 1) { this.x = source.x + source.width - 5; this.y = source.y + 16; } if (this.dir == -1) { this.x = source.x; this.y = source.y + 16; } } Bullet.prototype.update = function() { if (this.dir == 1) this.x += 8; if (this.dir == -1) this.x -= 8; for (var i in game.enemies) { checkCollisions(this, game.enemies[i]); } // Check if bullet leaves the viewport if (this.x < game.viewX * 32 || this.x > (game.viewX + game.tilesX) * 32) { removeFromList(game.bullets, this); } } Bullet.prototype.draw = function() { // bullet flipping uses orientation of the player var posX = game.player.scale == 1 ? this.x : (this.x + this.width) * -1; game.ctx.scale(game.player.scale, 1); game.ctx.drawImage(gameData.getGfx("bullet"), posX, this.y); } I handle removing with this function: function removeFromList(list, object) { for (i in list) { if (object == list[i]) { list.splice(i, 1); break; } } } And finally, in the main game loop I have this: for (var i in game.bullets) { game.bullets[i].update(); game.bullets[i].draw(); } I have tried adding if (game.bullets.length > 0) to the main game loop before the above draw&update calls, but I still get the same error.

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• Node.js Adventure - When Node Flying in Wind

  - by Shaun

  In the first post of this series I mentioned some popular modules in the community, such as underscore, async, etc.. I also listed a module named “Wind (zh-CN)”, which is created by one of my friend, Jeff Zhao (zh-CN). Now I would like to use a separated post to introduce this module since I feel it brings a new async programming style in not only Node.js but JavaScript world. If you know or heard about the new feature in C# 5.0 called “async and await”, or you learnt F#, you will find the “Wind” brings the similar async programming experience in JavaScript. By using “Wind”, we can write async code that looks like the sync code. The callbacks, async stats and exceptions will be handled by “Wind” automatically and transparently.   What’s the Problem: Dense “Callback” Phobia Let’s firstly back to my second post in this series. As I mentioned in that post, when we wanted to read some records from SQL Server we need to open the database connection, and then execute the query. In Node.js all IO operation are designed as async callback pattern which means when the operation was done, it will invoke a function which was taken from the last parameter. For example the database connection opening code would be like this. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: } 8: }); And then if we need to query the database the code would be like this. It nested in the previous function. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: conn.queryRaw(command, function(error, results) { 8: if(error) { 9: // failed to execute this command 10: } 11: else { 12: // records retrieved successfully 13: } 14: }; 15: } 16: }); Assuming if we need to copy some data from this database to another then we need to open another connection and execute the command within the function under the query function. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: conn.queryRaw(command, function(error, results) { 8: if(error) { 9: // failed to execute this command 10: } 11: else { 12: // records retrieved successfully 13: target.open(targetConnectionString, function(error, t_conn) { 14: if(error) { 15: // connect failed 16: } 17: else { 18: t_conn.queryRaw(copy_command, function(error, results) { 19: if(error) { 20: // copy failed 21: } 22: else { 23: // and then, what do you want to do now... 24: } 25: }; 26: } 27: }; 28: } 29: }; 30: } 31: }); This is just an example. In the real project the logic would be more complicated. This means our application might be messed up and the business process will be fragged by many callback functions. I would like call this “Dense Callback Phobia”. This might be a challenge how to make code straightforward and easy to read, something like below. 1: try 2: { 3: // open source connection 4: var s_conn = sqlConnect(s_connectionString); 5: // retrieve data 6: var results = sqlExecuteCommand(s_conn, s_command); 7: 8: // open target connection 9: var t_conn = sqlConnect(t_connectionString); 10: // prepare the copy command 11: var t_command = getCopyCommand(results); 12: // execute the copy command 13: sqlExecuteCommand(s_conn, t_command); 14: } 15: catch (ex) 16: { 17: // error handling 18: }   What’s the Problem: Sync-styled Async Programming Similar as the previous problem, the callback-styled async programming model makes the upcoming operation as a part of the current operation, and mixed with the error handling code. So it’s very hard to understand what on earth this code will do. And since Node.js utilizes non-blocking IO mode, we cannot invoke those operations one by one, as they will be executed concurrently. For example, in this post when I tried to copy the records from Windows Azure SQL Database (a.k.a. WASD) to Windows Azure Table Storage, if I just insert the data into table storage one by one and then print the “Finished” message, I will see the message shown before the data had been copied. This is because all operations were executed at the same time. In order to make the copy operation and print operation executed synchronously I introduced a module named “async” and the code was changed as below. 1: async.forEach(results.rows, 2: function (row, callback) { 3: var resource = { 4: "PartitionKey": row[1], 5: "RowKey": row[0], 6: "Value": row[2] 7: }; 8: client.insertEntity(tableName, resource, function (error) { 9: if (error) { 10: callback(error); 11: } 12: else { 13: console.log("entity inserted."); 14: callback(null); 15: } 16: }); 17: }, 18: function (error) { 19: if (error) { 20: error["target"] = "insertEntity"; 21: res.send(500, error); 22: } 23: else { 24: console.log("all done."); 25: res.send(200, "Done!"); 26: } 27: }); It ensured that the “Finished” message will be printed when all table entities had been inserted. But it cannot promise that the records will be inserted in sequence. It might be another challenge to make the code looks like in sync-style? 1: try 2: { 3: forEach(row in rows) { 4: var entity = { /* ... */ }; 5: tableClient.insert(tableName, entity); 6: } 7:  8: console.log("Finished"); 9: } 10: catch (ex) { 11: console.log(ex); 12: }   How “Wind” Helps “Wind” is a JavaScript library which provides the control flow with plain JavaScript for asynchronous programming (and more) without additional pre-compiling steps. It’s available in NPM so that we can install it through “npm install wind”. Now let’s create a very simple Node.js application as the example. This application will take some website URLs from the command arguments and tried to retrieve the body length and print them in console. Then at the end print “Finish”. I’m going to use “request” module to make the HTTP call simple so I also need to install by the command “npm install request”. The code would be like this. 1: var request = require("request"); 2:  3: // get the urls from arguments, the first two arguments are `node.exe` and `fetch.js` 4: var args = process.argv.splice(2); 5:  6: // main function 7: var main = function() { 8: for(var i = 0; i < args.length; i++) { 9: // get the url 10: var url = args[i]; 11: // send the http request and try to get the response and body 12: request(url, function(error, response, body) { 13: if(!error && response.statusCode == 200) { 14: // log the url and the body length 15: console.log( 16: "%s: %d.", 17: response.request.uri.href, 18: body.length); 19: } 20: else { 21: // log error 22: console.log(error); 23: } 24: }); 25: } 26: 27: // finished 28: console.log("Finished"); 29: }; 30:  31: // execute the main function 32: main(); Let’s execute this application. (I made them in multi-lines for better reading.) 1: node fetch.js 2: "http://www.igt.com/us-en.aspx" 3: "http://www.igt.com/us-en/games.aspx" 4: "http://www.igt.com/us-en/cabinets.aspx" 5: "http://www.igt.com/us-en/systems.aspx" 6: "http://www.igt.com/us-en/interactive.aspx" 7: "http://www.igt.com/us-en/social-gaming.aspx" 8: "http://www.igt.com/support.aspx" Below is the output. As you can see the finish message was printed at the beginning, and the pages’ length retrieved in a different order than we specified. This is because in this code the request command, console logging command are executed asynchronously and concurrently. Now let’s introduce “Wind” to make them executed in order, which means it will request the websites one by one, and print the message at the end.   First of all we need to import the “Wind” package and make sure the there’s only one global variant named “Wind”, and ensure it’s “Wind” instead of “wind”. 1: var Wind = require("wind");   Next, we need to tell “Wind” which code will be executed asynchronously so that “Wind” can control the execution process. In this case the “request” operation executed asynchronously so we will create a “Task” by using a build-in helps function in “Wind” named Wind.Async.Task.create. 1: var requestBodyLengthAsync = function(url) { 2: return Wind.Async.Task.create(function(t) { 3: request(url, function(error, response, body) { 4: if(error || response.statusCode != 200) { 5: t.complete("failure", error); 6: } 7: else { 8: var data = 9: { 10: uri: response.request.uri.href, 11: length: body.length 12: }; 13: t.complete("success", data); 14: } 15: }); 16: }); 17: }; The code above created a “Task” from the original request calling code. In “Wind” a “Task” means an operation will be finished in some time in the future. A “Task” can be started by invoke its start() method, but no one knows when it actually will be finished. The Wind.Async.Task.create helped us to create a task. The only parameter is a function where we can put the actual operation in, and then notify the task object it’s finished successfully or failed by using the complete() method. In the code above I invoked the request method. If it retrieved the response successfully I set the status of this task as “success” with the URL and body length. If it failed I set this task as “failure” and pass the error out.   Next, we will change the main() function. In “Wind” if we want a function can be controlled by Wind we need to mark it as “async”. This should be done by using the code below. 1: var main = eval(Wind.compile("async", function() { 2: })); When the application is running, Wind will detect “eval(Wind.compile(“async”, function” and generate an anonymous code from the body of this original function. Then the application will run the anonymous code instead of the original one. In our example the main function will be like this. 1: var main = eval(Wind.compile("async", function() { 2: for(var i = 0; i < args.length; i++) { 3: try 4: { 5: var result = $await(requestBodyLengthAsync(args[i])); 6: console.log( 7: "%s: %d.", 8: result.uri, 9: result.length); 10: } 11: catch (ex) { 12: console.log(ex); 13: } 14: } 15: 16: console.log("Finished"); 17: })); As you can see, when I tried to request the URL I use a new command named “$await”. It tells Wind, the operation next to $await will be executed asynchronously, and the main thread should be paused until it finished (or failed). So in this case, my application will be pause when the first response was received, and then print its body length, then try the next one. At the end, print the finish message.   Finally, execute the main function. The full code would be like this. 1: var request = require("request"); 2: var Wind = require("wind"); 3:  4: var args = process.argv.splice(2); 5:  6: var requestBodyLengthAsync = function(url) { 7: return Wind.Async.Task.create(function(t) { 8: request(url, function(error, response, body) { 9: if(error || response.statusCode != 200) { 10: t.complete("failure", error); 11: } 12: else { 13: var data = 14: { 15: uri: response.request.uri.href, 16: length: body.length 17: }; 18: t.complete("success", data); 19: } 20: }); 21: }); 22: }; 23:  24: var main = eval(Wind.compile("async", function() { 25: for(var i = 0; i < args.length; i++) { 26: try 27: { 28: var result = $await(requestBodyLengthAsync(args[i])); 29: console.log( 30: "%s: %d.", 31: result.uri, 32: result.length); 33: } 34: catch (ex) { 35: console.log(ex); 36: } 37: } 38: 39: console.log("Finished"); 40: })); 41:  42: main().start();   Run our new application. At the beginning we will see the compiled and generated code by Wind. Then we can see the pages were requested one by one, and at the end the finish message was printed. Below is the code Wind generated for us. As you can see the original code, the output code were shown. 1: // Original: 2: function () { 3: for(var i = 0; i < args.length; i++) { 4: try 5: { 6: var result = $await(requestBodyLengthAsync(args[i])); 7: console.log( 8: "%s: %d.", 9: result.uri, 10: result.length); 11: } 12: catch (ex) { 13: console.log(ex); 14: } 15: } 16: 17: console.log("Finished"); 18: } 19:  20: // Compiled: 21: /* async << function () { */ (function () { 22: var _builder_$0 = Wind.builders["async"]; 23: return _builder_$0.Start(this, 24: _builder_$0.Combine( 25: _builder_$0.Delay(function () { 26: /* var i = 0; */ var i = 0; 27: /* for ( */ return _builder_$0.For(function () { 28: /* ; i < args.length */ return i < args.length; 29: }, function () { 30: /* ; i ++) { */ i ++; 31: }, 32: /* try { */ _builder_$0.Try( 33: _builder_$0.Delay(function () { 34: /* var result = $await(requestBodyLengthAsync(args[i])); */ return _builder_$0.Bind(requestBodyLengthAsync(args[i]), function (result) { 35: /* console.log("%s: %d.", result.uri, result.length); */ console.log("%s: %d.", result.uri, result.length); 36: return _builder_$0.Normal(); 37: }); 38: }), 39: /* } catch (ex) { */ function (ex) { 40: /* console.log(ex); */ console.log(ex); 41: return _builder_$0.Normal(); 42: /* } */ }, 43: null 44: ) 45: /* } */ ); 46: }), 47: _builder_$0.Delay(function () { 48: /* console.log("Finished"); */ console.log("Finished"); 49: return _builder_$0.Normal(); 50: }) 51: ) 52: ); 53: /* } */ })   How Wind Works Someone may raise a big concern when you find I utilized “eval” in my code. Someone may assume that Wind utilizes “eval” to execute some code dynamically while “eval” is very low performance. But I would say, Wind does NOT use “eval” to run the code. It only use “eval” as a flag to know which code should be compiled at runtime. When the code was firstly been executed, Wind will check and find “eval(Wind.compile(“async”, function”. So that it knows this function should be compiled. Then it utilized parse-js to analyze the inner JavaScript and generated the anonymous code in memory. Then it rewrite the original code so that when the application was running it will use the anonymous one instead of the original one. Since the code generation was done at the beginning of the application was started, in the future no matter how long our application runs and how many times the async function was invoked, it will use the generated code, no need to generate again. So there’s no significant performance hurt when using Wind.   Wind in My Previous Demo Let’s adopt Wind into one of my previous demonstration and to see how it helps us to make our code simple, straightforward and easy to read and understand. In this post when I implemented the functionality that copied the records from my WASD to table storage, the logic would be like this. 1, Open database connection. 2, Execute a query to select all records from the table. 3, Recreate the table in Windows Azure table storage. 4, Create entities from each of the records retrieved previously, and then insert them into table storage. 5, Finally, show message as the HTTP response. But as the image below, since there are so many callbacks and async operations, it’s very hard to understand my logic from the code. Now let’s use Wind to rewrite our code. First of all, of course, we need the Wind package. Then we need to include the package files into project and mark them as “Copy always”. Add the Wind package into the source code. Pay attention to the variant name, you must use “Wind” instead of “wind”. 1: var express = require("express"); 2: var async = require("async"); 3: var sql = require("node-sqlserver"); 4: var azure = require("azure"); 5: var Wind = require("wind"); Now we need to create some async functions by using Wind. All async functions should be wrapped so that it can be controlled by Wind which are open database, retrieve records, recreate table (delete and create) and insert entity in table. Below are these new functions. All of them are created by using Wind.Async.Task.create. 1: sql.openAsync = function (connectionString) { 2: return Wind.Async.Task.create(function (t) { 3: sql.open(connectionString, function (error, conn) { 4: if (error) { 5: t.complete("failure", error); 6: } 7: else { 8: t.complete("success", conn); 9: } 10: }); 11: }); 12: }; 13:  14: sql.queryAsync = function (conn, query) { 15: return Wind.Async.Task.create(function (t) { 16: conn.queryRaw(query, function (error, results) { 17: if (error) { 18: t.complete("failure", error); 19: } 20: else { 21: t.complete("success", results); 22: } 23: }); 24: }); 25: }; 26:  27: azure.recreateTableAsync = function (tableName) { 28: return Wind.Async.Task.create(function (t) { 29: client.deleteTable(tableName, function (error, successful, response) { 30: console.log("delete table finished"); 31: client.createTableIfNotExists(tableName, function (error, successful, response) { 32: console.log("create table finished"); 33: if (error) { 34: t.complete("failure", error); 35: } 36: else { 37: t.complete("success", null); 38: } 39: }); 40: }); 41: }); 42: }; 43:  44: azure.insertEntityAsync = function (tableName, entity) { 45: return Wind.Async.Task.create(function (t) { 46: client.insertEntity(tableName, entity, function (error, entity, response) { 47: if (error) { 48: t.complete("failure", error); 49: } 50: else { 51: t.complete("success", null); 52: } 53: }); 54: }); 55: }; Then in order to use these functions we will create a new function which contains all steps for data copying. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: } 4: catch (ex) { 5: console.log(ex); 6: res.send(500, "Internal error."); 7: } 8: })); Let’s execute steps one by one with the “$await” keyword introduced by Wind so that it will be invoked in sequence. First is to open the database connection. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: } 7: catch (ex) { 8: console.log(ex); 9: res.send(500, "Internal error."); 10: } 11: })); Then retrieve all records from the database connection. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: } 10: catch (ex) { 11: console.log(ex); 12: res.send(500, "Internal error."); 13: } 14: })); After recreated the table, we need to create the entities and insert them into table storage. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage one by one 14: for (var i = 0; i < results.rows.length; i++) { 15: var entity = { 16: "PartitionKey": results.rows[i][1], 17: "RowKey": results.rows[i][0], 18: "Value": results.rows[i][2] 19: }; 20: $await(azure.insertEntityAsync(tableName, entity)); 21: console.log("entity inserted"); 22: } 23: } 24: } 25: catch (ex) { 26: console.log(ex); 27: res.send(500, "Internal error."); 28: } 29: })); Finally, send response back to the browser. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage one by one 14: for (var i = 0; i < results.rows.length; i++) { 15: var entity = { 16: "PartitionKey": results.rows[i][1], 17: "RowKey": results.rows[i][0], 18: "Value": results.rows[i][2] 19: }; 20: $await(azure.insertEntityAsync(tableName, entity)); 21: console.log("entity inserted"); 22: } 23: // send response 24: console.log("all done"); 25: res.send(200, "All done!"); 26: } 27: } 28: catch (ex) { 29: console.log(ex); 30: res.send(500, "Internal error."); 31: } 32: })); If we compared with the previous code we will find now it became more readable and much easy to understand. It’s very easy to know what this function does even though without any comments. When user go to URL “/was/copyRecords” we will execute the function above. The code would be like this. 1: app.get("/was/copyRecords", function (req, res) { 2: copyRecords(req, res).start(); 3: }); And below is the logs printed in local compute emulator console. As we can see the functions executed one by one and then finally the response back to me browser.   Scaffold Functions in Wind Wind provides not only the async flow control and compile functions, but many scaffold methods as well. We can build our async code more easily by using them. I’m going to introduce some basic scaffold functions here. In the code above I created some functions which wrapped from the original async function such as open database, create table, etc.. All of them are very similar, created a task by using Wind.Async.Task.create, return error or result object through Task.complete function. In fact, Wind provides some functions for us to create task object from the original async functions. If the original async function only has a callback parameter, we can use Wind.Async.Binding.fromCallback method to get the task object directly. For example the code below returned the task object which wrapped the file exist check function. 1: var Wind = require("wind"); 2: var fs = require("fs"); 3:  4: fs.existsAsync = Wind.Async.Binding.fromCallback(fs.exists); In Node.js a very popular async function pattern is that, the first parameter in the callback function represent the error object, and the other parameters is the return values. In this case we can use another build-in function in Wind named Wind.Async.Binding.fromStandard. For example, the open database function can be created from the code below. 1: sql.openAsync = Wind.Async.Binding.fromStandard(sql.open); 2:  3: /* 4: sql.openAsync = function (connectionString) { 5: return Wind.Async.Task.create(function (t) { 6: sql.open(connectionString, function (error, conn) { 7: if (error) { 8: t.complete("failure", error); 9: } 10: else { 11: t.complete("success", conn); 12: } 13: }); 14: }); 15: }; 16: */ When I was testing the scaffold functions under Wind.Async.Binding I found for some functions, such as the Azure SDK insert entity function, cannot be processed correctly. So I personally suggest writing the wrapped method manually.   Another scaffold method in Wind is the parallel tasks coordination. In this example, the steps of open database, retrieve records and recreated table should be invoked one by one, but it can be executed in parallel when copying data from database to table storage. In Wind there’s a scaffold function named Task.whenAll which can be used here. Task.whenAll accepts a list of tasks and creates a new task. It will be returned only when all tasks had been completed, or any errors occurred. For example in the code below I used the Task.whenAll to make all copy operation executed at the same time. 1: var copyRecordsInParallel = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage in parallal 14: var tasks = new Array(results.rows.length); 15: for (var i = 0; i < results.rows.length; i++) { 16: var entity = { 17: "PartitionKey": results.rows[i][1], 18: "RowKey": results.rows[i][0], 19: "Value": results.rows[i][2] 20: }; 21: tasks[i] = azure.insertEntityAsync(tableName, entity); 22: } 23: $await(Wind.Async.Task.whenAll(tasks)); 24: // send response 25: console.log("all done"); 26: res.send(200, "All done!"); 27: } 28: } 29: catch (ex) { 30: console.log(ex); 31: res.send(500, "Internal error."); 32: } 33: })); 34:  35: app.get("/was/copyRecordsInParallel", function (req, res) { 36: copyRecordsInParallel(req, res).start(); 37: });   Besides the task creation and coordination, Wind supports the cancellation solution so that we can send the cancellation signal to the tasks. It also includes exception solution which means any exceptions will be reported to the caller function.   Summary In this post I introduced a Node.js module named Wind, which created by my friend Jeff Zhao. As you can see, different from other async library and framework, adopted the idea from F# and C#, Wind utilizes runtime code generation technology to make it more easily to write async, callback-based functions in a sync-style way. By using Wind there will be almost no callback, and the code will be very easy to understand. Currently Wind is still under developed and improved. There might be some problems but the author, Jeff, should be very happy and enthusiastic to learn your problems, feedback, suggestion and comments. You can contact Jeff by - Email: [email protected] - Group: https://groups.google.com/d/forum/windjs - GitHub: https://github.com/JeffreyZhao/wind/issues   Source code can be download here.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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• Using R to Analyze G1GC Log Files

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  Using R to Analyze G1GC Log Files   Using R to Analyze G1GC Log Files Introduction Working in Oracle Platform Integration gives an engineer opportunities to work on a wide array of technologies. My team’s goal is to make Oracle applications run best on the Solaris/SPARC platform. When looking for bottlenecks in a modern applications, one needs to be aware of not only how the CPUs and operating system are executing, but also network, storage, and in some cases, the Java Virtual Machine. I was recently presented with about 1.5 GB of Java Garbage First Garbage Collector log file data. If you’re not familiar with the subject, you might want to review Garbage First Garbage Collector Tuning by Monica Beckwith. The customer had been running Java HotSpot 1.6.0_31 to host a web application server. I was told that the Solaris/SPARC server was running a Java process launched using a commmand line that included the following flags: -d64 -Xms9g -Xmx9g -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -XX:InitiatingHeapOccupancyPercent=80 -XX:PermSize=256m -XX:MaxPermSize=256m -XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC -XX:+PrintGCDateStamps -XX:+PrintFlagsFinal -XX:+DisableExplicitGC -XX:+UnlockExperimentalVMOptions -XX:ParallelGCThreads=8 Several sources on the internet indicate that if I were to print out the 1.5 GB of log files, it would require enough paper to fill the bed of a pick up truck. Of course, it would be fruitless to try to scan the log files by hand. Tools will be required to summarize the contents of the log files. Others have encountered large Java garbage collection log files. There are existing tools to analyze the log files: IBM’s GC toolkit The chewiebug GCViewer gchisto HPjmeter Instead of using one of the other tools listed, I decide to parse the log files with standard Unix tools, and analyze the data with R. Data Cleansing The log files arrived in two different formats. I guess that the difference is that one set of log files was generated using a more verbose option, maybe -XX:+PrintHeapAtGC, and the other set of log files was generated without that option. Format 1 In some of the log files, the log files with the less verbose format, a single trace, i.e. the report of a singe garbage collection event, looks like this: {Heap before GC invocations=12280 (full 61): garbage-first heap total 9437184K, used 7499918K [0xfffffffd00000000, 0xffffffff40000000, 0xffffffff40000000) region size 4096K, 1 young (4096K), 0 survivors (0K) compacting perm gen total 262144K, used 144077K [0xffffffff40000000, 0xffffffff50000000, 0xffffffff50000000) the space 262144K, 54% used [0xffffffff40000000, 0xffffffff48cb3758, 0xffffffff48cb3800, 0xffffffff50000000) No shared spaces configured. 2014-05-14T07:24:00.988-0700: 60586.353: [GC pause (young) 7324M->7320M(9216M), 0.1567265 secs] Heap after GC invocations=12281 (full 61): garbage-first heap total 9437184K, used 7496533K [0xfffffffd00000000, 0xffffffff40000000, 0xffffffff40000000) region size 4096K, 0 young (0K), 0 survivors (0K) compacting perm gen total 262144K, used 144077K [0xffffffff40000000, 0xffffffff50000000, 0xffffffff50000000) the space 262144K, 54% used [0xffffffff40000000, 0xffffffff48cb3758, 0xffffffff48cb3800, 0xffffffff50000000) No shared spaces configured. } A simple grep can be used to extract a summary: $ grep "\[ GC pause (young" g1gc.log 2014-05-13T13:24:35.091-0700: 3.109: [GC pause (young) 20M->5029K(9216M), 0.0146328 secs] 2014-05-13T13:24:35.440-0700: 3.459: [GC pause (young) 9125K->6077K(9216M), 0.0086723 secs] 2014-05-13T13:24:37.581-0700: 5.599: [GC pause (young) 25M->8470K(9216M), 0.0203820 secs] 2014-05-13T13:24:42.686-0700: 10.704: [GC pause (young) 44M->15M(9216M), 0.0288848 secs] 2014-05-13T13:24:48.941-0700: 16.958: [GC pause (young) 51M->20M(9216M), 0.0491244 secs] 2014-05-13T13:24:56.049-0700: 24.066: [GC pause (young) 92M->26M(9216M), 0.0525368 secs] 2014-05-13T13:25:34.368-0700: 62.383: [GC pause (young) 602M->68M(9216M), 0.1721173 secs] But that format wasn't easily read into R, so I needed to be a bit more tricky. I used the following Unix command to create a summary file that was easy for R to read. $ echo "SecondsSinceLaunch BeforeSize AfterSize TotalSize RealTime" $ grep "\[GC pause (young" g1gc.log | grep -v mark | sed -e 's/[A-SU-z\(\),]/ /g' -e 's/->/ /' -e 's/: / /g' | more SecondsSinceLaunch BeforeSize AfterSize TotalSize RealTime 2014-05-13T13:24:35.091-0700 3.109 20 5029 9216 0.0146328 2014-05-13T13:24:35.440-0700 3.459 9125 6077 9216 0.0086723 2014-05-13T13:24:37.581-0700 5.599 25 8470 9216 0.0203820 2014-05-13T13:24:42.686-0700 10.704 44 15 9216 0.0288848 2014-05-13T13:24:48.941-0700 16.958 51 20 9216 0.0491244 2014-05-13T13:24:56.049-0700 24.066 92 26 9216 0.0525368 2014-05-13T13:25:34.368-0700 62.383 602 68 9216 0.1721173 Format 2 In some of the log files, the log files with the more verbose format, a single trace, i.e. the report of a singe garbage collection event, was more complicated than Format 1. Here is a text file with an example of a single G1GC trace in the second format. As you can see, it is quite complicated. It is nice that there is so much information available, but the level of detail can be overwhelming. I wrote this awk script (download) to summarize each trace on a single line. #!/usr/bin/env awk -f BEGIN { printf("SecondsSinceLaunch IncrementalCount FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize\n") } ###################### # Save count data from lines that are at the start of each G1GC trace. # Each trace starts out like this: # {Heap before GC invocations=14 (full 0): # garbage-first heap total 9437184K, used 325496K [0xfffffffd00000000, 0xffffffff40000000, 0xffffffff40000000) ###################### /{Heap.*full/{ gsub ( "\\)" , "" ); nf=split($0,a,"="); split(a[2],b," "); getline; if ( match($0, "first") ) { G1GC=1; IncrementalCount=b[1]; FullCount=substr( b[3], 1, length(b[3])-1 ); } else { G1GC=0; } } ###################### # Pull out time stamps that are in lines with this format: # 2014-05-12T14:02:06.025-0700: 94.312: [GC pause (young), 0.08870154 secs] ###################### /GC pause/ { DateTime=$1; SecondsSinceLaunch=substr($2, 1, length($2)-1); } ###################### # Heap sizes are in lines that look like this: # [ 4842M->4838M(9216M)] ###################### /\[ .*]$/ { gsub ( "\\[" , "" ); gsub ( "\ \]" , "" ); gsub ( "->" , " " ); gsub ( "\\( " , " " ); gsub ( "\ \)" , " " ); split($0,a," "); if ( split(a[1],b,"M") > 1 ) {BeforeSize=b[1]*1024;} if ( split(a[1],b,"K") > 1 ) {BeforeSize=b[1];} if ( split(a[2],b,"M") > 1 ) {AfterSize=b[1]*1024;} if ( split(a[2],b,"K") > 1 ) {AfterSize=b[1];} if ( split(a[3],b,"M") > 1 ) {TotalSize=b[1]*1024;} if ( split(a[3],b,"K") > 1 ) {TotalSize=b[1];} } ###################### # Emit an output line when you find input that looks like this: # [Times: user=1.41 sys=0.08, real=0.24 secs] ###################### /\[Times/ { if (G1GC==1) { gsub ( "," , "" ); split($2,a,"="); UserTime=a[2]; split($3,a,"="); SysTime=a[2]; split($4,a,"="); RealTime=a[2]; print DateTime,SecondsSinceLaunch,IncrementalCount,FullCount,UserTime,SysTime,RealTime,BeforeSize,AfterSize,TotalSize; G1GC=0; } } The resulting summary is about 25X smaller that the original file, but still difficult for a human to digest. SecondsSinceLaunch IncrementalCount FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize ... 2014-05-12T18:36:34.669-0700: 3985.744 561 0 0.57 0.06 0.16 1724416 1720320 9437184 2014-05-12T18:36:34.839-0700: 3985.914 562 0 0.51 0.06 0.19 1724416 1720320 9437184 2014-05-12T18:36:35.069-0700: 3986.144 563 0 0.60 0.04 0.27 1724416 1721344 9437184 2014-05-12T18:36:35.354-0700: 3986.429 564 0 0.33 0.04 0.09 1725440 1722368 9437184 2014-05-12T18:36:35.545-0700: 3986.620 565 0 0.58 0.04 0.17 1726464 1722368 9437184 2014-05-12T18:36:35.726-0700: 3986.801 566 0 0.43 0.05 0.12 1726464 1722368 9437184 2014-05-12T18:36:35.856-0700: 3986.930 567 0 0.30 0.04 0.07 1726464 1723392 9437184 2014-05-12T18:36:35.947-0700: 3987.023 568 0 0.61 0.04 0.26 1727488 1723392 9437184 2014-05-12T18:36:36.228-0700: 3987.302 569 0 0.46 0.04 0.16 1731584 1724416 9437184 Reading the Data into R Once the GC log data had been cleansed, either by processing the first format with the shell script, or by processing the second format with the awk script, it was easy to read the data into R. g1gc.df = read.csv("summary.txt", row.names = NULL, stringsAsFactors=FALSE,sep="") str(g1gc.df) ## 'data.frame': 8307 obs. of 10 variables: ## $ row.names : chr "2014-05-12T14:00:32.868-0700:" "2014-05-12T14:00:33.179-0700:" "2014-05-12T14:00:33.677-0700:" "2014-05-12T14:00:35.538-0700:" ... ## $ SecondsSinceLaunch: num 1.16 1.47 1.97 3.83 6.1 ... ## $ IncrementalCount : int 0 1 2 3 4 5 6 7 8 9 ... ## $ FullCount : int 0 0 0 0 0 0 0 0 0 0 ... ## $ UserTime : num 0.11 0.05 0.04 0.21 0.08 0.26 0.31 0.33 0.34 0.56 ... ## $ SysTime : num 0.04 0.01 0.01 0.05 0.01 0.06 0.07 0.06 0.07 0.09 ... ## $ RealTime : num 0.02 0.02 0.01 0.04 0.02 0.04 0.05 0.04 0.04 0.06 ... ## $ BeforeSize : int 8192 5496 5768 22528 24576 43008 34816 53248 55296 93184 ... ## $ AfterSize : int 1400 1672 2557 4907 7072 14336 16384 18432 19456 21504 ... ## $ TotalSize : int 9437184 9437184 9437184 9437184 9437184 9437184 9437184 9437184 9437184 9437184 ... head(g1gc.df) ## row.names SecondsSinceLaunch IncrementalCount ## 1 2014-05-12T14:00:32.868-0700: 1.161 0 ## 2 2014-05-12T14:00:33.179-0700: 1.472 1 ## 3 2014-05-12T14:00:33.677-0700: 1.969 2 ## 4 2014-05-12T14:00:35.538-0700: 3.830 3 ## 5 2014-05-12T14:00:37.811-0700: 6.103 4 ## 6 2014-05-12T14:00:41.428-0700: 9.720 5 ## FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize ## 1 0 0.11 0.04 0.02 8192 1400 9437184 ## 2 0 0.05 0.01 0.02 5496 1672 9437184 ## 3 0 0.04 0.01 0.01 5768 2557 9437184 ## 4 0 0.21 0.05 0.04 22528 4907 9437184 ## 5 0 0.08 0.01 0.02 24576 7072 9437184 ## 6 0 0.26 0.06 0.04 43008 14336 9437184 Basic Statistics Once the data has been read into R, simple statistics are very easy to generate. All of the numbers from high school statistics are available via simple commands. For example, generate a summary of every column: summary(g1gc.df) ## row.names SecondsSinceLaunch IncrementalCount FullCount ## Length:8307 Min. : 1 Min. : 0 Min. : 0.0 ## Class :character 1st Qu.: 9977 1st Qu.:2048 1st Qu.: 0.0 ## Mode :character Median :12855 Median :4136 Median : 12.0 ## Mean :12527 Mean :4156 Mean : 31.6 ## 3rd Qu.:15758 3rd Qu.:6262 3rd Qu.: 61.0 ## Max. :55484 Max. :8391 Max. :113.0 ## UserTime SysTime RealTime BeforeSize ## Min. :0.040 Min. :0.0000 Min. : 0.0 Min. : 5476 ## 1st Qu.:0.470 1st Qu.:0.0300 1st Qu.: 0.1 1st Qu.:5137920 ## Median :0.620 Median :0.0300 Median : 0.1 Median :6574080 ## Mean :0.751 Mean :0.0355 Mean : 0.3 Mean :5841855 ## 3rd Qu.:0.920 3rd Qu.:0.0400 3rd Qu.: 0.2 3rd Qu.:7084032 ## Max. :3.370 Max. :1.5600 Max. :488.1 Max. :8696832 ## AfterSize TotalSize ## Min. : 1380 Min. :9437184 ## 1st Qu.:5002752 1st Qu.:9437184 ## Median :6559744 Median :9437184 ## Mean :5785454 Mean :9437184 ## 3rd Qu.:7054336 3rd Qu.:9437184 ## Max. :8482816 Max. :9437184 Q: What is the total amount of User CPU time spent in garbage collection? sum(g1gc.df$UserTime) ## [1] 6236 As you can see, less than two hours of CPU time was spent in garbage collection. Is that too much? To find the percentage of time spent in garbage collection, divide the number above by total_elapsed_time*CPU_count. In this case, there are a lot of CPU’s and it turns out the the overall amount of CPU time spent in garbage collection isn’t a problem when viewed in isolation. When calculating rates, i.e. events per unit time, you need to ask yourself if the rate is homogenous across the time period in the log file. Does the log file include spikes of high activity that should be separately analyzed? Averaging in data from nights and weekends with data from business hours may alias problems. If you have a reason to suspect that the garbage collection rates include peaks and valleys that need independent analysis, see the “Time Series” section, below. Q: How much garbage is collected on each pass? The amount of heap space that is recovered per GC pass is surprisingly low: At least one collection didn’t recover any data. (“Min.=0”) 25% of the passes recovered 3MB or less. (“1st Qu.=3072”) Half of the GC passes recovered 4MB or less. (“Median=4096”) The average amount recovered was 56MB. (“Mean=56390”) 75% of the passes recovered 36MB or less. (“3rd Qu.=36860”) At least one pass recovered 2GB. (“Max.=2121000”) g1gc.df$Delta = g1gc.df$BeforeSize - g1gc.df$AfterSize summary(g1gc.df$Delta) ## Min. 1st Qu. Median Mean 3rd Qu. Max. ## 0 3070 4100 56400 36900 2120000 Q: What is the maximum User CPU time for a single collection? The worst garbage collection (“Max.”) is many standard deviations away from the mean. The data appears to be right skewed. summary(g1gc.df$UserTime) ## Min. 1st Qu. Median Mean 3rd Qu. Max. ## 0.040 0.470 0.620 0.751 0.920 3.370 sd(g1gc.df$UserTime) ## [1] 0.3966 Basic Graphics Once the data is in R, it is trivial to plot the data with formats including dot plots, line charts, bar charts (simple, stacked, grouped), pie charts, boxplots, scatter plots histograms, and kernel density plots. Histogram of User CPU Time per Collection I don't think that this graph requires any explanation. hist(g1gc.df$UserTime, main="User CPU Time per Collection", xlab="Seconds", ylab="Frequency") Box plot to identify outliers When the initial data is viewed with a box plot, you can see the one crazy outlier in the real time per GC. Save this data point for future analysis and drop the outlier so that it’s not throwing off our statistics. Now the box plot shows many outliers, which will be examined later, using times series analysis. Notice that the scale of the x-axis changes drastically once the crazy outlier is removed. par(mfrow=c(2,1)) boxplot(g1gc.df$UserTime,g1gc.df$SysTime,g1gc.df$RealTime, main="Box Plot of Time per GC\n(dominated by a crazy outlier)", names=c("usr","sys","elapsed"), xlab="Seconds per GC", ylab="Time (Seconds)", horizontal = TRUE, outcol="red") crazy.outlier.df=g1gc.df[g1gc.df$RealTime > 400,] g1gc.df=g1gc.df[g1gc.df$RealTime < 400,] boxplot(g1gc.df$UserTime,g1gc.df$SysTime,g1gc.df$RealTime, main="Box Plot of Time per GC\n(crazy outlier excluded)", names=c("usr","sys","elapsed"), xlab="Seconds per GC", ylab="Time (Seconds)", horizontal = TRUE, outcol="red") box(which = "outer", lty = "solid") Here is the crazy outlier for future analysis: crazy.outlier.df ## row.names SecondsSinceLaunch IncrementalCount ## 8233 2014-05-12T23:15:43.903-0700: 20741 8316 ## FullCount UserTime SysTime RealTime BeforeSize AfterSize TotalSize ## 8233 112 0.55 0.42 488.1 8381440 8235008 9437184 ## Delta ## 8233 146432 R Time Series Data To analyze the garbage collection as a time series, I’ll use Z’s Ordered Observations (zoo). “zoo is the creator for an S3 class of indexed totally ordered observations which includes irregular time series.” require(zoo) ## Loading required package: zoo ## ## Attaching package: 'zoo' ## ## The following objects are masked from 'package:base': ## ## as.Date, as.Date.numeric head(g1gc.df[,1]) ## [1] "2014-05-12T14:00:32.868-0700:" "2014-05-12T14:00:33.179-0700:" ## [3] "2014-05-12T14:00:33.677-0700:" "2014-05-12T14:00:35.538-0700:" ## [5] "2014-05-12T14:00:37.811-0700:" "2014-05-12T14:00:41.428-0700:" options("digits.secs"=3) times=as.POSIXct( g1gc.df[,1], format="%Y-%m-%dT%H:%M:%OS%z:") g1gc.z = zoo(g1gc.df[,-c(1)], order.by=times) head(g1gc.z) ## SecondsSinceLaunch IncrementalCount FullCount ## 2014-05-12 17:00:32.868 1.161 0 0 ## 2014-05-12 17:00:33.178 1.472 1 0 ## 2014-05-12 17:00:33.677 1.969 2 0 ## 2014-05-12 17:00:35.538 3.830 3 0 ## 2014-05-12 17:00:37.811 6.103 4 0 ## 2014-05-12 17:00:41.427 9.720 5 0 ## UserTime SysTime RealTime BeforeSize AfterSize ## 2014-05-12 17:00:32.868 0.11 0.04 0.02 8192 1400 ## 2014-05-12 17:00:33.178 0.05 0.01 0.02 5496 1672 ## 2014-05-12 17:00:33.677 0.04 0.01 0.01 5768 2557 ## 2014-05-12 17:00:35.538 0.21 0.05 0.04 22528 4907 ## 2014-05-12 17:00:37.811 0.08 0.01 0.02 24576 7072 ## 2014-05-12 17:00:41.427 0.26 0.06 0.04 43008 14336 ## TotalSize Delta ## 2014-05-12 17:00:32.868 9437184 6792 ## 2014-05-12 17:00:33.178 9437184 3824 ## 2014-05-12 17:00:33.677 9437184 3211 ## 2014-05-12 17:00:35.538 9437184 17621 ## 2014-05-12 17:00:37.811 9437184 17504 ## 2014-05-12 17:00:41.427 9437184 28672 Example of Two Benchmark Runs in One Log File The data in the following graph is from a different log file, not the one of primary interest to this article. I’m including this image because it is an example of idle periods followed by busy periods. It would be uninteresting to average the rate of garbage collection over the entire log file period. More interesting would be the rate of garbage collect in the two busy periods. Are they the same or different? Your production data may be similar, for example, bursts when employees return from lunch and idle times on weekend evenings, etc. Once the data is in an R Time Series, you can analyze isolated time windows. Clipping the Time Series data Flashing back to our test case… Viewing the data as a time series is interesting. You can see that the work intensive time period is between 9:00 PM and 3:00 AM. Lets clip the data to the interesting period:     par(mfrow=c(2,1)) plot(g1gc.z$UserTime, type="h", main="User Time per GC\nTime: Complete Log File", xlab="Time of Day", ylab="CPU Seconds per GC", col="#1b9e77") clipped.g1gc.z=window(g1gc.z, start=as.POSIXct("2014-05-12 21:00:00"), end=as.POSIXct("2014-05-13 03:00:00")) plot(clipped.g1gc.z$UserTime, type="h", main="User Time per GC\nTime: Limited to Benchmark Execution", xlab="Time of Day", ylab="CPU Seconds per GC", col="#1b9e77") box(which = "outer", lty = "solid") Cumulative Incremental and Full GC count Here is the cumulative incremental and full GC count. When the line is very steep, it indicates that the GCs are repeating very quickly. Notice that the scale on the Y axis is different for full vs. incremental. plot(clipped.g1gc.z[,c(2:3)], main="Cumulative Incremental and Full GC count", xlab="Time of Day", col="#1b9e77") GC Analysis of Benchmark Execution using Time Series data In the following series of 3 graphs: The “After Size” show the amount of heap space in use after each garbage collection. Many Java objects are still referenced, i.e. alive, during each garbage collection. This may indicate that the application has a memory leak, or may indicate that the application has a very large memory footprint. Typically, an application's memory footprint plateau's in the early stage of execution. One would expect this graph to have a flat top. The steep decline in the heap space may indicate that the application crashed after 2:00. The second graph shows that the outliers in real execution time, discussed above, occur near 2:00. when the Java heap seems to be quite full. The third graph shows that Full GCs are infrequent during the first few hours of execution. The rate of Full GC's, (the slope of the cummulative Full GC line), changes near midnight.   plot(clipped.g1gc.z[,c("AfterSize","RealTime","FullCount")], xlab="Time of Day", col=c("#1b9e77","red","#1b9e77")) GC Analysis of heap recovered Each GC trace includes the amount of heap space in use before and after the individual GC event. During garbage coolection, unreferenced objects are identified, the space holding the unreferenced objects is freed, and thus, the difference in before and after usage indicates how much space has been freed. The following box plot and bar chart both demonstrate the same point - the amount of heap space freed per garbage colloection is surprisingly low. par(mfrow=c(2,1)) boxplot(as.vector(clipped.g1gc.z$Delta), main="Amount of Heap Recovered per GC Pass", xlab="Size in KB", horizontal = TRUE, col="red") hist(as.vector(clipped.g1gc.z$Delta), main="Amount of Heap Recovered per GC Pass", xlab="Size in KB", breaks=100, col="red") box(which = "outer", lty = "solid") This graph is the most interesting. The dark blue area shows how much heap is occupied by referenced Java objects. This represents memory that holds live data. The red fringe at the top shows how much data was recovered after each garbage collection. barplot(clipped.g1gc.z[,c("AfterSize","Delta")], col=c("#7570b3","#e7298a"), xlab="Time of Day", border=NA) legend("topleft", c("Live Objects","Heap Recovered on GC"), fill=c("#7570b3","#e7298a")) box(which = "outer", lty = "solid") When I discuss the data in the log files with the customer, I will ask for an explaination for the large amount of referenced data resident in the Java heap. There are two are posibilities: There is a memory leak and the amount of space required to hold referenced objects will continue to grow, limited only by the maximum heap size. After the maximum heap size is reached, the JVM will throw an “Out of Memory” exception every time that the application tries to allocate a new object. If this is the case, the aplication needs to be debugged to identify why old objects are referenced when they are no longer needed. The application has a legitimate requirement to keep a large amount of data in memory. The customer may want to further increase the maximum heap size. Another possible solution would be to partition the application across multiple cluster nodes, where each node has responsibility for managing a unique subset of the data. Conclusion In conclusion, R is a very powerful tool for the analysis of Java garbage collection log files. The primary difficulty is data cleansing so that information can be read into an R data frame. Once the data has been read into R, a rich set of tools may be used for thorough evaluation.

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• XNA Notes 008

  - by George Clingerman

  This week has been a rough one. I’ve been sick and then in some kind of slump for my afternoon coding sessions. It could be from the cold, could be I’m still tired from writing that Windows Phone 7 game development book (which is out now!) or it could just be I’m tired of winter and want some sunshine. All I know is that even while I’m stick, the XNA world keeps going along at it’s whirlwind pace. Below are the things I caught in between my coughing fits.. Time Critical XNA News: The 2011 MVP summit is almost here so pass along your feelings and thoughts so the MVPs can take them and share them with the team in person http://forums.create.msdn.com/forums/p/76317/464136.aspx#464136 Dream Build Play - there’s no new announcement yet, but you can’t get much more to the end of February than this! http://www.dreambuildplay.com/Main/Home.aspx XNA Team: Dean Johnson from the XNA team shares an excellent way of handling Guide.IsTrialMode on WP7 http://blogs.msdn.com/b/dejohn/archive/2011/02/21/calling-guide-istrialmode-on-windows-phone-7.aspx Nick Gravelyn tries a new tactic in deciding if there’s enough interest to develop a sequel or not. Don’t YOU want Pixel Man 2 to come out? http://nickgravelyn.com/pixelman2/ XNA MVPs: Andy “The ZMan” Dunn finally shares what he’s been secretly working on these past 4 months http://twitter.com/#!/The_Zman/status/40590269392887808 http://www.youtube.com/watch?v=Rg8Z0ZdYbvg&feature=youtu.be Joel Martinez lets developers around NYC know they should by signing up for Game Hack Day http://twitter.com/joelmartinez/statuses/41118590862102528 http://gamehackday.org/71fdk XNA Developers: Michael McLaughlin shares an XNA RenderTarget2D Sample http://geekswithblogs.net/mikebmcl/archive/2011/02/18/xna-rendertarget2d-sample.aspx Martin Caine starts a new series on Deferred Rendering in XNA 4.0 http://twitter.com/#!/MartinCaine/status/39735221339291648 http://martincaine.com/xna/deferred_rendering_in_xna_4_introduction ElemenyCy posts about his fun time with the IntermediateSerializer http://www.ubergamermonkey.com/xna/holy-bloated-xml-batman/ Ben Kane releases a narrated dev diary video for Project Splice. Let him know if you’d like to see more! (I know I do!) http://twitter.com/#!/benkane/status/39846959498002432 http://www.youtube.com/watch?v=1EmziXZUo08&feature=youtu.be Jason Swearingen (of Novaleaf) posts his part 1 of Spatial Partitioning solutions http://altdevblogaday.org/2011/02/21/spatial-partitioning-part-1-survey-of-spatial-partitioning-solutions/ Brian Lawson of Dark Flow Studios shares what his been up to lately with lots of pretty screenshots and hints of announcements from Microsoft... http://www.darkflowstudios.com/entry/short-and-sweet-part-1 Luke Avery starts a new blog where he plans on making XNA tutorials for beginners (and he’s got a few started already!) http://programmingwithovery.wordpress.com/ Xbox LIVE Indie Games (XBLIG): GameMarx Episode 10 http://www.gamemarx.com/video/the-show/24/ep-10-february-18-2010.aspx Minecraft clone FortressCraft coming to XBLIG http://www.eurogamer.net/articles/2011-02-23-minecraft-clone-fortresscraft-hits-xblig ezMuze+ starts an IndieGoGo fundraiser campaign to help fund their second game and get it onto even more devices! http://www.indiegogo.com/ezmuze Gamergeddon XBLIG round up http://www.gamergeddon.com/2011/02/20/xbox-indie-game-round-up-february-20th/?utm_campaign=twitter&utm_medium=twitter&utm_source=twitter JForce Games loses their Ego http://jforcegames.com/blog/index.php?itemid=121&catid=4 XNA Game Development: @BallerIndustry reminds all XNA developers that the Maths are important ;) http://twitter.com/#!/BallerIndustry/status/39317618280243200 http://www.youtube.com/watch?v=MjV3XDFsjP4&feature=player_embedded#at=106 @suhinini stumbles on an older but extremely useful post on XNA Content Pipeline debugging http://twitter.com/#!/suhinini/status/39270189476352000 http://badcorporatelogo.wordpress.com/2010/10/31/xna-content-pipeline-debugging-4-0/ XNA Game Development Workshops at Singapore Universities http://innovativesingapore.com/2011/02/xna-game-development-workshops-at-singapore-universities/ Indiefreaks announces that IGF v0.3 is out with Xbox 360 support, SunBurn 2.0.12 and it’s now Open Source! http://twitter.com/#!/indiefreaks/status/39391953971982336 @liotral announces a new series on properly designing a game http://twitter.com/#!/liortal53/status/39466905081217024 http://liortalblog.wordpress.com/2011/02/20/hello-cosmos/ Indies and XNA at CodeStock 2011 http://www.gamemarx.com/news/2011/02/20/indies-and-xna-at-codestock-2011.aspx Train Frontier Express posts about XNA Content Hotloading http://trainfrontierexpress.blogspot.com/2011/02/xna-content-hotloading-overview.html Slyprid announces a new character editor in Transmute http://twitter.com/#!/slyprid/status/40146992818696192 http://www.youtube.com/watch?v=OKhFAc78LDs&feature=youtu.be The XNA 2D from the ground up tutorial series http://xna-uk.net/blogs/darkgenesis/archive/2011/02/23/recap-the-xna-2d-from-the-ground-up-tutorial-series.aspx Sgt.Conker posts a “Clingerman” (hey that’s me!) to stay relevant http://www.sgtconker.com/2011/02/posting-a-clingerman-to-stay-relevant/

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• Pro/con of using Angular directives for complex form validation/ GUI manipulation

  - by tengen

  I am building a new SPA front end to replace an existing enterprise's legacy hodgepodge of systems that are outdated and in need of updating. I am new to angular, and wanted to see if the community could give me some perspective. I'll state my problem, and then ask my question. I have to generate several series of check boxes based on data from a .js include, with data like this: $scope.fieldMappings.investmentObjectiveMap = [ {'id':"CAPITAL PRESERVATION", 'name':"Capital Preservation"}, {'id':"STABLE", 'name':"Moderate"}, {'id':"BALANCED", 'name':"Moderate Growth"}, // etc {'id':"NONE", 'name':"None"} ]; The checkboxes are created using an ng-repeat, like this: <div ng-repeat="investmentObjective in fieldMappings.investmentObjectiveMap"> ... </div> However, I needed the values represented by the checkboxes to map to a different model (not just 2-way-bound to the fieldmappings object). To accomplish this, I created a directive, which accepts a destination array destarray which is eventually mapped to the model. I also know I need to handle some very specific gui controls, such as unchecking "None" if anything else gets checked, or checking "None" if everything else gets unchecked. Also, "None" won't be an option in every group of checkboxes, so the directive needs to be generic enough to accept a validation function that can fiddle with the checked state of the checkbox group's inputs based on what's already clicked, but smart enough not to break if there is no option called "NONE". I started to do that by adding an ng-click which invoked a function in the controller, but in looking around Stack Overflow, I read people saying that its bad to put DOM manipulation code inside your controller - it should go in directives. So do I need another directive? So far: (html): <input my-checkbox-group type="checkbox" fieldobj="investmentObjective" ng-click="validationfunc()" validationfunc="clearOnNone()" destarray="investor.investmentObjective" /> Directive code: .directive("myCheckboxGroup", function () { return { restrict: "A", scope: { destarray: "=", // the source of all the checkbox values fieldobj: "=", // the array the values came from validationfunc: "&" // the function to be called for validation (optional) }, link: function (scope, elem, attrs) { if (scope.destarray.indexOf(scope.fieldobj.id) !== -1) { elem[0].checked = true; } elem.bind('click', function () { var index = scope.destarray.indexOf(scope.fieldobj.id); if (elem[0].checked) { if (index === -1) { scope.destarray.push(scope.fieldobj.id); } } else { if (index !== -1) { scope.destarray.splice(index, 1); } } }); } }; }) .js controller snippet: .controller( 'SuitabilityCtrl', ['$scope', function ( $scope ) { $scope.clearOnNone = function() { // naughty jQuery DOM manipulation code that // looks at checkboxes and checks/unchecks as needed }; The above code is done and works fine, except the naughty jquery code in clearOnNone(), which is why I wrote this question. And here is my question: after ALL this, I think to myself - I could be done already if I just manually handled all this GUI logic and validation junk with jQuery written in my controller. At what point does it become foolish to write these complicated directives that future developers will have to puzzle over more than if I had just written jQuery code that 99% of us would understand with a glance? How do other developers draw the line? I see this all over Stack Overflow. For example, this question seems like it could be answered with a dozen lines of straightforward jQuery, yet he has opted to do it the angular way, with a directive and a partial... it seems like a lot of work for a simple problem. Specifically, I suppose I would like to know: how SHOULD I be writing the code that checks whether "None" has been selected (if it exists as an option in this group of checkboxes), and then check/uncheck the other boxes accordingly? A more complex directive? I can't believe I'm the only developer that is having to implement code that is more complex than needed just to satisfy an opinionated framework.

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• Is my implementation of A* wrong?

  - by Bloodyaugust

  I've implemented the A* algorithm in my program. However, it would seem to be functioning incorrectly at times. Below is a screenshot of one such time. The obviously shorter line is to go immediately right at the second to last row. Instead, they move down, around the tower, and continue to their destination (bottom right from top left). Below is my actual code implementation: nodeMap.prototype.findPath = function(p1, p2) { var openList = []; var closedList = []; var nodes = this.nodes; for (var i = 0; i < nodes.length; i++) { //reset heuristics and parents for nodes var curNode = nodes[i]; curNode.f = 0; curNode.g = 0; curNode.h = 0; curNode.parent = null; if (curNode.pathable === false) { closedList.push(curNode); } } openList.push(this.getNode(p1)); while(openList.length > 0) { // Grab the lowest f(x) to process next var lowInd = 0; for(i=0; i<openList.length; i++) { if(openList[i].f < openList[lowInd].f) { lowInd = i; } } var currentNode = openList[lowInd]; if (currentNode === this.getNode(p2)) { var curr = currentNode; var ret = []; while(curr.parent) { ret.push(curr); curr = curr.parent; } return ret.reverse(); } closedList.push(currentNode); for (i = 0; i < openList.length; i++) { //remove currentNode from openList if (openList[i] === currentNode) { openList.splice(i, 1); break; } } for (i = 0; i < currentNode.neighbors.length; i++) { if(closedList.indexOf(currentNode.neighbors[i]) !== -1 ) { continue; } if (currentNode.neighbors[i].isPathable === false) { closedList.push(currentNode.neighbors[i]); continue; } var gScore = currentNode.g + 1; // 1 is the distance from a node to it's neighbor var gScoreIsBest = false; if (openList.indexOf(currentNode.neighbors[i]) === -1) { //save g, h, and f then save the current parent gScoreIsBest = true; currentNode.neighbors[i].h = currentNode.neighbors[i].heuristic(this.getNode(p2)); openList.push(currentNode.neighbors[i]); } else if (gScore < currentNode.neighbors[i].g) { //current g better than previous g gScoreIsBest = true; } if (gScoreIsBest) { currentNode.neighbors[i].parent = currentNode; currentNode.neighbors[i].g = gScore; currentNode.neighbors[i].f = currentNode.neighbors[i].g + currentNode.neighbors[i].h; } } } return false; } Towers block pathability. Is there perhaps something I am missing here, or does A* not always find the shortest path in a situation such as this? Thanks in advance for any help.

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• ASP.NET MVC - Javascript array always passed to controller as null

  - by Xuan Vu

  I'm having some problem with passing a javascript array to the controller. I have several checkboxes on my View, when a checkbox is checked, its ID will be saved to an array and then I need to use that array in the controller. Here are the code: VIEW: var selectedSearchUsers = new Array(); $(document).ready(function () { $("#userSearch").click(function () { selectedSearchUsers.length = 0; ShowLoading(); $.ajax({ type: "POST", url: '/manage/searchusers', dataType: "json", data: $("#userSearchForm").serialize(), success: function (result) { UserSearchSuccess(result); }, cache: false, complete: function () { HideLoading(); } }); }); $(".userSearchOption").live("change", function () { var box = $(this); var id = box.attr("dataId"); var checked = box.attr("checked"); if (checked) { selectedSearchUsers.push(id); } else { selectedSearchUsers.splice(selectedSearchUsers.indexOf(id), 1); } }); $("#Send").click(function () { var postUserIDs = { values: selectedSearchUsers }; ShowLoading(); $.post("/Manage/ComposeMessage", postUserIDs, function (data) { }, "json"); }); }); When the "Send" button is clicked, I want to pass the selectedSearchUsers to the "ComposeMessage" action. Here is the Action code: public JsonResult ComposeMessage(List values) { //int count = selectedSearchUsers.Length; string count = values.Count.ToString(); return Json(count); } However, the List values is always null. Any idea why? Thank you very much.

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• Javascript Error with DataTable jQuery plugin

  - by stevoyoung

  I am getting a JS error and what to know what it means and how to solve it. (JS noob here) Error: "tId is not defined" Line of JS with error: "if (s[i].sInstance = tId) { " More Information I am using the Data Table (http://datatables.net) jQuery plugin. I have a two tables with a class of "dataTable" loaded on a page (inside of jQuery UI tabs). The tables render as expected but I get the error above in Firebug. Attached is my Data Table config file... $(document).ready(function() { //Take from: http://datatables.net/forums/comments.php?DiscussionID=1507 // before creating a table, make sure it is not already created. // And if it is, then remove old version before new one is created var currTable = $(".dataTable"); if (currTable) { // contains the dataTables master records var s = $(document).dataTableSettings; if (s != 'undefined') { var len = s.length; for (var i=0; i < len; i++) { // if already exists, remove from the array if (s[i].sInstance = tId) { s.splice(i,1); } } } } oTable = $('.dataTable').dataTable({ "bJQueryUI": true, "sPaginationType": "full_numbers", "bFilter": false }); }); What does the error mean and how do I resolve it?

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• Perl - How to get the number of elements in an anonymous array, for concisely trimming pathnames

  - by NXT

  Hi Everyone, I'm trying to get a block of code down to one line. I need a way to get the number of items in a list. My code currently looks like this: # Include the lib directory several levels up from this directory my @ary = split('/', $Bin); my @ary = @ary[0 .. $#ary-4]; my $res = join '/',@ary; lib->import($res.'/lib'); That's great but I'd like to make that one line, something like this: lib->import( join('/', ((split('/', $Bin)) [0 .. $#ary-4])) ); But of course the syntax $#ary is meaningless in the above line. Is there equivalent way to get the number of elements in an anonymous list? Thanks! PS: The reason for consolidating this is that it will be in the header of a bunch of perl scripts that are ancillary to the main application, and I want this little incantation to be more cut & paste proof. Thanks everyone There doesn't seem to be a shorthand for the number of elements in an anonymous list. That seems like an oversight. However the suggested alternatives were all good. I'm going with: lib->import(join('/', splice( @{[split('/', $Bin)]}, 0, -4)).'/lib'); But Ether suggested the following, which is much more correct and portable: my $lib = File::Spec->catfile( realpath(File::Spec->catfile($FindBin::Bin, ('..') x 4)), 'lib'); lib->import($lib);

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• Invalid argument in sendfile() with two regular files

  - by Daniel Hershcovich

  I'm trying to test the sendfile() system call under Linux 2.6.32 to zero-copy data between two regular files. As far as I understand, it should work: ever since 2.6.22, sendfile() has been implemented using splice(), and both the input file and the output file can be either regular files or sockets. The following is the content of sendfile_test.c: #include <sys/sendfile.h> #include <fcntl.h> #include <stdio.h> int main(int argc, char **argv) { int result; int in_file; int out_file; in_file = open(argv[1], O_RDONLY); out_file = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644); result = sendfile(out_file, in_file, NULL, 1); if (result == -1) perror("sendfile"); close(in_file); close(out_file); return 0; } And when I'm running the following commands: $ gcc sendfile_test.c $ ./a.out infile The output is sendfile: Bad file descriptor Which means that the system call resulted in errno = -EINVAL, I think. What am I doing wrong?

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• Why can't I add to the middle of an array with Perl's Tie::File?

  - by SCNCN2010

  File : #comment1 #comment2 #comment3 #START HERE a: [email protected] b: [email protected] my perl program : use Data::Dumper; use Tie::File; tie my @array, 'Tie::File', 'ala.txt' or die $!; my $rec = 'p: [email protected]'; my $flag =1 ; my $add_flag = 0; for my $i (0..$#array) { next if ($array[$i] =~ /^\s*$/); if ( $flag == 1 ) { if ($array[$i] =~ /#START HERE/ ) { $flag = 0; } else { next ; } } if (($array[$i] cmp $rec) == 1) { splice @array, $i, 0, $rec; $add_flag = 1; last ; } } if ( $add_flag == 0 ) { my $index = $#array+1; $array[$index] = $rec ; } the recording adding end of file always . I am trying to add to middle or begin or end like aplphbetical order Edit 2 : I want to do with Tie::FILE only . after add : (after 2 execution ) #comment1 #comment2 #comment3 #START HERE a: [email protected] b: [email protected] p: [email protected] a: [email protected] # if i add another record of a Expection : #comment1 #comment2 #comment3 #START HERE a: [email protected] a: [email protected] b: [email protected] p: [email protected] q: [email protected]

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• jquery ajax html response change 1.3.2 vs 1.4.2 (aka where is my script tag?)

  - by cmroanirgo

  I've been using jquery 1.3.2 to pull snippets of html (including script) from a server. A typical response might be: <div id="content"<div id="inner"... <script type=... alert("hello world");</script <pHello World</p </div</div I've been using the query .get function: $.get($(this).attr("href"), function(response) { $("#inner").replaceWith($("#inner", response)); }); And everything is fine and works as expected: the returned html snippets get loaded into the DOM and the scripts run. When I use 1.4.2 however, I notice that the script tags have been removed and no longer run. Stepping into the newer jquery codebase yields the lines of code (line 4498) : ret.splice.apply( ret, [i + 1, 0].concat(jQuery.makeArray(ret[i].getElementsByTagName("script"))) ); which seems to be the culprit 'removing' the script from its happy resting place as part of the selector process. But it doesn't help me in injecting exactly what i want into the DOM. Any idea why jquery is doing this? More importantly, how can I go about fixing this so that my scripts run?

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• Can't add object to Array in jQuery's getJSON data function (scope issue)

  - by seo20

  I have a person object and wants to store it into a global ArrayCollection I have made. Works great in normal scope: var s = new ArrayCollection(); s.add(new person("Knud", "Mikkelsen", 35)); The problem is when I want to add people inside my jQuery function "mainFunction". I can't seem to get it right. I know it's something to do with scope and I have to wrap something in functions like in my ArrayCollection. Please help me - thanks a lot. function ArrayCollection() { var myArray = new Array; return { empty: function () { myArray.splice(0, myArray.length); }, add: function (myElement) { myArray.push(myElement); }, getAll: function () { return myArray; } } } function person(firstName, lastName, age) { this.firstName = firstName; this.lastName = lastName; this.age = parseInt(parseFloat(age)); } function mainFunction() { //.... var s = new ArrayCollection(); s.add(new person("Knud", "Mikkelsen", 35)); $.getJSON(url, function (data) { for (var x = 0; x < data.length; x++) { var myPerson = new person(data[x].FirstName.toString(), data[x].LastName.toString(), data[x].Age.toString()); s.add(myPerson); } }); alert(drawArray(s.getAll())); } function drawArray(myArray) { var v = ""; for (var i = 0; i < myArray.length; i++) { v += myArray[i].firstName + " " + myArray[i].lastName + " (" + myArray[i].age + ")\n"; } return v; }

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• Mix Audio tracks with offset in SOX

  - by Laramie

  From ASP.Net, I am using FFMPEG to convert flv files on a Flash Media Server to wavs that I need to mix into a single MP3 file. I originally attempted this entirely with FFMPEG but eventually gave up on the mixing step because I don't believe it it possible to combine audio only tracks into a single result file. I would love to be wrong. I am now using FFMPEG to access the FLV files and extract the audio track to wav so that SOX can mix them. The problem is that I must offset one of the audio tracks by a few seconds so that they are synchronized. Each file is one half of a conversation between a student and a teacher. For example teacher.wav might need to begin 3.3 seconds after student.wav. I can only figure out how to mix the files with SOX where both tracks begin at the same time. My best attempt at this point is: ffmpeg -y -i rtmp://server/appName/instance/student.flv -ac 1 student.wav ffmpeg -y -i rtmp://server/appName/instance/teacher.flv -ac 1 teacher.wav sox -m student.wav teacher.wav combined.mp3 splice 3.3 These tools (FFMEG/SoX) were chosen based on my best research, but are not required. Any working solution would allow an ASP.Net service to input the two FMS flvs and create a combined MP3 using open-source or free tools.

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• Pseudo-quicksort time complexity

  - by Ord

  I know that quicksort has O(n log n) average time complexity. A pseudo-quicksort (which is only a quicksort when you look at it from far enough away, with a suitably high level of abstraction) that is often used to demonstrate the conciseness of functional languages is as follows (given in Haskell): quicksort :: Ord a => [a] -> [a] quicksort [] = [] quicksort (p:xs) = quicksort [y | y<-xs, y<p] ++ [p] ++ quicksort [y | y<-xs, y>=p] Okay, so I know this thing has problems. The biggest problem with this is that it does not sort in place, which is normally a big advantage of quicksort. Even if that didn't matter, it would still take longer than a typical quicksort because it has to do two passes of the list when it partitions it, and it does costly append operations to splice it back together afterwards. Further, the choice of the first element as the pivot is not the best choice. But even considering all of that, isn't the average time complexity of this quicksort the same as the standard quicksort? Namely, O(n log n)? Because the appends and the partition still have linear time complexity, even if they are inefficient.

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