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• Understanding VS2010 C# parallel profiling results

  - by Haggai

  I have a program with many independent computations so I decided to parallelize it. I use Parallel.For/Each. The results were okay for a dual-core machine - CPU utilization of about 80%-90% most of the time. However, with a dual Xeon machine (i.e. 8 cores) I get only about 30%-40% CPU utilization, although the program spends quite a lot of time (sometimes more than 10 seconds) on the parallel sections, and I see it employs about 20-30 more threads in those sections compared to serial sections. Each thread takes more than 1 second to complete, so I see no reason for them to work in parallel - unless there is a synchronization problem. I used the built-in profiler of VS2010, and the results are strange. Even though I use locks only in one place, the profiler reports that about 85% of the program's time is spent on synchronization (also 5-7% sleep, 5-7% execution, under 1% IO). The locked code is only a cache (a dictionary) get/add: bool esn_found; lock (lock_load_esn) esn_found = cache.TryGetValue(st, out esn); if(!esn_found) { esn = pData.esa_inv_idx.esa[term_idx]; esn.populate(pData.esa_inv_idx.datafile); lock (lock_load_esn) { if (!cache.ContainsKey(st)) cache.Add(st, esn); } } lock_load_esn is a static member of the class of type Object. esn.populate reads from a file using a separate StreamReader for each thread. However, when I press the Synchronization button to see what causes the most delay, I see that the profiler reports lines which are function entrance lines, and doesn't report the locked sections themselves. It doesn't even report the function that contains the above code (reminder - the only lock in the program) as part of the blocking profile with noise level 2%. With noise level at 0% it reports all the functions of the program, which I don't understand why they count as blocking synchronizations. So my question is - what is going on here? How can it be that 85% of the time is spent on synchronization? How do I find out what really is the problem with the parallel sections of my program? Thanks.

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• .NET: Avoidance of custom exceptions by utilising existing types, but which?

  - by Mr. Disappointment

  Consider the following code (ASP.NET/C#): private void Application_Start(object sender, EventArgs e) { if (!SetupHelper.SetUp()) { throw new ShitHitFanException(); } } I've never been too hesitant to simply roll my own exception type, basically because I have found (bad practice, or not) that mostly a reasonable descriptive type name gives us enough as developers to go by in order to know what happened and why something might have happened. Sometimes the existing .NET exception types even accommodate these needs - regardless of the message. In this particular scenario, for demonstration purposes only, the application should die a horrible, disgraceful death should SetUp not complete properly (as dictated by its return value), but I can't find an already existing exception type in .NET which would seem to suffice; though, I'm sure one will be there and I simply don't know about it. Brad Abrams posted this article that lists some of the available exception types. I say some because the article is from 2005, and, although I try to keep up to date, it's a more than plausible assumption that more have been added to future framework versions that I am still unaware of. Of course, Visual Studio gives you a nicely formatted, scrollable list of exceptions via Intellisense - but even on analysing those, I find none which would seem to suffice for this situation... ApplicationException: ...when a non-fatal application error occurs The name seems reasonable, but the error is very definitely fatal - the app is dead. ExecutionEngineException: ...when there is an internal error in the execution engine of the CLR Again, sounds reasonable, superficially; but this has a very definite purpose and to help me out here certainly isn't it. HttpApplicationException: ...when there is an error processing an HTTP request Well, we're running an ASP.NET application! But we're also just pulling at straws here. InvalidOperationException: ...when a call is invalid for the current state of an instance This isn't right but I'm adding it to the list of 'possible should you put a gun to my head, yes'. OperationCanceledException: ...upon cancellation of an operation the thread was executing Maybe I wouldn't feel so bad using this one, but I'd still be hijacking the damn thing with little right. You might even ask why on earth I would want to raise an exception here but the idea is to find out that if I were to do so then do you know of an appropriate exception for such a scenario? And basically, to what extent can we piggy-back on .NET while keeping in line with rationality?

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• Using multiple aggregate functions in an algebraic expression in (ANSI) SQL statement

  - by morpheous

  I have the following aggregate functions (AGG FUNCs): foo(), foobar(), fredstats(), barneystats(). I want to know if I can use multiple AGG FUNCs in an algebraic expression. This may seem a strange/simplistic question for seasoned SQL developers - however, the but the reason I ask is that so far, all AGG FUNCs examples I have seen are of the simplistic variety e.g. max(salary) < 100, rather than using the AGG FUNCs in an expression which involves using multiple AGG FUNCs in an expression (like agg_func1() agg_func2()). The information below should help clarify further. Given tables with the following schemas: CREATE TABLE item (id int, length float, weight float); CREATE TABLE item_info (item_id, name varchar(32)); # Is it legal (ANSI) SQL to write queries of this format ? SELECT id, name, foo, foobar, fredstats FROM A, B (SELECT id, foo(123) as foo, foobar('red') as foobar, fredstats('weight') as fredstats FROM item GROUP BY id HAVING [ALGEBRAIC EXPRESSION] ORDER BY id AS A), item_info AS B WHERE item.id = B.id Where: ALGEBRAIC EXPRESSION is the type of expression that can be used in a WHERE clause - for example: ((foo(x) < foobar(y)) AND foobar(y) IN (1,2,3)) OR (fredstats(x) <> 0)) I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible. Assuming it is legal to include AGG FUNCS in the way I have done above, I'd like to know: Is there a more efficient way to write the above query ? Is there any way I can speed up the query in terms of a judicious choice of indexes on the tables item and item_info ? Is there a performance hit of using AGG FUNCs in an algebraic expression like I am (i.e. an expression involving the output of aggregate functions rather than constants? Can the expression also include 'scaled' AGG FUNC? (for example: 2*foo(123) < -3*foobar(456) ) - will scaling (i.e. multiplying an AGG FUNC by a number have an effect on performance?) How can I write the query above using INNER JOINS instead?

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• OpenGL suppresses exceptions in MFC dialog-based application

  - by Mikhail

  Hello. I have an MFC-driven dialog-based application created with MSVS2005. Here is my problem step by step. I have button on my dialog and corresponding click-handler with code like this: int* i = 0; *i = 3; I'm running debug version of program and when I click on the button, Visual Studio catches focus and alerts "Access violation writing location" exception, program cannot recover from the error and all I can do is to stop debugging. And this is the right behavior. Now I add some OpenGL initialization code in the OnInitDialog() method: HDC DC = GetDC(GetSafeHwnd()); static PIXELFORMATDESCRIPTOR pfd = { sizeof(PIXELFORMATDESCRIPTOR), // size of this pfd 1, // version number PFD_DRAW_TO_WINDOW | // support window PFD_SUPPORT_OPENGL | // support OpenGL PFD_DOUBLEBUFFER, // double buffered PFD_TYPE_RGBA, // RGBA type 24, // 24-bit color depth 0, 0, 0, 0, 0, 0, // color bits ignored 0, // no alpha buffer 0, // shift bit ignored 0, // no accumulation buffer 0, 0, 0, 0, // accum bits ignored 32, // 32-bit z-buffer 0, // no stencil buffer 0, // no auxiliary buffer PFD_MAIN_PLANE, // main layer 0, // reserved 0, 0, 0 // layer masks ignored }; int pixelformat = ChoosePixelFormat(DC, &pfd); SetPixelFormat(DC, pixelformat, &pfd); HGLRC hrc = wglCreateContext(DC); ASSERT(hrc != NULL); wglMakeCurrent(DC, hrc); Of course this is not exactly what I do, it is the simplified version of my code. Well now the strange things begin to happen: all initialization is fine, there are no errors in OnInitDialog(), but when I click the button... no exception is thrown. Nothing happens. At all. If I set a break-point at the *i = 3; and press F11 on it, the handler-function halts immediately and focus is returned to the application, which continue to work well. I can click button again and the same thing will happen. It seems like someone had handled occurred exception of access violation and silently returned execution into main application message-receiving cycle. If I comment the line wglMakeCurrent(DC, hrc);, all works fine as before, exception is thrown and Visual Studio catches it and shows window with error message and program must be terminated afterwards. I experience this problem under Windows 7 64-bit, NVIDIA GeForce 8800 with latest drivers (of 11.01.2010) available at website installed. My colleague has Windows Vista 32-bit and has no such problem - exception is thrown and application crashes in both cases. Well, hope good guys will help me :) PS The problem originally where posted under this topic.

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• Twisted: why is it that passing a deferred callback to a deferred thread makes the thread blocking a

  - by surtyaarthoughts

  I unsuccessfully tried using txredis (the non blocking twisted api for redis) for a persisting message queue I'm trying to set up with a scrapy project I am working on. I found that although the client was not blocking, it became much slower than it could have been because what should have been one event in the reactor loop was split up into thousands of steps. So instead, I tried making use of redis-py (the regular blocking twisted api) and wrapping the call in a deferred thread. It works great, however I want to perform an inner deferred when I make a call to redis as I would like to set up connection pooling in attempts to speed things up further. Below is my interpretation of some sample code taken from the twisted docs for a deferred thread to illustrate my use case: #!/usr/bin/env python from twisted.internet import reactor,threads from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(): print 'doing lookup... this may take a while' time.sleep(10) return 'results from redis' def result(res): print res def main(): lc = LoopingCall(main_loop) lc.start(2) d = threads.deferToThread(aBlockingRedisCall) d.addCallback(result) reactor.run() if __name__=='__main__': main() And here is my alteration for connection pooling that makes the code in the deferred thread blocking : #!/usr/bin/env python from twisted.internet import reactor,defer from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(x): if x<5: #all connections are busy, try later print '%s is less than 5, get a redis client later' % x x+=1 d = defer.Deferred() d.addCallback(aBlockingRedisCall) reactor.callLater(1.0,d.callback,x) return d else: print 'got a redis client; doing lookup.. this may take a while' time.sleep(10) # this is now blocking.. any ideas? d = defer.Deferred() d.addCallback(gotFinalResult) d.callback(x) return d def gotFinalResult(x): return 'final result is %s' % x def result(res): print res def aBlockingMethod(): print 'going to sleep...' time.sleep(10) print 'woke up' def main(): lc = LoopingCall(main_loop) lc.start(2) d = defer.Deferred() d.addCallback(aBlockingRedisCall) d.addCallback(result) reactor.callInThread(d.callback, 1) reactor.run() if __name__=='__main__': main() So my question is, does anyone know why my alteration causes the deferred thread to be blocking and/or can anyone suggest a better solution?

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• Read variable-length records from a buffer - weird memory issues

  - by bsg

  Hi, I'm trying to implement an i/o intensive quicksort (C++ qsort) on a very large dataset. In the interests of speed, I'd like to read in a chunk of data at a time into a buffer and then use qsort to sort it inside the buffer. (I am currently working with text files but would like to move to binary soon.) However, my data is composed of variable-length records, and qsort needs to be told the length of the record in order to sort. Is there any way to standardize this? The only thing I could think of was rather convoluted: my program currently reads from the buffer until it hits a linefeed character ('10' in ascii), transferring each character over to another array. When it finds a linefeed (the delimiter in the input file), it fills the number of spaces remaining in the buffer for that record (record size is set to 30) with null characters. This way, I should end up with a buffer full of fixed-size records to give qsort. I know there are several problems with my approach, one being that it's just clumsy, another that the record size might conceivably be larger than 30, but is generally much less. Is there a better way of doing this? As well, my current code doesn't even work. When I debug it, it seems to be transferring characters from one buffer to the other, but when I try to print out the buffer, it contains only the first record. Here is my code: FILE *fp; unsigned char *buff; unsigned char *realbuff; FILE *inputFiles[NUM_INPUT_FILES]; buff = (unsigned char *) malloc(2048); realbuff = (unsigned char *) malloc(NUM_RECORDS * RECORD_SIZE); fp = fopen("postings0.txt", "r"); if(fp) { fread(buff, 1, 2048, fp); /*for(int i=0; i <30; i++) cout << buff[i] <<endl;*/ int y=0; int recordcounter = 0; //cout << buff; for(int i=0;i <100; i++) { if(buff[i] != char(10)) { realbuff[y] = buff[i]; y++; recordcounter++; } else { if(recordcounter < RECORD_SIZE) for(int j=recordcounter; j < RECORD_SIZE;j++) { realbuff[y] = char(0); y++; } recordcounter = 0; } } cout << realbuff <<endl; cout << buff; } else cout << "sorry"; Thank you very much, bsg

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• [NEWVERSION]algorithm || method to write prog[UNSOLVED] [closed]

  - by fatai

  I am one of the computer science student. Everyone solve problem with a different or same method, ( but actually I dont know whether they use method or I dont know whether there are such common method to approach problem.) if there are common method, What is it ? If there are different method, which method are you using ? All teacher give us problem which in simple form sometimes, but they donot introduce any approach or method(s) so that we cannot make a decision to choose the method then apply that one to problem , afterward find solution then write code.No help from teacher , push us to find method to solve homework. Ex: my friend is using no method , he says "I start to construct algorithm while I try to write prog." I have found one method when I failed the course, More accurately, my method: When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 now, my other question is ; What is/are other method(s) which have/has been; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c by other user? Some programmer uses generalized method without considering prog-language(java , perl .. ), what is this method ? Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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• Do you feel underappreciated or resent the geek/nerd stigma?

  - by dotnetdev

  At work we have a piece of A4 paper with the number of everyone in the office. The structure of this document is laid out in rectangles, by department. I work for the department that does all the technical stuff. That includes support—bear in mind that the support staff isn't educated in IT but just has experience in PC maintenance and providing support to a system we resell but don't have source code access to, project manager, team leader, a network administrator, a product manager, and me, a programmer. Anyway, on this paper, we are labelled as nerds and geeks. I did take a little offence to this, as much as it is light hearted (but annoying and old) humour. I have a vivid image that a geek is someone who doesn't go out but codes all day. I code all day at home and at work (when I have something to code...), but I keep balance by going out. I don't know why it is only people who work with computers that get such a stigma. No other profession really gets the same stigma—skilled, technical, or whatever. An account manager (and this is hardly a skilled job) says, "Perhaps [MY NAME HERE] could write some geeky code tomorrow to add this functionality to the website." It is funny how I get such an unfair stigma but I am so pivotal. In fact, if it wasn't for me, the company would have nothing to sell so the account managers would be redundant! I make systems, they get sold, and this is what pays the wages. It's funny how the account managers get a commission for how many systems they sell, or manage to make clients resubscribe to. Yet I built the thing in the first place! On top of that, my brother says all I do is type stuff on a keyboard all day. Surely if I did, I'd be typing at my normal typing speed of 100wpm+ as if I am writing a blog entry. Instead, I plan as I code along on the fly if commercial pressures and time prohibit proper planning. I never type as if I'm writing normal English. There is more to our jobs than just typing code. And my brother is a pipe fitter with no formal qualifications in his name. I could easily, and perhaps more justifiably, say he just manipulates a spanner or something. Does you feel underappreciated or that a geek/nerd stigma is undeserved or unfair?

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• JavaScript Resource Management Design Pattern

  - by Adam

  As a web developer, a common problem I find myself tackling is waiting for something to load before doing something else. In particular, I often hide (using either display: none; or visibility: hidden; depending on the situation) elements while waiting for a background image or a CSS file to load. Consider this example from Last.FM. They overlay a semi-transparant PNG over each album art image so that it looks like it's inside a jewel-case. They let it load when it loads, so depending on your internet speed, you may see the art image by itself (without the overlay) temporarily. In this case, the album art looks fine without the jewel-case effect. But in similar situations, I have found that I don't want the user to see the site's design mangled as resources incrementally load. So, in rare cases I have hidden everything from the user until the whole kit and kaboodle has loaded. But this is often a pain to write out, and may force the user to wait for a pretty long time to see anything (besides "loading..." text). I can think of (and have used on occasion) some obvious solutions/compromises: Use some inline CSS so that as certain parts of the DOM load and render, they will immediately have the correct size/position/etc. Immediately render the navigation part of the site, so that if the user wanted to use the current page purely to get somewhere else, they don't have to wait for the rest to load. Load pixelated images first as placeholders for layout while lazy-loading higher quality images as replacements. Something quirky like using a cute animated gif to distract the user during a "loading..." phase. Show useful information as a reference while loading the full UI. (Something akin to Gmail Inbox Preview, etc.) (Sorry if my question was basically just asked and answered...) Despite all of these ideas, I still find myself hoping there are better ways of doing some of these things. So I guess what I'm looking for is some inspiration and/or any creative ways of dealing with this problem that you guys may have seen out in the wild.

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• Managing multiple AJAX calls to PHP scripts

  - by relativelycoded

  I have a set of 5 HTML dropdowns that act as filters for narrowing results returned from a mySQL database. The three pertinent filters are for "Province", "Region", and "City" selection, respectively. I have three functions: findSchools(), which runs when any of the filters (marked with CSS class .filter) are changed, and fetches the results via AJAX from a PHP script. Once that is done, two other functions are called... changeRegionOptions(), which, upon changing the "Province" filter, and updates the available options using the same method as the first function, but posting to a different script. changeCityOptions(), which runs if the "Region" filter was changed, and updates options, again using the same method. The problem is that since I want these AJAX functions to run simultaneously, and they by nature run asynchronously, I've tried using $.when to control the execution of the functions, but it doesn't fix the problem. The functions run, but the Region and City filters return blank (no options); the FireBug report shows absolutely no output, even though the POST request went through. The posted parameter for filter_province gets sent normally, but the one for region gets cut off at the end -- it sends as filter_region=, with no value passed. So I'm presuming my logic is wrong somewhere. The code is below: // When any of the filters are changed, let's query the database... $("select.filter").change(function() { findSchools(); }); // First, we see if there are any results... function findSchools() { var sch_province = document.filterform.filter_province.value; var sch_region = document.filterform.filter_region.value; var sch_city = document.filterform.filter_city.value; var sch_cat = document.filterform.filter_category.value; var sch_type = document.filterform.filter_type.value; $.post("fetch_results.php", { filter_province : sch_province, filter_region : sch_region, filter_city : sch_city, filter_category : sch_cat, filter_type : sch_type }, function(data) { $("#results").html(""); $("#results").hide(); $("#results").html(data); $("#results").fadeIn(600); } ); // Once the results are fetched, we want to see if the filter they changed was the one for Province, and if so, update the Region and City options to match that selection... $("#filter_province").change(function() { $.when(findSchools()) .done(changeRegionOptions()); $.when(changeRegionOptions()) .done(changeCityOptions()); }); }; This is just one of the ways I've tried to solve it; I've tried using an IF statement, and tried calling the functions directly inside the general select.filter.change() function (after findSchools(); ), but they all return the same result. Any help with this would be great!

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• chaining array of tasks with continuation

  - by Andrei Cristof

  I have a Task structure that is a little bit complex(for me at least). The structure is: (where T = Task) T1, T2, T3... Tn. There's an array (a list of files), and the T's represent tasks created for each file. Each T has always two subtasks that it must complete or fail: Tn.1, Tn.2 - download and install. For each download (Tn.1) there are always two subtasks to try, download from two paths(Tn.1.1, Tn.1.2). Execution would be: First, download file: Tn1.1. If Tn.1.1 fails, then Tn.1.2 executes. If either from download tasks returns OK - execute Tn.2. If Tn.2 executed or failed - go to next Tn. I figured the first thing to do, was to write all this structure with jagged arrays: private void CreateTasks() { //main array Task<int>[][][] mainTask = new Task<int>[_queuedApps.Count][][]; for (int i = 0; i < mainTask.Length; i++) { Task<int>[][] arr = GenerateOperationTasks(); mainTask[i] = arr; } } private Task<int>[][] GenerateOperationTasks() { //two download tasks Task<int>[] downloadTasks = new Task<int>[2]; downloadTasks[0] = new Task<int>(() => { return 0; }); downloadTasks[1] = new Task<int>(() => { return 0; }); //one installation task Task<int>[] installTask = new Task<int>[1] { new Task<int>(() => { return 0; }) }; //operations Task is jagged - keeps tasks above Task<int>[][] operationTasks = new Task<int>[2][]; operationTasks[0] = downloadTasks; operationTasks[1] = installTask; return operationTasks; } So now I got my mainTask array of tasks, containing nicely ordered tasks just as described above. However after reading the docs on ContinuationTasks, I realise this does not help me since I must call e.g. Task.ContinueWith(Task2). I'm stumped about doing this on my mainTask array. I can't write mainTask[0].ContinueWith(mainTask[1]) because I dont know the size of the array. If I could somehow reference the next task in the array (but without knowing its index), but cant figure out how. Any ideas? Thank you very much for your help. Regards,

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• Should we denormalize database to improve performance?

  - by Groo

  We have a requirement to store 500 measurements per second, coming from several devices. Each measurement consists of a timestamp, a quantity type, and several vector values. Right now there is 8 vector values per measurement, and we may consider this number to be constant for needs of our prototype project. We are using HNibernate. Tests are done in SQLite (disk file db, not in-memory), but production will probably be MsSQL. Our Measurement entity class is the one that holds a single measurement, and looks like this: public class Measurement { public virtual Guid Id { get; private set; } public virtual Device Device { get; private set; } public virtual Timestamp Timestamp { get; private set; } public virtual IList<VectorValue> Vectors { get; private set; } } Vector values are stored in a separate table, so that each of them references its parent measurement through a foreign key. We have done a couple of things to ensure that generated SQL is (reasonably) efficient: we are using Guid.Comb for generating IDs, we are flushing around 500 items in a single transaction, ADO.Net batch size is set to 100 (I think SQLIte does not support batch updates? But it might be useful later). The problem Right now we can insert 150-200 measurements per second (which is not fast enough, although this is SQLite we are talking about). Looking at the generated SQL, we can see that in a single transaction we insert (as expected): 1 timestamp 1 measurement 8 vector values which means that we are actually doing 10x more single table inserts: 1500-2000 per second. If we placed everything (all 8 vector values and the timestamp) into the measurement table (adding 9 dedicated columns), it seems that we could increase our insert speed up to 10 times. Switching to SQL server will improve performance, but we would like to know if there might be a way to avoid unnecessary performance costs related to the way database is organized right now. [Edit] With in-memory SQLite I get around 350 items/sec (3500 single table inserts), which I believe is about as good as it gets with NHibernate (taking this post for reference: http://ayende.com/Blog/archive/2009/08/22/nhibernate-perf-tricks.aspx). But I might as well switch to SQL server and stop assuming things, right? I will update my post as soon as I test it.

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• What is your most productive shortcut with Vim?

  - by Olivier Pons

  I've heard a lot about Vim, both pros and cons. It really seems you should be (as a developer) faster with Vim than with any other editor. I'm using Vim to do some basic stuff and I'm at best 10 times less productive with Vim. The only two things you should care about when you talk about speed (you may not care enough about them, but you should) are: Using alternatively left and right hands is the fastest way to use the keyboard. Never touching the mouse is the second way to be as fast as possible. It takes ages for you to move your hand, grab the mouse, move it, and bring it back to the keyboard (and you often have to look at the keyboard to be sure you returned your hand properly to the right place) Here are two examples demonstrating why I'm far less productive with Vim. Copy/Cut & paste. I do it all the time. With all the classical editors you press Shift with the left hand, and you move the cursor with your right hand to select text. Then Ctrl+C copies, you move the cursor and Ctrl+V pastes. With Vim it's horrible: yy to copy one line (you almost never want the whole line!) [number xx]yy to copy xx lines into the buffer. But you never know exactly if you've selected what you wanted. I often have to do [number xx]dd then u to undo! Another example? Search & replace. In PSPad: Ctrl+f then type what you want you search for, then press Enter. In Vim: /, then type what you want to search for, then if there are some special characters put \ before each special character, then press Enter. And everything with Vim is like that: it seems I don't know how to handle it the right way. NB : I've already read the Vim cheat sheet :) My question is: What is the way you use Vim that makes you more productive than with a classical editor?

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• drag to pan on an UserControl

  - by Matías

  Hello, I'm trying to build my own "PictureBox like" control adding some functionalities. For example, I want to be able to pan over a big image by simply clicking and dragging with the mouse. The problem seems to be on my OnMouseMove method. If I use the following code I get the drag speed and precision I want, but of course, when I release the mouse button and try to drag again the image is restored to its original position. using System.Drawing; using System.Windows.Forms; namespace Testing { public partial class ScrollablePictureBox : UserControl { private Image image; private bool centerImage; public Image Image { get { return image; } set { image = value; Invalidate(); } } public bool CenterImage { get { return centerImage; } set { centerImage = value; Invalidate(); } } public ScrollablePictureBox() { InitializeComponent(); SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer, true); Image = null; AutoScroll = true; AutoScrollMinSize = new Size(0, 0); } private Point clickPosition; private Point scrollPosition; protected override void OnMouseDown(MouseEventArgs e) { base.OnMouseDown(e); clickPosition.X = e.X; clickPosition.Y = e.Y; } protected override void OnMouseMove(MouseEventArgs e) { base.OnMouseMove(e); if (e.Button == MouseButtons.Left) { scrollPosition.X = clickPosition.X - e.X; scrollPosition.Y = clickPosition.Y - e.Y; AutoScrollPosition = scrollPosition; } } protected override void OnPaint(PaintEventArgs e) { base.OnPaint(e); e.Graphics.FillRectangle(new Pen(BackColor).Brush, 0, 0, e.ClipRectangle.Width, e.ClipRectangle.Height); if (Image == null) return; int centeredX = AutoScrollPosition.X; int centeredY = AutoScrollPosition.Y; if (CenterImage) { //Something not relevant } AutoScrollMinSize = new Size(Image.Width, Image.Height); e.Graphics.DrawImage(Image, new RectangleF(centeredX, centeredY, Image.Width, Image.Height)); } } } But if I modify my OnMouseMove method to look like this: protected override void OnMouseMove(MouseEventArgs e) { base.OnMouseMove(e); if (e.Button == MouseButtons.Left) { scrollPosition.X += clickPosition.X - e.X; scrollPosition.Y += clickPosition.Y - e.Y; AutoScrollPosition = scrollPosition; } } ... you will see that the dragging is not smooth as before, and sometimes behaves weird (like with lag or something). What am I doing wrong? I've also tried removing all "base" calls on a desperate movement to solve this issue, haha, but again, it didn't work. Thanks for your time.

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• Is there anyway to exclude artifacts inherited from a parent POM?

  - by Miguel

  Artifacts from dependencies can be excluded by declaring an <exclusions> element inside a <dependency> But in this case it's needed to exclude an artifact inherited from a parent project. An excerpt of the POM under discussion follows: <project> <modelVersion>4.0.0</modelVersion> <groupId>test</groupId> <artifactId>jruby</artifactId> <version>0.0.1-SNAPSHOT</version> <parent> <artifactId>base</artifactId> <groupId>es.uniovi.innova</groupId> <version>1.0.0</version> </parent> <dependencies> <dependency> <groupId>com.liferay.portal</groupId> <artifactId>ALL-DEPS</artifactId> <version>1.0</version> <scope>provided</scope> <type>pom</type> </dependency> </dependencies> </project> base artifact, depends on javax.mail:mail-1.4.jar, and ALL-DEPS depends on another version of the same library. Due to the fact that mail.jar from ALL-DEPS exist on the execution environment, although not exported, collides with the mail.jar that exists on the parent, which is scoped as compile. A solution could be to rid off mail.jar from the parent POM, but most of the projects that inherit base, need it (as is a transtive dependency for log4j). So What I would like to do is to simply exclude parent's library from the child project, as it could be done if base was a dependency and not the parent pom: ... <dependency> <artifactId>base</artifactId> <groupId>es.uniovi.innova</groupId> <version>1.0.0</version> <type>pom<type> <exclusions> <exclusion> <groupId>javax.mail</groupId> <artifactId>mail</artifactId> </exclusion> </exclusions> </dependency> ...

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• how to implement a "soft barrier" in multithreaded c++

  - by Jason

  I have some multithreaded c++ code with the following structure: do_thread_specific_work(); update_shared_variables(); //checkpoint A do_thread_specific_work_not_modifying_shared_variables(); //checkpoint B do_thread_specific_work_requiring_all_threads_have_updated_shared_variables(); What follows checkpoint B is work that could have started if all threads have reached only checkpoint A, hence my notion of a "soft barrier". Typically multithreading libraries only provide "hard barriers" in which all threads must reach some point before any can continue. Obviously a hard barrier could be used at checkpoint B. Using a soft barrier can lead to better execution time, especially since the work between checkpoints A and B may not be load-balanced between the threads (i.e. 1 slow thread who has reached checkpoint A but not B could be causing all the others to wait at the barrier just before checkpoint B). I've tried using atomics to synchronize things and I know with 100% certainty that is it NOT guaranteed to work. For example using openmp syntax, before the parallel section start with: shared_thread_counter = num_threads; //known at compile time #pragma omp flush Then at checkpoint A: #pragma omp atomic shared_thread_counter--; Then at checkpoint B (using polling): #pragma omp flush while (shared_thread_counter > 0) { usleep(1); //can be removed, but better to limit memory bandwidth #pragma omp flush } I've designed some experiments in which I use an atomic to indicate that some operation before it is finished. The experiment would work with 2 threads most of the time but consistently fail when I have lots of threads (like 20 or 30). I suspect this is because of the caching structure of modern CPUs. Even if one thread updates some other value before doing the atomic decrement, it is not guaranteed to be read by another thread in that order. Consider the case when the other value is a cache miss and the atomic decrement is a cache hit. So back to my question, how to CORRECTLY implement this "soft barrier"? Is there any built-in feature that guarantees such functionality? I'd prefer openmp but I'm familiar with most of the other common multithreading libraries. As a workaround right now, I'm using a hard barrier at checkpoint B and I've restructured my code to make the work between checkpoint A and B automatically load-balancing between the threads (which has been rather difficult at times). Thanks for any advice/insight :)

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• Choosing a distributed shared memory solution

  - by mindas

  I have a task to build a prototype for a massively scalable distributed shared memory (DSM) app. The prototype would only serve as a proof-of-concept, but I want to spend my time most effectively by picking the components which would be used in the real solution later on. The aim of this solution is to take data input from an external source, churn it and make the result available for a number of frontends. Those "frontends" would just take the data from the cache and serve it without extra processing. The amount of frontend hits on this data can literally be millions per second. The data itself is very volatile; it can (and does) change quite rapidly. However the frontends should see "old" data until the newest has been processed and cached. The processing and writing is done by a single (redundant) node while other nodes only read the data. In other words: no read-through behaviour. I was looking into solutions like memcached however this particular one doesn't fulfil all our requirements which are listed below: The solution must at least have Java client API which is reasonably well maintained as the rest of app is written in Java and we are seasoned Java developers; The solution must be totally elastic: it should be possible to add new nodes without restarting other nodes in the cluster; The solution must be able to handle failover. Yes, I realize this means some overhead, but the overall served data size isn't big (1G max) so this shouldn't be a problem. By "failover" I mean seamless execution without hardcoding/changing server IP address(es) like in memcached clients when a node goes down; Ideally it should be possible to specify the degree of data overlapping (e.g. how many copies of the same data should be stored in the DSM cluster); There is no need to permanently store all the data but there might be a need of post-processing of some of the data (e.g. serialization to the DB). Price. Obviously we prefer free/open source but we're happy to pay a reasonable amount if a solution is worth it. In any way, paid 24hr/day support contract is a must. The whole thing has to be hosted in our data centers so SaaS offerings like Amazon SimpleDB are out of scope. We would only consider this if no other options would be available. Ideally the solution would be strictly consistent (as in CAP); however, eventual consistence can be considered as an option. Thanks in advance for any ideas.

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• Python: Script works, but seems to deadlock after some time

  - by sberry2A

  I have the following script, which is working for the most part Link to PasteBin The script's job is to start a number of threads which in turn each start a subprocess with Popen. The output from each subprocess is as follows: 1 2 3 . . . n Done Bascially the subprocess is transferring 10M records from tables in one database to different tables in another db with a lot of data massaging/manipulation in between because of the different schemas. If the subprocess fails at any time in it's execution (bad records, duplicate primary keys, etc), or it completes successfully, it will output "Done\n". If there are no more records to select against for transfer then it will output "NO DATA\n" My intent was to create my script "tableTransfer.py" which would spawn a number of these processes, read their output, and in turn output information such as number of updates completed, time remaining, time elapsed, and number of transfers per second. I started running the process last night and checked in this morning to see it had deadlocked. There were not subprocceses running, there are still records to be updated, and the script had not exited. It was simply sitting there, no longer outputting the current information because no subprocces were running to update the total number complete which is what controls updates to the output. This is running on OS X. I am looking for three things: I would like to get rid of the possibility of this deadlock occurring so I don't need to check in on it as frequently. Is there some issue with locking? Am I doing this in a bad way (gThreading variable to control looping of spawning additional thread... etc.) I would appreciate some suggestions for improving my overall methodology. How should I handle ctrl-c exit? Right now I need to kill the process, but assume I should be able to use the signal module or other to catch the signal and kill the threads, is that right? I am not sure whether I should be pasting my entire script here, since I usually just paste snippets. Let me know if I should paste it here as well.

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• EF4 Import/Lookup thousands of records - my performance stinks!

  - by Dennis Ward

  I'm trying to setup something for a movie store website (using ASP.NET, EF4, SQL Server 2008), and in my scenario, I want to allow a "Member" store to import their catalog of movies stored in a text file containing ActorName, MovieTitle, and CatalogNumber as follows: Actor, Movie, CatalogNumber John Wayne, True Grit, 4577-12 (repeated for each record) This data will be used to lookup an actor and movie, and create a "MemberMovie" record, and my import speed is terrible if I import more than 100 or so records using these tables: Actor Table: Fields = {ID, Name, etc.} Movie Table: Fields = {ID, Title, ActorID, etc.} MemberMovie Table: Fields = {ID, CatalogNumber, MovieID, etc.} My methodology to import data into the MemberMovie table from a text file is as follows (after the file has been uploaded successfully): Create a context. For each line in the file, lookup the artist in the Actor table. For each Movie in the Artist table, lookup the matching title. If a matching Movie is found, add a new MemberMovie record to the context and call ctx.SaveChanges(). The performance of my implementation is terrible. My expectation is that this can be done with thousands of records in a few seconds (after the file has been uploaded), and I've got something that times out the browser. My question is this: What is the best approach for performing bulk lookups/inserts like this? Should I call SaveChanges only once rather than for each newly created MemberMovie? Would it be better to implement this using something like a stored procedure? A snippet of my loop is roughly this (edited for brevity): while ((fline = file.ReadLine()) != null) { string [] token = fline.Split(separator); string Actor = token[0]; string Movie = token[1]; string CatNumber = token[2]; Actor found_actor = ctx.Actors.Where(a => a.Name.Equals(actor)).FirstOrDefault(); if (found_actor == null) continue; Movie found_movie = found_actor.Movies.Where( s => s.Title.Equals(title, StringComparison.CurrentCultureIgnoreCase)).FirstOrDefault(); if (found_movie == null) continue; ctx.MemberMovies.AddObject(new MemberMovie() { MemberProfileID = profile_id, CatalogNumber = CatNumber, Movie = found_movie }); try { ctx.SaveChanges(); } catch { } } Any help is appreciated! Thanks, Dennis

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• Need Help with Consolidating RoR Google Map Results

  - by Kevin

  I have a project that returns geocoded results within 20 miles of the user. I want these results grouped on the map by zip code, then within the info window show the individual results. The code posted below works, but for some reason it only displays the 1.png rather than looking at the results and using the correct .png icon associated with the number. When I look at the infowindows, it displays the correct png like "/images/2.png" or "/images/5.png" but the actual image is always 1. @ziptickets = Ticket.find(:all, :origin => coords, :select => 'DISTINCT zip, lat, lng', :within => @user.distance_to_travel, :conditions => "status_id = 1") for t in @ziptickets zips = Ticket.find(:all, :conditions => ["zip = ?", t.zip]) currentzip = t.zip.to_s tixinzip = zips.size.to_s imagelocation = "/images/" + tixinzip + ".png" shadowlocation = "/images/" + tixinzip + "s.png" @map.icon_global_init(GIcon.new(:image => imagelocation, :shadow => shadowlocation, :shadow_size => GSize.new(60,40), :icon_anchor => GPoint.new(20,20), :info_window_anchor => GPoint.new(9,2)), "test") newicon = Variable.new("test") new_marker = GMarker.new([t.lat, t.lng], :icon => newicon, :title => imagelocation, :info_window => currentzip) @map.overlay_init(new_marker) end I tried changing the last part of the mapicon from: :info_window_anchor => GPoint.new(9,2)), "test") newicon = Variable.new("test") to: :info_window_anchor => GPoint.new(9,2)), currentzip) newicon = Variable.new(currentzip) but the strangest thing is that any string that has numbers in it causes the map to fail to render in the view and just show a blank screen... same if I replace it with :info_window_anchor => GPoint.new(9,2)), "123") newicon = Variable.new("123") Any advice would be helpful... also it runs a bit slower than my previous code which just set up 4 standard icons and used them outside of the loop so any hints as to speed up execution would be appreciated greatly. Thanks!

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• SelectList in Asp-mvc and data from the database

  - by George

  Hello guys. I'm having some troubles with SelectList in ASP.MVC. Here is the issue: I have a Create View and begind a ViewModel model. The page load just fine (GET verb). But when posting, something happens, and my model is considered invalid, and it cannot insert. Here's what i've tried so far. public class DefinitionFormViewModel { private Repository<Category> categoryRepository = new Repository<Category>(); public Definition ViewDefinition { get; private set; } public SelectList Categories { get; private set; } public DefinitionFormViewModel(Definition def) { ViewDefinition = def; // here i wanted to place it directly, like shown in NerdDinner Tutorial // new SelectList(categoryRepository.All(),ViewDefinition.Category); Categories = new SelectList(categoryRepository.All(), "CategoryId", "CategoryName", ViewDefinition.CategoryId); } } // pageview which inherits DefinitionFormViewModel <div class=editor-field"> <%= Html.DropDownList("Category",Model.Categories) %> <%= Html.ValidationMessageFor(model => Model.ViewDefinition.Category) %> </div> // controller methods [Authorize] public ActionResult Create() { Definition definition = new Definition(); return View(new DefinitionFormViewModel(definition)); } [AcceptVerbs(HttpVerbs.Post), Authorize] public ActionResult Create(int id,Definition definition) { Term term = termRepository.SingleOrDefault(t => t.TermId == id); if (term == null) { return View("NotFound", new NotFoundModel("Termo não encontrado", "Termo não encontrado", "Nos desculpe, mas não conseguimos encontrar o termo solicitado.", "Indíce de Termos", "Index", "Term")); } else { if (ModelState.IsValid) { try { definition.TermId = term.TermId; definition.ResponsibleUser = User.Identity.Name; UpdateModel(definition); term.Definitions.Add(definition); termRepository.SaveAll(); return RedirectToAction("Details", "Term", new { id = term.TermId }); } catch (System.Data.SqlClient.SqlException sqlEx) { ModelState.AddModelError("DatabaseError", "Houve um erro na inserção desta nova definição"); } catch { foreach (RuleViolation rv in definition.GetRuleViolations()) { ModelState.AddModelError(rv.PropertyName, rv.ErrorMessage); } } } } return View(new DefinitionFormViewModel(definition)); } I'm sorry about the long post, but I cant figure this out. I got no graphic errors or exceptions. My execution terminates in if (ModelState.IsValid). Thanks for your time George

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• Parameters not being passed into template when using the .Net transform classes

  - by Chris F

  I am using the .Net XslCompiledTranform to run some simple XSLT (see below for a simplified example). The example XSLT is meant to do simply show the value of the parameter that is passed in to the template. The output is what I expect it to be (i.e. <result xmlns:p1="http://www.doesnotexist.com"> <valueOfParamA>valueA</valueOfParamA> </result> when I use Saxon 9.0, but when I use XslCompiledTransform (XslTransform) in .net I get <result xmlns:p1="http://www.doesnotexist.com"> <valueOfParamA></valueOfParamA> </result> The problem is that that the parameter value of paramA is not being passed into the template when I use the .Net classes. I completely stumped as to why. when I step through in Visual Studio, the debugger says that the template will be called with paramA='valueA' but when execution switches to the template the value of paramA is blank. Can anyone explain why this is happening? Is this a bug in the MS implementation or (more likely) am I doing something that is forbidden in XSLT? Any help greatly appreciated. This is the XSLT that I am using <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:extfn="http://exslt.org/common" exclude-result-prefixes="extfn" xmlns:p1="http://www.doesnotexist.com"> <!-- Replace msxml with xmlns:extfn="http://exslt.org/common" xmlns:extfn="urn:schemas-microsoft-com:xslt" --> <xsl:output method="xml" indent="yes"/> <xsl:template match="/"> <xsl:variable name="resultTreeFragment"> <p1:foo> </p1:foo> </xsl:variable> <xsl:variable name="nodeset" select="extfn:node-set($resultTreeFragment)"/> <result> <xsl:apply-templates select="$nodeset" mode="AParticularMode"> <xsl:with-param name="paramA" select="'valueA'"/> </xsl:apply-templates> </result> </xsl:template> <xsl:template match="@* | node()" mode="AParticularMode"> <xsl:param name="paramA"/> <valueOfParamA> <xsl:value-of select="$paramA"/> </valueOfParamA> </xsl:template> </xsl:stylesheet>

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• sharepoint custom aspx page with database connection

  - by Megini

  hi there i have created a custom aspx page whithin my sharepoint site with a sql server connection to a database on that server to select data when i view the page it works but when another user tries to view it it gives the following error : Server Error in '/' Application. Login failed for user 'GRINCOR\GuguK'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Login failed for user 'GRINCOR\GuguK'. Source Error: The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL: Add a "Debug=true" directive at the top of the file that generated the error. Example: <%@ Page Language="C#" Debug="true" % or: 2) Add the following section to the configuration file of your application: Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode. Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario. Stack Trace: [SqlException (0x80131904): Login failed for user 'GRINCOR\GuguK'.] System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +248 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +245 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +2811 System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) +53 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +327 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +2445370 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +2445224 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +354 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +703 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +54 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +2414776 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +92 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +1657 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +84 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +1645767 System.Data.SqlClient.SqlConnection.Open() +258 ASP.d7922f0d_ac20_4f87_91a2_a99a52c2b2fa__233736835.DisplayData() in C:\inetpub\wwwroot\wss\VirtualDirectories\80\sites\hrportal2\tester.aspx:151 ASP.d7922f0d_ac20_4f87_91a2_a99a52c2b2fa_233736835._RenderMain(HtmlTextWriter __w, Control parameterContainer) in C:\inetpub\wwwroot\wss\VirtualDirectories\80\sites\hrportal2\tester.aspx:346 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +115 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240 System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +42 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240 System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +253 System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +87 System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +53 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240 System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +42 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240 System.Web.UI.Page.Render(HtmlTextWriter writer) +38 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4240 Version Information: Microsoft .NET Framework Version:2.0.50727.3603; ASP.NET Version:2.0.50727.3601 can someone give me a solution to this problem ? i am using sharepoint services 3.0

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• Which programming language to choose? (for a specific problem/domain, details inside)

  - by Bijan

  I am building a trading portfolio management system that is responsible for production, optimization, and simulation of non-high frequency trading portfolios (dealing with 1min or 3min bars of data, not tick data). I plan on employing Amazon web services to take on the entire load of the application. I have four choices that I am considering as language. a) Java b) C++ c) C# d) Python Here is the scope of the extremes of the project scope. This isn't how it will be, maybe ever, but it's within the scope of the requirements: Weekly simulation of 10,000,000 trading systems. (Each trading system is expected to have its own data mining methods, including feature selection algorithms which are extremely computationally-expensive. Imagine 500-5000 features using wrappers. These are not run often by any means, but it's still a consideration) Real-time production of portfolio w/ 100,000 trading strategies Taking in 1 min or 3 min data from every stock/futures market around the globe (approx 100,000) Portfolio optimization of portfolios with up to 100,000 strategies. (rather intensive algorithm) Speed is a concern, but I believe that Java can handle the load. I just want to make sure that Java CAN handle the above requirements comfortably. I don't want to do the project in C++, but I will if it's required. The reason C# is on there is because I thought it was a good alternative to Java, even though I don't like Windows at all and would prefer Java if all things are the same. Python - I've read somethings on PyPy and pyscho that claim python can be optimized with JIT compiling to run at near C-like speeds.... That's pretty much the only reason it is on this list, besides that fact that Python is a great language and would probably be the most enjoyable language to code in, which is not a factor at all for this project, but a perk. To sum up: - real time production - weekly simulations of a large number of systems - weekly/monthly optimizations of portfolios - large numbers of connections to collect data from There is no dealing with millisecond or even second based trades. The only consideration is if Java can possibly deal with this kind of load when spread out of a necessary amount of EC2 servers. Thank you guys so much for your wisdom.

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• How to access controller dynamic properties within a base controller's constructor in Grails?

  - by 4h34d

  Basically, I want to be able to assign objects created within filters to members in a base controller from which every controller extends. Any possible way to do that? Here's how I tried, but haven't got to make it work. What I'm trying to achieve is to have all my controllers extend a base controller. The base controller's constructor would be used to assign values to its members, those values being pulled from the session map. Example below. File grails-app/controllers/HomeController.groovy: class HomeController extends BaseController { def index = { render username } } File grails-app/controllers/BaseController.groovy: abstract class BaseController { public String username public BaseController() { username = session.username } } When running the app, the output shown is: 2010-06-15 18:17:16,671 [main] ERROR [localhost].[/webapp] - Exception sending context initialized event to listener instance of class org.codehaus.groovy.grails.web.context.GrailsContextLoaderListener org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'pluginManager' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.RuntimeException: Unable to locate constructor with Class parameter for class org.codehaus.groovy.grails.commons.DefaultGrailsControllerClass ... Caused by: java.lang.RuntimeException: Unable to locate constructor with Class parameter for class org.codehaus.groovy.grails.commons.DefaultGrailsControllerClass ... Caused by: java.lang.reflect.InvocationTargetException ... Caused by: org.codehaus.groovy.grails.exceptions.NewInstanceCreationException: Could not create a new instance of class [com.my.package.controller.HomeController]! ... Caused by: groovy.lang.MissingPropertyException: No such property: session for class: com.my.package.controller.HomeController at com.my.package.controller.BaseController.<init>(BaseController.groovy:16) at com.my.package.controller.HomeController.<init>(HomeController.groovy) ... 2010-06-15 18:17:16,687 [main] ERROR core.StandardContext - Error listenerStart 2010-06-15 18:17:16,687 [main] ERROR core.StandardContext - Context [/webapp] startup failed due to previous errors And the app won't run. This is just an example as in my case I wouldn't want to assign a username to a string value, but rather a few objects pulled from the session map. The objects pulled from the session map are being set within filters. The alternative I see is being able to access the controller's instance within the filter's execution. Is that possible? Please help! Thanks a bunch!

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