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• Finding a picture in a picture with java?

  - by tarrasch

  what i want to to is analyse input from screen in form of pictures. I want to be able to identify a part of an image in a bigger image and get its coordinates within the bigger picture. Example: would have to be located in And the result would be the upper right corner of the picture in the big picture and the lower left of the part in the big picture. As you can see, the white part of the picture is irrelevant, what i basically need is just the green frame. Is there a library that can do something like this for me? Runtime is not really an issue. What i want to do with this is just generating a few random pixel coordinates and recognize the color in the big picture at that position, to recognize the green box fast later. And how would it decrease performance, if the white box in the middle is transparent? The question has been asked several times on SO as it seems without a single answer. I found i found a solution at http://werner.yellowcouch.org/Papers/subimg/index.html . Unfortunately its in C++ and i do not understand a thing. Would be nice to have a Java implementation on SO.

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• Count rows against to SQL server (2005) table?

  - by David.Chu.ca

  I have a simple question with two options to get count of rows in a SQL server (2005). I am using VS 2005. There are two options to get the count: SELECT id FROM Table1 WHERE dt >= startDt AND dt < endDt;; I get a list of ids from above call in cache and then I get count by List.Count. Another option is SELECT COUNT(*) FROM Table1 WHERE dt >= startDt AND dt < endDt; The above call will get the count directly. The issue is that I had several cases of exceptions with the second method: timeout. What I found is that the table1 is too big with millions of data. When I used the first option, it seems OK. I am confused by the fact that Count() takes more time than getting all the rows(is that true?). Not sure if the aggregation call with Count() would cause SQL server to create temporary table or cache on server side and it would result in slow performance when table is too big? I am not sure what is the best way to get the count?

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• how do i work bool!

  - by user350217

  HI! im a beginner and im really getting frustrated with this whole concept. i dont understand how to exactly use the bool function. i know what it is but i cantfigure out how to make it work in my program. Im trying to say that if my variable "selection" is any letter beween 'A' and 'I' then it is valid and can continue on to the next function which is called calcExchangeAmt(amtExchanged, selection). if it is false i want it to ask the user if they want to repeat the program and if they agree to repeat i want it to clear the screen and restart to the main function. please help edit my work! this is my bool function: bool isSelectionValid(char selection, char yesNo, double amtExchanged) { bool validData; validData = true; if((selection >= 'a' && selection <= 'i') || (selection >= 'A' && selection <= 'I')) { validData = calcExchangeAmt (amtExchanged, selection); } else(validData == false); { cout<<"Do you wish to continue? (Y for Yes / N for No)"; cin>>yesNo; } do { main(); } while ((yesNo =='y')||(yesNo == 'Y')); { system("cls"); } return 0; } this is the warning that im gettng: warning C4800: 'double' : forcing value to bool 'true' or 'false' (performance warning)

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• Model login constraints based on time

  - by DaDaDom

  Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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• Caching page by parts; how to pass variables calculated in cached parts into never-cached parts?

  - by Kirzilla

  Hello, Let's imagine that I have a code like this... if (!$data = $cache->load("part1_cache_id")) { $item_id = $model->getItemId(); ob_start(); echo 'Here is the cached item id: '.$item_id; $data = ob_get_contents(); ob_end_clean(); $cache->save($data, "part1_cache_id"); } echo $data; echo never_cache_function($item_id); if (!$data_2 = $cache->load("part2_cache_id")) { ob_start(); echo 'Here is the another cached part of the page...'; $data_2 = ob_get_contents(); ob_end_clean(); $cache->save("part2_cache_id"); } echo $data_2; As far as you can see I need to pass $item_id variable into never_cache_function, but if fist part is cached (part1_cache_id) then I have no way to get $item_id value. I see the only solution - serialize all data from fist part (including $item_id value); then cache serialized string and unserialize it everytime when script is executed... Something like this... if (!$data = $cache->load("part1_cache_id")) { $item_id = $model->getItemId(); $data['item_id'] = $item_id; ob_start(); echo 'Here is the cached item id: '.$item_id; $data['html'] = ob_get_contents(); ob_end_clean(); $cache->save( serialize($data), "part1_cache_id" ); } $data = unserialize($data); echo $data['html'] echo never_cache_function($data['item_id']); Is there any other ways for doing such trick? I'm looking for the most high performance solution. Thank you UPDATED And another question is - how to implement such caching into controller without separating page into two templates? Is it possible? PS: Please, do not suggest Smarty, I'm really interested in implementing custom caching.

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• is mysql index useful on column 'state' when only doing bit-operations on the column?

  - by Geert-Jan

  I have a lot of domain entities (stored in mysql) which undergo lots of different operations. Each operation is executed from a different program. I need to keep (flow)-state for these entities which I implemented in as a long field 'flowstate' used as a bitset. to query mysql for entities which have undergone a certain operation I do something like: select * from entities where state >> 7 & 1 = 1 Indicating bit 7 (cooresponding to operation 7) has run. (<-- simplified) Anyway, I really didn't pay attention to the performance implications of this setup in the beginning, and I think I'm in a bit of trouble since queries as the above run pretty slow. What I'd like to know: Does an mysql index on 'flowstate' help at all? After all it's not a single value Mysql can quickly find using a binary sort or whatever. If it doesn't, are there any other things I could do to speed things up? . Are there special 'mask-indices' for fields with use-cases as the above? TIA, Geert-jan

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• Automatic .NET code, nhibernate session, and LINQ datacontext clean-up?

  - by AverageJoe719

  Hi all, in my goal to adopt better coding practices I have a few questions in general about automatic handling of code. I have heard different answers both from online and talking with other developers/programmers at my work. I am not sure if I should have split them into 3 questions, but they all seem sort of related: 1) How does .NET handle instances of classes and other code things that take up memory? I recently found out about using the factory pattern for certain things like service classes so that they are only instantiated once in the entire application, but then I was told that '.NET handles a lot of that stuff automatically when mentioning it.' 2) How does Nhibernate's session handle automatic clean-up of un-used things? I've seen some say that it is great at handling things automatically and you should just use a session factory and that's it, no need to close it. But I have also read and seem many examples where people close the hibernate session. 3) How does LINQ's datacontext handle this? Most of the time I never .disposed my datacontext's and the app didn't see to take a performance hit (though I am not running anything super intensively), but it seems like most people recommend disposing of your datacontext after you are done with it. However, I have seen many many code examples where the dispose method is never called. Also in general I found it kind of annoying that you couldn't access even one-deep child related objects after disposing of the datacontext unless you explicity also grabbed them in the query. Thanks all. I am loving this site so far, I kind of get lost and spend hours just reading things on here. =)

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• sem-dynamic cdn

  - by dwi kristianto

  i'm developing couple of websites using php (directory script, etc.) and wordpress as cms. i need to improve its performance, by using cdn for static files (css, js, images). the problem is, css and javascript files are generated on the fly. i did that due to yahoo and some expert advice to combine the files into one file. also changing basic color of css files. for the time being, i use couple of small vps but still its not fast enough. i already contact maxcdn and the support guy said that they dont have such kind of services. what i need is: a cdn that will serve the request from user/visitor and there's no file in local disk, the cdn will redirect/fetch it from another domain/server. in vps, it could be done easily using combination of .htaccess and php, but NOT in the cdn. most of cdn only support purely static files. is there any such cdn that will server semi-dynamic files?

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• Using variables inside macros in SQL

  - by Tim

  Hello I'm wanting to use variables inside my macro SQL on Teradata. I thought I could do something like the following: REPLACE MACRO DbName.MyMacro ( MacroNm VARCHAR(50) ) AS ( /* Variable to store last time the macro was run */ DECLARE V_LAST_RUN_DATE TIMESTAMP; /* Get last run date and store in V_LAST_RUN_DATE */ SELECT LastDate INTO V_LAST_RUN_DATE FROM DbName.RunLog WHERE MacroNm = :MacroNm; /* Update the last run date to now and save the old date in history */ EXECUTE MACRO DbName.RunLogUpdater( :MacroNm ,V_LAST_RUN_DATE ,CURRENT_TIMESTAMP ); ); However, that didn't work, so I thought of this instead: REPLACE MACRO DbName.MyMacro ( MacroNm VARCHAR(50) ) AS ( /* Variable to store last time the macro was run */ CREATE VOLATILE TABLE MacroVars AS ( SELECT LastDate AS V_LAST_RUN_DATE FROM DbName.RunLog WHERE MacroNm = :MacroNm; ) WITH DATA ON COMMIT PRESERVE ROWS; /* Update the last run date to now and save the old date in history */ EXECUTE MACRO DbName.RunLogUpdater( :MacroNm ,SELECT V_LAST_RUN_DATE FROM MacroVars ,CURRENT_TIMESTAMP ); ); I can do what I'm looking for with a Stored Procedure, however I want to avoid for performance. Do you have any ideas about this? Is there anything else I can try? Cheers Tim

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• In .NET, What Is Fastest Way to Initialize Multi-Dimensional Array to Non-Default Value

  - by AMissico

  How do I initialize a multi-dimensional array of a primitive type as fast as possible? I am stuck with using multi-dimensional arrays. My problem is performance. The following routine initializes a 100x100 array in approx. 500 ticks. Removing the int.MaxValue initialization results in approx. 180 ticks just for the looping. Approximately 100 ticks to create the array without looping and without initializing to int.MaxValue. Routines similiar to this are called a few tens-of-thousands to several million times. I am open to suggestions on how to optimize this non-default initialization of an array. One idea I had is to use a smaller primitive type when available. For instance, using byte instead of int, saves 100 ticks. I would be happy with this, but I am hoping that I don't have to change the primitive data type. public int[,] CreateArray(Size size) { int[,] array = new int[size.Width, size.Height]; for (int x = 0; x < size.Width; x++) { for (int y = 0; y < size.Height; y++) { array[x, y] = int.MaxValue; } } return array; }

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• Quartz 2D or OpenGL ES? Pros and cons in the long term, possibility of migration to other platforms.

  - by fspirit

  Hi all! I'm having a hard time deciding whether to go with Quartz2D or OpenGL for an iPad game. It will be 2D mostly, but effect-intense (simultaneous lighting effects for 10-30 objects, 10-20 simultaneous animations on the screen). So far, assuming i'm equally dumb in both technologies and have to learn them from the ground, i came to this list. (I've read several topics here, on SO, with names like "Quartz or OpenGL", but i'm still left with some questions) Quartz: Better time-to-market, because of ready to use absractions like UIView, UIImageView, CoreAnimation abstractions Open GL ES Closer to hardware, thus, performance is better. App, implemented with OpenGL ES can be easier migrated to Android, MeeGo, Windows Phone, etc. My questions are: How time will it take to rewrite Quartz 2d app to use OpenGL? Lets say it took me 2 man-month to write Quartz app, how much time will i need to rewrite it? (Please, just some subjective opinions, i'll try to summarize them somehow) Regarding the ease of migration to other platforms, when using OpenGL, is it really so? Or efforts when migrating Quartz app from iPhoneOS to Android will be not so much bigger, compared to OpenGL app migration? (Ease of migration is quite important criterion) Regarding OpenGL, should i go with OpenGL 1.1 or 2.0, concerning migration? (Android supports 2.0 through NDK, but dont know whether NDK's use will increase or decrease migration efforts)

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• Rails : fighting long http response times with ajax. Is it a good idea? Please, help with implementa

  - by baranov

  Hi, everybody! I've googled some tutorials, browsed some SO answers, and was unable to find a recipe for my problem. I'm writing a web site which is supposed to display almost realtime stock chart. Data is stored in constantly updating MySQL database, I wrote a find_by_sql query code which fetches all the data I need to get my chart drawn. Everything is ok, except performance - it takes from one second to one minute for different queries to fetch all the data from the database, this time includes necessary (My)SQL-server side calculations. This is simply unacceptable. I got the following idea: if the data is queried from the MySQL server one point a time instead of entire dataset, it takes only about 1-100ms to get an individual point. I imagine the data fetch process might be browser-driven. After the user presses the button in order to get a chart drawn, controller makes one request to the database and renders, say, a progress bar, say 1% ready. When the browser gets the response, it immediately makes an (ajax) request, and the server fetches the next piece of data and renders "2%". And so on, until all the data is ready and the server displays the requested chart. Could this be implemented in rails+js, is there a tutorial for solving a similar problem on the Web? I suppose if the thing is feasible at all, somebody should have already done this before. I have read several articles about ajax, I believe I do understand general principles, but never did nontrivial ajax programming myself. Thanks for your time!

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• Python socket error on UDP data receive. (10054)

  - by Charles

  I currently have a problem using UDP and Python socket module. We have a server and clients. The problem occurs when we send data to a user. It's possible that user may have closed their connection to the server through a client crash, disconnect by ISP, or some other improper method. As such, it is possible to send data to a closed socket. Of course with UDP you can't tell if the data really reached or if it's closed, as it doesn't care (atleast, it doesn't bring up an exception). However, if you send data and it is closed off, you get data back somehow (???), which ends up giving you a socket error on sock.recvfrom. [Errno 10054] An existing connection was forcibly closed by the remote host. Almost seems like an automatic response from the connection. Although this is fine, and can be handled by a try: except: block (even if it lowers performance of the server a little bit). The problem is, I can't tell who this is coming from or what socket is closed. Is there anyway to find out 'who' (ip, socket #) sent this? It would be great as I could instantly just disconnect them and remove them from the data. Any suggestions? Thanks.

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• Custom UIView using CALayers disappears after 180º rotation or navigation controller pop

  - by Steve Madsen

  I have a created a custom UIView subclass that is exhibiting some strange behavior. It is a spinning wheel selector, and for performance reasons it is drawn entirely into two CALayer instances. The bottom layer is the wheel itself, which is rotated using setAffineTransform: according to touches. The top layer is eye candy. drawRect: is fairly simple. If the control hasn't been drawn yet (or it's been invalidated), it calls a method that creates the images and assigns them to the layer contents property. - (void) drawRect:(CGRect)rect { if (imageLayer == nil) { [self drawIntoImageLayer]; } [self updateWheelRotation]; } When the view controller using this view first appears, everything is fine. There are two instances where the view completely disappears, however: If the device is rotated a full 180°. After a view controller is popped off the navigation stack and the view becomes visible again. drawRect: is not called either time. Interestingly enough, it IS called after a 90° orientation change, and that causes the view to re-appear. How can I ensure that a custom view using CALayers is redrawn properly in these situations?

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• How to react when asked a question you already know during an interview

  - by DevNull

  The short story:- If you are asked a tough algorithmic/puzzle question during an interview, whose solution is already known to you, do you:- Honestly tell the interviewer that you know this question already? -- this could result in bursting the interviewer's ego and him increasing the complexity level of the subsequent questions. Do an Oscar deserving performance and act as if you are thinking and trying hard and slowly getting to the solution? -- depending on your acting skills, could majorly impress the interviewer making the rest of the interview easier. Long story:- OK, this question comes as a result of what happened to me in a recent telephonic interview that I gave - the interview was supposed to be all algorithmic. The interviewer started with an algorithmic question which I had luckily already seen here on Stackoverflow. The best solution to that problem is not very intuitive and is more of a you-get-it-if-you-know-it kind. Now, just to not disappoint the interviewer too much, I took a few seconds as if I was pondering on the problem and then blurted out the answer which I knew too well having read and admired it on SO already. But I guess that gave it away to the interviewer that I already knew this question and since then, he started asking me for more efficient solutions and I kept coming up with approaches (even if not correct or more efficient, but I did touch a lot of different data structures and algos) and he kept asking for more efficient solutions and generally seemed put off by my initial salvo which was unexpected. What should I have done? Cheers!

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• Bulk Insert of hundreds of millions of records

  - by Dave Jarvis

  What is the fastest way to insert 237 million records into a table that has rules (for distributing the data across 84 child tables)? First I tried inserts. No go. Then I tried inserts with BEGIN/COMMIT. Not nearly fast enough. Next, I tried COPY FROM, but then noticed the documentation states that the rules are ignored. (And it was having difficulties with the column order and date format -- it said that '1984-07-1' was not a valid integer; true, but a bit unexpected.) Some example data: station_id,taken,amount,category_id,flag 1,'1984-07-1',0,4, 1,'1984-07-2',0,4, 1,'1984-07-3',0,4, 1,'1984-07-4',0,4,T Here is the table structure (with one rule included): CREATE TABLE climate.measurement ( id bigserial NOT NULL, station_id integer NOT NULL, taken date NOT NULL, amount numeric(8,2) NOT NULL, category_id smallint NOT NULL, flag character varying(1) NOT NULL DEFAULT ' '::character varying ) WITH ( OIDS=FALSE ); ALTER TABLE climate.measurement OWNER TO postgres; CREATE OR REPLACE RULE i_measurement_01_001 AS ON INSERT TO climate.measurement WHERE date_part('month'::text, new.taken)::integer = 1 AND new.category_id = 1 DO INSTEAD INSERT INTO climate.measurement_01_001 (id, station_id, taken, amount, category_id, flag) VALUES (new.id, new.station_id, new.taken, new.amount, new.category_id, new.flag); I can generate the data into any format. Am looking for something that won't take four days. I originally had the data in MySQL (still do), but am hoping to get a performance increase by switching to PostgreSQL and am eager to use its PL/R extensions for stats. I was also thinking about using: http://pgbulkload.projects.postgresql.org/ Any help, tips, or guidance would be greatly appreciated. Thank you!

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• SQL to get list of dates as well as days before and after without duplicates

  - by Nathan Koop

  I need to display a list of dates, which I have in a table SELECT mydate AS MyDate, 1 AS DateType FROM myTable WHERE myTable.fkId = @MyFkId; Jan 1, 2010 - 1 Jan 2, 2010 - 1 Jan 10, 2010 - 1 No problem. However, I now need to display the date before and the date after as well with a different DateType. Dec 31, 2009 - 2 Jan 1, 2010 - 1 Jan 2, 2010 - 1 Jan 3, 2010 - 2 Jan 9, 2010 - 2 Jan 10, 2010 - 1 Jan 11, 2010 - 2 I thought I could use a union SELECT MyDate, DateType FROM ( SELECT mydate - 1 AS MyDate, 2 AS DateType FROM myTable WHERE myTable.fkId = @MyFkId; UNION SELECT mydate + 1 AS MyDate, 2 AS DateType FROM myTable WHERE myTable.fkId = @MyFkId; UNION SELECT mydate AS MyDate, 1 AS DateType FROM myTable WHERE myTable.fkId = @MyFkId; ) AS myCombinedDateTable This however includes duplicates of the original dates. Dec 31, 2009 - 2 Jan 1, 2009 - 2 Jan 1, 2010 - 1 Jan 2, 2010 - 2 Jan 2, 2010 - 1 Jan 3, 2010 - 2 Jan 9, 2010 - 2 Jan 10, 2010 - 1 Jan 11, 2010 - 2 How can I best remove these duplicates? I am considering a temporary table, but am unsure if that is the best way to do it. This also appears to me that it may provide performance issues as I am running the same query three separate times. What would be the best way to handle this request?

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• How to lazy load scripts in YUI that accompany ajax html fragments

  - by Chris Beck

  I have a web app with Tabs for Messages and Contacts (think gmail). Each Tab has a Y.on('click') event listener that retrieves an HTML fragment via Y.io() and renders the fragment via node.setContent(). However, the Contact Tab also requires contact.js to enable an Edit button in the fragment. How do I defer the cost of loading contact.js until the user clicks on the Contacts tab? How should contact.js add it's listener to the Edit button? The Complete function of my Tab's on('click') event could serialize Get.script('contact.js') after Y.io('fragment'). However, for better performance, I would prefer to download the script in parallel to downloading the HTML fragment. In that case, I would need to defer adding an event listener to the Edit button until the Edit button is available. This seems like a common RIA design pattern. What is the best way to implement this with YUI? How should I get the script? How should I defer sections of the script until elements in the fragment are available in the DOM?

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• Mysql Server Optimization

  - by Ish Kumar

  Hi Geeks, We are having serious MySQL(InnoDB) performance issues at a moment when we do: (10-20) insertions on TABLE1 (10-20) updates on TABLE2 Note: Both above operations happens within fraction of a second. And this occurs every few (10-15) minutes. And all online users (approx 400-600) doing read operation on join of TABLE1 & TABLE2 every 1 second. Here is our mysql configuration info: http://docs.google.com/View?id=dfrswh7c_117fmgcmb44 Issues: Lot queries wait and expire later (saw it from phpmyadmin / processes). My poor MySQL server crashes sometimes Questions Q1: Any suggestions to optimize at MySQL level? Q2: I thinking to use persistent connections at application level, is it right? Info Added Later: Database Engine: InnoDB TABLE1 : 400,000 rows (inserting 8,000 daily) & TABLE2: 8,000 rows 1 second query: SELECT b.id, b.user_id, b.description, b.debit, b.created, b.price, u.username, u.email, u.mobile FROM TABLE1 b, TABLE2 u WHERE b.credit = 0 AND b.user_id = u.id AND b.auction_id = "12345" ORDER BY b.id DESC LIMIT 10; // there are few more but they are not so critical. Indexing is good, we are using them wisely. In above query all id's are indexed And TABLE1 has frequent insertions and TABLE2 has frequent updates.

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• How to choose light version of databse system

  - by adopilot

  I am starting one POS (Point of sale) project. Targeting system is going to be written in C# .NET 2 WinForms and as main database server We are going to use MS-SQL Server. As we have a lot of POS devices in chain for one store I will love to have backend local data base system on each POS device. Scenario are following: When main server goes down!! POS application should continue working "off-line" with local database, until connection to main server come up again. Now I am in dilemma which local database is going to be most adoptable for me. Here is some notes for helping me point me in right direction: To be Light "My POS devices art usually old and suffering with performances" To be Free "I have a lot of devices and I do not wont additional cost beside main SQL serer" One day Ill love to try all that port on Mono and Linux OS. Here is what I've researched so far: Simple XML "Light but I am afraid of performance, My main table of items is average of 10K records" SQL-Expres "I am afraid that my POS devices is poor with hardware for SQLExpres, and also hard to install on each device and configure" Less known Advantage Database Server have free distribution of offline ADT system. DBF with extended Library,"Respect for good old DBFs but that era is behind Me with clipper and DBFs" MS Access Sqlite "Mostly like for now, but I am afraid how it is going to pair with MS SQL do they have same Data taypes". I know that in this SO is a lot of subjective data, but at least can someone recommended some others lite database system, or things that I shod most take attention before I choice database.

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• Can parser combinators be made efficient?

  - by Jon Harrop

  Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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• How/when to hire new programmers, and how to integrate them?

  - by Shaul

  Hiring new programmers, especially in a small company, can often present a Catch-22 situation. We have too much work to do, so we need to hire new programmers. But we can't hire new programmers now, because they will need mentoring and several months of learning curve in your industry/product/environment before they're useful, and none of the programmers has time to be a mentor to a new programmer, because they're all completely swamped with the current work load. That may be a slightly frivolous way of describing the situation, but nevertheless, it's difficult for a small company on a tight budget to justify hiring someone who is not only going to be unproductive for a long time, but will also take away from the performance of the current programmers. How have you dealt with this kind of situation? When is the best time to hire someone? What are the best tasks to assign to a new team member so that they can learn their way around your code base and start getting their hands dirty as quickly as possible? How do you get the new guy useful without bogging your existing programmers down in too much mentoring? Any comments & suggestions you have are much appreciated!

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• Java SSH2 libraries in depth: Trilead/Ganymed/Orion [/other?]

  - by Bernd Haug

  I have been searching for a pure Java SSH library to use for a project. The single most important needed feature is that it has to be able to work with command-line git, but remote-controlling command-line tools is also important. A pretty common choice, e.g. used in the IntelliJ IDEA git integration (which works very well), seems to be Trilead SSH2. Looking at their website, it's not being maintained any more. Trilead seems to have been a fork of Ganymed SSH2, which was a ETH Zurich project that didn't see releases for a while, but had a recent release by its new owner, Christian Plattner. There is another actively maintained fork from that code base, Orion SSH, that saw an even more recent release, but which seems to get mentioned online much less than the other 2 forks. Has anybody here worked with any of (or, if possible, both) of Ganymed and Orion and could kindly describe the development experience with either/both? Accuracy of documentation [existence of documentation?], stability, buggyness... - all of these would be highly interesting to me. Performance is not so important for my current project. If there is another pure-Java SSH implementation that should be used instead, please feel free to mention it, but please don't just mention a name...describe your judgment from actual experience. Sorry if this question may seem a bit "do my homework"-y, but I've really searched for reviews. Everything out there seems to be either a listing of implementations or short "use this! it's great!" snippets.

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• When are SQL views appropriate in ASP.net MVC?

  - by sslepian

  I've got a table called Protocol, a table called Eligibility, and a Protocol_Eligibilty table that maps the two together (a many to many relationship). If I wanted to make a perfect copy of an entry in the Protocol table, and create all the needed mappings in the Protocol_Eligibility table, would using an SQL view be helpful, from a performance standpoint? Protocol will have around 1000 rows, Eligibility will have about 200, and I expect each Protocol to map to about 10 Eligibility rows and each Eligibility to map to over 100 rows in Protocol. Here's how I'm doing this with the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility_View where pel.pid == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = (from pel in _documentDataModel.Eligibility where pel.ID == pel_item.eid select pel).First(); newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); } And this is without the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility where pel.Protocol.ID == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { pel_item.EligibilityReference.Load(); newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = pel_item.Eligibility; newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); }

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• spam and dirty words comment post filtering in python (django)

  - by sintaloo

  Hi All, My basic question is how to filter spam and dirty words in a comment post system under python (django). I have a collection of phrases (approximately 3000 phrases) to be filtered. Question (1), are there any existing open source python (or django) package/module/plugin which can handle this job? I knew there was one called Akismet. But from what I understood, it will not solve my problem. Akismet is just a web service and filter the words dictionary defined by Akismet. But I have my own collection of words. Please correct me if I am wrong. Question (2), If there is no such open source package I can use, how to create my own one? The only thing I can think of it's to use regular expression and join all the word phrases with 'or' in a regular expression. but I have 3000 phrases, I think it won't work in term of performance and filter every comment post. any suggestions where should I start from? Thank you very much for your help and time.

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