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• Autocomplete server-side implementation

  - by toluju

  What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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• Strange behavior of move with strings

  - by Umair Ahmed

  I am testing some enhanced string related functions with which I am trying to use move as a way to copy strings around for faster, more efficient use without delving into pointers. While testing a function for making a delimited string from a TStringList, I encountered a strange issue. The compiler referenced the bytes contained through the index when it was empty and when a string was added to it through move, index referenced the characters contained. Here is a small downsized barebone code sample:- unit UI; interface uses System.SysUtils, System.Types, System.UITypes, System.Rtti, System.Classes, System.Variants, FMX.Types, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.Layouts, FMX.Memo; type TForm1 = class(TForm) Results: TMemo; procedure FormCreate(Sender: TObject); end; var Form1: TForm1; implementation {$R *.fmx} function StringListToDelimitedString ( const AStringList: TStringList; const ADelimiter: String ): String; var Str : String; Temp1 : NativeInt; Temp2 : NativeInt; DelimiterSize : Byte; begin Result := ' '; Temp1 := 0; DelimiterSize := Length ( ADelimiter ) * 2; for Str in AStringList do Temp1 := Temp1 + Length ( Str ); SetLength ( Result, Temp1 ); Temp1 := 1; for Str in AStringList do begin Temp2 := Length ( Str ) * 2; // Here Index references bytes in Result Move ( Str [1], Result [Temp1], Temp2 ); // From here the index seems to address characters instead of bytes in Result Temp1 := Temp1 + Temp2; Move ( ADelimiter [1], Result [Temp1], DelimiterSize ); Temp1 := Temp1 + DelimiterSize; end; end; procedure TForm1.FormCreate(Sender: TObject); var StrList : TStringList; Str : String; begin // Test 1 : StringListToDelimitedString StrList := TStringList.Create; Str := ''; StrList.Add ( 'Hello1' ); StrList.Add ( 'Hello2' ); StrList.Add ( 'Hello3' ); StrList.Add ( 'Hello4' ); Str := StringListToDelimitedString ( StrList, ';' ); Results.Lines.Add ( Str ); StrList.Free; end; end. Please devise a solution and if possible, some explanation. Alternatives are welcome too.

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• Checking if an int is prime more efficiently

  - by SipSop

  I recently was part of a small java programming competition at my school. My partner and I have just finished our first pure oop class and most of the questions were out of our league so we settled on this one (and I am paraphrasing somewhat): "given an input integer n return the next int that is prime and its reverse is also prime for example if n = 18 your program should print 31" because 31 and 13 are both prime. Your .class file would then have a test case of all the possible numbers from 1-2,000,000,000 passed to it and it had to return the correct answer within 10 seconds to be considered valid. We found a solution but with larger test cases it would take longer than 10 seconds. I am fairly certain there is a way to move the range of looping from n,..2,000,000,000 down as the likely hood of needing to loop that far when n is a low number is small, but either way we broke the loop when a number is prime under both conditions is found. At first we were looping from 2,..n no matter how large it was then i remembered the rule about only looping to the square root of n. Any suggestions on how to make my program more efficient? I have had no classes dealing with complexity analysis of algorithms. Here is our attempt. public class P3 { public static void main(String[] args){ long loop = 2000000000; long n = Integer.parseInt(args[0]); for(long i = n; i<loop; i++) { String s = i +""; String r = ""; for(int j = s.length()-1; j>=0; j--) r = r + s.charAt(j); if(prime(i) && prime(Long.parseLong(r))) { System.out.println(i); break; } } System.out.println("#"); } public static boolean prime(long p){ for(int i = 2; i<(int)Math.sqrt(p); i++) { if(p%i==0) return false; } return true; } } ps sorry if i did the formatting for code wrong this is my first time posting here. Also the output had to have a '#' after each line thats what the line after the loop is about Thanks for any help you guys offer!!!

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• Create Duplicate Records on SELECT for Calendar Date Range

  - by peterallcdn

  Hey all, I've built a pretty shnazzy calendar system but there is one tweak that I need to make so that I'm completely happy with it. My calendar has three tables: calevents - The calendared event. caldates - The occurrences and date-range of each occurrence for each event. calcats - The categories that can be applied to an event. The short: For each calevent, there can be many caldates, one for each occurrence of calevent. So a calevent that repeats weekly and spans 3 days might have caldates like this: date_id date_eid date_start date_end 2 37 2010-06-21 2010-06-23 3 37 2010-06-28 2010-06-30 7 37 2010-07-05 2010-07-07 9 37 2010-07-12 2010-07-14 What I want to do, is when selecting all the caldates for a specified month such as 2010-06, to return not just the two records above, but instead a record for each date in the range of date_start and date_end for each caldate. So if I searched for 2010-06, I would get: date_id date_eid date_start date_end date_day 2 37 2010-06-21 2010-06-23 2010-06-21 2 37 2010-06-21 2010-06-23 2010-06-22 2 37 2010-06-21 2010-06-23 2010-06-23 3 37 2010-06-28 2010-06-30 2010-06-28 3 37 2010-06-28 2010-06-30 2010-06-29 3 37 2010-06-28 2010-06-30 2010-06-30 The Long: The reason I want to do this, is so when displaying a list of events(calevents) for a specified month, an occurrence(caldates) of that event will be displayed for EACH of the days it spans. I could do this with php by looping through each day of the current month and displaying a copy of each caldate if the month day falls between date_start and date_end. But doing it this way will prevent me from using record pagination if needed. For example, if for a specified month the following caldates were returned: date_id date_eid date_start date_end 2 37 2010-06-21 2010-06-27 94 53 2010-06-09 2010-07-08 Doing record pagination would see this as only 2 records("rows"). But looping through them with PHP would generate 29 "rows". So, I figure if I use mysql to create each row instead of PHP, I can achieve the same thing AND still be able to use pagination if a month has a lot of events/dates. As far as performance goes, I'm not sure which option is more efficient. Both would send the same amount of info to the browser, so it's really only the work required to generate the info that matters. My current query which fetches all the occurrences for a specified month, and to make things just a little more complicated... joins them with their event and category, looks like this: $sql_to_execute = " SELECT date_id, date_eid, date_start, date_end, event_id, event_title, event_category, event_private, event_location, SUBSTRING_INDEX(event_detailsstripped, ' ', 40) AS event_detailsstripped, event_time, event_starttime, event_endtime, event_active, cat_colour FROM ( caldates LEFT JOIN calevents ON caldates.date_eid = calevents.event_id ) LEFT JOIN calcats ON calevents.event_category = calcats.cat_id WHERE date_start <= '".mysql_real_escape_string($dbi_list_end_date)."' AND date_end >= '".mysql_real_escape_string($dbi_list_start_date)."' ".$dbi_category." ORDER BY date_start ASC "; Any help or advice would be greatly appreciated! Thanks, Peter

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• Performance of looping over an Unboxed array in Haskell

  - by Joey Adams

  First of all, it's great. However, I came across a situation where my benchmarks turned up weird results. I am new to Haskell, and this is first time I've gotten my hands dirty with mutable arrays and Monads. The code below is based on this example. I wrote a generic monadic for function that takes numbers and a step function rather than a range (like forM_ does). I compared using my generic for function (Loop A) against embedding an equivalent recursive function (Loop B). Having Loop A is noticeably faster than having Loop B. Weirder, having both Loop A and B together is faster than having Loop B by itself (but slightly slower than Loop A by itself). Some possible explanations I can think of for the discrepancies. Note that these are just guesses: Something I haven't learned yet about how Haskell extracts results from monadic functions. Loop B faults the array in a less cache efficient manner than Loop A. Why? I made a dumb mistake; Loop A and Loop B are actually different. Note that in all 3 cases of having either or both Loop A and Loop B, the program produces the same output. Here is the code. I tested it with ghc -O2 for.hs using GHC version 6.10.4 . import Control.Monad import Control.Monad.ST import Data.Array.IArray import Data.Array.MArray import Data.Array.ST import Data.Array.Unboxed for :: (Num a, Ord a, Monad m) => a -> a -> (a -> a) -> (a -> m b) -> m () for start end step f = loop start where loop i | i <= end = do f i loop (step i) | otherwise = return () primesToNA :: Int -> UArray Int Bool primesToNA n = runSTUArray $ do a <- newArray (2,n) True :: ST s (STUArray s Int Bool) let sr = floor . (sqrt::Double->Double) . fromIntegral $ n+1 -- Loop A for 4 n (+ 2) $ \j -> writeArray a j False -- Loop B let f i | i <= n = do writeArray a i False f (i+2) | otherwise = return () in f 4 forM_ [3,5..sr] $ \i -> do si <- readArray a i when si $ forM_ [i*i,i*i+i+i..n] $ \j -> writeArray a j False return a primesTo :: Int -> [Int] primesTo n = [i | (i,p) <- assocs . primesToNA $ n, p] main = print $ primesTo 30000000

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• The Math of a Jump in a 2D game.

  - by ONi

  I have been all around with this question and I can't find the correct answer! So, behold, the description of my question: I'm working in J2ME, I have my gameloop that do the following: public void run() { Graphics g = this.getGraphics(); while (running) { long diff = System.currentTimeMillis() - lastLoop; lastLoop = System.currentTimeMillis(); input(); this.level.doLogic(); render(g, diff); try { Thread.sleep(10); } catch (InterruptedException e) { stop(e); } } } so it's just a basic gameloop, the doLogic() function calls for all the logic functions of the characters in the scene and render(g, diff) calls the animateChar function of every character on scene, following this, the animChar function in the Character class sets up everything in the screen as this: protected void animChar(long diff) { this.checkGravity(); this.move((int) ((diff * this.dx) / 1000), (int) ((diff * this.dy) / 1000)); if (this.acumFrame > this.framerate) { this.nextFrame(); this.acumFrame = 0; } else { this.acumFrame += diff; } } This ensures me that everything must to move according to the time that the machine takes to go from cycle to cycle (remember it's a phone, not a gaming rig). I'm sure it's not the most efficient way to achieve this behavior so I'm totally open for criticism of my programming skills in the comments, but here my problem: When I make I character jump, what I do is that I put his dy to a negative value, say -200 and I set the boolean jumping to true, that makes the character go up, and then I have this function called checkGravity() that ensure that everything that goes up has to go down, checkGravity also checks for the character being over platforms so I will strip it down a little for the sake of your time: public void checkGravity() { if (this.jumping) { this.jumpSpeed += 10; if (this.jumpSpeed > 0) { this.jumping = false; this.falling = true; } this.dy = this.jumpSpeed; } if (this.falling) { this.jumpSpeed += 10; if (this.jumpSpeed > 200) this.jumpSpeed = 200; this.dy = this.jumpSpeed; if (this.collidesWithPlatform()) { this.falling = false; this.standing = true; this.jumping = false; this.jumpSpeed = 0; this.dy = this.jumpSpeed; } } } So, the problem is, that this function updates the dy regardless of the diff, making the characters fly like Superman in slow machines, and I have no idea how to implement the diff factor so that when a character is jumping, his speed decrement in a proportional way to the game speed. Can anyone help me fix this issue? or give me pointers on how to make a 2D Jump in J2ME the right way. Thank you very much for your time.

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• Increase efficiency for an R simulator of the Monty Hall Puzzle

  - by jahan_m

  The Monty Hall Problem is a simple puzzle involving probability that even stumps professionals in careers dealing with some heavy-duty math. Here's the basic problem: Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice? You can find numerous explanations of the solution here: http://en.wikipedia.org/wiki/Monty_Hall_problem Goal of my simulation: Prove that a switching strategy will win you the car 2/3 of the time. I got curious and wanted to write a little function that simulates the problem many times and returns the proportion of wins if you switched and the proportion of wins if you stayed with your first choice. The function then plots the cumulative wins. First and foremost, I'm interested in hearing if my simulation is indeed replicating the Monty Problem, or if some aspect of the code got it wrong. Secondly, this function takes a long time to run once I get to about 10,000 simulations. I know I don't need this many simulations to prove this but I'd love to hear some ideas on how to make it more efficient. Thanks for your feedback! Monty_Hall=function(repetitions){ doors=c('A','B','C') stay_wins=0 switch_wins=0 series=data.frame(sim_num=seq(repetitions),cum_sum_stay=replicate(repetitions,0),cum_sum_switch=replicate(repetitions,0)) for(i in seq(repetitions)){ winning_door=sample(doors,1) contestant_chooses=sample(doors,1) if(contestant_chooses==winning_door) stay_wins=stay_wins+1 else switch_wins=switch_wins+1 series[i,'cum_sum_stay']=stay_wins series[i,'cum_sum_switch']=switch_wins } plot(series$sim_num,series$cum_sum_switch,col=2,ylab='Cumulative # of wins', xlab='Simulation #',main=sprintf('%d Simulations of the Monty Hall Paradox',repetitions),type='l') lines(series$sim_num,series$cum_sum_stay,col=4) legend('topleft',legend=c('Cumulative wins from switching', 'Cumulative wins from staying'),col=c(2,4),lty=1) result=list(series=series,stay_wins=stay_wins,switch_wins=switch_wins, proportion_stay_wins=stay_wins/repetitions, proportion_switch_wins=switch_wins/repetitions) return(result) } #Theory predicts that it is to the contestant's advantage if he #switches his choice to the other door. This function simulates the game #many times, and shows you the proportion of games in which staying or #switching would win the car. It also plots the cumulative wins for each strategy. Monty_Hall(100)

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• Merge Mutliple Excel Workbooks

  - by IRHM

  I wonder whether someone may be able to help me please. I'm trying to use the code below to allow the user to select multiple Excel Workbooks, amalgamating the data into one 'Summary' sheet. Sub Merge() Dim DestWB As Workbook, WB As Workbook, WS As Worksheet, SourceSheet As String Set DestWB = ActiveWorkbook SourceSheet = "Input" startrow = 7 FileNames = Application.GetOpenFilename( _ filefilter:="Excel Files (*.xls*),*.xls*", _ Title:="Select the workbooks to merge.", MultiSelect:=True) If IsArray(FileNames) = False Then If FileNames = False Then Exit Sub End If End If For n = LBound(FileNames) To UBound(FileNames) Set WB = Workbooks.Open(Filename:=FileNames(n), ReadOnly:=True) For Each WS In WB.Worksheets If WS.Name = SourceSheet Then With WS If .UsedRange.Cells.Count > 1 Then dr = DestWB.Worksheets("Input").Range("C" & Rows.Count).End(xlUp).Row + 1 lastrow = .Range("C" & Rows.Count).End(xlUp).Row For j = lastrow To startrow Step -1 Select Case .Range("E" & j).Value Case "Manager", "Lead", "Technical", "Analyst" 'do nothing Case Else .Rows(j).EntireRow.Delete End Select Next lastrow = .Range("C" & Rows.Count).End(xlUp).Row If lastrow >= startrow Then .Range("B" & startrow & ":AD" & lastrow).Copy DestWB.Worksheets("Input").Cells(dr, "B").PasteSpecial xlValues .Range("AF" & startrow & ":AQ" & lastrow).Copy DestWB.Worksheets("Input").Cells(dr, "AF").PasteSpecial xlValues .Range("AS" & startrow & ":AS" & lastrow).Copy DestWB.Worksheets("Input").Cells(dr, "AS").PasteSpecial xlValues End If End If End With Exit For End If Next WS WB.Close savechanges:=False Next n End Sub The code works fine except for one issue which I've been trying to solve for the last few weeks. The following line of code looks in column E of the Source file, and if any of the entries match the values shown in the code it copies that row of data to paste into the Destination file. If Range("E" & j) <> "Manager" And Range("E" & j) <> "Lead" And Range("E" & j) <> "Technical" And Range("E" & j) <> "Analyst" Then Rows(j).Delete The problem I have is that if none of these values are found in the Source file, I receive the following error: Run time error '1004': Delete method of range class failed and in Debug mode it highlights this part of the line as the source of the error, but I've no idea why. Rows(j).Delete I just wondered whether someone may be able to look at this please and let me know where I'm going wrong, or perhaps even suggest a more efficient process of allowing the user to merge the workbooks. Many thanks and kind regards

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• Best method for converting several sets of numbers with several different ratios

  - by C Patton

  I'm working on an open-source harm reduction application for opioid addicts. One of the features in this application is the conversion (in mg/mcg) between common opioids, so people don't overdose by accident. If you're morally against opioid addiction and wouldn't respond because of your morals, please consider that this application is for HARM REDUCTION.. So people don't end up dead. I have this data.. 3mg morphine IV = 10mcg fentanyl IV 2mg morphine oral = 1mg oxycodone oral 3mg oral morphine = 1mg oxymorphone oral 7.0mg morphine oral = 1mg hydromorphone oral 1mg morphine iv = .10mg oxymorphone iv 1mg morphine oral = 1mg hydrocodone oral 1mg morphine oral = 6.67mg codeine oral 1mg morphine oral = .10mg methadone oral And I have a textbox that is the source dosage in mg (a double) that the user can enter in. Underneath this, I have radio boxes for the source substance (ie: morphine) and the destination substance (ie oxycodone) for conversion.. I've been trying to think of the most efficient way to do this, but nearly every seems sloppy. If I were to do something like public static double MorphinetoOxycodone(string morphineValue) { double morphine = Double.Parse(morphineValue); return (morphine / 2 ); } I would also have to make a function for OxycodonetoMorphine, OxycodonetoCodeine, etc.. and then would end up with dozens functions.. There must be an easier way than this that I'm missing. If you'll notice, all of my conversions use morphine as the base value.. what might be the easiest way to use the morphine value to convert one opioid to another? For example, if 1mg morphine oral is equal to 1mg hydrocodone and 1mg morphine oral is equal to .10mg methadone, wouldn't I just multiply 1*.10 to get the hydrocodone-methadone value? Implementing this idea is what I'm having the most trouble with. Any help would be GREATLY appreciated.. and if you'd like, I would add your name/nickname to the credits in this program. It's possible that many, many people around the world will use this (I'm translating it into several languages as well) and to know that your work could've helped an addict from dying.. I think that's a great thing :) -cory

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• Flatten date range memberships retaining only the highest priority membership (TRANSACT-SQL)

  - by shadowranger

  Problem statement: A table contains an item_id, a category_id and a date range (begin_date and end_date). No item may be in more than one category on any given date (in general; during daily rebuilding it can be in an invalid state temporarily). By default, all items are added (and re-added if removed) to a category (derived from outside data) automatically on a daily basis, and their membership in that category matches the lifespan of the item (items have their own begin and end date, and usually spend their entire lives in the same category, which is why this matches). For items in category X, it is occasionally desirable to override the default category by adding them to category Y. Membership in category Y could entirely replace membership in category X (that is, the begin and end dates for membership in category Y would match the begin and end dates of the item itself), or it could override it for an arbitrary period of time (at the beginning, middle or end the item's lifespan, possibly overriding for short periods at multiple times). Membership in category Y is not renewed automatically and additions to that category is done by manual data entry. Every day, when category X is rebuilt, we get an overlap, where any item in category Y will now be in category X as well (which is forbidden, as noted previously). Goal: After each repopulation of category X (which is done in a rather complicated and fragile manner, and ideally would be left alone), I'm trying to find an efficient means of writing a stored procedure that: Identifies the overlaps Changes existing entries, adds new ones where necessary (such as in the case where an item starts in category X, switches to category Y, then eventually switches back to category X before ending), or removes entries (when an item is in category Y for its entire life) such that every item remains in category Y (and only Y) where specified, while category X membership is maintained when not overridden by category Y. Does not affect memberships of categories A, B, C, Z, etc., which do not have override categories and are built separately, by completely different rules. Note: It can be assumed that X membership covers the entire lifespan of the item before this procedure is called, so it is unnecessary to query any data outside this table. Bonus credit: If for some reason there are two adjacent or overlapping memberships in for the same item in category Y, stitching them together into a single entry is appreciated, but not necessary. Example: item_id category_id begin_date end_date 1 X 20080101 20090628 1 Y 20090101 20090131 1 Y 20090601 20090628 2 X 20080201 20080731 2 Y 20080201 20080731 Should become: item_id category_id begin_date end_date 1 X 20080101 20081231 1 Y 20090101 20090131 1 X 20090201 20090531 1 Y 20090601 20090628 2 Y 20080201 20080731 If it matters, this needs to work on SQL Server 2005 and SQL Server 2008

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• Question about Architecture for Viewing Images in ASP.NET MVC App

  - by Charlie Flowers

  I have an approach in mind for an image viewer in a web app, and want to get a sanity check and any thoughts you stackoverflowers might have. Here's the whirlwind nutshell summary: I'm working on an ASP.NET MVC application that will run in my company's retail stores. Even though it is a web application, we own the store machines and have control over them. We have a "windows agent" running on the store machine which we can talk to from the browser via javascript (it is a WCF service, and our web app has permission to talk to it from the browser). One of the web pages needs to be an "image viewer" page with some common things like Rotate & Zoom. Now, there are some WebForms controls that offer Rotate and Zoom. However, they take up server resources and generate a good bit of traffic between the server and the browser. For example, the Rotate function would cause an ajax call to the server, which would then generate a new image written to a .NET Canvas object, which would then be written to a file on the server, which would then be returned from the ajax call and refreshed inside the browser. Normally, that's a pretty good way of doing things. But in our case, we have code running on the store machine that we can communicate with. This leads me to consider the following approach: When the user asks to view an image, we tell our "windows agent" to download it from our image server to the store machine. We then redirect our browser to our image viewer page, which will pull the image from the local file we just wrote to the store machine. When the user clicks "Rotate", we cause JavaScript code in the browser to call our "windows agent" software, asking it to perform the "Rotate" function. The "windows agent" does the rotation using the same kind of imaging control that would formerly have been used on the server, but it does so now on the store machine. Javascript in the browser then refreshes the image on the page to show the newly rotated image. Zoom and similar features would be implemented the same way. This seems to be much more efficient, scalable, and responsive for the end-users. However, I've never heard of anything like it being done, mostly because it's rare to have this combination of a web app plus a "windows agent" on the client machine. What do you think? Feasible? Reasonable? Any pitfalls I overlooked or improvements / suggestions you can see? Has anyone done anything like this who would like to offer the wisdom of experience? Thanks!

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• MSSQL 2005: Update rows in a specified order (like ORDER BY)?

  - by JMTyler

  I want to update rows of a table in a specific order, like one would expect if including an ORDER BY clause, but MS SQL does not support the ORDER BY clause in UPDATE queries. I have checked out this question which supplied a nice solution, but my query is a bit more complicated than the one specified there. UPDATE TableA AS Parent SET Parent.ColA = Parent.ColA + (SELECT TOP 1 Child.ColA FROM TableA AS Child WHERE Child.ParentColB = Parent.ColB ORDER BY Child.Priority) ORDER BY Parent.Depth DESC; So, what I'm hoping that you'll notice is that a single table (TableA) contains a hierarchy of rows, wherein one row can be the parent or child of any other row. The rows need to be updated in order from the deepest child up to the root parent. This is because TableA.ColA must contain an up-to-date concatenation of its own current value with the values of its children (I realize this query only concats with one child, but that is for the sake of simplicity - the purpose of the example in this question does not necessitate any more verbosity), therefore the query must update from the bottom up. The solution suggested in the question I noted above is as follows: UPDATE messages SET status=10 WHERE ID in (SELECT TOP (10) Id FROM Table WHERE status=0 ORDER BY priority DESC ); The reason that I don't think I can use this solution is because I am referencing column values from the parent table inside my subquery (see WHERE Child.ParentColB = Parent.ColB), and I don't think two sibling subqueries would have access to each others' data. So far I have only determined one way to merge that suggested solution with my current problem, and I don't think it works. UPDATE TableA AS Parent SET Parent.ColA = Parent.ColA + (SELECT TOP 1 Child.ColA FROM TableA AS Child WHERE Child.ParentColB = Parent.ColB ORDER BY Child.Priority) WHERE Parent.Id IN (SELECT Id FROM TableA ORDER BY Parent.Depth DESC); The WHERE..IN subquery will not actually return a subset of the rows, it will just return the full list of IDs in the order that I want. However (I don't know for sure - please tell me if I'm wrong) I think that the WHERE..IN clause will not care about the order of IDs within the parentheses - it will just check the ID of the row it currently wants to update to see if it's in that list (which, they all are) in whatever order it is already trying to update... Which would just be a total waste of cycles, because it wouldn't change anything. So, in conclusion, I have looked around and can't seem to figure out a way to update in a specified order (and included the reason I need to update in that order, because I am sure I would otherwise get the ever-so-useful "why?" answers) and I am now hitting up Stack Overflow to see if any of you gurus out there who know more about SQL than I do (which isn't saying much) know of an efficient way to do this. It's particularly important that I only use a single query to complete this action. A long question, but I wanted to cover my bases and give you guys as much info to feed off of as possible. :) Any thoughts?

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• What is the most effective way to test for combined keyboard arrow direction in ActionScript 3.0?

  - by Relee

  I need to monitor the direction a user is indicating using the four directional arrow keys on a keyboard in ActionScript 3.0 and I want to know the most efficient and effective way to do this. I've got several ideas of how to do it, and I'm not sure which would be best. I've found that when tracking Keyboard.KEY_DOWN events, the event repeats as long as the key is down, so the event function is repeated as well. This broke the method I had originally chosen to use, and the methods I've been able to think of require a lot of comparison operators. The best way I've been able to think of would be to use bitwise operators on a uint variable. Here's what I'm thinking var _direction:uint = 0x0; // The Current Direction That's the current direction variable. In the Keyboard.KEY_DOWN event handler I'll have it check what key is down, and use a bitwise AND operation to see if it's already toggled on, and if it's not, I'll add it in using basic addition. So, up would be 0x1 and down would be 0x2 and both up and down would be 0x3, for example. It would look something like this: private function keyDownHandler(e:KeyboardEvent):void { switch(e.keyCode) { case Keyboard.UP: if(!(_direction & 0x1)) _direction += 0x1; break; case Keyboard.DOWN: if(!(_direction & 0x2)) _direction += 0x2; break; // And So On... } } The keyUpHandler wouldn't need the if operation since it only triggers once when the key goes up, instead of repeating. I'll be able to test the current direction by using a switch statement labeled with numbers from 0 to 15 for the sixteen possible combinations. That should work, but it doesn't seem terribly elegant to me, given all of the if statements in the repeating keyDown event handler, and the huge switch. private function checkDirection():void { switch(_direction) { case 0: // Center break; case 1: // Up break; case 2: // Down break; case 3: // Up and Down break; case 4: // Left break; // And So On... } } Is there a better way to do this?

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• programming question

  - by shivam

  using System; using System.Data; using System.Collections.Generic; using System.ComponentModel; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Data.SqlClient; namespace datasynchronization { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { string connectString = @"Data Source=MOON\SQL2005;Initial Catalog=databaseA;Integrated Security=True"; using (var srcCon = new SqlConnection(connectString)) //connection to source table { srcCon.Open();//source table connection open SqlCommand cmd = new SqlCommand();// sqlobject for source table cmd.Connection = srcCon; string connectionString = @"Data Source=MOON\SQL2005;Initial Catalog=databaseB;Integrated Security=True"; using (var tgtCon = new SqlConnection(connectionString)) //connection to target table { tgtCon.Open(); //target table connection open SqlCommand objcmd1 = new SqlCommand();//sqlobject for target table objcmd1.Connection = tgtCon; objcmd1.CommandText = "SELECT MAX(date) FROM Table_2"; //query to findout the max date from target table var maxdate = objcmd1.ExecuteScalar(); // store the value of max date into the variable maxdate cmd.CommandText = string.Format("SELECT id,date,name,city,salary,region FROM Table_1 where date >'{0}'", maxdate); //select query to fetch rows from source table using (var reader = cmd.ExecuteReader()) { SqlCommand objcmd = new SqlCommand(); objcmd.Connection = tgtCon; objcmd.CommandText = "INSERT INTO Table_2(id,date,name,city,salary,region)VALUES(@id,@date,@name,@city,@salary,@region)"; objcmd.Parameters.Add("@id", SqlDbType.Int); objcmd.Parameters.Add("@date", SqlDbType.DateTime); objcmd.Parameters.Add("@name", SqlDbType.NVarChar); objcmd.Parameters.Add("@city", SqlDbType.NVarChar); objcmd.Parameters.Add("@salary", SqlDbType.Int); objcmd.Parameters.Add("@region", SqlDbType.Char); while (reader.Read()) { var order1 = reader[0].ToString(); var order2 = reader[1].ToString(); var order3 = reader[2].ToString(); var order4 = reader[3].ToString(); var order5 = reader[4].ToString(); var order6 = reader[5].ToString(); objcmd.Parameters["@id"].Value = order1; objcmd.Parameters["@date"].Value = order2; objcmd.Parameters["@name"].Value = order3; objcmd.Parameters["@city"].Value = order4; objcmd.Parameters["@salary"].Value = order5; objcmd.Parameters["@region"].Value = order6; objcmd.ExecuteNonQuery(); } } tgtCon.Close(); } srcCon.Close(); } } } } how can i organize the above written code in an efficient way?

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• Function Point Analysis -- a seriously overestimating technique?

  - by kizzx2

  I know questions about FPA has been asked numerous times before, but this time I'm taking a more analytical angle at it, backed up with data. 1. First, some data This question is based on a tutorial. He had a "Sample Count" section where he demonstrated it step by step. You can see some screenshots of his sample application here. In the end, he calculated the unadjusted FP to be 99. There is another article on InformIT with industry data on typical hour/FP. It ranges from 2 hours/FP to 27.4 hours/FP. Let's try to stick with 2 for the moment (since SO readers are probably the more efficient crowd :p). 2. Reality check!? Now just check out the screenshots again. Do a little math here 99 * 2 = 198 hours 198 hours / 40 hours per week = 5 weeks Seriously? That sample application is going to take 5 weeks to implement? Is it just my feeling that it wouldn't take any decent programmer longer than one week (I"m not even saying weekend) to have it completed? Now let's try estimating the cost of the project. We'll use New York's minimum wage at the moment (Wikipedia), which is $7.25 198 * 7.25 = $1435.5 From what I could see from the screenshots, this application is a small excel-improvement app. I could have bought MS Office Pro for 200 bucks which gives me greater interoperability (.xls files) and flexibility (spreadsheets). (For the record, that same Web site has another article discussing productivity. It seems like they typically use 4.2 hours/FP, which gives us even more shocking stats: 99 * 4.2 = 415 hours = 10 weeks = almost 3 whopping months! 415 hours * $7.25 = $3000 zomg (That's even assuming that all our poor coders get the minimum wage!) 3. Am I missing something here? Right now, I could come up with several possible explanation: FPA is really only suited for bigger projects (1000+ FPs) so it becomes extremely inaccurate at smaller scale. The hours/FP metric fluctuates abruptly from team to team, project to project. For a small project like this, we could have used something like 0.5 hour/FP or something. (Now this kind of makes the whole estimation thing pointless, unless my firm does the same type of projects for several years with the same team, not really common.) From my experience with several software metrics, Function Point is really not a lightweight metric. If the hour/FP thing fluctuates so much, then what's the point, maybe I could have gone with User Story Points which is a lot faster to get and arguably almost as uncertain. What would be the FP experts' answers to this?

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• Building a QueryExpression where name field is either A or B

  - by Mike

  I'm trying to build a Dynamics CRM 4 query so that I can get calendar events that are named either "Event A" or "Event B". A QueryByAttribute doesn't seem to do the job as I cannot specify a condition where the field called "event_name" = "Event A" of "event_name" = "Event B". When using the QueryExpression, I've found the FilterExpression applies to the Referencing Entity. I don't know if the FilterExpression can be used on the Referenced Entity at all. The example below is something like what I want to achieve, though this would return an empty result set as it will go looking in the entity called "my_event_response" for a "name" attribute. It's starting to look like I will need to run several queries to get this but this is less efficient than if I can submit it all at once. ColumnSet columns = new ColumnSet(); columns.Attributes = new string[]{ "event_name", "eventid", "startdate", "city" }; ConditionExpression eventname1 = new ConditionExpression(); eventname1.AttributeName = "event_name"; eventname1.Operator = ConditionOperator.Equal; eventname1.Values = new string[] { "Event A" }; ConditionExpression eventname2 = new ConditionExpression(); eventname2.AttributeName = "event_name"; eventname2.Operator = ConditionOperator.Equal; eventname2.Values = new string[] { "Event B" }; FilterExpression filter = new FilterExpression(); filter.FilterOperator = LogicalOperator.Or; filter.Conditions = new ConditionExpression[] { eventname1, eventname2 }; LinkEntity link = new LinkEntity(); link.LinkCriteria = filter; link.LinkFromEntityName = "my_event"; link.LinkFromAttributeName = "eventid"; link.LinkToEntityName = "my_event_response"; link.LinkToAttributeName = "eventid"; QueryExpression query = new QueryExpression(); query.ColumnSet = columns; query.EntityName = EntityName.mbs_event.ToString(); query.LinkEntities = new LinkEntity[] { link }; RetrieveMultipleRequest request = new RetrieveMultipleRequest(); request.Query = query; return (RetrieveMultipleResponse)crmService.Execute(request); I'd appreciate some advice on how to get the data I need.

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• jQuery bind efficiency

  - by chelfers

  I'm having issue with load speed using multiple jQuery binds on a couple thousands elements and inputs, is there a more efficient way of doing this? The site has the ability to switch between product lists via ajax calls, the page cannot refresh. Some lists have 10 items, some 100, some over 2000. The issue of speed arises when I start flipping between the lists; each time the 2000+ item list is loaded the system drags for about 10 seconds. Before I rebuild the list I am setting the target element's html to '', and unbinding the two bindings below. I'm sure it has something to do with all the parent, next, and child calls I am doing in the callbacks. Any help is much appreciated. loop 2500 times <ul> <li><input type="text" class="product-code" /></li> <li>PROD-CODE</li> ... <li>PRICE</li> </ul> end loop $('li.product-code').bind( 'click', function(event){ selector = '#p-'+ $(this).prev('li').children('input').attr('lm'); $(selector).val( ( $(selector).val() == '' ? 1 : ( parseFloat( $(selector).val() ) + 1 ) ) ); Remote.Cart.lastProduct = selector; Remote.Cart.Products.Push( Remote.Cart.customerKey, { code : $(this).prev('li').children('input').attr('code'), title : $(this).next('li').html(), quantity : $('#p-'+ $(this).prev('li').children('input').attr('lm') ).val(), price : $(this).prev('li').children('input').attr('price'), weight : $(this).prev('li').children('input').attr('weight'), taxable : $(this).prev('li').children('input').attr('taxable'), productId : $(this).prev('li').children('input').attr('productId'), links : $(this).prev('li').children('input').attr('productLinks') }, '#p-'+ $(this).prev('li').children('input').attr('lm'), false, ( parseFloat($(selector).val()) - 1 ) ); return false; }); $('input.product-qty').bind( 'keyup', function(){ Remote.Cart.lastProduct = '#p-'+ $(this).attr('lm'); Remote.Cart.Products.Push( Remote.Cart.customerKey, { code : $(this).attr('code') , title : $(this).parent().next('li').next('li').html(), quantity : $(this).val(), price : $(this).attr('price'), weight : $(this).attr('weight'), taxable : $(this).attr('taxable'), productId : $(this).attr('productId'), links : $(this).attr('productLinks') }, '#p-'+ $(this).attr('lm'), false, previousValue ); });

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• Moving a unit precisely along a path in x,y coordinates

  - by Adam Eberbach

  I am playing around with a strategy game where squads move around a map. Each turn a certain amount of movement is allocated to a squad and if the squad has a destination the points are applied each turn until the destination is reached. Actual distance is used so if a squad moves one position in the x or y direction it uses one point, but moving diagonally takes ~1.4 points. The squad maintains actual position as float which is then rounded to allow drawing the position on the map. The path is described by touching the squad and dragging to the end position then lifting the pen or finger. (I'm doing this on an iPhone now but Android/Qt/Windows Mobile would work the same) As the pointer moves x, y points are recorded so that the squad gains a list of intermediate destinations on the way to the final destination. I'm finding that the destinations are not evenly spaced but can be further apart depending on the speed of the pointer movement. Following the path is important because obstacles or terrain matter in this game. I'm not trying to remake Flight Control but that's a similar mechanic. Here's what I've been doing, but it just seems too complicated (pseudocode): getDestination() { - self.nextDestination = remove_from_array(destinations) - self.gradient = delta y to destination / delta x to destination - self.angle = atan(self.gradient) - self.cosAngle = cos(self.angle) - self.sinAngle = sin(self.angle) } move() { - get movement allocation for this turn - if self.nextDestination not valid - - getNextDestination() - while(nextDestination valid) && (movement allocation remains) { - - find xStep and yStep using movement allocation and sinAngle/cosAngle calculated for current self.nextDestination - - if current position + xStep crosses the destination - - - find x movement remaining after self.nextDestination reached - - - calculate remaining direct path movement allocation (xStep remaining / cosAngle) - - - make self.position equal to self.nextDestination - - else - - - apply xStep and yStep to current position - } - round squad's float coordinates to integer screen coordinates - draw squad image on map } That's simplified of course, stuff like sign needs to be tweaked to ensure movement is in the right direction. If trig is the best way to do it then lookup tables can be used or maybe it doesn't matter on modern devices like it used to. Suggestions for a better way to do it? an update - iPhone has zero issues with trig and tracking tens of positions and tracks implemented as described above and it draws in floats anyway. The Bresenham method is more efficient, trig is more precise. If I was to use integer Bresenham I would want to multiply by ten or so to maintain a little more positional accuracy to benefit collisions/terrain detection.

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• Best way to run remote VBScript in ASP.net? WMI or PsExec?

  - by envinyater

  I am doing some research to find out the best and most efficient method for this. I will need to execute remote scripts on a number of Window Servers/Computers (while we are building them). I have a web application that is going to automate this task, I currently have my prototype working to use PsExec to execute remote scripts. This requires PsExec to be installed on the system. A colleague suggested I should use WMI for this. I did some research in WMI and I couldn't find what I'm looking for. I want to either upload the script to the server and execute it and read the results, or already have the script on the server and execute it and read the results. I would prefer the first option though! Which is more ideal, PsExec or WMI? For reference, this is my prototype PsExec code. This script is only executing a small script to get the Windows OS and Service Pack Info. Protected Sub windowsScript(ByVal COMPUTERNAME As String) ' Create an array to store VBScript results Dim winVariables(2) As String nameLabel.Text = Name.Text ' Use PsExec to execute remote scripts Dim Proc As New System.Diagnostics.Process ' Run PsExec locally Proc.StartInfo = New ProcessStartInfo("C:\Windows\psexec.exe") ' Pass in following arguments to PsExec Proc.StartInfo.Arguments = COMPUTERNAME & " -s cmd /C c:\systemInfo.vbs" Proc.StartInfo.RedirectStandardInput = True Proc.StartInfo.RedirectStandardOutput = True Proc.StartInfo.UseShellExecute = False Proc.Start() ' Pause for script to run System.Threading.Thread.Sleep(1500) Proc.Close() System.Threading.Thread.Sleep(2500) 'Allows the system a chance to finish with the process. Dim filePath As String = COMPUTERNAME & "\TTO\somefile.txt" 'Download file created by script on Remote system to local system My.Computer.Network.DownloadFile(filePath, "C:\somefile.txt") System.Threading.Thread.Sleep(1000) ' Pause so file gets downloaded ''Import data from text file into variables textRead("C:\somefile.txt", winVariables) WindowsOSLbl.Text = winVariables(0).ToString() SvcPckLbl.Text = winVariables(1).ToString() System.Threading.Thread.Sleep(1000) ' ''Delete the file on server - we don't need it anymore Dim Proc2 As New System.Diagnostics.Process Proc2.StartInfo = New ProcessStartInfo("C:\Windows\psexec.exe") Proc2.StartInfo.Arguments = COMPUTERNAME & " -s cmd /C del c:\somefile.txt" Proc2.StartInfo.RedirectStandardInput = True Proc2.StartInfo.RedirectStandardOutput = True Proc2.StartInfo.UseShellExecute = False Proc2.Start() System.Threading.Thread.Sleep(500) Proc2.Close() ' Delete file locally File.Delete("C:\somefile.txt") End Sub

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• Approach for authentication and storing user details.

  - by cappuccino

  Hey folks, I am using the Zend Framework but my question is broadly about sessions / databases / auth (PHP MySQL). Currently this is my approach to authentication: 1) User signs in, the details are checked in database. - Standard stuff really. 2) If the details are correct only the user's unique ID is stored in the session and a security token (user unique ID + IP + Browser info + salt). The session in written to the filesystem. I've been reading around and many are saying that storing stuff in sessions is not a good idea, and that you should really only write a unique ID which refers back to the user's details and a security token to prevent session hijacking. So this is the approach i've taken, i use to write the user's details in session, but i've moved that out. Wanted to know your opinions on this. I'm keeping sessions in the filesystem since i don't run on multiple servers, and since i'm only writting a tiny tiny bit of data to sessions, i thought that performance would be greater keeping sessions in the filesystem to reduce load on the database. Once the session is written on authentication, it really is only read-only from then on. 3) The rest of the user's details (like subscription details, permissions, account info etc) are cached in the filesystem (this can always be easily moved to memory if i wanted even more performance). So rather than keeping the user's details in session, the user's details are cached in the file system. I'm using Zend_Cache and the unique cache id is something like md5(/cache/auth/2892), the number is the unique id of the user. I guess the benefit of this method is that once the user is logged in, there is essentially not database queries being run to get the user's details. Just wonder if this approach is better than keeping the whole lot in session... 4) As the user moves throughout the site the only thing that is checked is the ID in the session and the security token. So, overall the first question is 1) is the filesystem more efficient than a database for this purpose 2) have i taken enough security precautions 3) is separating user detail's from the session into a cached file a pointless task? Thanks.

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• How to efficently build an interpreter (lexer+parser) in C?

  - by Rizo

  I'm trying to make a meta-language for writing markup code (such as xml and html) wich can be directly embedded into C/C++ code. Here is a simple sample written in this language, I call it WDI (Web Development Interface): /* * Simple wdi/html sample source code */ #include <mySite> string name = "myName"; string toCapital(string str); html { head { title { mySiteTitle; } link(rel="stylesheet", href="style.css"); } body(id="default") { // Page content wrapper div(id="wrapper", class="some_class") { h1 { "Hello, " + toCapital(name) + "!"; } // Lists post ul(id="post_list") { for(post in posts) { li { a(href=post.getID()) { post.tilte; } } } } } } } Basically it is a C source with a user-friendly interface for html. As you can see the traditional tag-based style is substituted by C-like, with blocks delimited by curly braces. I need to build an interpreter to translate this code to html and posteriorly insert it into C, so that it can be compiled. The C part stays intact. Inside the wdi source it is not necessary to use prints, every return statement will be used for output (in printf function). The program's output will be clean html code. So, for example a heading 1 tag would be transformed like this: h1 { "Hello, " + toCapital(name) + "!"; } // would become: printf("<h1>Hello, %s!</h1>", toCapital(name)); My main goal is to create an interpreter to translate wdi source to html like this: tag(attributes) {content} = <tag attributes>content</tag> Secondly, html code returned by the interpreter has to be inserted into C code with printfs. Variables and functions that occur inside wdi should also be sorted in order to use them as printf parameters (the case of toCapital(name) in sample source). I am searching for efficient (I want to create a fast parser) way to create a lexer and parser for wdi. Already tried flex and bison, but as I am not sure if they are the best tools. Are there any good alternatives? What is the best way to create such an interpreter? Can you advise some brief literature on this issue?

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• How to stream semi-live audio over internet

  - by Thomas Tempelmann

  I want to write something like Skype, i.e. I have a constant audio stream on one computer and then recompress it in a format that's suitable for a latent internet connection, receive it on the other end and play it. Let's also assume that the internet connection is fairly modern and fast, i.e. DSL or alike, no slow connections over phone and such. The involved computers will also be rather modern (Dual Core Intel CPUs at 2GHz or more). I know how to handle the audio on the machines. What I don't know is how to transmit the audio in an efficient way. The challenges are: I'd like get good audio quality across the line. The stream should be received without drops. The stream may, however, be received with a little delay (a second delay is acceptable). I imagine that the transport software could first determine the average (and max) latency, then start the stream and tell the receiver to wait for that max latency before starting to play the audio. With that, if the latency doesn't get any higher, the entire stream will be playable on the other side without stutter or drops. If, due to unexpected IP latencies or blockages, the stream does get cut off, I want to be able to notice this so that I can take actions (e.g. abort the stream) and eventually start a new transmission. What are my options if I want do use ready-made software for the compression and tranmission? I have no intention to write my own audio compression engine, really. OTOH, I plan to sell the solution in a vertical market, meaning I can afford a few dollars of license fees per copy, but not $100s. I guess the simplest solution would be to just open a TCP stream, send a few packets back and forth to determine their running time (or even use UDP for that), then use the results as the guide for my max latency value, then simply fire the audio data in its raw form (uncompressed 16 bit stereo), along with a timing code over the TCP connection. The receiver reads the data and plays it with the pre-determined delay. That might just work with the type of fast connection I expect. I just wonder if there are better solutions to reach this goal, with better performance (lower latency) and less data (compressed). BTW, I first try to implement this on OS X, but might want to do it on Windows, too, if it proves successful.

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• How to define and work with an array of bits in C?

  - by Eddy

  I want to create a very large array on which I write '0's and '1's. I'm trying to simulate a physical process called random sequential adsorption, where units of length 2, dimers, are deposited onto an n-dimensional lattice at a random location, without overlapping each other. The process stops when there is no more room left on the lattice for depositing more dimers (lattice is jammed). Initially I start with a lattice of zeroes, and the dimers are represented by a pair of '1's. As each dimer is deposited, the site on the left of the dimer is blocked, due to the fact that the dimers cannot overlap. So I simulate this process by depositing a triple of '1's on the lattice. I need to repeat the entire simulation a large number of times and then work out the average coverage %. I've already done this using an array of chars for 1D and 2D lattices. At the moment I'm trying to make the code as efficient as possible, before working on the 3D problem and more complicated generalisations. This is basically what the code looks like in 1D, simplified: int main() { /* Define lattice */ array = (char*)malloc(N * sizeof(char)); total_c = 0; /* Carry out RSA multiple times */ for (i = 0; i < 1000; i++) rand_seq_ads(); /* Calculate average coverage efficiency at jamming */ printf("coverage efficiency = %lf", total_c/1000); return 0; } void rand_seq_ads() { /* Initialise array, initial conditions */ memset(a, 0, N * sizeof(char)); available_sites = N; count = 0; /* While the lattice still has enough room... */ while(available_sites != 0) { /* Generate random site location */ x = rand(); /* Deposit dimer (if site is available) */ if(array[x] == 0) { array[x] = 1; array[x+1] = 1; count += 1; available_sites += -2; } /* Mark site left of dimer as unavailable (if its empty) */ if(array[x-1] == 0) { array[x-1] = 1; available_sites += -1; } } /* Calculate coverage %, and add to total */ c = count/N total_c += c; } For the actual project I'm doing, it involves not just dimers but trimers, quadrimers, and all sorts of shapes and sizes (for 2D and 3D). I was hoping that I would be able to work with individual bits instead of bytes, but I've been reading around and as far as I can tell you can only change 1 byte at a time, so either I need to do some complicated indexing or there is a simpler way to do it? Thanks for your answers

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• multithreading with database

  - by Darsin

  I am looking out for a strategy to utilize multithreading (probably asynchronous delegates) to do a synchronous operation. I am new to multithreading so i will outline my scenario first. This synchronous operation right now is done for one set of data (portfolio) based on the the parameters provided. The (psudeo-code) implementation is given below: public DataSet DoTests(int fundId, DateTime portfolioDate) { // Get test results for the portfolio // Call the database adapter method, which in turn is a stored procedure, // which in turns runs a series of "rule" stored procs and fills a local temp table and returns it back. DataSet resultsDataSet = GetTestResults(fundId, portfolioDate); try { // Do some local processing on the results DoSomeProcessing(resultsDataSet); // Save the results in Test, TestResults and TestAllocations tables in a transaction. // Sets a global transaction which is provided to all the adapter methods called below // It is defined in the Base class StartTransaction("TestTransaction"); // Save Test and get a testId int testId = UpdateTest(resultsDataSet); // Adapter method, uses the same transaction // Update testId in the other tables in the dataset UpdateTestId(resultsDataSet, testId); // Update TestResults UpdateTestResults(resultsDataSet); // Adapter method, uses the same transaction // Update TestAllocations UpdateTestAllocations(resultsDataSet); // Adapter method, uses the same transaction // It is defined in the base class CommitTransaction("TestTransaction"); } catch { RollbackTransaction("TestTransaction"); } return resultsDataSet; } Now the requirement is to do it for multiple set of data. One way would be to call the above DoTests() method in a loop and get the data. I would prefer doing it in parallel. But there are certain catches: StartTransaction() method creates a connection (and transaction) every time it is called. All the underlying database tables, procedures are the same for each call of DoTests(). (obviously). Thus my question are: Will using multithreading anyway improve performance? What are the chances of deadlock especially when new TestId's are being created and the Tests, TestResults and TestAllocations are being saved? How can these deadlocked be handled? Is there any other more efficient way of doing the above operation apart from looping over the DoTests() method repeatedly?

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• Emulating Button Press Using Kinect/SimpleOpenNI + Processing Depth

  - by Alex Lu

  I am using Kinect with Simple OpenNI and Processing, and I was trying to use the Z position of a hand to emulate a button press. So far when I try it using one hand it works really well, however, when I try to get it to work with a second hand, only one of the hands work. (I know it can be more efficient by moving everything except the fill out of the if statements, but I kept those in there just in case I want to change the sizes or something.) irz and ilz are the initial Z positions of the hands when they are first recognized by onCreateHands and rz and lz are the current Z positions. As of now, the code works fine with one hand, but the other hand will either stay pressed or unpressed. If i comment one of the sections out, it works fine as well. if (rz - irz > 0) { pushStyle(); fill(60); ellipse(rx, ry, 10, 10); popStyle(); rpressed = true; } else { pushStyle(); noFill(); ellipse(rx, ry, 10, 10); popStyle(); rpressed = false; } if (lz - ilz > 0) { pushStyle(); fill(60); ellipse(lx, ly, 10, 10); popStyle(); lpressed = true; } else { pushStyle(); noFill(); ellipse(lx, ly, 10, 10); popStyle(); lpressed = false; } I tried outputting the values of rz - irz and lz - ilz and the numbers range from small negative values to small positive values (around -8 to 8) for lz - ilz. But rz - irz outputs numbers from around 8-30 depending on each time I run it and is never consistent. Also, when I comment out the code for the lz-ilz, the values for rz-irz look just fine and it operates as intended. Is there a reason tracking both Z positions throws off one hand? And is there a way to get it to work? Thanks!

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