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• How to optimize Dijkstra algorithm for a single shortest path between 2 nodes?

  - by Nazgulled

  Hi, I was trying to understand this implementation in C of the Dijkstra algorithm and at the same time modify it so that only the shortest path between 2 specific nodes (source and destination) is found. However, I don't know exactly what do to. The way I see it, there's nothing much to do, I can't seem to change d[] or prev[] cause those arrays aggregate some important data for the shortest path calculation. The only thing I can think of is stopping the algorithm when the path is found, that is, break the cycle when mini = destination when it's being marked as visited. Is there anything else I could do to make it better or is that enough? P.S: I just noticed that the for loops start at 1 until <=, why can't it start at 0 and go until <?

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• Bejeweled Blitz - How does it assert there is always a move?

  - by EvilTeach

  I have been playing Bejeweled Blitz for a while now. Yes, it is an addiction. In thinking about the game, I have observed that on some boards, the bottom runs dry (no moves) leaving only the top part of the board playable. Frequently that part of the board drys up, and one is left with moves in area cleared by the last move. The board never runs completely dry, so clearly the program is doing some sorts of calculation that allows it to choose what to drop to prevent it from running dry. I have noticed in this 'mode' that it is very common for the algorithm to drop jewels which causes more non-dry area to appear in the horizontal area. Perhaps less frequent is a drop which seems designed to open up the bottom part of the board again. So my question is "How would one go about designing an algorithm guarantee that there is always a move available.?"

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• postgresql weighted average?

  - by milovanderlinden

  say I have a postgresql table with the following values: id | value ---------- 1 | 4 2 | 8 3 | 100 4 | 5 5 | 7 If I use postgresql to calculate the average, it gives me an average of 24.8 because the high value of 100 has great impact on the calculation. While in fact I would like to find an average somewhere around 6 and eliminate the extreme(s). I am looking for a way to eliminate extremes and want to do this "statistically correct". The extreme's cannot be fixed. I cannot say; If a value is over X, it has to be eliminated. I have been bending my head on the postgresql aggregate functions but cannot put my finger on what is right for me to use. Any suggestions?

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• Why can't I share a variable between two content sections in an ASP.NET MVC View?

  - by Dave Van den Eynde

  I have an ASP.NET MVC View with the typical TitleContent and MainContent, with a fairly complicated title that I want to calculate once and then share between these two content sections, like so: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<dynamic>" %> <% var complicatedTitle = string.Format("{0} - {1}", Model.FirstThing, Model.SecondThing); %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server"> <%: complicatedTitle %> </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <h2><%: complicatedTitle %></h2> </asp:Content> This, however, doesn't work, as the resulting error message would say that only Content controls are allowed directly in a content page that contains Content controls. The calculation definately belongs in the view. How do you solve this problem?

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• add new column in birt report based on generated grand total column in crosstab

  - by Sanga

  Hi there, Thanks for reading my question. Please I need your help here. I am trying to add a column that is based on a cross-tab's grand total. The cross-tab was added by clicking on the totals option for the column. Now I want to use this total for another calculation in my cross-tab but its so difficult adding a column after the grand total column. Secondly its difficult getting a reference to the results in the grand total column. Please what do you advice? Thanks Ime

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• Binomial test in Python

  - by Morlock

  I need to do a binomial test in Python that allows calculation for 'n' numbers of the order of 10000. I have implemented a quick binomial_test function using scipy.misc.comb, however, it is pretty much limited around n = 1000, I guess because it reaches the biggest representable number while computing factorials or the combinatorial itself. Here is my function: from scipy.misc import comb def binomial_test(n, k): """Calculate binomial probability """ p = comb(n, k) * 0.5**k * 0.5**(n-k) return p How could I use a native python (or numpy, scipy...) function in order to calculate that binomial probability? If possible, I need scipy 0.7.2 compatible code. Many thanks!

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• Drag Rotate UIImageView by touch

  - by rockstardev

  I have an UIImageView that is a subview of an UIView. I'm trying to create a drag rotate effect with the UIImageView similar to spinning a bottle but I'm having trouble calculating the radians to rotate the image by. My code below seems like it should work because I've seen a similar calculation in Flash examples. Can anyone shed some light on what I'm doing wrong? Thanks. This is the code contained in my image view subclass: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [[event allTouches] anyObject]; lastLocation = [touch locationInView:[self superview]]; } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [[event allTouches] anyObject]; CGPoint location = [touch locationInView:[self superview]]; CGFloat xDisplacement = location.x - lastLocation.x; CGFloat yDisplacement = location.y - lastLocation.y; CGFloat rad = atan2f(yDisplacement,xDisplacement); self.transform = CGAffineTransformMakeRotation(rad); }

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• Excel 2007 Visual Basic Editor: eats spaces, throws cursor around

  - by Vincent

  I can't resolve this issue, I found a similar question here but: setting the workbook to Manual calculation (alt-m-x-m or alt-t-oformulas) didn't work Setting editor options to disable: Auto syntax check & Background compile didn't work anybody have any idea how to fix this very annoying behaviour, I'm used to quickly pop up VBA (alt-f11), f7 to get into code and write some quick procedures there... and it's hard to get out of that habit, I don't want to write any office extension to just add a single quote to every cell in the range For Each rg In Selection rg = chr(39) & rg.value Next F5, done...

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• What is going on with the "return fibonacci( number-1 ) + fibonacci( number-2 )"?

  - by user1478598

  I have problem understanding what the return fibonacci( number-1 ) + fibonacci( number-2 ) does in the following program: import sys def fibonacci( number ): if( number <= 2 ): return 1 else: return fibonacci( number-1 ) + fibonacci( number-2 ) The problem is that I can't imagine how this line works: return fibonacci( number-1 ) + fibonacci( number-2 ) Does the both of the "fibonacci( number-1 )" and "fibonacci( number-2 )" being processed at the same time? or the "fibonacci( number-1 )" is the first to be processed and then the second one? I only see that processing both of them would eventually return '1' so the last result I expect to see it is a '1 + 1' = '2' I would appreciate a lot, If someone can elaborately explain the process of its calculation. I think this is a very newb question but I can't really get a picture of its process.

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• Console appliction with Multithreading on Single core.

  - by Harsha

  Hello all, I am reposting my question on Multithreading on Single core processor. Original question is: http://stackoverflow.com/questions/2856239/will-multi-threading-increase-the-speed-of-the-calculation-on-single-processor I have been asked a question, At any given time, only one thread is allowed to run on a single core. If so, why people use multithreading in a application. Lets say you are running console application and It is very much possible to write the application to run on the main thread. But still people go for multithreading.

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• Need a formula for calculating the tax portion of a total amount.

  - by pawz

  In Australia we have to advertise products with tax already added, so rather than say a product is $10 + $1 GST = $11, we normally work backwards and say "ok, total is $10, how much of that is GST ?" For example, for a $10 total, you do 10 * (1 /11) = 0.91, which is the tax component of the $10 total. My problem is I need calculate a formula for working out the taxable component when the tax rate is a variable. So far I've made this calculation although I'm not sure how correct an assertion it is: 10 * (1 / x) = 0.09 * (1 / y) where y = 10, x = 11 Basically i want to work out x on the left hand side when I know that the tax rate is 0.05 for example, which will give me a formula that I can use to calculate the taxable component of an total figure. I want a function into which I can plug in the total price and the tax rate, and get back the taxable component of the total price. I'd really appreciate the help with this as it really makes my head hurt ! :")

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• .NET Data Adapter Timeout SP Issue

  - by A-B

  We have a SQL Server stored procedure that runs fine in SQL Manager directly, does a rather large calculation but only takes 50-10 seconds max to run. However when we call this from the .NET app via a data adapter it times out. The timeout however happens before the timeout period should, we set it to 60 seconds and it still times out in about 20 seconds or less. I've Googled the issue and seen others note issues where a SP works fien directly but is slow via a data adpater call. Any ideas on how to resolve this?

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• Access to selection in gmail message body with Google Apps Script

  - by Mike Ellis

  Can app scripts access the current selection in a gmail message? I frequently compose messages that include engineering calculations and make use of the Google Calc feature do the calculation or convert to the desired units, e.g. 4000 Btu/hr * 8 hrs in kWh It would be really convenient to be able to select the above, hit a mapped key (e.g. Ctrl-K) and have the inserted after the expression 4000 Btu/hr * 8 hrs in kWh = 0.9378 kWh instead of having to paste the expression into a search box and then copy and paste the answer. I could certainly write a solution using a keymapper and a small python script to grab the current selection, send it to the gcalc api, etc ..., but my real motivation is to get familiar with Apps Scripts's capabilities and limitations. I suppose the uber-question here is "what kinds of user actions and state information can App Script access in Gmail messages (and/or Google docs) that are being edited?"

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• How can I call model methods or properties from Django Admin?

  - by kg

  Is there a natural way to display model methods or properties in the Django admin site? In my case I have base statistics for a character that are part of the model, but other things such as status effects which affect the total calculation for that statistic: class Character(models.Model): base_dexterity = models.IntegerField(default=0) @property def dexterity(stat_name): total = self.base_dexterity total += sum(s.dexterity for s in self.status.all()]) return total It would be nice if I could display the total calculated statistic alongside the field to change the base statistic in the Change Character admin page, but it is not clear to me how to incorporate that information into the page.

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• pyplot: really slow creating heatmaps

  - by cvondrick

  I have a loop that executes the body about 200 times. In each loop iteration, it does a sophisticated calculation, and then as debugging, I wish to produce a heatmap of a NxM matrix. But, generating this heatmap is unbearably slow and significantly slow downs an already slow algorithm. My code is along the lines: import numpy import matplotlib.pyplot as plt for i in range(200): matrix = complex_calculation() plt.set_cmap("gray") plt.imshow(matrix) plt.savefig("frame{0}.png".format(i)) The matrix, from numpy, is not huge --- 300 x 600 of doubles. Even if I do not save the figure and instead update an on-screen plot, it's even slower. Surely I must be abusing pyplot. (Matlab can do this, no problem.) How do I speed this up?

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• Use case modelling for calculator

  - by kyrogue

  hi, i need help modelling a use case diagram from a topic, it will be in java GUI Design a Calculator that 1.Allow user to key in a legitimate arithmetic statement that involves number, operator +, - and bracket '(' and ')' ; 2.When user press “Calculate” button, display result; 3.Some legitimate statement would be ((3+2)-4+2) (equals 3) and (-2+3)-(3-1) (equals -1); 4.You should NOT use a pre-existing function that just take in the statement as a parameter and returns the result but you should write the logic of parsing every character in your code. 5.Store the last statement and answer so it is displayed when user press the “Last calculation” button. i have designed two use case diagrams using UML on netbeans 6.5.1, one of the use case i am not sure whether is it containing too much use cases etc, while the other is what i think could be too vague for the topic.i hope to get some feedback on whether the use case diagram are appropriate, thanks.

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• Convert Date to Datetime field.

  - by infant programmer

  The argument my C# function is getting is a string which is merely a Date or a DateTime. I am suppose to convert this String to DateTime, to carry on furthure calculation. Now I need to test whether the incoming data is a Date, if it is date(examle:"12/31/2009"), then I need to add "00:00:00" (24 hours format) to it, so that it will become "12/31/2009 00:00:00". If string manipulation is one possible way, I want to confirm whether there is some other way where we can automate the testing and conversion within DateTime.TryParseExact() method. This is my sample C# code : (which is now only able to convert string of format "MM/dd/yyyy HH:mm:ss" to DateTime.) private static string[] formats = new string[] { "MM/dd/yyyy HH:mm:ss" }; public string date_conv(string date_str) { DateTime date_value; DateTime.TryParseExact(date_str, formats, new global::System.Globalization.CultureInfo("en-US"), global::System.Globalization.DateTimeStyles.None, out date_value); /*Some useful instruction to use date_value*/ return(date_value.ToString("MM/dd/yyyy HH:mm:ss")); }

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• Type mismatch in expression in Delphi 7 on SQL append

  - by Demonick

  I have a code, that checks the current date when a form is loaded, performs a simple calculation, and appends a SQL in Delphi. It works on Windows 7 with Delphi 7, and on another computer with Xp, but doesn't on 3 other computers with Xp. When the form is loaded it shows a "Type mismatch in expression", and points to the line after the append. What could be the problem? procedure TfmJaunumi.FormCreate(Sender: TObject); var d1, d2: TDate; begin d1:= Date; d2:= Date-30; With qrJaunumi do begin Open; SQL.Append('WHERE Sanem_datums BETWEEN' + #39 + DateToStr(d1) + #39 + 'AND' + #39 + DateToStr(d2) + #39); Active := True; end; end;

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• NSTimer calculate hours

  - by Nic Hubbard

  I am using an NSTimer which I have working to show minutes and seconds. But I am confused about the math needed to calculate hours. I am using: - (void)updateCounter:(NSTimer *)theTimer { static int count = 0; count += 1; int seconds = count % 60; int minutes = (count - seconds) / 60; // Not sure how to calculate hours int hours = (count - minutes) / 60; self.timer.text = [NSString stringWithFormat:@"%.2d:%.2d:%.2d", hours, minutes, seconds]; } What calculation should I use for hours?

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• Adding a calculated field to a Query at run time.

  - by JamesB

  I'm getting data using a query in Delphi, and would like to add a calculated field to the query before it runs. The calculated field is using values in code as well as the query so I can't just calculate it in SQL. I know I can attach an OnCalcFields Event to actually make the calculation, but the problem is after adding the calculated field there are no other fields in the query... I did some digging and found that all of the field defs are created but the actual fields are only created if DefaultFields then CreateFields Default Fields is specified procedure TDataSet.DoInternalOpen; begin FDefaultFields := FieldCount = 0; ... end; Which would indicate that if you add fields you only get the fields you added. I would like all the fields in the query AS WELL AS the ones I Add. Is this possible or do I have to add all the fields I'm using as well?

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• Math/numerical formula every computer programmer should know

  - by aaa

  This is a follow-up question to What should every programmer know and Is mathematics necessary. So the question is, as a computer programmer, what is the most important/useful mathematical or numerical formula that you use? By Formula I mean anything that involves less obvious manipulations, whenever binomial coefficients or bit hacks. I work with multidimensional arrays and various matrix representations. So for me most commonly used formulas are: A(i,j,k,..) = a[i + j*Dim0 + k*Dim0*Dim1 + ... to map indexes to one dimension ( which is basic address calculation which many people do not seem to know). And triangular number T(i) = (i*i + i)/2 which is related to binomial coefficients, used to calculate address in triangular matrixes and many other things. What is your workhorse formula that you think programmer should know?

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• Complex select query question for hardcore SQL designers

  - by eugeneK

  Very complex query been trying to construct it for few days with more real success. I'm using SQL-SERVER 2005 Standard What i need is : 5 CampaignVariants from Campaigns whereas 2 are with the largest PPU number set and 3 are random. Next condition is that CampaignDailyBudget and CampaignTotalBudget are below what is set in Campaign ( calculation is number of clicks in Visitors table connected to Campaigns via CampaignVariants on which users click) Next condition CampaignLanguage, CampaignCategory, CampaignRegion and CampaignCountry must be the ones i send to this select with (languageID,categoryID,regionID and countryID). Next condition is that IP address i send to this select statement won't be in IPs list for current Campaign ( i delete inactive for 24 hours IPs ). In other words it gets 5 CampaignVariants for user that enters the site, when i take from user PublisherRegionUID,IP,Language,Country and Region view diagram

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• Compute divergence of vector field using python

  - by nyvltak

  Is there a function that could be used for calculation of the divergence of the vectorial field? (in matlab http://www.mathworks.ch/help/techdoc/ref/divergence.html) I would expect it exists in numpy/scipy but I can not find it using google :(. # I need to calculate div[A * grad(F)], where F = np.array([[1,2,3,4],[5,6,7,8]]) (2D numpy ndarray) A = np.array([[1,2,3,4],[1,2,3,4]]) (2D numpy ndarray) so grad(F) is a set of 2D ndarrays # I know, I can calculate divergence like this: http://en.wikipedia.org/wiki/Divergence#Application_in_Cartesian_coordinates but do not want to reinvent the wheel. (and also I expent there is some optimized function)

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• How do I increase Relevance value in an advanced MySQL query?

  - by morgant

  I've got a MySQL query similar to the following: SELECT *, MATCH (`Description`) AGAINST ('+ipod +touch ' IN BOOLEAN MODE) * 8 + MATCH(`Description`) AGAINST ('ipod touch' IN BOOLEAN MODE) AS Relevance FROM products WHERE ( MATCH (`Description`) AGAINST ('+ipod +touch' IN BOOLEAN MODE) OR MATCH(`LongDescription`) AGAINST ('+ipod +touch' IN BOOLEAN MODE) ) HAVING Relevance > 1 ORDER BY Relevance DESC Now, I've made the query more advanced by also searching for UPC: SELECT *, MATCH (`Description`) AGAINST ('+ipod +touch ' IN BOOLEAN MODE) * 8 + MATCH(`Description`) AGAINST ('ipod touch' IN BOOLEAN MODE) + `UPC` = '123456789012' * 16 AS Relevance FROM products WHERE ( MATCH (`Description`) AGAINST ('+ipod +touch' IN BOOLEAN MODE) OR MATCH(`LongDescription`) AGAINST ('+ipod +touch' IN BOOLEAN MODE) ) AND `UPC` = '123456789012' HAVING Relevance > 1 ORDER BY Relevance DESC That'll return results, but the fact that I had a successful match on the UPC does not increase the value of Relevance. Can I only do that kind of calculation w/full text searches like MATCH() AGAINST()? Clarification: Okay, so my real question is, why does the following not have a Relevance = 16? SELECT `UPC`, `UPC` = '123456789012' * 16 AS Relevance FROM products WHERE `UPC` = '123456789012' HAVING Relevance > 1 ORDER BY Relevance DESC

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• How do I throttle my site's API users?

  - by scotts

  The legitimate users of my site occasionally hammer the server with API requests that cause undesirable results. I want to institute a limit of no more than say one API call every 5 seconds or n calls per minute (haven't figured out the exact limit yet). I could obviously log every API call in a DB and do the calculation on every request to see if they're over the limit, but all this extra overhead on EVERY request would be defeating the purpose. What are other less resource-intensive methods I could use to institute a limit? I'm using PHP/Apache/Linux, for what it's worth.

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