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  • Learning MVC - Maintaining model state

    - by GenericTypeTea
    First of all, I'm very new to MVC. Bought the books, but not got the T-Shirt yet. I've put together my first little application, but I'm looking at the way I'm maintaining my model and I don't think it looks right. My form contains the following: <% using (Html.BeginForm("Reconfigured", null, FormMethod.Post, new { id = "configurationForm" })) { %> <%= Html.DropDownList("selectedCompany", new SelectList(Model.Companies, Model.SelectedCompany), new { onchange = "$('#configurationForm').submit()" })%> <%= Html.DropDownList("selectedDepartment", new SelectList(Model.Departments, Model.SelectedDepartment), new { onchange = "$('#configurationForm').submit()" })%> <%=Html.TextArea("comment", Model.Comment) %> <%} %> My controller has the following: public ActionResult Index(string company, string department, string comment) { TestModel form = new TestModel(); form.Departments = _someRepository.GetList(); form.Companies = _someRepository.GetList(); form.Comment = comment; form.SelectedCompany = company; form.SelectedDepartment = department; return View(form); } [HttpPost] public ActionResult Reconfigured(string selectedCompany, string selectedDepartment, string comment) { return RedirectToAction("Index", new { company = selectedCompany, department = selectedDepartment, comment = comment}); } And finally, this is my route: routes.MapRoute( "Default", "{controller}/{company}/{department}", new { controller = "CompanyController", action = "Index", company="", department="" } ); Now, every time I change DropDownList value, all my values are maintained. I end up with a URL like the following after the Reconfigure action is called: http://localhost/Main/Index/Company/Sales?comment=Foo%20Bar Ideally I'd like the URL to remain as: http://localhost/Main/Index My routing object is probably wrong. This can't be the right way? It seems totally wrong to me as for each extra field I add, I have to add the property into the Index() method? I had a look at this answer where the form is passed through TempData. This is obviously an improvement, but it's not strongly typed? Is there a way to do something similar but have it strongly typed? This may be a simple-enough question, but the curse of 10 years of WinForms/WebForms makes this MVC malarky hard to get your head 'round.

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  • How to show percentage of 'memory used' in a win32 process?

    - by pj4533
    I know that memory usage is a very complex issue on Windows. I am trying to write a UI control for a large application that shows a 'percentage of memory used' number, in order to give the user an indication that it may be time to clear up some memory, or more likely restart the application. One implementation used ullAvailVirtual from MEMORYSTATUSEX as a base, then used HeapWalk() to walk the process heap looking for additional free memory. The HeapWalk() step was needed because we noticed that after a while of running the memory allocated and freed by the heap was never returned and reported by the ullAvailVirtual number. After hours of intensive working, the ullAvailVirtual number no longer would accurately report the amount of memory available. However, this method proved not ideal, due to occasional odd errors that HeapWalk() would return, even when the process heap was not corrupted. Further, since this is a UI control, the heap walking code was executing every 5-10 seconds. I tried contacting Microsoft about why HeapWalk() was failing, escalated a case via MSDN, but never got an answer other than "you probably shouldn't do that". So, as a second implementation, I used PagefileUsage from PROCESS_MEMORY_COUNTERS as a base. Then I used VirtualQueryEx to walk the virtual address space adding up all regions that weren't MEM_FREE and returned a value for GetMappedFileNameA(). My thinking was that the PageFileUsage was essentially 'private bytes' so if I added to that value the total size of the DLLs my process was using, it would be a good approximation of the amount of memory my process was using. This second method seems to (sorta) work, at least it doesn't cause crashes like the heap walker method. However, when both methods are enabled, the values are not the same. So one of the methods is wrong. So, StackOverflow world...how would you implement this? which method is more promising, or do you have a third, better method? should I go back to the original method, and further debug the odd errors? should I stay away from walking the heap every 5-10 seconds? Keep in mind the whole point is to indicate to the user that it is getting 'dangerous', and they should either free up memory or restart the application. Perhaps a 'percentage used' isn't the best solution to this problem? What is? Another idea I had was a color based system (red, yellow, green, which I could base on more factors than just a single number)

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  • Calling/selecting variables (float valued) with user input in Python

    - by Jonathan Straus
    I've been working on a computational physics project (plotting related rates of chemical reactants with respect to eachother to show oscillatory behavior) with a fair amount of success. However, one of my simulations involves more than two active oscillating agents (five, in fact) which would obviously be unsuitable for any single visual plot... My scheme was hence to have the user select which two reactants they wanted plotted on the x-axis and y-axis respectively. I tried (foolishly) to convert string input values into the respective variable names, but I guess I need a radically different approach if any exist? If it helps clarify any, here is part of my code: def coupledBrusselator(A, B, t_trial,display_x,display_y): t = 0 t_step = .01 X = 0 Y = 0 E = 0 U = 0 V = 0 dX = (A) - (B+1)*(X) + (X**2)*(Y) dY = (B)*(X) - (X**2)*(Y) dE = -(E)*(U) - (X) dU = (U**2)*(V) -(E+1)*(U) - (B)*(X) dV = (E)*(U) - (U**2)*(V) array_t = [0] array_X = [0] array_Y = [0] array_U = [0] array_V = [0] while t <= t_trial: X_1 = X + (dX)*(t_step/2) Y_1 = Y + (dY)*(t_step/2) E_1 = E + (dE)*(t_step/2) U_1 = U + (dU)*(t_step/2) V_1 = V + (dV)*(t_step/2) dX_1 = (A) - (B+1)*(X_1) + (X_1**2)*(Y_1) dY_1 = (B)*(X_1) - (X_1**2)*(Y_1) dE_1 = -(E_1)*(U_1) - (X_1) dU_1 = (U_1**2)*(V_1) -(E_1+1)*(U_1) - (B)*(X_1) dV_1 = (E_1)*(U_1) - (U_1**2)*(V_1) X_2 = X + (dX_1)*(t_step/2) Y_2 = Y + (dY_1)*(t_step/2) E_2 = E + (dE_1)*(t_step/2) U_2 = U + (dU_1)*(t_step/2) V_2 = V + (dV_1)*(t_step/2) dX_2 = (A) - (B+1)*(X_2) + (X_2**2)*(Y_2) dY_2 = (B)*(X_2) - (X_2**2)*(Y_2) dE_2 = -(E_2)*(U_2) - (X_2) dU_2 = (U_2**2)*(V_2) -(E_2+1)*(U_2) - (B)*(X_2) dV_2 = (E_2)*(U_2) - (U_2**2)*(V_2) X_3 = X + (dX_2)*(t_step) Y_3 = Y + (dY_2)*(t_step) E_3 = E + (dE_2)*(t_step) U_3 = U + (dU_2)*(t_step) V_3 = V + (dV_2)*(t_step) dX_3 = (A) - (B+1)*(X_3) + (X_3**2)*(Y_3) dY_3 = (B)*(X_3) - (X_3**2)*(Y_3) dE_3 = -(E_3)*(U_3) - (X_3) dU_3 = (U_3**2)*(V_3) -(E_3+1)*(U_3) - (B)*(X_3) dV_3 = (E_3)*(U_3) - (U_3**2)*(V_3) X = X + ((dX + 2*dX_1 + 2*dX_2 + dX_3)/6) * t_step Y = Y + ((dX + 2*dY_1 + 2*dY_2 + dY_3)/6) * t_step E = E + ((dE + 2*dE_1 + 2*dE_2 + dE_3)/6) * t_step U = U + ((dU + 2*dU_1 + 2*dY_2 + dE_3)/6) * t_step V = V + ((dV + 2*dV_1 + 2*dV_2 + dE_3)/6) * t_step dX = (A) - (B+1)*(X) + (X**2)*(Y) dY = (B)*(X) - (X**2)*(Y) t_step = .01 / (1 + dX**2 + dY**2) ** .5 t = t + t_step array_X.append(X) array_Y.append(Y) array_E.append(E) array_U.append(U) array_V.append(V) array_t.append(t) where previously display_x = raw_input("Choose catalyst you wish to analyze in the phase/field diagrams (X, Y, E, U, or V) ") display_y = raw_input("Choose one other catalyst from list you wish to include in phase/field diagrams ") coupledBrusselator(A, B, t_trial, display_x, display_y) Thanks!

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  • Arguments for moving from LINQtoSQL to Nhibernate?

    - by sah302
    Backstory: Hi all, I just spent a lot of time reading many of the LINQ vs Nhibernate threads here and on other sites. I work in a small development team of 4 people and we don't even have really any super experienced developers. We work for a small company that has a lot of technical needs but not enough developers to implement them (and hiring more is out of the question right now). Typically our projects (which individually are fairly small) have been coded separately and weren't really layered in anyway, code wasn't re-used, no class libraries, and we just use the LINQtoSQL .dbml files for our pojects, we really don't even use objects but pass around values and stuff, the only time we use objects is when inserting to a database (heck not even querying since you don't need to assign it to a type and can just bind to gridview). Despite all this as I said our company has a lot of technical needs, no one could come to us for a year and we would have plenty of work to implement requested features. Well I have decided to change that a bit first by creating class libraries and actually adding layers to our applications. I am trying to meet these guys halfway by still using LINQtoSQL as the ORM yet and still use VB as the language. However I am finding it a b***h of a time dealing with so many thing in LINQtoSQL that I found easy in Nhibernate (automatic handling of the session, criteria creation easier than expression trees, generic an dynamic querying easier etc.) So... Question: How can I convince my lead developers and other senior programmers that switching to Nhibernate is a good thing? That being in control of our domain objects is a good thing? That being able to implement interfaces is a good? I've tried exlpaining the advantages of this before but it's not understood by them because they've never programmed in a true OO & layered way. Also one of the counter arguments to this I can see is sqlMetal generates those classes automatically and therefore it saves a lot of time. I can't really counter that other than saying spending more time on infrastructure to make it more scalable and flexible is good, but they can't see how. Again, I know the features and advantages (somewhat enough I believe) of each, but I need arguments applicable to my context, hence why I provided the context. I just am not a very good arguer I guess. (Caveat: For all the LINQtoSQL lovers, I may just not be super proficient as LINQ, but I find it very cumbersome that you are required to download some extra library for dynamic queries which don't by default support guid comparisons, and I also find the way of updating entitites to be cumbersome as well in terms of data context managing, so it could just be that I suck hehe.)

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  • Undesired "flashing" in Jquery dropdown menu?

    - by Tom
    Hi, I've got the following piece of Jquery: $("#collapse-menu > li > a").click(function() { $(this).toggleClass("expanded").toggleClass("collapsed").find("+ ul").slideToggle("medium"); }); What it basically does is expands or collapses a menu of nested "lists" which contain dropdowns (simplified example): <ul id="collapse-menu"> <li><a class="expanded">Basic Details</a> <ul> <li> <select> .... </select> </li> <li> <select> .... </select> </li> The code works absolutely fine EXCEPT when a large value is selected in any of the dropdowns. At that point, when clicked, the menu will still expand/collapse correctly but "flash" quickly while doing so, as if the entire element was being reset somehow. The data itself is fine but it's the flashing that's unwanted. The strange thing is that if a small value is selected in a dropdown, there's no flashing. When a large value is selected (say, above 30 in an age dropdown of 18-99), the flashing starts happening. Can anyone tell me why this is happening? Or whether there's something not right about the Jquery that's causing this. Thanks. UPDATE: Adding a bounty to this. Have tried a few similar plugins/solutions out there on the net but they all seem to suffer from this "flashing" problem when large dropdown values are selected by default. If it helps, here's a typical similar solution: http://www.i-marco.nl/weblog/jquery-accordion-menu/index_collapsed.html# ... but it suffers from the same problem when dropdowns are added inside the accordion. I hope someone has a clean solution, instead of needing to hack this somehow.

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  • Newbie's problems with MySQL and php

    - by Mirage81
    I'm a real newbie with php and MySQL. Now I'm working on the following code which should search the database for eg. all the Lennons living in Liverpool. 1) How should I modify "get.php" to get the text "no results" to appear if there are no search results. 2) How should I modify "index.php" to get the option values (city and lastname) straight from the database instead of having to type them one by one? 3) Am I using mysql_real_escape_string the right way? 4) Any other mistakes in the code? index.php: <form action="get.php" method="post"> <p> <select name="city"> <option value="Birmingham">Birmingham</option> <option value="Liverpool">Liverpool</option> <option value="London">London</option> </select> </p> <p> <select name="lastname"> <option value="Lennon">Lennon</option> <option value="McCartney">McCartney</option> <option value="Osbourne">Osbourne</option> </select> </p> <p> <input value="Search" type="submit"> </p> </form> get.php: <?php $city = $_POST['city']; $lastname = $_POST['lastname']; $conn = mysql_connect('localhost', 'user', 'password'); mysql_select_db("database", $conn) or die("connection failed"); $query = "SELECT * FROM users WHERE city = '$city' AND lastname = '$lastname'"; $result = mysql_query($query, $conn); $city = mysql_real_escape_string($_POST['city']); $lastname = mysql_real_escape_string($_POST['lastname']); echo $rowcount; while ($row = mysql_fetch_row($result)) { if ($rowcount == '0') echo 'no results'; else { echo '<b>City: </b>'.htmlspecialchars($row[0]).'<br />'; echo '<b>Last name: </b>'.htmlspecialchars($row[1]).'<br />'; echo '<b>Information: </b>'.htmlspecialchars($row[2]); } } mysql_close($conn);

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  • can we use both custom button and inbuilt button in datagridview

    - by Srikanth Mattihalli
    HI all, I am using Datagridview in asp.net. I have used custom buttons of up and down in the datagridview along with edit,delete and paging options. I am handling the up down buttons by raising events in rowcommand and the code is as below string command = e.CommandName; Response.Write(e.CommandArgument.ToString()); int index = Convert.ToInt32(e.CommandArgument.ToString()); int count = GridView1.Rows.Count; int keyValue = Convert.ToInt32(GridView1.Rows[index].Cells1.Text); string value = GridView1.Rows[index].Cells[4].Text; SqlConnection conn = new SqlConnection(SqlDataSource1.ConnectionString); SqlCommand cmd = new SqlCommand(); if (command == "up") { if (index > 0) { index = index - 1; int keyValue1 = Convert.ToInt32(GridView1.Rows[index].Cells[1].Text); string value1 = GridView1.Rows[index].Cells[4].Text; cmd.Connection = conn; cmd.CommandText = "UPDATE [category] SET [order_id] = '" + value + "' WHERE [category_id]=" + keyValue1 + ";UPDATE [category] SET [order_id] = '" + value1 + "' WHERE [category_id]=" + keyValue + ";"; conn.Open(); cmd.ExecuteNonQuery(); conn.Close(); } } else if (command == "down") { if (index < count - 1) { index = index + 1; int keyValue1 = Convert.ToInt32(GridView1.Rows[index].Cells[1].Text); string value1 = GridView1.Rows[index].Cells[4].Text; cmd.Connection = conn; cmd.CommandText = "UPDATE [category] SET [order_id] = '" + value + "' WHERE [category_id]=" + keyValue1 + ";UPDATE [category] SET [order_id] = '" + value1 + "' WHERE [category_id]=" + keyValue + ";"; conn.Open(); cmd.ExecuteNonQuery(); conn.Close(); } } Response.Redirect("Default.aspx"); Designer file " DeleteCommand="DELETE FROM [category] WHERE [category_id] = @category_id" InsertCommand="INSERT INTO [category] ([categoryname], [navigation_url], [order_id]) VALUES (@categoryname, @navigation_url, @order_id)" SelectCommand="SELECT * FROM [category] order by order_id" UpdateCommand="UPDATE [category] SET [categoryname] = @categoryname, [navigation_url] = @navigation_url, [order_id] = @order_id WHERE [category_id] = @category_id" After this my edit,delete and paging is not working bcoz of event conflicts. Can anyone plz help me on this, so that i will be able to use both custom buttons(up and down) and edit,delete and paging features.

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  • iPhone noob - setting NSMutableDictionary entry inside Singleton?

    - by codemonkey
    Yet another iPhone/Objective-C noob question. I'm using a singleton to store app state information. I'm including the singleton in a Utilities class that holds it (and eventually other stuff). This utilities class is in turn included and used from various view controllers, etc. The utilities class is set up like this: // Utilities.h #import <Foundation/Foundation.h> @interface Utilities : NSObject { } + (id)GetAppState; - (id)GetAppDelegate; @end // Utilities.m #import "Utilities.h" #import "CHAPPAppDelegate.h" #import "AppState.h" @implementation Utilities CHAPPAppDelegate* GetAppDelegate() { return (CHAPPAppDelegate *)[UIApplication sharedApplication].delegate; } AppState* GetAppState() { return [GetAppDelegate() appState]; } @end ... and the AppState singleton looks like this: // AppState.h #import <Foundation/Foundation.h> @interface AppState : NSObject { NSMutableDictionary *challenge; NSString *challengeID; } @property (nonatomic, retain) NSMutableDictionary *challenge; @property (nonatomic, retain) NSString *challengeID; + (id)appState; @end // AppState.m #import "AppState.h" static AppState *neoAppState = nil; @implementation AppState @synthesize challengeID; @synthesize challenge; # pragma mark Singleton methods + (id)appState { @synchronized(self) { if (neoAppState == nil) [[self alloc] init]; } return neoAppState; } + (id)allocWithZone:(NSZone *)zone { @synchronized(self) { if (neoAppState == nil) { neoAppState = [super allocWithZone:zone]; return neoAppState; } } return nil; } - (id)copyWithZone:(NSZone *)zone { return self; } - (id)retain { return self; } - (unsigned)retainCount { return UINT_MAX; //denotes an object that cannot be released } - (void)release { // never release } - (id)init { if (self = [super init]) { challengeID = [[NSString alloc] initWithString:@"0"]; challenge = [NSMutableDictionary dictionary]; } return self; } - (void)dealloc { // should never be called, but just here for clarity [super dealloc]; } @end ... then, from a view controller I'm able to set the singleton's "challengeID" property like this: [GetAppState() setValue:@"wassup" forKey:@"challengeID"]; ... but when I try to set one of the "challenge" dictionary entry values like this: [[GetAppState() challenge] setObject:@"wassup" forKey:@"wassup"]; ... it fails giving me an "unrecognized selector sent..." error. I'm probably doing something really obviously dumb? Any insights/suggestions will be appreciated.

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  • How do I print out objects in an array in python?

    - by Jonathan
    I'm writing a code which performs a k-means clustering on a set of data. I'm actually using the code from a book called collective intelligence by O'Reilly. Everything works, but in his code he uses the command line and i want to write everything in notepad++. As a reference his line is >>>kclust=clusters.kcluster(data,k=10) >>>[rownames[r] for r in k[0]] Here is my code: from PIL import Image,ImageDraw def readfile(filename): lines=[line for line in file(filename)] # First line is the column titles colnames=lines[0].strip( ).split('\t')[1:] rownames=[] data=[] for line in lines[1:]: p=line.strip( ).split('\t') # First column in each row is the rowname rownames.append(p[0]) # The data for this row is the remainder of the row data.append([float(x) for x in p[1:]]) return rownames,colnames,data from math import sqrt def pearson(v1,v2): # Simple sums sum1=sum(v1) sum2=sum(v2) # Sums of the squares sum1Sq=sum([pow(v,2) for v in v1]) sum2Sq=sum([pow(v,2) for v in v2]) # Sum of the products pSum=sum([v1[i]*v2[i] for i in range(len(v1))]) # Calculate r (Pearson score) num=pSum-(sum1*sum2/len(v1)) den=sqrt((sum1Sq-pow(sum1,2)/len(v1))*(sum2Sq-pow(sum2,2)/len(v1))) if den==0: return 0 return 1.0-num/den class bicluster: def __init__(self,vec,left=None,right=None,distance=0.0,id=None): self.left=left self.right=right self.vec=vec self.id=id self.distance=distance def hcluster(rows,distance=pearson): distances={} currentclustid=-1 # Clusters are initially just the rows clust=[bicluster(rows[i],id=i) for i in range(len(rows))] while len(clust)>1: lowestpair=(0,1) closest=distance(clust[0].vec,clust[1].vec) # loop through every pair looking for the smallest distance for i in range(len(clust)): for j in range(i+1,len(clust)): # distances is the cache of distance calculations if (clust[i].id,clust[j].id) not in distances: distances[(clust[i].id,clust[j].id)]=distance(clust[i].vec,clust[j].vec) #print 'i' #print i #print #print 'j' #print j #print d=distances[(clust[i].id,clust[j].id)] if d<closest: closest=d lowestpair=(i,j) # calculate the average of the two clusters mergevec=[ (clust[lowestpair[0]].vec[i]+clust[lowestpair[1]].vec[i])/2.0 for i in range(len(clust[0].vec))] # create the new cluster newcluster=bicluster(mergevec,left=clust[lowestpair[0]], right=clust[lowestpair[1]], distance=closest,id=currentclustid) # cluster ids that weren't in the original set are negative currentclustid-=1 del clust[lowestpair[1]] del clust[lowestpair[0]] clust.append(newcluster) return clust[0] def kcluster(rows,distance=pearson,k=4): # Determine the minimum and maximum values for each point ranges=[(min([row[i] for row in rows]),max([row[i] for row in rows])) for i in range(len(rows[0]))] # Create k randomly placed centroids clusters=[[random.random( )*(ranges[i][1]-ranges[i][0])+ranges[i][0] for i in range(len(rows[0]))] for j in range(k)] lastmatches=None for t in range(100): print 'Iteration %d' % t bestmatches=[[] for i in range(k)] # Find which centroid is the closest for each row for j in range(len(rows)): row=rows[j] bestmatch=0 for i in range(k): d=distance(clusters[i],row) if d<distance(clusters[bestmatch],row): bestmatch=i bestmatches[bestmatch].append(j) # If the results are the same as last time, this is complete if bestmatches==lastmatches: break lastmatches=bestmatches # Move the centroids to the average of their members for i in range(k): avgs=[0.0]*len(rows[0]) if len(bestmatches[i])>0: for rowid in bestmatches[i]: for m in range(len(rows[rowid])): avgs[m]+=rows[rowid][m] for j in range(len(avgs)): avgs[j]/=len(bestmatches[i]) clusters[i]=avgs return bestmatches

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  • Trying to write a loop that uses an OutputStream to write to a text file.

    - by Steve McLain
    I'm not a java programmer, I'm a VB programmer. I am doing this as part of an assignment, however, I'm not asking for help on something assignment related. I'd like to figure out how to get the OutputStreamWriter to work properly in this instance. I just want to capture the values I'm generating and place them into a text document. The file is generated, but only one entry exists, not the 40 I'm expecting. I could do this in a heartbeat with VB, but java feels very strange to me right now. Your help is appreciated. Thanks, Steve Here's the code: public static void main(String[] args){ long start, end; double result,difference; try {//OutputStream code assistance from http://tutorials.jenkov.com/java-io/outputstreamwriter.html OutputStream outputStream = new FileOutputStream("c:\\Temp\\output1.txt"); Writer out = new OutputStreamWriter(outputStream); for(int n=1; n<=20; n++){ //Calculate the Time for n^2. start = System.nanoTime(); //Add code to call method to calculate n^2 result = mN2(n); end = System.nanoTime(); difference = (end - start); //Output results to a file out.write("N^2 End time: " + end + " Difference: " + difference + "\n"); out.close(); } } catch (IOException e){ } try { OutputStream outputStream = new FileOutputStream("c:\\Temp\\output1.txt"); Writer out = new OutputStreamWriter(outputStream); for(int n=1; n<=20; n++){ //Calculate the Time for 2^n. start = System.nanoTime(); //Add code to call method to calculate 2^n result = m2N(n); end = System.nanoTime(); difference = (end - start); //Output results to a file out.write("N^2 End time: " + end + " Difference: " + difference + "\n"); out.close(); } } catch (IOException e){ } } //Calculate N^2 public static double mN2(double n) { n = n*n; return n; } //Calculate 2N public static double m2N (double n) { n = 2*n; return n; }

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  • Getting a KeyError in DB backend of django-digest

    - by rtmie
    I have just started to integrate django_digest into my app. As a start I have added the @httpdigest decorator to one of my views. If I try to connect to it I get a KeyError exception thrown in django_digest/backend/db.py . Depending on which db I configure I get a different KeyError in a different location. I am using Django 1.2.1, with MySql (also tested with sqlite). I am using the default values for all the settings options. As far as I can see I have followed all instructions but am struggling all day with this. I am using the repository versions of django-digest and python-digest. Any steer would be greatly appreciated. Tracebacks for sqlite and mysql below: with sqlite: Traceback (most recent call last): File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/core/servers/basehttp.py", line 674, in __call__ return self.application(environ, start_response) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/core/handlers/wsgi.py", line 248, in __call__ signals.request_finished.send(sender=self.__class__) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/dispatch/dispatcher.py", line 162, in send response = receiver(signal=self, sender=sender, **named) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django_digest-1.8-py2.5.egg/django_digest/backend/db.py", line 16, in close_connection _connection.close() File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/db/backends/sqlite3/base.py", line 186, in close if self.settings_dict['NAME'] != ":memory:": KeyError: 'NAME' with mysql: Traceback (most recent call last): File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/core/servers/basehttp.py", line 674, in __call__ return self.application(environ, start_response) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/core/handlers/wsgi.py", line 241, in __call__ response = self.get_response(request) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/core/handlers/base.py", line 142, in get_response return self.handle_uncaught_exception(request, resolver, exc_info) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/core/handlers/base.py", line 166, in handle_uncaught_exception return debug.technical_500_response(request, *exc_info) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/core/handlers/base.py", line 80, in get_response response = middleware_method(request) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django_digest-1.8-py2.5.egg/django_digest/middleware.py", line 13, in process_request if (not self._authenticator.authenticate(request) and File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django_digest-1.8-py2.5.egg/django_digest/__init__.py", line 86, in authenticate partial_digest = self._account_storage.get_partial_digest(digest_response.username) File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django_digest-1.8-py2.5.egg/django_digest/backend/db.py", line 97, in get_partial_digest cursor = get_connection().cursor() File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/db/backends/__init__.py", line 75, in cursor cursor = self._cursor() File "/home/robm/projects/gcs/server/gcs2.5/lib/python2.5/site-packages/django/db/backends/mysql/base.py", line 281, in _cursor if settings_dict['USER']: KeyError: 'USER'

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  • JBOSS 7 encoding not working as expected

    - by Fofole
    I had problems with my listgrids not showing diacritcs corectly and I found out that when I inserted from java into the db the values where already bugged. A post here helped and I changed my project properties - Text encoding - other - UTF-8 and this fixed my problem. Thing is this only fixes my problem locally. What I need to do is on my Jboss server also set the encoding somehow. This is what I put in my configuration file: <?xml version='1.0' encoding='UTF-8'?> <server name="vali-ubuntu" xmlns="urn:jboss:domain:1.0"> extensions> extension module="org.jboss.as.clustering.infinispan"/> extension module="org.jboss.as.connector"/> extension module="org.jboss.as.deployment-scanner"/> extension module="org.jboss.as.ee"/> extension module="org.jboss.as.ejb3"/> extension module="org.jboss.as.jaxrs"/> extension module="org.jboss.as.jmx"/> extension module="org.jboss.as.logging"/> extension module="org.jboss.as.naming"/> extension module="org.jboss.as.osgi"/> extension module="org.jboss.as.remoting"/> extension module="org.jboss.as.sar"/> extension module="org.jboss.as.security"/> extension module="org.jboss.as.threads"/> extension module="org.jboss.as.transactions"/> extension module="org.jboss.as.web"/> extension module="org.jboss.as.weld"/> /extensions> system-properties> property name="org.apache.catalina.connector.URI_ENCODING" value="UTF-8"/> property name="org.apache.catalina.connector.USE_BODY_ENCODING_FOR_QUERY_STRING" value="tru e"/> /system-properties> //..... This doesn't work so maybe I need to add something else. I tried everything I could find with no succes so any help is appreciated. Thanks. EDIT:From what I read, this will work only in jboss 7.1.0 beta 1 or highier. (URIEncoding) and I use JBoss 7.0.2 so I need a replacement for 7.0.2

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  • How build my own Application Setting

    - by adisembiring
    I want to build a ApplicationSetting for my application. The ApplicationSetting can be stored in a properties file or in a database table. The settings are stored in key-value pairs. E.g. ftp.host = blade ftp.username = dummy ftp.pass = pass content.row_pagination = 20 content.title = How to train your dragon. I have designed it as follows: Application settings reader: interface IApplicationSettingReader { read(); } DatabaseApplicationSettingReader { dao appSettingDao; AppSettings read() { List<AppSettingEntity> listEntity = appSettingsDao.findAll(); Map<String, String> map = new HaspMap<String, String>(); foreach (AppSettingEntity entity : listEntity) { map.put(entity.getConfigName(), entity.getConfigValue()); } return new AppSettings(map); } } DatabaseApplicationSettingReader { dao appSettingDao; AppSettings read() { //read from some properties file return new AppSettings(map); } } Application settings class: AppSettings { private static AppSettings instance; private Map map; Public AppSettings(Map map) { this.map = map; } public static AppSettings getInstance() { if (instance == null) { throw new RuntimeException("Object not configure yet"); } return instance; } public static configure(IApplicationSettingReader reader) { instance = reader.read(); } public String getFtpSetting(String param) { return map.get("ftp." + param); } public String getContentSetting(String param) { return map.get("content." + param); } } Test class: AppSettingsTest { IApplicationSettingReader reader; @Before public void setUp() throws Exception { reader = new DatabaseApplicationSettingReader(); } @Test public void getContentSetting_should_get_content_title() { AppSettings.configure(reader); Instance settings = AppSettings.getInstance(); String title = settings.getContentSetting("title"); assertNotNull(title); Sysout(title); } } My questions are: Can you give your opinion about my code, is there something wrong? I configure my application setting once, while the application start, I configure the application setting with appropriate reader (DbReader or PropertiesReader), I make it singleton. The problem is, when some user edit the database or file directly to database or file, I can't get the changed values. Now, I want to implement something like ApplicationSettingChangeListener. So if the data changes, I will refresh my application settings. Do you have any suggestions how this can be implemented?

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  • Calculating a Sample Covariance Matrix for Groups with plyr

    - by John A. Ramey
    I'm going to use the sample code from http://gettinggeneticsdone.blogspot.com/2009/11/split-apply-and-combine-in-r-using-plyr.html for this example. So, first, let's copy their example data: mydata=data.frame(X1=rnorm(30), X2=rnorm(30,5,2), SNP1=c(rep("AA",10), rep("Aa",10), rep("aa",10)), SNP2=c(rep("BB",10), rep("Bb",10), rep("bb",10))) I am going to ignore SNP2 in this example and just pretend the values in SNP1 denote group membership. So then, I may want some summary statistics about each group in SNP1: "AA", "Aa", "aa". Then if I want to calculate the means for each variable, it makes sense (modifying their code slightly) to use: > ddply(mydata, c("SNP1"), function(df) data.frame(meanX1=mean(df$X1), meanX2=mean(df$X2))) SNP1 meanX1 meanX2 1 aa 0.05178028 4.812302 2 Aa 0.30586206 4.820739 3 AA -0.26862500 4.856006 But what if I want the sample covariance matrix for each group? Ideally, I would like a 3D array, where the I have the covariance matrix for each group, and the third dimension denotes the corresponding group. I tried a modified version of the previous code and got the following results that have convinced me that I'm doing something wrong. > daply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) , , = 1 SNP1 1 2 aa 1.4961210 -0.9496134 Aa 0.8833190 -0.1640711 AA 0.9942357 -0.9955837 , , = 2 SNP1 1 2 aa -0.9496134 2.881515 Aa -0.1640711 2.466105 AA -0.9955837 4.938320 I was thinking that the dim() of the 3rd dimension would be 3, but instead, it is 2. Really this is a sliced up version of the covariance matrix for each group. If we manually compute the sample covariance matrix for aa, we get: [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 Using plyr, the following gives me what I want in list() form: > dlply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) $aa [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 $Aa [,1] [,2] [1,] 0.8833190 -0.1640711 [2,] -0.1640711 2.4661046 $AA [,1] [,2] [1,] 0.9942357 -0.9955837 [2,] -0.9955837 4.9383196 attr(,"split_type") [1] "data.frame" attr(,"split_labels") SNP1 1 aa 2 Aa 3 AA But like I said earlier, I would really like this in a 3D array. Any thoughts on where I went wrong with daply() or suggestions? Of course, I could typecast the list from dlply() to a 3D array, but I'd rather not do this because I will be repeating this process many times in a simulation. As a side note, I found one method (http://www.mail-archive.com/[email protected]/msg86328.html) that provides the sample covariance matrix for each group, but the outputted object is bloated. Thanks in advance.

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  • Importing a large delimited file to a MySQL table

    - by Tom
    I have this large (and oddly formatted txt file) from the USDA's website. It is the NUT_DATA.txt file. But the problem is that it is almost 27mb! I was successful in importing the a few other smaller files, but my method was using file_get_contents which it makes sense why an error would be thrown if I try to snag 27+ mb of RAM. So how can I import this massive file to my MySQL DB without running into a timeout and RAM issue? I've tried just getting one line at a time from the file, but this ran into timeout issue. Using PHP 5.2.0. Here is the old script (the fields in the DB are just numbers because I could not figure out what number represented what nutrient, I found this data very poorly document. Sorry about the ugliness of the code): <? $file = "NUT_DATA.txt"; $data = split("\n", file_get_contents($file)); // split each line $link = mysql_connect("localhost", "username", "password"); mysql_select_db("database", $link); for($i = 0, $e = sizeof($data); $i < $e; $i++) { $sql = "INSERT INTO `USDA` (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17) VALUES("; $row = split("\^", trim($data[$i])); // split each line by carrot for ($j = 0, $k = sizeof($row); $j < $k; $j++) { $val = trim($row[$j], '~'); $val = (empty($val)) ? 0 : $val; $sql .= ((empty($val)) ? 0 : $val) . ','; // this gets rid of those tildas and replaces empty strings with 0s } $sql = rtrim($sql, ',') . ");"; mysql_query($sql) or die(mysql_error()); // query the db } echo "Finished inserting data into database.\n"; mysql_close($link); ?>

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  • Dynamic Data Manipulation using XSLT from XML

    - by Imrul
    I am not working with XSLT not too long. I read that variable of XSLT can't be updated on the fly, so how can i do the following task. I want to sum up Purchase & Sales and put them into a variable, and make some decision according to these values. (For example, if Purchase is greater then sales then do something if not, do something else) <rows> <row> <col attr2="Purchase" >100.00</col> <col attr2="Sales" >100.00</col> </row> <row > <col attr2="Purchase" >19.16</col> <col attr2="Sales" >12.94</col> </row> <row > <col attr2="Purchase" >0.67</col> <col attr2="Sales" >2.74</col> </row> <row > <col attr2="Purchase" >71.95</col> <col attr2="Sales" >61.54</col> </row> <row > <col attr2="Purchase" >3.62</col> <col attr2="Sales" >14.72</col> </row> <row > <col attr2="Purchase">8.80</col> <col attr2="Sales">1.22</col> </row> <row > <col attr2="Purchase" >-4.28</col> <col attr2="Sales" >6.53</col> </row> </rows> if anyone knows, please help me.

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  • select option in Safari ?

    - by Karandeep Singh
    < select size="2" multiple> < option value="1">1< /option> < option value="2">2< /option> < option value="3">3< /option> < option value="4">4< /option> < option value="5">5< /option> < option value="6">6< /option> < option value="7">7< /option> < option value="8">8< /option> < option value="9">9< /option> < option value="10">10< /option> < option value="11">11< /option> < option value="12">12< /option> < option value="13">13< /option> < /select> size attribute of Select tag is not working properly in Safari. if size attribute's value is greater than four then there have no problem, its working. But when I set the value of size less than four then it show four values. above example displays four options in safari but I want two options. What is the reason for this ?

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  • Why do I get rows of zeros in my 2D fft?

    - by Nicholas Pringle
    I am trying to replicate the results from a paper. "Two-dimensional Fourier Transform (2D-FT) in space and time along sections of constant latitude (east-west) and longitude (north-south) were used to characterize the spectrum of the simulated flux variability south of 40degS." - Lenton et al(2006) The figures published show "the log of the variance of the 2D-FT". I have tried to create an array consisting of the seasonal cycle of similar data as well as the noise. I have defined the noise as the original array minus the signal array. Here is the code that I used to plot the 2D-FT of the signal array averaged in latitude: import numpy as np from numpy import ma from matplotlib import pyplot as plt from Scientific.IO.NetCDF import NetCDFFile ### input directory indir = '/home/nicholas/data/' ### get the flux data which is in ### [time(5day ave for 10 years),latitude,longitude] nc = NetCDFFile(indir + 'CFLX_2000_2009.nc','r') cflux_southern_ocean = nc.variables['Cflx'][:,10:50,:] cflux_southern_ocean = ma.masked_values(cflux_southern_ocean,1e+20) # mask land nc.close() cflux = cflux_southern_ocean*1e08 # change units of data from mmol/m^2/s ### create an array that consists of the seasonal signal fro each pixel year_stack = np.split(cflux, 10, axis=0) year_stack = np.array(year_stack) signal_array = np.tile(np.mean(year_stack, axis=0), (10, 1, 1)) signal_array = ma.masked_where(signal_array > 1e20, signal_array) # need to mask ### average the array over latitude(or longitude) signal_time_lon = ma.mean(signal_array, axis=1) ### do a 2D Fourier Transform of the time/space image ft = np.fft.fft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log(mgft) log_mgft= np.log(mgft) Every second row of the ft consists completely of zeros. Why is this? Would it be acceptable to add a randomly small number to the signal to avoid this. signal_time_lon = signal_time_lon + np.random.randint(0,9,size=(730, 182))*1e-05 EDIT: Adding images and clarify meaning The output of rfft2 still appears to be a complex array. Using fftshift shifts the edges of the image to the centre; I still have a power spectrum regardless. I expect that the reason that I get rows of zeros is that I have re-created the timeseries for each pixel. The ft[0, 0] pixel contains the mean of the signal. So the ft[1, 0] corresponds to a sinusoid with one cycle over the entire signal in the rows of the starting image. Here are is the starting image using following code: plt.pcolormesh(signal_time_lon); plt.colorbar(); plt.axis('tight') Here is result using following code: ft = np.fft.rfft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log1p(mgft) plt.pcolormesh(log_ps); plt.colorbar(); plt.axis('tight') It may not be clear in the image but it is only every second row that contains completely zeros. Every tenth pixel (log_ps[10, 0]) is a high value. The other pixels (log_ps[2, 0], log_ps[4, 0] etc) have very low values.

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  • How does this Singleton-like web class persists session data, even though session is not updated in

    - by Micah Burnett
    Ok, I've got this singleton-like web class which uses session to maintain state. I initially thought I was going to have to manipulate the session variables on each "set" so that the new values were updated in the session. However I tried using it as-is, and somehow, it remembers state. For example, if run this code on one page: UserContext.Current.User.FirstName = "Micah"; And run this code in a different browser tab, FirstName is displayed correctly: Response.Write(UserContext.Current.User.FirstName); Can someone tell me (prove) how this data is getting persisted in the session? Here is the class: using System; using System.Collections.Generic; using System.Linq; using System.Web; public class UserContext { private UserContext() { } public static UserContext Current { get { if (System.Web.HttpContext.Current.Session["UserContext"] == null) { UserContext uc = new UserContext(); uc.User = new User(); System.Web.HttpContext.Current.Session["UserContext"] = uc; } return (UserContext)System.Web.HttpContext.Current.Session["UserContext"]; } } private string HospitalField; public string Hospital { get { return HospitalField; } set { HospitalField = value; ContractField = null; ModelType = null; } } private string ContractField; public string Contract { get { return ContractField; } set { ContractField = value; ModelType = string.Empty; } } private string ModelTypeField; public string ModelType { get { return ModelTypeField; } set { ModelTypeField = value; } } private User UserField; public User User { get { return UserField; } set { UserField = value; } } public void DoSomething() { } } public class User { public int UserId { get; set; } public string FirstName { get; set; } } I added this to a watch, and can see that the session variable is definitely being set somewhere: (UserContext)System.Web.HttpContext.Current.Session["UserContext"]; As soon as a setter is called the Session var is immediately updated: set { HospitalField = value; //<--- here ContractField = null; ModelType = null; }

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  • What is causing this SQL 2005 Primary Key Deadlock between two real-time bulk upserts?

    - by skimania
    Here's the scenario: I've got a table called MarketDataCurrent (MDC) that has live updating stock prices. I've got one process called 'LiveFeed' which reads prices streaming from the wire, queues up inserts, and uses a 'bulk upload to temp table then insert/update to MDC table.' (BulkUpsert) I've got another process which then reads this data, computes other data, and then saves the results back into the same table, using a similar BulkUpsert stored proc. Thirdly, there are a multitude of users running a C# Gui polling the MDC table and reading updates from it. Now, during the day when the data is changing rapidly, things run pretty smoothly, but then, after market hours, we've recently started seeing an increasing number of Deadlock exceptions coming out of the database, nowadays we see 10-20 a day. The imporant thing to note here is that these happen when the values are NOT changing. Here's all the relevant info: Table Def: CREATE TABLE [dbo].[MarketDataCurrent]( [MDID] [int] NOT NULL, [LastUpdate] [datetime] NOT NULL, [Value] [float] NOT NULL, [Source] [varchar](20) NULL, CONSTRAINT [PK_MarketDataCurrent] PRIMARY KEY CLUSTERED ( [MDID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] - stackoverflow wont let me post images until my reputation goes up to 10, so i'll add them as soon as you bump me up, hopefully as a result of this question. ![alt text][1] [1]: http://farm5.static.flickr.com/4049/4690759452_6b94ff7b34.jpg I've got a Sql Profiler Trace Running, catching the deadlocks, and here's what all the graphs look like. stackoverflow wont let me post images until my reputation goes up to 10, so i'll add them as soon as you bump me up, hopefully as a result of this question. ![alt text][2] [2]: http://farm5.static.flickr.com/4035/4690125231_78d84c9e15_b.jpg Process 258 is called the following 'BulkUpsert' stored proc, repeatedly, while 73 is calling the next one: ALTER proc [dbo].[MarketDataCurrent_BulkUpload] @updateTime datetime, @source varchar(10) as begin transaction update c with (rowlock) set LastUpdate = getdate(), Value = t.Value, Source = @source from MarketDataCurrent c INNER JOIN #MDTUP t ON c.MDID = t.mdid where c.lastUpdate < @updateTime and c.mdid not in (select mdid from MarketData where LiveFeedTicker is not null and PriceSource like 'LiveFeed.%') and c.value <> t.value insert into MarketDataCurrent with (rowlock) select MDID, getdate(), Value, @source from #MDTUP where mdid not in (select mdid from MarketDataCurrent with (nolock)) and mdid not in (select mdid from MarketData where LiveFeedTicker is not null and PriceSource like 'LiveFeed.%') commit And the other one: ALTER PROCEDURE [dbo].[MarketDataCurrent_LiveFeedUpload] AS begin transaction -- Update existing mdid UPDATE c WITH (ROWLOCK) SET LastUpdate = t.LastUpdate, Value = t.Value, Source = t.Source FROM MarketDataCurrent c INNER JOIN #TEMPTABLE2 t ON c.MDID = t.mdid; -- Insert new MDID INSERT INTO MarketDataCurrent with (ROWLOCK) SELECT * FROM #TEMPTABLE2 WHERE MDID NOT IN (SELECT MDID FROM MarketDataCurrent with (NOLOCK)) -- Clean up the temp table DELETE #TEMPTABLE2 commit To clarify, those Temp Tables are being created by the C# code on the same connection and are populated using the C# SqlBulkCopy class. To me it looks like it's deadlocking on the PK of the table, so I tried removing that PK and switching to a Unique Constraint instead but that increased the number of deadlocks 10-fold. I'm totally lost as to what to do about this situation and am open to just about any suggestion. HELP!!

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  • current location too slow for view

    - by Christian
    Hi, I make an App with a Map in the App and a button to change to the google.Map-App. The code for my position is: -(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { float avgAccuracy = (newLocation.verticalAccuracy + newLocation.horizontalAccuracy)/2.0; if (avgAccuracy < 500) { [locationManager stopUpdatingLocation]; locationManager.delegate = nil; } storedLocation = [newLocation coordinate]; The code for the view is: - (void)viewDidLoad { [super viewDidLoad]; UIImage *image = [UIImage imageNamed: @"LogoNavBar.png"]; UIImageView *imageview = [[UIImageView alloc] initWithImage: image]; UIBarButtonItem *button = [[UIBarButtonItem alloc] initWithCustomView: imageview]; self.navigationItem.rightBarButtonItem = button; [imageview release]; [button release]; locationManager=[[CLLocationManager alloc] init]; locationManager.delegate = self; locationManager.desiredAccuracy = kCLLocationAccuracyBest; locationManager.distanceFilter = kCLDistanceFilterNone; [locationManager startUpdatingLocation]; mapView.showsUserLocation = YES; NSLog(@"storedLocation-latitude für MKregion: %f", storedLocation.latitude); MKCoordinateRegion region; region.center.latitude = (storedLocation.latitude + 45.58058)/2.0; region.center.longitude = (storedLocation.longitude - 0.546835)/2.0; region.span.latitudeDelta = ABS(storedLocation.latitude - 45.58058); region.span.longitudeDelta = ABS(storedLocation.longitude + 0.546835); [mapView setRegion:region animated:TRUE]; MKCoordinateRegion hotel; hotel.center.latitude = 45.58058; hotel.center.longitude = -0.546835; HotelPositionMarker* marker = [[HotelPositionMarker alloc] initWithCoordinate:hotel.center]; [mapView addAnnotation:marker]; [marker release]; } My problem: when the "viewDidLoad" start, the "storedLocation" is still 0.0000 it takes a bit longer to get the own position than to start the view. The Log for the "storedLocation" in the "viewDidLoad"-section is 0 while the Log of the "storedLocation" in the "-(IBAction)" when the map is visible contains the right values. How can I manage it to have my coordinates before the view load? I need them to center the view concerning the own position and the position given by me. MKCoordinateRegion region; region.center.latitude = (storedLocation.latitude + 45.58058)/2.0; region.center.longitude = (storedLocation.longitude - 0.546835)/2.0; region.span.latitudeDelta = ABS(storedLocation.latitude - 45.58058); region.span.longitudeDelta = ABS(storedLocation.longitude + 0.546835); [mapView setRegion:region animated:TRUE];

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  • Opinion on "loop invariants", and are these frequently used in the industry?

    - by Michael Aaron Safyan
    I was thinking back to my freshman year at college (five years ago) when I took an exam to place-out of intro-level computer science. There was a question about loop invariants, and I was wondering if loop invariants are really necessary in this case or if the question was simply a bad example... the question was to write an iterative definition for a factorial function, and then to prove that the function was correct. The code that I provided for the factorial function was as follows: public static int factorial(int x) { if ( x < 0 ){ throw new IllegalArgumentException("Parameter must be = 0"); }else if ( x == 0 ){ return 1; }else{ int result = 1; for ( int i = 1; i <= x; i++ ){ result*=i; } return result; } } My own proof of correctness was a proof by cases, and in each I asserted that it was correct by definition (x! is undefined for negative values, 0! is 1, and x! is 1*2*3...*x for a positive value of x). The professor wanted me to prove the loop using a loop invariant; however, my argument was that it was correct "by definition", because the definition of "x!" for a positive integer x is "the product of the integers from 1... x", and the for-loop in the else clause is simply a literal translation of this definition. Is a loop invariant really needed as a proof of correctness in this case? How complicated must a loop be before a loop invariant (and proper initialization and termination conditions) become necessary for a proof of correctness? Additionally, I was wondering... how often are such formal proofs used in the industry? I have found that about half of my courses are very theoretical and proof-heavy and about half are very implementation and coding-heavy, without any formal or theoretical material. How much do these overlap in practice? If you do use proofs in the industry, when do you apply them (always, only if it's complicated, rarely, never)?

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  • Persistent (purely functional) Red-Black trees on disk performance

    - by Waneck
    I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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  • Serious Memory Clash: Variables clashing in C

    - by Soham
    int main(int argc, char*argv[]) { Message* newMessage; Asset* Check; //manipulation and initialization of Check, so that it holds proper values. newMessage = parser("N,2376,01/02/2011 09:15:01.342,JPASSOCIAT FUTSTK 24FEB2011,B,84.05,2000,0,0",newMessage); // MessageProcess(newMessage,AssetMap); printf("LAST TRADE ADDRESS %p LAST TRADE TIME %s\n",Check->TradeBook,Check->Time); } Message* parser(char *message,Message* new_Message) { char a[9][256]; char* tmp =message; bool inQuote=0; int counter=0; int counter2=0; new_Message = (Message*)malloc(sizeof(Message)); while(*tmp!='\0') { switch(*tmp) { case ',': if(!inQuote) { a[counter][counter2]='\0'; counter++; counter2=0; } break; case '"': inQuote=!inQuote; break; default: a[counter][counter2]=*tmp; counter2++; break; } tmp++; } a[counter][counter2]='\0'; new_Message->type = *a[0]; new_Message->Time = &a[2][11]; new_Message->asset = a[3]; if(*a[4]=='S') new_Message->BS = 0; else new_Message->BS = 1; new_Message->price1=atof(a[5]); new_Message->shares1=atol(a[6]); new_Message->price2=atof(a[7]); new_Message->shares2=atol(a[8]); new_Message->idNum = atoi(a[1]); return(new_Message); } Here there is a serious memory clash, in two variables of different scope. I have investigated using gdb and it seems the address of new_Message->Time is equalling to the address of Check->Time. They both are structures of different types I am trying to resolve this issue, because, when parser changes the value of new_Message->Time it manipulates the contents of Check-Time Please do suggest how to solve this problem. I have lost(spent) around 10 hours and counting to resolve this issue, and tons of hair. Soham

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  • String manipulation in Linux kernel module

    - by user577066
    I am having a hard time in manipulating strings while writing module for linux. My problem is that I have a int Array[10] with different values in it. I need to produce a string to be able send to the buffer in my_read procedure. If my array is {0,1,112,20,4,0,0,0,0,0} then my output should be: 0:(0) 1:-(1) 2:-------------------------------------------------------------------------------------------------------(112) 3:--------------------(20) 4:----(4) 5:(0) 6:(0) 7:(0) 8:(0) 9:(0) when I try to place the above strings in char[] arrays some how weird characters end up there here is the code int my_read (char *page, char **start, off_t off, int count, int *eof, void *data) { int len; if (off > 0){ *eof =1; return 0; } /* get process tree */ int task_dep=0; /* depth of a task from INIT*/ get_task_tree(&init_task,task_dep); char tmp[1024]; char A[ProcPerDepth[0]],B[ProcPerDepth[1]],C[ProcPerDepth[2]],D[ProcPerDepth[3]],E[ProcPerDepth[4]],F[ProcPerDepth[5]],G[ProcPerDepth[6]],H[ProcPerDepth[7]],I[ProcPerDepth[8]],J[ProcPerDepth[9]]; int i=0; for (i=0;i<1024;i++){ tmp[i]='\0';} memset(A, '\0', sizeof(A));memset(B, '\0', sizeof(B));memset(C, '\0', sizeof(C)); memset(D, '\0', sizeof(D));memset(E, '\0', sizeof(E));memset(F, '\0', sizeof(F)); memset(G, '\0', sizeof(G));memset(H, '\0', sizeof(H));memset(I, '\0', sizeof(I));memset(J, '\0', sizeof(J)); printk("A:%s\nB:%s\nC:%s\nD:%s\nE:%s\nF:%s\nG:%s\nH:%s\nI:%s\nJ:%s\n",A,B,C,D,E,F,G,H,I,J); memset(A,'-',sizeof(A)); memset(B,'-',sizeof(B)); memset(C,'-',sizeof(C)); memset(D,'-',sizeof(D)); memset(E,'-',sizeof(E)); memset(F,'-',sizeof(F)); memset(G,'-',sizeof(G)); memset(H,'-',sizeof(H)); memset(I,'-',sizeof(I)); memset(J,'-',sizeof(J)); printk("A:%s\nB:%s\nC:%s\nD:%s\nE:%s\nF:%s\nG:%s\nH:%s\nI:%s\nJ:%\n",A,B,C,D,E,F,G,H,I,J); len = sprintf(page,"0:%s(%d)\n1:%s(%d)\n2:%s(%d)\n3:%s(%d)\n4:%s(%d)\n5:%s(%d)\n6:%s(%d)\n7:%s(%d)\n8:%s(%d)\n9:%s(%d)\n",A,ProcPerDepth[0],B,ProcPerDepth[1],C,ProcPerDepth[2],D,ProcPerDepth[3],E,ProcPerDepth[4],F,ProcPerDepth[5],G,ProcPerDepth[6],H,ProcPerDepth[7],I,ProcPerDepth[8],J,ProcPerDepth[9]); return len; }

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