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• Workaround for GNU Make 3.80 eval bug

  - by bengineerd

  I'm trying to create a generic build template for my Makefiles, kind of like they discuss in the eval documentation. I've run into a known bug with GNU Make 3.80. When $(eval) evaluates a line that is over 193 characters, Make crashes with a "Virtual Memory Exhausted" error. The code I have that causes the issue looks like this. SRC_DIR = ./src/ PROG_NAME = test define PROGRAM_template $(1)_SRC_DIR = $$(SRC_DIR)$(1)/ $(1)_SRC_FILES = $$(wildcard $$($(1)_SRC_DIR)*.c) $(1)_OBJ_FILES = $$($(1)_SRC_FILES):.c=.o) $$($(1)_OBJ_FILES) : $$($(1)_SRC_FILES) # This is the problem line endef $(eval $(call PROGRAM_template,$(PROG_NAME))) When I run this Makefile, I get gmake: *** virtual memory exhausted. Stop. The expected output is that all .c files in ./src/test/ get compiled into .o files (via an implicit rule). The problem is that $$($(1)_SRC_FILES) and $$($(1)_OBJ_FILES) are together over 193 characters long (if there are enough source files). I have tried running the make file on a directory where there is only 2 .c files, and it works fine. It's only when there are many .c files in the SRC directory that I get the error. I know that GNU Make 3.81 fixes this bug. Unfortunately I do not have the authority or ability to install the newer version on the system I'm working on. I'm stuck with 3.80. So, is there some workaround? Maybe split $$($(1)_SRC_FILES) up and declare each dependency individually within the eval?

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• Pros and cons of making database IDs consistent and "readable"

  - by gmale

  Question Is it a good rule of thumb for database IDs to be "meaningless?" Conversely, are there significant benefits from having IDs structured in a way where they can be recognized at a glance? What are the pros and cons? Background I just had a debate with my coworkers about the consistency of the IDs in our database. We have a data-driven application that leverages spring so that we rarely ever have to change code. That means, if there's a problem, a data change is usually the solution. My argument was that by making IDs consistent and readable, we save ourselves significant time and headaches, long term. Once the IDs are set, they don't have to change often and if done right, future changes won't be difficult. My coworkers position was that IDs should never matter. Encoding information into the ID violates DB design policies and keeping them orderly requires extra work that, "we don't have time for." I can't find anything online to support either position. So I'm turning to all the gurus here at SA! Example Imagine this simplified list of database records representing food in a grocery store, the first set represents data that has meaning encoded in the IDs, while the second does not: ID's with meaning: Type 1 Fruit 2 Veggie Product 101 Apple 102 Banana 103 Orange 201 Lettuce 202 Onion 203 Carrot Location 41 Aisle four top shelf 42 Aisle four bottom shelf 51 Aisle five top shelf 52 Aisle five bottom shelf ProductLocation 10141 Apple on aisle four top shelf 10241 Banana on aisle four top shelf //just by reading the ids, it's easy to recongnize that these are both Fruit on Aisle 4 ID's without meaning: Type 1 Fruit 2 Veggie Product 1 Apple 2 Banana 3 Orange 4 Lettuce 5 Onion 6 Carrot Location 1 Aisle four top shelf 2 Aisle four bottom shelf 3 Aisle five top shelf 4 Aisle five bottom shelf ProductLocation 1 Apple on aisle four top shelf 2 Banana on aisle four top shelf //given the IDs, it's harder to see that these are both fruit on aisle 4 Summary What are the pros and cons of keeping IDs readable and consistent? Which approach do you generally prefer and why? Is there an accepted industry best-practice?

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• Separation of multipage tiff with compression "CCITT T.6" very slow

  - by Alex

  I need to separate multiframe tiff files, and use the following method: public static Image[] GetFrames(Image sourceImage) { Guid objGuid = sourceImage.FrameDimensionsList[0]; FrameDimension objDimension = new FrameDimension(objGuid); int frameCount = sourceImage.GetFrameCount(objDimension); Image[] images = new Image[frameCount]; for (int i = 0; i < frameCount; i++) { MemoryStream ms = new MemoryStream(); sourceImage.SelectActiveFrame(objDimension, i); sourceImage.Save(ms, ImageFormat.Tiff); images[i] = Image.FromStream(ms); } return images; } It works fine, but if the source image was encoded using the CCITT T.6 compression, separating a 20-frame-file takes up to 15 seconds on my 2,5ghz CPU.(edit: One core is at 100% during the process) When saving the images afterward to a single file using standard compression (LZW), the separation time of the LZW-file is under 1 second. Saving with CCITT compression also takes very long. Is there a way to speed up the process?

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• xp_smtp_sendmail blank space added to html randomly

  - by Igor Timofeyev

  I have a proc where I generate small html doc with a link and send it out via xp_smtp_sendmail proc. Link is generated based on query results and is long. This works in most cases. However, sometimes the link gets broken due to spaces being inserted into querystring variable names, i.e. &Na me=John. This might vary between email clients(same link works in Gmail, but might not work in comcast due to spaces. The space seems to be randomly inserted, so in each broken email link space might break other querystring variables. When I do PRINT from proc the link is clean, no spaces. Here's my sample of the mail proc being executed within main proc(that gets query results and generates html for @Message). The space seems to be inserted regardless of whether I encode the url or not. Thank you in advance for your help. I can send a cleaner version of the code if it's not displayed properly here. ....query results above SET @Message = NULL SET @Message = @Message + + '<br/>Dear ' + @FirstName + ' ' + @LastName + ',' + '<br/><br/>Recently you took "' + @Title + '". ' + 'In response to the question "What is it?" ' + 'you responded "' + @Response + '".' + '<br/><br/>Following up on previous mailing' + '<br/><br/>Please click on the link below' + '<br/><br/><a href="' + @Link + '">Please click here</a>' + '<br/><br/>plain text' + '<br/><br/>plain text,' + '<br/><br/>plain text<br/> plain text<br/> plain text<br/> plain text<br/> plain text<br/> plain text EXEC @rc = master.dbo.xp_smtp_sendmail @FROM = '[email protected]', @FROM_NAME = 'Any User', @TO = @Email, @priority = N'NORMAL', @subject = N'My email', @message = @Message, @messagefile = N'', @type = N'text/html', @attachment = N'', @attachments = N'', @codepage = 0, @server = 'smtp.server.any'

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• Static linking in Qt --> link errors in VS 2008

  - by ChruS

  Today I dediced to make static linking in Qt. I used Qt4 with Visual Studio and static C runtime article. The 3rd step took quite a long time. When it was finished I opened my project in VS 2008, made Build->Clean Solution and try to Release. Unfortunately I got link errors: warning LNK4098: defaultlib 'libcmt.lib' conflicts with use of other libs; use /NODEFAULTLIB:library error LNK2019: unresolved external symbol "private: static struct QString::Data QString::shared_null" (?shared_null@QString@@0UData@1@A) referenced in function "public: __thiscall QString::QString(void)" (??0QString@@QAE@XZ) error LNK2019: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) referenced in function "public: __thiscall QByteArray::QByteArray(void)" (??0QByteArray@@QAE@XZ) error LNK2001: unresolved external symbol "private: static struct QByteArray::Data QByteArray::shared_null" (?shared_null@QByteArray@@0UData@1@A) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2001: unresolved external symbol "public: static struct QMetaObject const QDialog::staticMetaObject" (?staticMetaObject@QDialog@@2UQMetaObject@@B) error LNK2019: unresolved external symbol "public: static enum QSysInfo::WinVersion const QSysInfo::WindowsVersion" (?WindowsVersion@QSysInfo@@2W4WinVersion@1@B) referenced in function _WinMain@16 What i did wrong? Help to fix this pls.

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• Jetty startup delay

  - by Tauren

  I'm trying to figure out what would be causing a 1 minute delay in the startup of Jetty. Is it a configuration problem, my application, or something else? I have Jetty 7 (jetty-7.0.1.v20091125 25 November 2009) installed on a server and I deploy a 45MB ROOT.war file into the webapps directory. This is the only webapp configured in Jetty. I then start Jetty with the command: java -DSTOP.PORT=8079 -DSTOP.KEY=mystopkey -Denv=stage -jar start.jar etc/jetty-logging.xml etc/jetty.xml & I get two lines of output right after doing this: 2010-03-07 14:20:06.642:INFO::Logging to StdErrLog::DEBUG=false via org.eclipse.jetty.util.log.StdErrLog 2010-03-07 14:20:06.710:INFO::Redirecting stderr/stdout to /home/zing/jetty-distribution-7.0.1.v20091125/logs/2010_03_07.stderrout.log When I press the enter key, I get my command prompt back. Looking at the log file (logs/2010_03_07.stderrout.log), I see the following at the beginning: 2010-03-07 14:08:50.396:INFO::jetty-7.0.1.v20091125 2010-03-07 14:08:50.495:INFO::Extract jar:file:/home/zing/jetty-distribution-7.0.1.v20091125/webapps/ROOT.war!/ to /tmp/Jetty_0_0_0_0_8080_ROOT.war___.8te0nm/webapp 2010-03-07 14:08:52.599:INFO::NO JSP Support for , did not find org.apache.jasper.servlet.JspServlet 2010-03-07 14:09:51.379:INFO::Set web app root system property: 'webapp.root' = [/tmp/Jetty_0_0_0_0_8080_ROOT.war___.8te0nm/webapp] 2010-03-07 14:09:51.585:INFO::Initializing Spring root WebApplicationContext INFO - ContextLoader - Root WebApplicationContext: initialization started INFO - XmlWebApplicationContext - Refreshing Root WebApplicationContext: startup date [Sun Mar 07 14:09:51 PST 2010]; root of context hierarchy ... Notice the 1 minute long pause between the 3rd and 4th lines. What is Jetty doing at this point? What other things could be going on? It doesn't even look like it has started my Spring initialization yet. Note that I checked my /tmp directory to see if it was simply the time to unpack my war file, but the file had been completely unpacked even at the start of this 1 minute delay.

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• git branch naming best practices

  - by skiphoppy

  I've been using a local git repository interacting with my group's CVS repository for several months, now. I've made an almost neurotic number of branches, most of which have thankfully merged back into my trunk. But naming is starting to become an issue. If I have a task easily named with a simple label, but I accomplish it in three stages which each include their own branch and merge situation, then I can repeat the branch name each time, but that makes the history a little confusing. If I get more specific in the names, with a separate description for each stage, then the branch names start to get long and unwieldy. I did learn looking through old threads here that I could start naming branches with a / in the name, i.e., topic/task, or something like that. I may start doing that and seeing if it helps keep things better organized. What are some best practices for naming git branches? Edit: Nobody has actually suggested any naming conventions. I do delete branches when I'm done with them. I just happen to have several around due to management constantly adjusting my priorities. :) As an example of why I might need more than one branch on a task, suppose I need to commit the first discrete milestone in the task to the group's CVS repository. At that point, due to my imperfect interaction with CVS, I would perform that commit and then kill that branch. (I've seen too much weirdness interacting with CVS if I try to continue to use the same branch at that point.)

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• PHP preg_replace - Don't match with h1 tags

  - by James

  Hi there. I am using preg_replace to add a link to keywords if they are found within a long HTML string. I don't want to add a link if the keyword is found within h1 tags or strong tags. The below regex nearly works and basically says (I think): If the keyword is not immediately wrapped by either a h1 tag or a strong tag then replace with the keyword that was matched, as a bolded link to google. $result = preg_replace('%(?!<h1>)(?!<strong>)\b(bobs widgets)\b(?!<\/strong>)(?!<\/h1>)%i','<a href="http://www.google.com"><strong>$1</strong></a>', $result, -1); (the reason I don't want to match if in strong tags is because I am recursing through a lot of keywords so don't want to link an already linked keyword on subsequent passes) the above works fine and won't match: <h1>bobs widgets</h1> It will however match the keyword in the following text, because the h1 tag isn't immediately either side of the keyword: <h1>Here are bobs widgets for sale</h1> I need to make the spaces either side optional and have tried adding \s* but that doesn't get me anywhere. I'd be very grateful for a push in the right direction here.

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• OpenNETCF.Stopwatch -> only ticks changing, not Elapsed

  - by pithyless

  I've been trying to track down a bug I thought was thread-related, but I think instead there is an issue with the way I am using OpenNETCF's Stopwatch. I am using OpenNETCF.IoC in my application, but for the sake of simplicity I moved the following code directly into a view: public partial class WorkoutView : SmartPart { ... private Stopwatch stopwatch; public WorkoutView() { ... stopwatch = new Stopwatch(); stopwatch.Reset(); stopwatch.Start(); WorkoutDisplayTimer = new Timer(); WorkoutDisplayTimer.Interval = 500; WorkoutDisplayTimer.Tick += new EventHandler(WorkoutDisplayTimer_Tick); WorkoutDisplayTimer.Enabled = true; } void WorkoutDisplayTimer_Tick(object sender, EventArgs e) { ... stopwatch.Stop(); lbl.Text = stopwatch.ElapsedTicks.ToString() + "NOT WORKING: " + stopwatch.Elapsed.ToString(); stopwatch.Start(); } ... } Long story short, looking at stopwatch in the debugger, the only values that ever get updated are ElapsedTicks, mElapsed, mStartPerfCount. Everything else is always zero. Is this expected behavior? Do I need to call an additional method to have the stopwatch calculate the Elapsed struct? (Note: stopwatch.ElapsedMilliseconds is also zero)

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• JSF:Resourcebundle Problem with Internationalization

  - by Sven

  I implemented internationalization like in that tutorial! When I change the language in my app. It works. But only until the next request happens. Then language settings are reset to my standard language -.- What am I missing here: LanguageBean.java @ManagedBean(name="language") @SessionScoped public class LanguageBean implements Serializable{ private static final long serialVersionUID = 1L; private String localeCode; private static Map<String,Object> countries; static{ countries = new LinkedHashMap<String,Object>(); countries.put("Deutsch", Locale.GERMAN); //label, value countries.put("English", Locale.ENGLISH); } public Map<String, Object> getCountriesInMap() { return countries; } public String getLocaleCode() { return localeCode; } public void setLocaleCode(String localeCode) { this.localeCode = localeCode; } //value change event listener public void countryLocaleCodeChanged(ValueChangeEvent e){ String newLocaleValue = e.getNewValue().toString(); //loop country map to compare the locale code for (Map.Entry<String, Object> entry : countries.entrySet()) { if(entry.getValue().toString().equals(newLocaleValue)){ FacesContext.getCurrentInstance() .getViewRoot().setLocale((Locale)entry.getValue()); } } } } my facelets template: <h:selectOneMenu value="#{language.localeCode}" onchange="submit()" valueChangeListener="#{language.countryLocaleCodeChanged}"> <f:selectItems value="#{language.countriesInMap}" /> </h:selectOneMenu> faces-config: <application> <locale-config> <default-locale>de</default-locale> </locale-config> <resource-bundle> <base-name>org.dhbw.stg.wwi2008c.mopro.ui.text</base-name> <var>msg</var> </resource-bundle> </application>

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• Problem setText UITextView

  - by Mat

  Hi i have a problem. I have 2 viewcontroller, in the first there is a mapView that implements the function "calloutAccessoryControlTapped" to tap a button on an annotation on the mapView; in the second there is just a UITextView. I want to change the text of the UITextView (and show the SecondViewController) in the second controller once the button on annotation is clicked; here is my code (FirstViewController) Header @interface FirstViewController<MKMapViewDelegate>{ IBOutlet MKMapView *mapView; SecondViewController *secondV;} @end Implementation @implementation FirstViewController - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control{ secondV = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil]; NSString *myS = @"some text here"; [secondV.myTextView setText:myS]; //Switch from this to the secondview [self presentModalViewController:secondV animated:YES]; @end (SecondViewController) Header @interface SecondViewController{ IBOutlet UITextView *myTextView; } @property(nonatomic, retain)UITextView *postitTextView; - (IBAction)backToMAp; - (void)setText:(NSString *)string; @end Implementation @implementation SecondViewController - (IBAction)backToMAp{ //Back To First View; [self dismissModalViewControllerAnimated:YES];} - (void)setText:(NSString *)string{ myTextView.text = string;} In this code when i tap on the button ([self presentModalViewController:secondV animated:YES];) on annotation the first time the second view show up but the text of UITextView don't change, when i back on the FirstView ([self dismissModalViewControllerAnimated:YES];) and then again tap the button to switch again to secondView the text of UITextView change..... Sorry for long thread and for my bad english!! Thank you stack!

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• Wrapping mailmessage headers in .net for Sendgrid

  - by mickyjtwin

  Am using SendGrid for some email notifications, specifically utilising their SMTP API's. While they have PHP examples, c# is not so helpful. Essentially, a json string is built that contains the to email addresses, and other custom filters etc, which is then added to a MailMessage header to send. // json string example {"to":["[email protected]", [email protected]", "", ""],"sub":{"<name>":["Name1", Name2"]}} MailMessage m = new MailMessage("[email protected]", "[email protected]"); m.Headers.Add("X-SMTPAPI", jsonString); The problem I am having is that for some MTA's, headers can only be 1000 characters long, and also quoted-principle encoding required only 76 character per line. In their php example, they are splitting the string and adding a linebreak (\n) every 72 characters. While I am doing this in .NET, I am receiving a invalid character exception. After some digging, it seems that pre-.NET4.0 Beta2 MailMessage will not process CLLR characters. Sengrid support is not proving helpful, and looking at ways to make this work?

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• Setting specified flags before serializing objects

  - by Bernard

  We have a schema that we serialize and deserialize into an object hierarchy. Some elements are optional in the schema. The xsd tool creates a cs file that inserts a property for each optional element. This property ends in "Specified", i.e. nameSpecified tells the serializer and deserializer to include the optional "name" element when processing. I'm trying to write a method that rips through the object hierarchy using reflection and if a property has a value and it has a "Specified" corresponding property, I want to set the Specified property to true. I've tried to do this using reflection, ie. foreach(PropertyInfo p in MyObject.GetType().GetNestedTypes().GetType().GetProperties() { if the field name ends in Specified check if there is a field with the same name without Specied. If there is, and that field name has a value, then set the field name that ends in Specified to true; } Its the middle bit that I'm having trouble with. I preferably don't want to rip through the hierarchy and create a list of properties ending in Specified and then rip through it again to see if the corresponding name without the ending "Specified" exists and then check if it has a value. And the rip through it again to update all the Specified fields to true. Seems a bit of a long way around :( Anyone have any bright ideas?

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• accelerating Wheel - psychtoolbox in matlab

  - by ariel

  Hi I am trying to write a code that will show an acceleration wheel. as long as the user press 'a' the wheel should accelerate counterclock wize. the thing is that it turn in the right direction but it doesn't accelerate. This is the code I am using . PTB-3 windows XP. img=imread('c:\images.jpg'); [yimg,ximg,z]=size(img); rot_spd = 1; larrow = KbName('a'); % modify this for Windows rarrow = KbName('b'); [w,rect]=Screen('OpenWindow',0,[0 0 0]); sx = 400; % desired x-size of image (pixels) sy = yimg*sx/ximg; % desired y-size--keep proportional t = Screen('MakeTexture',w,img); bdown=0; th = 0; % initial rotation angle (degrees) HideCursor while(~any(bdown)) % exit loop if mouse button is pressed [x,y,bdown]=GetMouse; [keyisdown,secs,keycode] = KbCheck; if(keycode(larrow)) th = th - rot_spd-1; % accelerate counterclockwise th end if(keycode(rarrow)) th = th + rot_spd+1; % accelerate clockwise th end destrect=[x-sx/2,y-sy/2,x+sx/2,y+sy/2]; Screen('DrawTexture',w,t,[],destrect,th); Screen('Flip',w); end Screen('Close',w) ShowCursor If anyone has an odea why it doesn't accelerate I'd appriciate it very much. Ariel

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• Flash vs. Ajax Abilities

  - by Alex

  Hey everyone. I want to develop an application that does a bunch of cool stuff. The first thing that I need in it is to get information about the page a person is browsing. With that said, I need for example to know how long a user stayed in a page and where was the scrollbar. While getting that data, It's all saved to a database. The thing is, I prefer doing that in Flash [although I have no experience in it] over Ajax since I want to hide the code - which as far as I know not possible in Javascript/Ajax. So, can I do all that in Flash? - Read the content of the page, get the status of the scroll bar.. Plus, I then need to go threw the gathered information that is saved in the database. Since there could be many calculations i thought C++ .Net is better than PHP [which I know better]. Is that all possible or am I just crazy? :) Thanks ahead.

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• Difference in performance between Stax and DOM parsing

  - by Fazal

  I have been using DOM for a long time and as such DOM parsing performance wise has been pretty good. Even when dealing with XML of about 4-7 MB the parsing has been fast. The issue we face with DOM is the memory footprint which become huge as soon as we start dealing with large XMLs. Lately I tried moving to Stax (Streaming parsers for XML) which are supposed top be second generation parsers (reading about Stax it said its the fastest parser now). When I tried stax parser for large XML for about 4MB memory footprint definitely reduced drastically but time take to parse entire XML and create java object out of it increased almost by 5 times over DOM. I used sjsxp.jar implementation of Stax. I can deuce to some extent logically that performance may not be extremely good due to streaming nature of the parser but a reduction of 5 time (e.g. DOM takes about 8 seconds to build object for this XML, whereas Stax parsing took about 40 seconds on average) is definitely not going to be acceptable. Am I missing some point here completely as I am not able to come to terms with these performance numbers

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• How to avoid an HttpException due to timeout

  - by Dan

  I'm working on a website powered by .NET asp/C# code. The clients require that sessions have a 25 minute timeout. However, sometimes the site is used, and a user stays connected for long periods of time (longer than 25 mins). Session_End is triggered: protected void Session_End(Object sender, EventArgs e) { Hashtable trackingInformaiton = (Hashtable)Application["trackingInformation"]; trackingInformaiton.Remove(Session["trackingID"]); } The user returns some time later, but when they interact with the website, they get an error, and we get this email notification: User: Unauthenticated User Error: System.Web.HttpException Description: Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request... The telling part of the stack trace is System.Web.UI.Control.AddedControl. Apparently, the server has thrown away the session data, and is sending new data, but the client is trying to deal with old data. Hence the error that "the control tree into which viewstate is being loaded [doesn't] match the control tree that was used to save the viewstate during the prevoius request." So here's the question. How can I force instruct the user's browser to redirect to a "you're logged out" screen when the connection times out? (Is it something I should add to the Session_End method?)

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• Two strange efficiency problems in Mathematica

  - by Jess Riedel

  FIRST PROBLEM I have timed how long it takes to compute the following statements (where V[x] is a time-intensive function call): Alice = Table[V[i],{i,1,300},{1000}]; Bob = Table[Table[V[i],{i,1,300}],{1000}]^tr; Chris_pre = Table[V[i],{i,1,300}]; Chris = Table[Chris_pre,{1000}]^tr; Alice, Bob, and Chris are identical matricies computed 3 slightly different ways. I find that Chris is computed 1000 times faster than Alice and Bob. It is not surprising that Alice is computed 1000 times slower because, naively, the function V must be called 1000 more times than when Chris is computed. But it is very surprising that Bob is so slow, since he is computed identically to Chris except that Chris stores the intermediate step Chris_pre. Why does Bob evaluate so slowly? SECOND PROBLEM Suppose I want to compile a function in Mathematica of the form f(x)=x+y where "y" is a constant fixed at compile time (but which I prefer not to directly replace in the code with its numerical because I want to be able to easily change it). If y's actual value is y=7.3, and I define f1=Compile[{x},x+y] f2=Compile[{x},x+7.3] then f1 runs 50% slower than f2. How do I make Mathematica replace "y" with "7.3" when f1 is compiled, so that f1 runs as fast as f2? Many thanks!

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• Servlet/JSP Flow Control: Enums, Exceptions, or Something Else?

  - by Christopher Parker

  I recently inherited an application developed with bare servlets and JSPs (i.e.: no frameworks). I've been tasked with cleaning up the error-handling workflow. Currently, each <form> in the workflow submits to a servlet, and based on the result of the form submission, the servlet does one of two things: If everything is OK, the servlet either forwards or redirects to the next page in the workflow. If there's a problem, such as an invalid username or password, the servlet forwards to a page specific to the problem condition. For example, there are pages such as AccountDisabled.jsp, AccountExpired.jsp, AuthenticationFailed.jsp, SecurityQuestionIncorrect.jsp, etc. I need to redesign this system to centralize how problem conditions are handled. So far, I've considered two possible solutions: Exceptions Create an exception class specific to my needs, such as AuthException. Inherit from this class to be more specific when necessary (e.g.: InvalidUsernameException, InvalidPasswordException, AccountDisabledException, etc.). Whenever there's a problem condition, throw an exception specific to the condition. Catch all exceptions via web.xml and route them to the appropriate page(s) with the <error-page> tag. enums Adopt an error code approach, with an enum keeping track of the error code and description. The descriptions can be read from a resource bundle in the finished product. I'm leaning more toward the enum approach, as an authentication failure isn't really an "exceptional condition" and I don't see any benefit in adding clutter to the server logs. Plus, I'd just be replacing one maintenance headache with another. Instead of separate JSPs to maintain, I'd have separate Exception classes. I'm planning on implementing "error" handling in a servlet that I'm writing specifically for this purpose. I'm also going to eliminate all of the separate error pages, instead setting an error request attribute with the error message to display to the user and forwarding back to the referrer. Each target servlet (Logon, ChangePassword, AnswerProfileQuestions, etc.) would add an error code to the request and redirect to my new servlet in the event of a problem. My new servlet would look something like this: public enum Error { INVALID_PASSWORD(5000, "You have entered an invalid password."), ACCOUNT_DISABLED(5002, "Your account has been disabled."), SESSION_EXPIRED(5003, "Your session has expired. Please log in again."), INVALID_SECURITY_QUESTION(5004, "You have answered a security question incorrectly."); private final int code; private final String description; Error(int code, String description) { this.code = code; this.description = description; } public int getCode() { return code; } public String getDescription() { return description; } }; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String sendTo = "UnknownError.jsp"; String message = "An unknown error has occurred."; int errorCode = Integer.parseInt((String)request.getAttribute("errorCode"), 10); Error errors[] = Error.values(); Error error = null; for (int i = 0; error == null && i < errors.length; i++) { if (errors[i].getCode() == errorCode) { error = errors[i]; } } if (error != null) { sendTo = request.getHeader("referer"); message = error.getDescription(); } request.setAttribute("error", message); request.getRequestDispatcher(sendTo).forward(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } Being fairly inexperienced with Java EE (this is my first real exposure to JSPs and servlets), I'm sure there's something I'm missing, or my approach is suboptimal. Am I on the right track, or do I need to rethink my strategy?

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• Experience migrating legacy Cobol/PL1 to Java

  - by MadMurf

  ORIGINAL Q: I'm wondering if anyone has had experience of migrating a large Cobol/PL1 codebase to Java? How automated was the process and how maintainable was the output? How did the move from transactional to OO work out? Any lessons learned along the way or resources/white papers that may be of benefit would be appreciated. EDIT 7/7: Certainly the NACA approach is interesting, the ability to continue making your BAU changes to the COBOL code right up to the point of releasing the JAVA version has merit for any organization. The argument for procedural Java in the same layout as the COBOL to give the coders a sense of comfort while familiarizing with the Java language is a valid argument for a large organisation with a large code base. As @Didier points out the $3mil annual saving gives scope for generous padding on any BAU changes going forward to refactor the code on an ongoing basis. As he puts it if you care about your people you find a way to keep them happy while gradually challenging them. The problem as I see it with the suggestion from @duffymo to Best to try and really understand the problem at its roots and re-express it as an object-oriented system is that if you have any BAU changes ongoing then during the LONG project lifetime of coding your new OO system you end up coding & testing changes on the double. That is a major benefit of the NACA approach. I've had some experience of migrating Client-Server applications to a web implementation and this was one of the major issues we encountered, constantly shifting requirements due to BAU changes. It made PM & scheduling a real challenge. Thanks to @hhafez who's experience is nicely put as "similar but slightly different" and has had a reasonably satisfactory experience of an automatic code migration from Ada to Java. Thanks @Didier for contributing, I'm still studying your approach and if I have any Q's I'll drop you a line.

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• DrScheme versus mzscheme: treatment of definitions

  - by speciousfool

  One long term project I have is working through all the exercises of SICP. I noticed something a bit odd with the most recent exercise. I am testing a Huffman encoding tree. When I execute the following code in DrScheme I get the expected result: (a d a b b c a) However, if I execute this same code in mzscheme by calling (load "2.67.scm") or by running mzscheme -f 2.67.scm, it reports: symbols: expected symbols as arguments, given: (leaf D 1) My question is: why? Is it because mzscheme and drscheme use different rules for loading program definitions? The program code is below. ;; Define an encoding tree and a sample message ;; Use the decode procedure to decode the message, and give the result. (define (make-leaf symbol weight) (list 'leaf symbol weight)) (define (leaf? object) (eq? (car object) 'leaf)) (define (symbol-leaf x) (cadr x)) (define (weight-leaf x) (caddr x)) (define (make-code-tree left right) (list left right (append (symbols left) (symbols right)) (+ (weight left) (weight right)))) (define (left-branch tree) (car tree)) (define (right-branch tree) (cadr tree)) (define (symbols tree) (if (leaf? tree) (list (symbol-leaf tree)) (caddr tree))) (define (weight tree) (if (leaf? tree) (weight-leaf tree) (cadddr tree))) (define (decode bits tree) (define (decode-1 bits current-branch) (if (null? bits) '() (let ((next-branch (choose-branch (car bits) current-branch))) (if (leaf? next-branch) (cons (symbol-leaf next-branch) (decode-1 (cdr bits) tree)) (decode-1 (cdr bits) next-branch))))) (decode-1 bits tree)) (define (choose-branch bit branch) (cond ((= bit 0) (left-branch branch)) ((= bit 1) (right-branch branch)) (else (error "bad bit -- CHOOSE-BRANCH" bit)))) (define (test s-exp) (display s-exp) (newline)) (define sample-tree (make-code-tree (make-leaf 'A 4) (make-code-tree (make-leaf 'B 2) (make-code-tree (make-leaf 'D 1) (make-leaf 'C 1))))) (define sample-message '(0 1 1 0 0 1 0 1 0 1 1 1 0)) (test (decode sample-message sample-tree))

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• Which CEP product to start with?

  - by Andreas

  Hi, I want to learn more on how to build CEP based applications. So I looked around and found several products (overview found here: http://rulecore.com/CEPblog/?page_id=47). But as there are quite a few at the moment, I don't know which is the best to start with. And overall I just would consider the one available for free. The rest is a bit to expensive for just private use ;) Esper is for free, but without Esper studio it seems quite tedious to develop a cep app. Streambase offers a free trial, but I couldn't find out how long you can use this (if only for a month, no that helpful for longer research). Oracle CEP suite seems quite complete, but in the cep scene - as far as I can see - it is the least recognized compared to Esper or Streambase. So do you have any hints on what is the best way to start with cep development? Is it worth to spent time on working through the oracle documenation or is it better to start with Esper or Streambase? Cheers, Andreas

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• javascript class calling XMLHttpRequest internally, then handling onreadystatechange

  - by Radu M

  this thing almost works: function myClass(url) { this.source = url; this.rq = null; this.someOtherProperty = "hello"; // open connection to the ajax server this.start = function() { if (window.XMLHttpRequest) { this.rq = new XMLHttpRequest(); if (this.rq.overrideMimeType) this.rq.overrideMimeType("text/xml"); } else this.rq = new ActiveXObject("Microsoft.XMLHTTP"); try { this.rq.onreadystatechange = connectionEvent; this.rq.open("GET", this.source, true); this.rq.send(null); this.state = 1; } catch (err) { // some error handler here } } function connectionEvent() { alert("i'm here"); alert("this doesnt work: " + this.someOtherProperty); } } // myClass so it's nothing more than having the XMLHttpRequest object as a member of my class, instead of globally defined, and invoking it in the traditional way. however, inside my connectionEvent callback function, the meaning of "this" is lost, even though the function itself is scoped inside myClass. i also made sure that the object that i instantiate from myClass is kept alive long enough (declared global in the script). in all the examples of using javascript classes that i saw, "this" was still available inside the inner functions. for me, it is not, even if i take my function outside and make it a myClass.prototype.connectionEvent. what am i doing wrong? thank you.

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• JavaScript To Clear Form Field On Submit Before Form Submission To Perl Script

  - by Russell C.

  We have a very long form that has a number of fields and 2 different submit buttons. When a user clicks the 1st submit button ("Photo Search") the form should POST and our script will do a search for matching photos based on what the user entered in the text input ("photo_search_text") next to the 1st submit button and reload the entire form with matching photos added to the form. Upon clicking the 2nd submit button ("Save Changes") at the end of the form, it should POST and our script should update the database with the information the user entered in the form. Unfortunately the layout of the form makes it impossible to separate it into 2 separate forms. I checked the entire form POST and unfortunately the submitted fields are identical to the perl script processing the form submission no matter which submit button is clicked so the perl script can't differentiate which action to perform based on which submit button is pushed. The only thing I can think of is to update the onclick action of the 2nd submit button so it clears the "photo_search_text" field before the form is submitted and then only perform a photo search if that fields has a value. Based on all this, my question is what does the JavaScript look that could clear out the "photo_search_text" field when someone clicks on the 2nd submit button? Here is what I've tried so far none of which has worked successfully: <input type="submit" name="submit" onclick="document.update-form.photo_search_text.value='';" value="Save Changes"> <input type="submit" name="submit" onsubmit="document.update-form.photo_search_text.value='';" value="Save Changes"> <input type="submit" name="submit" onclick="document.getElementById('photo_search_text')='';" value="Save Changes"> We also use JQuery on the site so if there is a way to do this with jQuery instead of plain JavaScript feel free to provide example code for that instead. Lastly, if there is another way to handle this that I'm not thinking of any and all suggestions would be welcome. Thanks in advance for your help!

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• JPA 2 Criteria API: why is isNull being ignored when in conjunction with equal?

  - by Vítor Souza

  I have the following entity class (ID inherited from PersistentObjectSupport class): @Entity public class AmbulanceDeactivation extends PersistentObjectSupport implements Serializable { private static final long serialVersionUID = 1L; @Temporal(TemporalType.DATE) @NotNull private Date beginDate; @Temporal(TemporalType.DATE) private Date endDate; @Size(max = 250) private String reason; @ManyToOne @NotNull private Ambulance ambulance; /* Get/set methods, etc. */ } If I do the following query using the Criteria API: CriteriaBuilder cb = em.getCriteriaBuilder(); CriteriaQuery<AmbulanceDeactivation> cq = cb.createQuery(AmbulanceDeactivation.class); Root<AmbulanceDeactivation> root = cq.from(AmbulanceDeactivation.class); EntityType<AmbulanceDeactivation> model = root.getModel(); cq.where(cb.isNull(root.get(model.getSingularAttribute("endDate", Date.class)))); return em.createQuery(cq).getResultList(); I get the following SQL printed in the log: FINE: SELECT ID, REASON, ENDDATE, UUID, BEGINDATE, VERSION, AMBULANCE_ID FROM AMBULANCEDEACTIVATION WHERE (ENDDATE IS NULL) However, if I change the where() line in the previous code to this one: cq.where(cb.isNull(root.get(model.getSingularAttribute("endDate", Date.class))), cb.equal(root.get(model.getSingularAttribute("ambulance", Ambulance.class)), ambulance)); I get the following SQL: FINE: SELECT ID, REASON, ENDDATE, UUID, BEGINDATE, VERSION, AMBULANCE_ID FROM AMBULANCEDEACTIVATION WHERE (AMBULANCE_ID = ?) That is, the isNull criterion is totally ignored. It is as if it wasn't even there (if I provide only the equal criterion to the where() method I get the same SQL printed). Why is that? Is it a bug or am I missing something?

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