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• Which to use, XMP or RDF?

  - by zotty

  What's the difference between RDF and XMP? From what I can tell, XMP is derived from RDF... so what does it offer that RDF doesn't? My particular situation is this: I've got some images which need tagging with details of how an experiment was performed, and what sort of data analysis has been performed on the images. A colleague of mine is pushing for XMP, but he's thinking of the images as photos - they're not really, they're just bits of data. From what I've seen (mainly by opening images in notepad++) the XMP data looks very similar to RDF - even so far as using RDF in the tag names (e.g. <rdf:Seq>). I'd like this data to be usable by other people who use similar instruments for similar experiments, so creating a mini standard (schema?) seems like the way to go. Apologies for the lack of fundemental understanding - I'm a Doctor, not a programmer! If it makes any difference, the language of choice will be C#. Edit for more information: First off, thanks for the excellent replies - thinking of XMP as a vocabulary for RDF makes things a lot clearer. The sort of data I'll be storing wont be avaliable in any of the pre-defined sets. It'll detail experimental set ups, locations and results. I think using RDF is the way to go.

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• Java For-Each Loop to Deal to multiple Hands

  - by qwertyRocker

  I'm trying to find a good way to 'deal' cards to 4 difference hands. System.out.println("Deal to 4 Hands: "); Hand hand1 = new Hand(); Hand hand2 = new Hand(); Hand hand3 = new Hand(); Hand hand4 = new Hand(); hand1.addSingleCard(Deck.deal()); hand2.addSingleCard(Deck.deal()); hand3.addSingleCard(Deck.deal()); hand4.addSingleCard(Deck.deal()); hand1.addSingleCard(Deck.deal()); hand2.addSingleCard(Deck.deal()); hand3.addSingleCard(Deck.deal()); hand4.addSingleCard(Deck.deal()); System.out.println("Cards left in deck: " + Deck.size()); System.out.println("Player 1's Hand: \n" + hand1.getHand()); System.out.println("Player 2's Hand: \n" + hand2.getHand()); System.out.println("Player 3's Hand: \n" + hand3.getHand()); System.out.println("Player 4's Hand: \n" + hand4.getHand()); Is there an easier way to deal to hands? For example using a For-Each loop? I tried this: but it doesn't work. I haven't really used this type of loop very must... for(Hand card : hand1){ System.out.println("Player 1's Hand: \n" + hand1); } By the way, this deals 2 cards to 4 difference hands, then prints each hand.

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• Bilinear interpolation - DirectX vs. GDI+

  - by holtavolt

  I have a C# app for which I've written GDI+ code that uses Bitmap/TextureBrush rendering to present 2D images, which can have various image processing functions applied. This code is a new path in an application that mimics existing DX9 code, and they share a common library to perform all vector and matrix (e.g. ViewToWorld/WorldToView) operations. My test bed consists of DX9 output images that I compare against the output of the new GDI+ code. A simple test case that renders to a viewport that matches the Bitmap dimensions (i.e. no zoom or pan) does match pixel-perfect (no binary diff) - but as soon as the image is zoomed up (magnified), I get very minor differences in 5-10% of the pixels. The magnitude of the difference is 1 (occasionally 2)/256. I suspect this is due to interpolation differences. Question: For a DX9 ortho projection (and identity world space), with a camera perpendicular and centered on a textured quad, is it reasonable to expect DirectX.Direct3D.TextureFilter.Linear to generate identical output to a GDI+ TextureBrush filled rectangle/polygon when using the System.Drawing.Drawing2D.InterpolationMode.Bilinear setting? For this (magnification) case, the DX9 code is using this (MinFilter,MipFilter set similarly): Device.SetSamplerState(0, SamplerStageStates.MagFilter, (int)TextureFilter.Linear); and the GDI+ path is using: g.InterpolationMode = InterpolationMode.Bilinear; I thought that "Bilinear Interpolation" was a fairly specific filter definition, but then I noticed that there is another option in GDI+ for "HighQualityBilinear" (which I've tried, with no difference - which makes sense given the description of "added prefiltering for shrinking") Followup Question: Is it reasonable to expect pixel-perfect output matching between DirectX and GDI+ (assuming all external coordinates passed in are equal)? If not, why not? Finally, there are a number of other APIs I could be using (Direct2D, WPF, GDI, etc.) - and this question generally applies to comparing the output of "equivalent" bilinear interpolated output images across any two of these. Thanks!

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• Impossible to remove directory

  - by Mark

  Evidently I've never had to delete a directory using win32 sdk before, because its apparently an impossible task. I've tried anything and everything - RemoveDirectory, SHFileOperation with FO_DELETE, etc. Currently I call CreateDirectory in one thread, start another thread, copy some files to this directory in the new thread, then delete all the files in the directory in the new thread, and then back in the original thread that created the directory, try to delete the now empty directory and it fails. The directory really and truly is empty when I try to delete it, but it makes no difference. The whole thread aspect is irrelevant I think because at one point everything was in one thread and it didn't work. I'm currently setting a SecurityAttributes structure on CreateDirectory to grant access to everyone, but it makes no difference. RemoveDirectory in the past has returned '32' on GetLastError, which I believe is Sharing violation. But even if I just try to delete the empty directory from the command line, it refuses saying, "The process cannot access the file because it is being used by another process." until I shut down the entire application that created the directory. (Note: the directory is created in GetTempPath.)

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• jndi binding on jboss4.2.3 and ejb3

  - by broschb

  I am trying to deploy a stateless ejb on jboss 4.2.3 using ejb3 annotations. Everything builds and deploys correctly, and I do not get any errors when jboss starts up. However the ejb is not getting bound to any JNDI location for lookup when I look at the bindings in jboss. Below is what I have for my ejb. Remote @Remote public interface TestWebService { public String TestWebMethod(String param1, String param2); } Stateless EJB @Stateless @RemoteBinding(jndiBinding="TestWeb") @Remote(TestWebService.class) public class TestWebServiceBean implements TestWebService{ public String TestWebMethod(String param1, String param2) { System.out.println("HELLO "+param1+" "+param2); return "Welcome!!"; } } I have tried not having the @Remote and @RemoteBinding and it doesn't make a difference. I have also added and ejb-jar.xml file (which should not be needed with ejb3) and that does not appear to make a difference. Below is the output I see in the jboss log on startup. installing MBean: jboss.j2ee:ear=ejb_web_service_ear-0.0.1- SNAPSHOT.ear,jar=ejb_web_service-0.0.1-SNAPSHOT.jar,name=TestWebServiceBean,service=EJB3 with dependencies: 21:56:00,633 INFO [EJBContainer] STARTED EJB: com.tomax.ejb.TestWebServiceBean ejbName: TestWebServiceBean

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• Programming methods design phase assignment

  - by Shakir

  Hey, i have an assignment (NCC) which deals with the design phase. The Scenario is that you have four soccer divisions (divisions 1,2,3 and 4) which consist of 22 teams each and hence each team plays 42 games (home and away). The concept is similar to the barclays premier league whereby ranking is based on points or else goal difference or else goals scored by team. The difference is that the top 2 teams are promoted and the bottom 2 are relegated and this includes Div 1 and Div 4 as the top 2 of Div1 are promoted to the national league which is above division 1 regional league and bottom 2 of Div4 are relegated to the local league below Division 4 regional league. Hence there are 3 total leagues and 4 divisions in the regional league (which has 22 teams each). Now the referee has to add the result of the match and thus automatic tables have to be generated now, There are two reports League Tables for 4 divisions List of all results for any chosen team during the season by date it was played on There are a couple of things to be done... i know its gonna be terrible to make everything but atleast explain to me how i should go about drawing these and what things i should include (generally) Logical Data Structure Diagram (DSD) for each report Preliminary Program Structure (PSD) for each report Detailed Program Specification for each report Flowchart for each report There are other things but i think our teacher will give us clear "clues" for it Thanks a lot Update - Project so far: Data Structure Diagram Preliminary Program Structure

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• Calculating rotation in > 360 deg. situations

  - by danglebrush

  I'm trying to work out a problem I'm having with degrees. I have data that is a list of of angles, in standard degree notation -- e.g. 26 deg. Usually when dealing with angles, if an angle exceeds 360 deg then the angle continues around and effectively "resets" -- i.e. the angle "starts again", e.g. 357 deg, 358 deg, 359 deg, 0 deg, 1 deg, etc. What I want to happen is the degree to continue increasing -- i.e. 357 deg, 358 deg, 359 deg, 360 deg, 361 deg, etc. I want to modify my data so that I have this converted data in it. When numbers approach the 0 deg limit, I want them to become negative -- i.e. 3 deg, 2 deg, 1 deg, 0 deg, -1 deg, -2 deg, etc. With multiples of 360 deg (both positive and negative), I want the degrees to continue, e.g. 720 deg, etc. Any suggestions on what approach to take? There is, no doubt, a frustratingly simple way of doing this, but my current solution is kludgey to say the least .... ! My best attempt to date is to look at the percentage difference between angle n and angle n - 1. If this is a large difference -- e.g. 60% -- then this needs to be modified, by adding or subtracting 360 deg to the current value, depending on the previous angle value. That is, if the previous angle is negative, substract 360, and add 360 if the previous angle is positive. Any suggestions on improving this? Any improvements?

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• Protected and Private methods

  - by cabaret

  I'm reading through Beginning Ruby and I'm stuck at the part about private and protected methods. This is a newbie question, I know. I searched through SO for a bit but I couldn't manage to find a clear and newbie-friendly explanation of the difference between private and protected methods. The book gives two examples, the first one for private methods: class Person def initialize(name) set_name(name) end def name @first_name + ' ' + @last_name end private def set_name(name) first_name, last_name = name.split(/\s+/) set_first_name(first_name) set_last_name(last_name) end def set_first_name(name) @first_name = name end def set_last_name(name) @last_name = name end end In this case, if I try p = Person.new("Fred Bloggs") p.set_last_name("Smith") It will tell me that I can't use the set_last_name method, because it's private. All good till there. However, in the other example, they define an age method as protected and when I do fred = Person.new(34) chris = Person.new(25) puts chris.age_difference_with(fred) puts chris.age It gives an error: :20: protected method 'age' called for #<Person:0x1e5f28 @age=25> (NoMethodError) I honestly fail to see the difference between the private and protected methods, it sounds the same to me. Could someone provide me with a clear explanation so I'll never get confused about this again? I'll provide the code for the second example if necessary.

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• Some clarification needed about synchronous versus asynchronous asio operations

  - by Old newbie

  As far as I know, the main difference between synchronous and asynchronous operations. I.e. write() or read() vs async_write() and async_read() is that the former, don't return until the operation finish -or error-, and the last ones, returns inmediately. Due the fact that the asynchronous operations are controlled by an io_service.run() that does not finish until the controlled operations has finalized. It seems to me that in sequencial operations as those involved in TCP/IP connections with protocols such as POP3, in which the operaton is a sequence such as: C: <connect> S: Ok. C: User... S: Ok. C: Password S: Ok. C: Command S: answer C: Command S: answer ... C: bye S: <close> The difference between synchronous/asynchronous opperatons does not make much sense. Of course, in both operations there is allways the risk that the program flow stops indefinitely by some circunstance -there the use of timers-, but I would like know some more authorized opinions in this matter. I must admit that the question is rather ill-defined, but I like hear some advices about when use one or other, because I've problems in debugging with MS Visual Studio, asynchronous SSL operations in a POP3 client in wich I'm working now -about some of who surely I would write here soon-, and sometimes think that perhaps is a bad idea use asynchronous in this. Not to say that I'm an absolute newbie with this librarys, that additionally to the difficult with the idioma, and some obscure concepts in the STL, must suffer the brevity of the asio documentation.

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• Debugging an XBAP application with 64-bit browser

  - by Anne Schuessler

  We have an XBAP application that fails when opened in Internet Explorer 8 64 bit. We only get a pretty generic error which makes it hard to determine where the error is coming from. I'm trying to find a way to debug the application with IE 8 64 bit, but I haven't figured out how to do this. I can't set the 64 bit version as the standard browser and overwriting the browser path in the browsers.xml for Visual Studio doesn't work as well. It just gets overwritten as soon as I hit F5 to debug to point to the 32 bit IE. I have figured out how to start the application from Debug with the 64 bit browser by changing the Debug options from "Start browser with URL" to "Start external program" and setting the command line arguments to point to the bin folder. Unfortunately then the XBAP is looking for its config.deploy file which doesn't seem to be generated during regular debug. This doesn't happen when using "Start browser with URL" and the application doesn't seem to care for this file then. Does anybody know why there's a difference between "Start browser with URL" and "Start external program" in the Debug options which might cause this difference in behavior when Debug is started? Also, does anybody know how to successfully debug an XBAP with a 64-bit browser?

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• Help me write my LISP :) LISP environments, Ruby Hashes...

  - by MikeC8

  I'm implementing a rudimentary version of LISP in Ruby just in order to familiarize myself with some concepts. I'm basing my implementation off of Peter Norvig's Lispy (http://norvig.com/lispy.html). There's something I'm missing here though, and I'd appreciate some help... He subclasses Python's dict as follows: class Env(dict): "An environment: a dict of {'var':val} pairs, with an outer Env." def __init__(self, parms=(), args=(), outer=None): self.update(zip(parms,args)) self.outer = outer def find(self, var): "Find the innermost Env where var appears." return self if var in self else self.outer.find(var) He then goes on to explain why he does this rather than just using a dict. However, for some reason, his explanation keeps passing in through my eyes and out through the back of my head. Why not use a dict, and then inside the eval function, when a new "sub-environment" needs to be created, just take the existing dict and update the key/value pairs that need to be updated, and pass that new dict into the next eval? Won't the Python interpreter keep track of the previous "outer" envs? And won't the nature of the recursion ensure that the values are pulled out from "inner" to "outer"? I'm using Ruby, and I tried to implement things this way. Something's not working though, and it might be because of this, or perhaps not. Here's my eval function, env being a regular Hash: def eval(x, env = $global_env) ........ elsif x[0] == "lambda" then ->(*args) { eval(x[2], env.merge(Hash[*x[1].zip(args).flatten(1)])) } ........ end The line that matters of course is the "lambda" one. If there is a difference, what's importantly different between what I'm doing here and what Norvig did with his Env class? If there's no difference, then perhaps someone can enlighten me as to why Norvig uses the Env class. Thanks :)

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• (Cpp) Linker, Libraries & Directories Information

  - by m00st

  I've finished both my C++ 1/2 classes and we did not cover anything on Linking to libraries or adding additional libraries to C++ code. I've been having a hay-day trying to figure this out; I've been unable to find basic information linking to objects. Initially I thought the problem was the IDE (Netbeans; and Code::Blocks). However I've been unable to get wxWidgets and GTKMM setup. Can someone point me in the right direction on the terminology and basic information about #including files and linking files in a Cpp application? Basically I want/need to know everything in regards to this process. The difference between .dll, .lib, .o, .lib.a, .dll.a. The difference between a .h and a "library" (.dll, .lib correct?) I understand I need to read the compiler documentation I am using; however all compilers (that I know of) use linker and headers; I need to learn this information. Please point me in the right direction! :] Thanks

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• Why would certain browsers request all pages on my ASP.Net Web site twice?

  - by Deane

  Firefox is issuing duplicate requests to my ASP.Net web site. It will request a page, get the response, then immediately issue the same request again (well, almost the same -- see below). This happens on every page of this particular Web site (but not any others). IE does not do this, but Chrome also does this. I have confirmed that there is no Location header in the response, and no Javascript or meta tag in the page which would cause the page to be re-requested (if any of these were true, IE would be re-requesting pages as well). I have confirmed this behavior on multiple Firefox installs on multiple machines. Versions vary, but all are 3.x. The only difference between the two requests is the Accepts header. For the first request, it looks like this: Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 For the second request, it looks like this: Accept: */* The Content-Type response header in all cases is: Content-Type: text/html; charset=utf-8 Something else odd -- even though Firefox requests the page twice, it uses the first response and discards the second. I put a counter on a page that increments with every request. I can watch the responses come back (via the Charles proxy). Firefox will get a "1" the first time, and a "2" the second time. Yet it will display the "1," for some reason. Chrome exhibits this exact same behavior. I suspect it's a protocol-level issue, given the difference in Accepts header, but I've never seen this before.

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• Should not a tail-recursive function also be faster?

  - by Balint Erdi

  I have the following Clojure code to calculate a number with a certain "factorable" property. (what exactly the code does is secondary). (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (factor-9 (quot n 10)))))) Now, I'm into TCO and realize that Clojure can only provide tail-recursion if explicitly told so using the recur keyword. So I've rewritten the code to do that (replacing factor-9 with recur being the only difference): (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (recur (quot n 10)))))) To my knowledge, TCO has a double benefit. The first one is that it does not use the stack as heavily as a non tail-recursive call and thus does not blow it on larger recursions. The second, I think is that consequently it's faster since it can be converted to a loop. Now, I've made a very rough benchmark and have not seen any difference between the two implementations although. Am I wrong in my second assumption or does this have something to do with running on the JVM (which does not have automatic TCO) and recur using a trick to achieve it? Thank you.

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• Ant: use include and exclude together

  - by Ken

  OK, this seems like it should be really simple. I'm using Apache Ant 1.8, and I have a target which does: <delete file="output/program.tar.bz2"/> <tar basedir="input" destfile="output/program.tar.bz2" compression="bzip2"> <tarfileset dir="input"> <include name="goodfolder1/**"/> <include name="goodfolder2/**"/> <exclude name="**/badfile"/> <exclude name="**/*.badext"/> </tarfileset> </tar> I want it to make a .tar.bz2 of input/goodfolder1 and input/goodfolder2, excluding files named "badfile", and excluding files with extension ".badext". It's giving me a .tar.bz2, but it's including badfile and *.badext -- the excludes seem to be ignored. The order of include/exclude doesn't seem to make a difference. I tried wrapping the includes/excludes in a (the docs say it's implicit?), but it made no difference. I'm sure there's something simple I'm missing, since the manual has a very similar example, though in a somewhat different context. EDIT: It looks like it could be related to the dir="input" attribute: it's adding everything in "input", and then adding everything in the tarfileset to that. Files I want appear twice in the program.tar.bz2, but files that are excluded only appear once. But dir is mandatory, and I don't see how this is different from the examples in the manual.

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• Fastest inline-assembly spinlock

  - by sigvardsen

  I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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• jQuery display text nested in paragraphs inside a div

  - by user961627

  I have HTML that looks something like this: <div class='textbox' data-title='Sometitle'> <div class='textareaedit'> <p><strong>Test sample text</strong></p> </div> </div> I'm sometimes going to have a few different <p> tags inside the textareaedit divs, and sometimes strong tags around the text inside the <p> (as in this example), and sometimes a span tag, and sometimes it's going to be without further tags inside the <p>. I want to iterate through each textbox on my page, grab its title and also the text nested inside <p> tags in textareaedit. I'm giving the output via console for testing. This is my jQuery code, but I get no output for the second console.log() line: $('.textbox').each(function() { $this = $(this); console.log($this.attr('data-title')+ ":\n"); $this.children('textareadit').children('p').each(function(){ console.log($(this).html()); // not giving any output, it's blank }); }); I tried $(this).text() as well, but no difference. You may think this example has the sample text inside <strong> tags within the <p>, but I've also tried the same example without the strong, where the text was the direct child of <p>, but it didn't make a difference. How can I capture the text?

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• Diff/Merge functionality for objects (not files!)

  - by gehho

  I have a collection of objects of the same type, let's call it DataItem. The user can view and edit these items in an editor. It should also be possible to compare and merge different items, i.e. some sort of diff/merge for DataItem instances. The DIFF functionality should compare all (relevant) properties/fields of the items and detect possible differences. The MERGE functionality should then be able to merge two instances by applying selected differences to one of the items. For example (pseudo objects): DataItem1 { DataItem2 { Prop1 = 10 Prop1 = 10 Prop2 = 25 Prop2 = 13 Prop3 = 0 Prop3 = 5 Coll = { 7, 4, 8 } Coll = { 7, 4, 8, 12 } } } Now, the user should be provided with a list of differences (i.e. Prop2, Prop3, and Coll) and he should be able to select which differences he wants to eliminate by assigning the value from one item to the other. He should also be able to choose if he wants to assign the value from DataItem1 to DataItem2 or vice versa. Are there common practices which should be used to implement this functionality? Since the same editor should also provide undo/redo functionality (using the Command pattern), I was thinking about reusing the ICommand implementations because both scenarios basically handle with property assignments, collection changes, and so on... My idea was to create Difference objects with ICommand properties which can be used to perform a merge operation for this specific Difference. Btw: The programming language will be C# with .NET 3.5SP1/4.0. However, I think this is more of a language-independent question. Any design pattern/idea/whatsoever is welcome!

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• [solved] IE6 PNG-transparency CSS hack not working

  - by John

  I looked around and decided to use a CSS approach rather than rely on JS... I figure the kind of corporate users stuck with IE6 might also have JS disabled by IT departments. So In my HTML I have: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> <title>My Page</title> <link rel="stylesheet" type="text/css" href="default.css" /> <!--[if IE 6]><link rel="stylesheet" type="text/css" href="ie6.css"><![endif]--> </head> <body> <img src="media/logo.png"/> </body> Then my ie6.css consists simply of: img { filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(...); } However none of this makes the slightest difference, no transparency. I commented out all the rest of the page so it is literally that one and still no luck. I removed the default.css stylesheet and still no difference. EDIT: I now got it working, using the .htc method, loading that file in a conditional IE6 test block. It turned out the problem I was having was that Windows 7 had 'locked' the file (I don't even know what this means) and this blocked IE from loading/using it.

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• Why is this Java Calendar comparison bad?

  - by joe7pak

  Hello folks. I'm having an inexplicable problem with the Java Calendar class when I'm trying to compare to dates. I'm trying to compare to Calendars and determine if their difference is than 1 day, and do things bases on that difference or not. But it doesn't work. If I do this with the two dates: String currDate = aCurrentUTCCalendar.getTime().toString(); String localDate = aLocalCalendar.getTime().toString(); I get these results: currDate = "Thu Jan 06 05:58:00 MST 2010" localDate = "Tue Jan 05 00:02:00 MST 2010" This is correct. But if I do this: long curr = aCurrentUTCCalendar.getTime().getTime(); long local = aLocalCalendar.getTime().getTime(); I get these results: ( in milliseconds since the epoch ) curr = -125566110120000 local = 1262674920000 Since there is only about a 30 hour different between the two, the magnitudes are vastly different, not to mention that annoying negative sign. This causes problems if I do this: long day = 60 * 60 * 24 * 1000; // 86400000 millis, one day if( local - curr > day ) { // do something } What's wrong? Why are the getTime().toString() calls correct, but the getTime().getTime() calls are vastly different? I'm using jdk 1.6_06 on WinXP. I can't upgrade the JDK for various reasons.

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• how does MySQL implement the "group by"?

  - by user188916

  I read from the MySQL Reference Manual and find that when it can take use of index,it just do index scan,other it will create tmp tables and do things like filesort. And I also read from other article that the "Group By" result will sort by group by columns by default,if "order by null" clause added,it won't don filesort. The difference can be found from the "explain ..." clause. so my problem is:what is the difference between "group by" clause that with "order by null" and which doesn't have? I try to use profiling to see what mysql do on the background,and only see result like: result for group clause without order by null: |preparing | 0.000016 | | Creating tmp table | 0.000048 | | executing | 0.000009 | | Copying to tmp table | 0.000109 | **| Sorting result | 0.000023 |** | Sending data | 0.000027 | result for clause with "order by null": preparing | 0.000016 | | Creating tmp table | 0.000052 | | executing | 0.000009 | | Copying to tmp table | 0.000114 | | Sending data | 0.000028 | So I guess what MySQL do when the "order by null" added,it does not use filesort algorithm,maybe when it creates the tmp table,it uses index as well,and then use the index to do group by operation,when completed,it just read result from the table rows and does not sort the result. But my original opinion is that MySQL can use quicksort to sort the items and then do group by,so the result will be sorted as well. Any opinion appreciated,thanks.

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• Code Contracts: Do we have to specify Contract.Requires(...) statements redundantly in delegating me

  - by herzmeister der welten

  I'm intending to use the new .NET 4 Code Contracts feature for future development. This made me wonder if we have to specify equivalent Contract.Requires(...) statements redundantly in a chain of methods. I think a code example is worth a thousand words: public bool CrushGodzilla(string weapon, int velocity) { Contract.Requires(weapon != null); // long code return false; } public bool CrushGodzilla(string weapon) { Contract.Requires(weapon != null); // specify contract requirement here // as well??? return this.CrushGodzilla(weapon, int.MaxValue); } For runtime checking it doesn't matter much, as we will eventually always hit the requirement check, and we will get an error if it fails. However, is it considered bad practice when we don't specify the contract requirement here in the second overload again? Also, there will be the feature of compile time checking, and possibly also design time checking of code contracts. It seems it's not yet available for C# in Visual Studio 2010, but I think there are some languages like Spec# that already do. These engines will probably give us hints when we write code to call such a method and our argument currently can or will be null. So I wonder if these engines will always analyze a call stack until they find a method with a contract that is currently not satisfied? Furthermore, here I learned about the difference between Contract.Requires(...) and Contract.Assume(...). I suppose that difference is also to consider in the context of this question then?

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• What limits scaling in this simple OpenMP program?

  - by Douglas B. Staple

  I'm trying to understand limits to parallelization on a 48-core system (4xAMD Opteron 6348, 2.8 Ghz, 12 cores per CPU). I wrote this tiny OpenMP code to test the speedup in what I thought would be the best possible situation (the task is embarrassingly parallel): // Compile with: gcc scaling.c -std=c99 -fopenmp -O3 #include <stdio.h> #include <stdint.h> int main(){ const uint64_t umin=1; const uint64_t umax=10000000000LL; double sum=0.; #pragma omp parallel for reduction(+:sum) for(uint64_t u=umin; u<umax; u++) sum+=1./u/u; printf("%e\n", sum); } I was surprised to find that the scaling is highly nonlinear. It takes about 2.9s for the code to run with 48 threads, 3.1s with 36 threads, 3.7s with 24 threads, 4.9s with 12 threads, and 57s for the code to run with 1 thread. Unfortunately I have to say that there is one process running on the computer using 100% of one core, so that might be affecting it. It's not my process, so I can't end it to test the difference, but somehow I doubt that's making the difference between a 19~20x speedup and the ideal 48x speedup. To make sure it wasn't an OpenMP issue, I ran two copies of the program at the same time with 24 threads each (one with umin=1, umax=5000000000, and the other with umin=5000000000, umax=10000000000). In that case both copies of the program finish after 2.9s, so it's exactly the same as running 48 threads with a single instance of the program. What's preventing linear scaling with this simple program?

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• c++ struct size

  - by kiokko89

  struct CExample { int a; } int main(int argc, char* argv[]) { CExample ce; CExample ce2; cout << "Size:" << sizeof(ce)<< " Address: "<< &ce<< endl; cout << "Size:" << sizeof(ce2)<< " Address: "<< &ce2 << endl; CExample ceArr[2]; cout << "Size:" << sizeof(ceArr[0])<< " Address: "<<&ceArr[0]<<endl; cout << "Size:" << sizeof(ceArr[1])<< " Address: "<<&ceArr[1]<<endl; return 0; } Excuse me I'm just a beginner but i'd like to know why with this code, there is a difference of 12 bytes between the addresses of the first two objects(ce and ce2) (i thought about data allignment), but there is only a difference of 4 bytes between the two objects in the array. Sorry for my bad English...

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• Data historian queries

  - by Scott Dennis

  Hi, I have a table that contains data for electric motors the format is: DATE(DateTime) | TagName(VarChar(50) | Val(Float) | 2009-11-03 17:44:13.000 | Motor_1 | 123.45 2009-11-04 17:44:13.000 | Motor_1 | 124.45 2009-11-05 17:44:13.000 | Motor_1 | 125.45 2009-11-03 17:44:13.000 | Motor_2 | 223.45 2009-11-04 17:44:13.000 | Motor_2 | 224.45 Data for each motor is inserted daily, so there would be 31 Motor_1s and 31 Motor_2s etc. We do this so we can trend it on our control system displays. I am using views to extract last months max val and last months min val. Same for this months data. Then I join the two and calculate the difference to get the actual run hours for that month. The "Val" is a nonresetable Accumulation from a PLC(Controller). This is my query for Last months Max Value: SELECT TagName, Val AS Hours FROM dbo.All_Data_From_Last_Mon AS cur WHERE (NOT EXISTS (SELECT TagName, Val FROM dbo.All_Data_From_Last_Mon AS high WHERE (TagName = cur.TagName) AND (Val > cur.Val))) This is my query for Last months Max Value: SELECT TagName, Val AS Hours FROM dbo.All_Data_From_Last_Mon AS cur WHERE (NOT EXISTS (SELECT TagName, Val FROM dbo.All_Data_From_Last_Mon AS high WHERE (TagName = cur.TagName) AND (Val < cur.Val))) This is the query that calculates the difference and runs a bit slow: SELECT dbo.Motors_Last_Mon_Max.TagName, STR(dbo.Motors_Last_Mon_Max.Hours - dbo.Motors_Last_Mon_Min.Hours, 12, 2) AS Hours FROM dbo.Motors_Last_Mon_Min RIGHT OUTER JOIN dbo.Motors_Last_Mon_Max ON dbo.Motors_Last_Mon_Min.TagName = dbo.Motors_Last_Mon_Max.TagName I know there is a better way. Ultimately I just need last months total and this months total. Any help would be appreciated. Thanks in advance

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