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  • floor of double(time_t)

    - by plok
    I cannot understand why this throws undefined reference to `floor'": double curr_time = (double)time(NULL); return floor(curr_time); Hasn't it been casted to double, which is what floor receives?

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  • Float addition promoted to double?

    - by Andreas Brinck
    I had a small WTF moment this morning. Ths WTF can be summarized with this: float x = 0.2f; float y = 0.1f; float z = x + y; assert(z == x + y); //This assert is triggered! (Atleast with visual studio 2008) The reason seems to be that the expression x + y is promoted to double and compared with the truncated version in z. (If i change z to double the assert isn't triggered). I can see that for precision reasons it would make sense to perform all floating point arithmetics in double precision before converting the result to single precision. I found the following paragraph in the standard (which I guess I sort of already knew, but not in this context): 4.6.1. "An rvalue of type float can be converted to an rvalue of type double. The value is unchanged" My question is, is x + y guaranteed to be promoted to double or is at the compiler's discretion? UPDATE: Since many people has claimed that one shouldn't use == for floating point, I just wanted to state that in the specific case I'm working with, an exact comparison is justified. Floating point comparision is tricky, here's an interesting link on the subject which I think hasn't been mentioned.

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  • Double paging definition

    - by Albinoswordfish
    This is not a programming question but more of an operating system question Right now I'm trying to learn what exactly Double paging means. I see two different terms, double paging on disk and double paging in memory. Apparently this problem arises when we introduce a buffer cache to store disk blocks when doing File I/O But I'm not really sure what exactly this term means. If anybody could specify it would be very helpful.

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  • What does it mean to double license?

    - by Adrian Panasiuk
    What does it mean to double license code? I can't just put both licenses in the source files. That would mean that I mandate users to follow the rules of both of them, but the licenses will probably be contradictory (otherwise there'd be no reason to double license). I guess this is something like in cryptographic chaining, cipher = crypt_2(crypt_1(clear)) (generally) means, that cipher is neither the output of crypt_2 on clear nor the output of crypt_1 on clear. It's the output of the composition. Likewise, in double-licensing, in reality my code has one license, it's just that this new license says please follow all of the rules of license1, or all of the rules of license2, and you are hereby granted the right to redistribute this application under this "double" license, license1 or license2, or any license under which license1 or license2 allow you to redistribute this software, in which case you shall replace the relevant licensing information in this application with that of the new license. (Does this mean that before someone may use the app under license1, he has to perform the operation of redistributing to self? How would he document the fact that he did that operation?) Am I correct. What LICENSE file and what text to put in the source files would I need if I wanted to double license on, for the sake of example, Apachev2 and GPLv3 ?

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  • system out output for double numbers in a java program

    - by Nikunj Chauhan
    I have a program where I am generating two double numbers by adding several input prices from a file based on a condition. String str; double one = 0.00; double two = 0.00; BufferedReader in = new BufferedReader(new FileReader(myFile)); while((str = in.readLine()) != null){ if(str.charAt(21) == '1'){ one += Double.parseDouble(str.substring(38, 49) + "." + str.substring(49, 51)); } else{ two += Double.parseDouble(str.substring(38, 49) + "." + str.substring(49, 51)); } } in.close(); System.out.println("One: " + one); System.out.println("Two: " + two); The output is like: One: 2773554.02 Two: 6.302505836000001E7 Question: None of the input have more then two decimals in them. The way one and two are getting calculated exactly same. Then why the output format is like this. What I am expecting is: One: 2773554.02 Two: 63025058.36 Why the printing is in two different formats ? I want to write the outputs again to a file and thus there must be only two digits after decimal.

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  • Memory leaks while using array of double

    - by Gacek
    I have a part of code that operates on large arrays of double (containing about 6000 elements at least) and executes several hundred times (usually 800) . When I use standard loop, like that: double[] singleRow = new double[6000]; int maxI = 800; for(int i=0; i<maxI; i++) { singleRow = someObject.producesOutput(); //... // do something with singleRow // ... } The memory usage rises for about 40MB (from 40MB at the beggining of the loop, to the 80MB at the end). When I force to use the garbage collector to execute at every iteration, the memory usage stays at the level of 40MB (the rise is unsignificant). double[] singleRow = new double[6000]; int maxI = 800; for(int i=0; i<maxI; i++) { singleRow = someObject.producesOutput(); //... // do something with singleRow // ... GC.Collect() } But the execution time is 3 times longer! (it is crucial) How can I force the C# to use the same area of memory instead of allocating new ones? Note: I have the access to the code of someObject class, so if it would be needed, I can change it.

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  • Java code optimization leads to numerical inaccuracies and errors

    - by rano
    I'm trying to implement a version of the Fuzzy C-Means algorithm in Java and I'm trying to do some optimization by computing just once everything that can be computed just once. This is an iterative algorithm and regarding the updating of a matrix, the clusters x pixels membership matrix U, this is the update rule I want to optimize: where the x are the element of a matrix X (pixels x features) and v belongs to the matrix V (clusters x features). And m is a parameter that ranges from 1.1 to infinity. The distance used is the euclidean norm. If I had to implement this formula in a banal way I'd do: for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < V.length; j++) { double num = D[i][j]; double sumTerms = 0; for(int k = 0; k < V.length; k++) { double thisDistance = D[i][k]; sumTerms += Math.pow(num / thisDistance, (1.0 / (m - 1.0))); } U[i][j] = (float) (1f / sumTerms); } } In this way some optimization is already done, I precomputed all the possible squared distances between X and V and stored them in a matrix D but that is not enough, since I'm cycling througn the elements of V two times resulting in two nested loops. Looking at the formula the numerator of the fraction is independent of the sum so I can compute numerator and denominator independently and the denominator can be computed just once for each pixel. So I came to a solution like this: int nClusters = V.length; double exp = (1.0 / (m - 1.0)); for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < nClusters; j++) { double distance = D[i][j]; double denominator = D[i][nClusters]; double numerator = Math.pow(distance, exp); U[i][j] = (float) (1f / (numerator * denominator)); } } Where I precomputed the denominator into an additional column of the matrix D while I was computing the distances: for (int i = 0; i < X.length; i++) { for (int j = 0; j < V.length; j++) { double sum = 0; for (int k = 0; k < nDims; k++) { final double d = X[i][k] - V[j][k]; sum += d * d; } D[i][j] = sum; D[i][B.length] += Math.pow(1 / D[i][j], exp); } } By doing so I encounter numerical differences between the 'banal' computation and the second one that leads to different numerical value in U (not in the first iterates but soon enough). I guess that the problem is that exponentiate very small numbers to high values (the elements of U can range from 0.0 to 1.0 and exp , for m = 1.1, is 10) leads to ver y small values, whereas by dividing the numerator and the denominator and THEN exponentiating the result seems to be better numerically. The problem is it involves much more operations. Am I doing something wrong? Is there a possible solution to get both the code optimized and numerically stable? Any suggestion or criticism will be appreciated.

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  • Double multiplied by 100 and then cast to long is giving wrong value

    - by xyz
    I have the following code: Double i=17.31; long j=(long) (i*100); System.out.println(j); O/P : 1730 //Expected:1731 Double i=17.33; long j=(long) (i*100); System.out.println(j); O/P : 1732 //Expected:1733 Double i=17.32; long j=(long) (i*100); System.out.println(j); O/P : 1732 //Expected:1732{As expected} Double i=15.33; long j=(long) (i*100); System.out.println(j); O/P : 1533 //Expected:1533{as Expected} I have tried to Google but unable to find reason.I am sorry if the question is trivial.

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  • Detect double-tap on UISlider?

    - by Randy
    I can detect single/double-taps in specific views with: NSSet *myTouches = [event touchesForView:mySpecificView.view]; but I want to detect a double-tap on the button of a slider and can't find any reference to it. Is there a replacement for "touchesForView:" where I can enter the name of my slider? usage: I have three sliders with their default value being directly in the center of the slider. Once the position of the slider has changed, I want a quick way to individually reset each slider to its default position. I currently have each slider's containing view set to respond to a double-tap, updating each slider. It works fine, but doesn't seem natural. ie.I can't double-tap on the slider itself because the slider intercepts the taps and doesn't pass them on to the surrounding view. thanks in advance

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  • Dividing a double with integer

    - by hardcoder
    I am facing an issue while dividing a double with an int. Code snippet is : double db = 10; int fac = 100; double res = db / fac; The value of res is 0.10000000000000001 instead of 0.10. Does anyone know what is the reason for this? I am using cc to compile the code.

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  • ILNumerics multiply complex with matrix<double>

    - by nik
    I m looking at ILNumerics to translate some matlab code into c#. How would I multiply a complex and a double? Simplified description: In Matlab: A=[1 2 3] i*A*A' Returns a complex number. How would I do the same in ILNumerics: ILArray<double> A = ILMath.array(1.0, 2.0, 3.0); complex B = complex.i * ILMath.multiply(A,A.T); Throws the error: Operator '*' cannot be applied to operands of type 'ILNumerics.complex' and 'ILNumerics.ILRetArray<double>' Update This works: double C = 14.0; complex D = complex.i * C; But shouldnt: ILMath.multiply(A,A.T) also return 14.0?

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  • Eclipse question - panels don't get restored when double clicking

    - by llm
    You know how, in Eclipse, when you double click on a file tab (which shows the class name), the editor gets expanded to the whole screen minimizing other panels? Well normally I just double click again on the tab to restore everything, but all of the sudden double clicking again doesnt do anything (the editor remains in full screen and all other panels minimized)! I am not sure what I did to cause this. Any ideas how to get it back to normal? Thanks.

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  • Double.ToString with N Number of Decimal Places

    - by Ngu Soon Hui
    I know that if we want to display a double as a two decimal digit, one would just have to use public void DisplayTwoDecimal(double dbValue) { Console.WriteLine(dbValue.ToString("0.00")); } But how to extend this to N decimal places, where N is determined by the user? public void DisplayNDecimal(double dbValue, int nDecimal) { // how to display }

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  • Double root folder vs single root folder

    - by Tomas
    On my Linux box, in bash, I have access to a "double root" folder denoted by two forward slashes: tomas:~ $ cd / tomas:/ $ ls bin/ cdrom@ ... tomas:/ $ cd // tomas:// $ ls bin/ cdrom@ ... The content of the folder and its subfolder is identical to the "normal" single slash root. The double slash does not go away when I access its subfolders. The annomaly does not repeat itself with three or more slashes; these are simple synonyms for the root: tomas:// $ cd home/tomas tomas://home/tomas $ cd /// tomas:/ $ cd //// tomas:/ $ What kindof place is it? Is it a bug? Can anyone explain the annomaly?

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  • bash and arithmetic comparison: double quotes or not?

    - by Martin
    when comparing two integers in bash, do we have to put double quotes ? In the official document http://tldp.org/LDP/abs/html/comparison-ops.html I can read that double quotes should appear every time... But what is the differences in the following examples: [ "$VAR" -eq "1" ] [ $VAR -eq "1" ] [ "$VAR" -eq 1 ] [ $VAR -eq 1 ] As I am curious, a took a look at Ubuntu init scripts in /etc/init.d and there are many usage of arithmetic comparison in it, at least [ "$VAR" -eq "1" ] and [ $VAR -eq 1 ] are used... but it seems no one really "knows" what is the official way to do it. Thanks !

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  • Avoiding double NAT with PPPoA connection

    - by user498429
    I've got an ASUS RT-N56U wending its way to me and have been thinking about how to set this up on my home network. I currently have a Netgear DG634g V5 and was hoping to use this device as a modem only, with everything else being done by the router. Problem is, my ISP uses PPPoA and the asus seems only to support PPPoE. I'm aware that a double NAT configuration should be avoided and I've seen some instructions here: http://www.tomshardware.co.uk/forum/33700-17-ultimate-modem-router-setup-thread Specifically, I was going to follow the guidance in the section entitled "Chaining Two Networks Together In a Cascading Fashion (Modem handles PPPoA)". That seems like it could work. However, is this a double NAT configuration or even a good way to do it? Would UPnP still work? The other option, I understand, is to buy the Draytek Vigor 120 but I'd ideally like to avoid the cost of that if its not necessary.

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  • Can't double click files to open them in inDesign (CS5)

    - by Matt
    I cannot open a file unless I open inDesign (the program) and then do File-Open If I double click, it starts to open, then just hangs forever. AFTER I close it, and look in the directory where they're saved, I see a (temporary?) "lock" file. Now I can double click the original file and it opens just fine. However, now when I close iD it deletes the file and the whole process starts again... I have tried updating the software, uninstalled COMPLETELY and reinstalled, tried a brand new Win7 install. These files are all saved on a network drive, the computer is a new quad-core Dell with 12GB of RAM and a fresh x64 Win7 install on the SSD. Does not happen with other programs.

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  • strod() and sprintf() inconsistency under GCC and MSVC

    - by Dmitry Sapelnikov
    I'm working on a cross-platform app for Windows and Mac OS X, and I have a problem with two standard C library functions: strtod() (string-to-double conversion) ? sprintf (when used for outputting double-precision floating point numbers) -- their GCC and MSVC versions return different results. I'm looking for a well-tested cross-platform open-source implementation of those functions, or just for a pair of functions that would correctly and consistently convert double to string and back. I've already tried the clib GCC implementation, but the code is too long and too dependent on other source files, so I expect the adaptation to be difficult. What implementations of string-to-double and double-to-string functions would you recommend?

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  • Different kinds of doubles in vb.net?

    - by Jonathan
    Hey all- I'm using QBFC to generate invoices in a Quickbooks integrating app. I'm getting an exception thrown for lineItem.Amount.SetValue(val as Double) when I try to enter a programmatically generated double. The following does not work: lineItem = invoice.ORInvoiceLineAddList.Append.InvoiceLineAdd Dim amount as Double amount = summary.dailySold * summary.dailyRate loggingTxtBox.AppendText("Amount is " & amount & vbNewLine) lineItem.Amount.SetValue(amount) The exception I receive is System.Runtime.InteropServices.COMException (0x80040305): Invalid Amount format. at Interop.QBFC8.IQBAmountType.SetValue(Double val) The following works: lineItem.Amount.SetValue(20.3) Any suggestions? Is .NET interpretting a hard-coded double differently than a programmatically calculated one? Thanks- Jonathan

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  • strtod() and sprintf() inconsistency under GCC and MSVC

    - by Dmitry Sapelnikov
    I'm working on a cross-platform app for Windows and Mac OS X, and I have a problem with two standard C library functions: strtod() - string-to-double conversion sprintf() - when used for outputting double-precision floating point numbers) Their GCC and MSVC versions return different results. I'm looking for a well-tested cross-platform open-source implementation of those functions, or just for a pair of functions that would correctly and consistently convert double to string and back. I've already tried the clib GCC implementation, but the code is too long and too dependent on other source files, so I expect the adaptation to be difficult. What implementations of string-to-double and double-to-string functions would you recommend?

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  • DLL Exports: not all my functions are exported

    - by carmellose
    I'm trying to create a Windows DLL which exports a number of functions, howver all my functions are exported but one !! I can't figure it out. The macro I use is this simple one : __declspec(dllexport) void myfunction(); It works for all my functions except one. I've looked inside Dependency Walker and here they all are, except one. How can that be ? What would be the cause for that ? I'm stuck. Edit: to be more precise, here is the function in the .h : namespace my { namespace great { namespace namespaaace { __declspec(dllexport) void prob_dump(const char *filename, const double p[], int nx, const double Q[], const double xlow[], const char ixlow[], const double xupp[], const char ixupp[], const double A[], int my, const double bA[], const double C[], int mz, const double clow[], const char iclow[], const double cupp[], const char icupp[] ); }}} And in the .cpp file it goes like this: namespace my { namespace great { namespace namespaaace { namespace { void dump_mtx(std::ostream& ostr, const double *mtx, int rows, int cols, const char *ind = 0) { /* some random code there, nothing special, no statics whatsoever */ } } // end anonymous namespace here // dump the problem specification into a file void prob_dump( const char *filename, const double p[], int nx, const double Q[], const double xlow[], const char ixlow[], const double xupp[], const char ixupp[], const double A[], int my, const double bA[], const double C[], int mz, const double clow[], const char iclow[], const double cupp[], const char icupp[] ) { std::ofstream fout; fout.open(filename, std::ios::trunc); /* implementation there */ dump_mtx(fout, Q, nx, nx); } }}} Thanks

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  • Network Restructure Method for Double-NAT network

    - by Adrian
    Due to a series of poor network design decisions (mostly) made many years ago in order to save a few bucks here and there, I have a network that is decidedly sub-optimally architected. I'm looking for suggestions to improve this less-than-pleasant situation. We're a non-profit with a Linux-based IT department and a limited budget. (Note: None of the Windows equipment we have runs does anything that talks to the Internet nor do we have any Windows admins on staff.) Key points: We have a main office and about 12 remote sites that essentially double NAT their subnets with physically-segregated switches. (No VLANing and limited ability to do so with current switches) These locations have a "DMZ" subnet that are NAT'd on an identically assigned 10.0.0/24 subnet at each site. These subnets cannot talk to DMZs at any other location because we don't route them anywhere except between server and adjacent "firewall". Some of these locations have multiple ISP connections (T1, Cable, and/or DSLs) that we manually route using IP Tools in Linux. These firewalls all run on the (10.0.0/24) network and are mostly "pro-sumer" grade firewalls (Linksys, Netgear, etc.) or ISP-provided DSL modems. Connecting these firewalls (via simple unmanaged switches) is one or more servers that must be publically-accessible. Connected to the main office's 10.0.0/24 subnet are servers for email, tele-commuter VPN, remote office VPN server, primary router to the internal 192.168/24 subnets. These have to be access from specific ISP connections based on traffic type and connection source. All our routing is done manually or with OpenVPN route statements Inter-office traffic goes through the OpenVPN service in the main 'Router' server which has it's own NAT'ing involved. Remote sites only have one server installed at each site and cannot afford multiple servers due to budget constraints. These servers are all LTSP servers several 5-20 terminals. The 192.168.2/24 and 192.168.3/24 subnets are mostly but NOT entirely on Cisco 2960 switches that can do VLAN. The remainder are DLink DGS-1248 switches that I am not sure I trust well enough to use with VLANs. There is also some remaining internal concern about VLANs since only the senior networking staff person understands how it works. All regular internet traffic goes through the CentOS 5 router server which in turns NATs the 192.168/24 subnets to the 10.0.0.0/24 subnets according to the manually-configured routing rules that we use to point outbound traffic to the proper internet connection based on '-host' routing statements. I want to simplify this and ready All Of The Things for ESXi virtualization, including these public-facing services. Is there a no- or low-cost solution that would get rid of the Double-NAT and restore a little sanity to this mess so that my future replacement doesn't hunt me down? Basic Diagram for the main office: These are my goals: Public-facing Servers with interfaces on that middle 10.0.0/24 network to be moved in to 192.168.2/24 subnet on ESXi servers. Get rid of the double NAT and get our entire network on one single subnet. My understanding is that this is something we'll need to do under IPv6 anyway, but I think this mess is standing in the way.

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