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  • Sqlite3 Database versus populating Arrays

    - by Kenoy
    hi, I am working on a program that requires me to input values for 12 objects, each with 4 arrays, each with 100 values. (4800) values. The 4 arrays represent possible outcomes based on 2 boolean values... i.e. YY, YN, NN, NY and the 100 values to the array are what I want to extract based on another inputted variable. I previously have all possible outcomes in a csv file, and have imported these into sqlite where I can query then for the value using sql. However, It has been suggested to me that sqlite database is not the way to go, and instead I should populate using arrays hardcoded. Which would be better during run time and for memory management?

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  • best method of turning millions of x,y,z positions of particles into visualisation

    - by Griff
    I'm interested in different algorithms people use to visualise millions of particles in a box. I know you can use Cloud-In-Cell, adaptive mesh, Kernel smoothing, nearest grid point methods etc to reduce the load in memory but there is very little documentation on how to do these things online. i.e. I have array with: x,y,z 1,2,3 4,5,6 6,7,8 xi,yi,zi for i = 100 million for example. I don't want a package like Mayavi/Paraview to do it, I want to code this myself then load the decomposed matrix into Mayavi (rather than on-the-fly rendering) My poor 8Gb Macbook explodes if I try and use the particle positions. Any tutorials would be appreciated.

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  • Elapsed time of running a C program

    - by yCalleecharan
    Hi, I would like to know what lines of C code to add to a program so that it tells me the total time that the program takes to run. I guess there should be counter initialization near the beginning of main and one after the main function ends. Is the right header clock.h? Thanks a lot... Update I have a Win Xp machine. Is it just adding clock() at the beginning and another clock() at the end of the program? Then I can estimate the time difference. Yes, you're right it's time.h. Here's my code: #include <stdio.h> #include <stdlib.h> #include <math.h> #include <share.h> #include <time.h> void f(long double fb[], long double fA, long double fB); int main() { clock_t start, end; start = clock(); const int ARRAY_SIZE = 11; long double* z = (long double*) malloc(sizeof (long double) * ARRAY_SIZE); int i; long double A, B; if (z == NULL) { printf("Out of memory\n"); exit(-1); } A = 0.5; B = 2; for (i = 0; i < ARRAY_SIZE; i++) { z[i] = 0; } z[1] = 5; f(z, A, B); for (i = 0; i < ARRAY_SIZE; i++) printf("z is %.16Le\n", z[i]); free(z); z = NULL; end = clock(); printf("Took %ld ticks\n", end-start); printf("Took %f seconds\n", (double)(end-start)/CLOCKS_PER_SEC); return 0; } void f(long double fb[], long double fA, long double fB) { fb[0] = fb[1]* fA; fb[1] = fb[1] - 1; return; } Some errors with MVS2008: testim.c(16) : error C2143: syntax error : missing ';' before 'const' testim.c(18) :error C2143: syntax error : missing ';' before 'type' testim.c(20) :error C2143: syntax error : missing ';' before 'type' testim.c(21) :error C2143: syntax error : missing ';' before 'type' testim.c(23) :error C2065: 'z' : undeclared identifier testim.c(23) :warning C4047: '==' : 'int' differs in levels of indirection from 'void *' testim.c(28) : error C2065: 'A' : undeclared identifier testim.c(28) : warning C4244: '=' : conversion from 'double' to 'int', possible loss of data and it goes to 28 errors. Note that I don't have any errors/warnings without your clock codes. LATEST NEWS: I unfortunately didn't get a good reply here. But after a search on Google, the code is working. Here it is: #include <stdio.h> #include <stdlib.h> #include <math.h> #include <share.h> #include <time.h> void f(long double fb[], long double fA, long double fB); int main() { clock_t start = clock(); const int ARRAY_SIZE = 11; long double* z = (long double*) malloc(sizeof (long double) * ARRAY_SIZE); int i; long double A, B; if (z == NULL) { printf("Out of memory\n"); exit(-1); } A = 0.5; B = 2; for (i = 0; i < ARRAY_SIZE; i++) { z[i] = 0; } z[1] = 5; f(z, A, B); for (i = 0; i < ARRAY_SIZE; i++) printf("z is %.16Le\n", z[i]); free(z); z = NULL; printf("Took %f seconds\n", ((double)clock()-start)/CLOCKS_PER_SEC); return 0; } void f(long double fb[], long double fA, long double fB) { fb[0] = fb[1]* fA; fb[1] = fb[1] - 1; return; } Cheers

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  • Insert into a generic dictionary with possibility of duplicate keys?

    - by Chris Clark
    Is there any reason to favor one of these approaches over the other when inserting into a generic dictionary with the possibility of a key conflict? I'm building an in-memory version of a static collection so in the case of a conflict it doesn't matter whether the old or new value is used. If Not mySettings.ContainsKey(key) Then mySettings.Add(key, Value) End If Versus mySettings(key) = Value And then of course there is this, which is obviously not the right approach: Try mySettings.Add(key, Value) Catch End Try Clearly the big difference here is that the first and second approaches actually do different things, but in my case it doesn't matter. It seems that the second approach is cleaner, but I'm curious if any of you .net gurus have any deeper insight. Thanks!

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  • Load a bitmap from file in RGB format (without alpha)

    - by Robert
    Hi, i simply want to load a .BMP file and get the Bitmap object in 24bit RGB format (or 32bit in RGB format). All methods I tried return a Bitmap/Image object with PixelFormat = Format32bppArgb. Even if of course BMPs don't have alpha. new Bitmap(System.Drawing.Image.FromFile(fileName, true)); new Bitmap(fileName); I currently solve the problem by copying the first object to another in memory bitmap at 24bit RBG. Is there a single method to do it? Thanks

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  • Generating a Grid of NSTextField Objects From NSDictionary Items

    - by SteveStifler
    I'm trying to create an vocabulary study application using Obj-C and the Cocoa frameworks. I have about two week's experience in both areas and have reached an edge of my current knowledge. Here's where I'm stuck. When I press a checkbox, a corresponding plist is loaded into memory as an NSDictionary. I want to generate a "Label: Textfield" pair for each key:value pair, where the Label is the key. When the text typed into the Textfield matches the key's value, I want the Label's text to turn green. So how would I generate this grid, and once generated, how would I make the text green upon correct input? Thanks!

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  • python class attribute

    - by chnet
    Hi, i have a question about class attribute in python. class base : def __init__ (self): pass derived_val = 1 t1 = base() t2 = base () t2.derived_val +=1 t2.__class__.derived_val +=2 print t2.derived_val # its value is 2 print t2.__class__.derived_val # its value is 3 The results are different. I also use id() function to find t2.derived_val and t2.class.derived_val have different memory address. My problem is derived_val is class attribute. Why it is different in above example? Is it because the instance of class copy its own derived_val beside the class attribute?

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  • Combining Session and Cache

    - by Zyphrax
    To make my extranet web application even faster/more scalable I think of using some of the caching mechanisms. For some of the pages we'll use HTML caching, please ignore that technique for this question. E.g.: at some point in time 2500 managers will simultaneously login on our application (most of them with the same Account/Project) I think of storing an Account-cachekey and Project-cachekey into the user's Session and use that to get the item from the Cache. I could have simply stored the Account into the session, but that would result in 2500 of the same Accounts in memory. Is there a better solution to this or does it make sense :)?

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  • Problems with delete in destructor

    - by Vera
    Hello, I wrote this code. The constructor works normally, but in the destructor I get "Windows has triggered a breakpoint." How should I correct this? template class CyclicalArray { private: T* mem_ptr; public: CyclicalArray(size_t capacity, const T& default_value) { this->default_value = default_value; this->capacity = capacity; head_index = 0; mem_ptr = ::new T[capacity]; //memory allocating for(T* p = mem_ptr; p < mem_ptr + capacity * sizeof(T); p += sizeof(T)) { ::new (p) T (default_value); //initialization } } ~CyclicalArray() { for(T* p = mem_ptr + sizeof(T); p < mem_ptr + capacity * sizeof(T); p += sizeof(T)) { p->~T(); } delete[] mem_ptr; }

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  • Which Ipod touch generation should I buy? 2nd or 3rd?

    - by kukabunga
    I want to create games for Iphone/Ipod touch. Unfortunately I don't have a lot of money so I can buy only one device. Ipod is cheaper than Iphone, so I decided to bought Ipod touch. But I am afraid of buying 3rd generation - because it has more memory, more faster CPU, etc. And I think if I post my app on appstore - people with 2nd generation Ipod might have trouble with my app (because I was testing it on 3rd generation). But on the other hand - I am planning to create 3d/cpu demanding game - and it would be easy for me to implement it on device with more calculation power... What should I do in this situation? Any advice is appreciate.

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  • Forbid GridView to load all views at once

    - by efpies
    I have about 700 items to display in the grid view. On a Samsung Galaxy Tab 10.1 this is not a problem: it has enough memory. On a HTC Explorer the heap is overflown. So I want to load data dynamically regarding current scroll position (N rows for screen + 5 rows as a tail). And I want to show a scrollbar which represents the position in total rows. But I don't want to draw items that I don't see. In other words, I want to create something similar to UITableView in iOS. How can I do this?

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  • Arrays of different types

    - by Tyler
    Hi - Is it possible to have an array that contains two different types of data? I want to have an array that contains a double and also a string. I attempted: ArrayList<double><String> array; But that didn't work. Sorry for the silly question, but it has been a while since I have used something like this.. Can you refresh my memory on how would I declare and populate such an array? And then to take it a step further, I would like to sort the array by the double if possible? Thanks!

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  • MATLAB - Delete elements of binary files without loading entire file

    - by Doresoom
    This may be a stupid question, but Google and MATLAB documentation have failed me. I have a rather large binary file (10 GB) that I need to open and delete the last forty million bytes or so. Is there a way to do this without reading the entire file to memory in chunks and printing it out to a new file? It took 6 hours to generate the file, so I'm cringing at the thought of re-reading the whole thing. EDIT: The file is 14,440,000,000 bytes in size. I need to chop it to 14,400,000,000.

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  • Using Timer only once

    - by zaidwaqi
    Hi, I want to use a timer only once, at 1 second after the initialization of my main form. I thought the following would have a message box saying "Hello World" just once, but actually a new message box says "Hello World" every one second. Why so? I had put t.Stop() in the tick event. Also, do I need to dispose the timer somehow to avoid memory leakage? Timer t = new Timer(); t.Interval = 1000; t.Tick += delegate(System.Object o, System.EventArgs e) { MessageBox.Show("Hello World"); t.Stop(); }; t.Start(); Please help and show if there is a better way of doing this? Thanks.

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  • Loading a DB table into nested dictionaries in Python

    - by Hossein
    Hi, I have a table in MySql DB which I want to load it to a dictionary in python. the table columns is as follows: id,url,tag,tagCount tagCount is the number of times that a tag has been repeated for a certain url. So in that case I need a nested dictionary, in other words a dictionary of dictionary, to load this table. Because each url have several tags for which there are different tagCounts.the code that I used is this:( the whole table is about 22,000 records ) cursor.execute( ''' SELECT url,tag,tagCount FROM wtp ''') urlTagCount = cursor.fetchall() d = defaultdict(defaultdict) for url,tag,tagCount in urlTagCount: d[url][tag]=tagCount print d first of all I want to know if this is correct.. and if it is why it takes so much time? Is there any faster solutions? I am loading this table into memory to have fast access to get rid of the hassle of slow database operations, but with this slow speed it has become a bottleneck itself, it is even much slower than DB access. and anyone help? thanks

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  • Flash crash on long JSON load time

    - by MooCow
    I have a Flex program that gets a JSON array from a PHP script. The PHP script doesn't contain just a simple JSON array but it grabs data from Activecollab and do some work on the data before encoding the data. The first test involve a small JSON array that took a short time to encode by PHP. However, when I try to scale up the test, the Flash movie will crash trying to load the JSON data from PHP. There's no code difference between the tests, just the amount of data and amount of time it takes PHP to encode. Am I looking at a memory problem or a time out problem?

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  • Using MonadPlus in FRP.Reactive.FieldTrip

    - by ony
    I'm studying FRP at this moment through FieldTrip adaptor. And hit the problem with strange way of frames scheduling and integration. So now I'm trying to build own marker Event for aligning Behaviour stepping. So... flipflop :: Behavior String flipflop = stepper "none" (xflip 2) where xflip t0 = do t <- withTimeE_ (atTime t0) return "flip" `mplus` xflop (t+3) xflop t0 = do t <- withTimeE_ (atTime t0) return "flop" `mplus` xflip (t+2) txtGeom = ((uscale2 (0.5::Float) *%) . utext . show <$>) main = anim2 (txtGeom . pure flipflop) Questions is: Why this example leads to memory leak? Is there safe way to build sequence of events where each next one is scheduled depending on previous?

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  • Solution: Android INSTALL_FAILED_INSUFFICIENT_STORAGE error.

    - by Andrew Smith
    The INSTALL_FAILED_INSUFFICIENT_STORAGE error is the bane of every Android developer's life. It happens regardless of app size, or how much storage is available. Rebooting the target device fixes the problem briefly, but it soon comes back. There are hundreds (if not thousands) of message board posts from people asking why the problem occurs, but the folks at Google are frustratingly silent on the issue. There is a simple workaround. If your test device is running Android 2.2 or later then add the android:installLocation attribute to your application's manifest file, with the value "preferExternal". This will force the app to be installed on the device's external storage, such as a phone's SD card. For example: <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.andrewsmith.android.darkness" android:installLocation="preferExternal" This is more of a band-aid than a fix, and it may not be ideal if you want your finished app to install on the device's internal memory. But it will at least make the development process a lot less frustrating.

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  • Remove from a std::set<shared_ptr<T>> by T*

    - by Autopulated
    I have a set of shared pointers: std::set<boost::shared_ptr<T>> set; And a pointer: T* p; I would like to efficiently remove the element of set equal to p, but I can't do this with any of the members of set, or any of the standard algorithms, since T* is a completely different type to boost::shared_ptr<T>. A few approaches I can think of are: somehow constructing a new shared_ptr from the pointer that won't take ownership of the pointed to memory (ideal solution, but I can't see how to do this) wrapping / re-implementing shared_ptr so that I can do the above just doing my own binary search over the set Help!

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  • How to initialize an std::string using ""?

    - by Mohsin
    I'm facing problems with initializing a std::string variable using "" (i.e. an empty string). It's causing strange behavior in code that was previously working. Is the following statement wrong? std::string operationalReason = ""; When I use the following code everything works fine: std::string operationalReason; operationalReason.clear(); I believe that string literals are stored in a separate memory location that is compiler-dependent. Could the problem I'm seeing actually be indicating a corruption of that storage? If so, it would get hidden by my usage of the clear() function. Thanks.

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  • Tool to diagonalize large matrices

    - by Xodarap
    I want to compute a diffusion kernel, which involves taking exp(b*A) where A is a large matrix. In order to play with values of b, I'd like to diagonalize A (so that exp(A) runs quickly). My matrix is about 25k x 25k, but is very sparse - only about 60k values are non-zero. Matlab's "eigs" function runs of out memory, as does octave's "eig" and R's "eigen." Is there a tool to find the decomposition of large, sparse matrices? Dunno if this is relevant, but A is an adjacency matrix, so it's symmetric, and it is full rank.

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  • Is there a way to write System.Drawing.Graphics to PDF from C#?

    - by Brett Ryan
    I have a whole bunch of 2D graphics that is being used for both rendering controls on screen and used to print, it's pretty custom graphics that couldn't be done by any 3rd party reporting tools or off the shelf controls. The program can generate PDF files of the printed content but when I wrote it I cheated and just print the Graphics object to an in memory image and then embed that into the PDF page. Since the users are emailing the documents they're finding they are too large. I've started writing the PDF from scratch using iText, however is there a way to get System.Drawing.Graphics content directly into PDF? The way iText works and Graphics works is completely different.

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  • numpy array C api

    - by wiso
    I have a C++ function returning a std::vector and I want to use it in python, so I'm using the C numpy api: static PyObject * py_integrate(PyObject *self, PyObject *args){ ... std::vector<double> integral; cpp_function(integral); // this change integral npy_intp size = {integral.size()}; PyObject *out = PyArray_SimpleNewFromData(1, &size, NPY_DOUBLE, &(integral[0])); return out; } when I call it from python, if I do import matplotlib.pyplot as plt a = py_integrate(parameters) print a fig = plt.figure() ax = fig.add_subplot(111) ax.plot(a) print a the first print is ok, the values are correct, but when I plot a they are not, and in particular in the second print I see very strange values like 1E-308 1E-308 ... or 0 0 0 ... as an unitialized memory. I don't understand why the first print is ok.

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  • double fork using vfork

    - by Oren S
    HI I am writing a part of a server which should dispatch some other child processes. Because I want to wait on some of the processes, and dispatch others without waiting for completion, I use double fork for the second kind of processes (thus avoiding the zombie processes). Problem is, my server holds a lot of memory, so forking takes a long time (even the copy-on-write fork used in Linux which copies only the paging tables) I want to replace the fork() with vfork(), and it's easy for the second fork (as it only calls execve() in the child), but I couldn't find any way I can replace the first one. Does anyone know how I can do that? Thanks! The server is a linux (RH5U4), written in C++.

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  • SQLite Transaction fills a table BEFORE the transaction is commited

    - by user1500403
    Halo I have a code that creates a datatable (in memory) from a select SQL statement. However I realised that this datatable is filling during the procedure rather as a result of the transaction comit statment, it does the job but its slow. WHat amI doing wrong ? Inalready.Clear() 'clears a dictionary Using connection As New SQLite.SQLiteConnection(conectionString) connection.Open() Dim sqliteTran As SQLite.SQLiteTransaction = connection.BeginTransaction() Try oMainQueryR = "SELECT * FROM detailstable Where name= :name AND Breed= :Breed" Dim cmdSQLite As SQLite.SQLiteCommand = connection.CreateCommand() Dim oAdapter As New SQLite.SQLiteDataAdapter(cmdSQLite) With cmdSQLite .CommandType = CommandType.Text .CommandText = oMainQueryR .Parameters.Add(":name", SqlDbType.VarChar) .Parameters.Add(":Breed", SqlDbType.VarChar) End With Dim c As Long = 0 For Each row As DataRow In list.Rows 'this is the list with 500 names If Inalready.ContainsKey(row.Item("name")) Then Else c = c + 1 Form1.TextBox1.Text = " Fill .... " & c Application.DoEvents() Inalready.Add(row.Item("name"), row.Item("Breed")) cmdSQLite.Parameters(":name").Value = row.Item("name") cmdSQLite.Parameters(":Breed").Value = row.Item("Breed") oAdapter.Fill(newdetailstable) End If Next oAdapter.FillSchema(newdetailstable, SchemaType.Source) Dim z = newdetailstable.Rows.Count 'At this point the newdetailstable is already filled up and I havent even comited the transaction ' sqliteTran.Commit() Catch ex As Exception End Try End Using

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