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• Recommended textbook for machine-level programming?

  - by Norman Ramsey

  I'm looking at textbooks for an undergraduate course in machine-level programming. If the perfect book existed, this is what it would look like: Uses examples written in C or assembly language, or both. Covers machine-level operations such as two's-complement integer arithmetic, bitwise operations, and floating-point arithmetic. Explains how caches work and how they affect performance. Explains machine instructions or assembly instructions. Bonus if the example assembly language includes x86; triple bonus if it includes x86-64 (aka AMD64). Explains how C values and data structures are represented using hardware registers and memory. Explains how C control structures are translated into assembly language using conditional and unconditional branch instructions. Explains something about procedure calling conventions and how procedure calls are implemented at the machine level. Books I might be interested in would probably have the words "machine organization" or "computer architecture" in the title. Here are some books I'm considering but am not quite happy with: Computer Systems: A Programmer's Perspective by Randy Bryant and Dave O'Hallaron. This is quite a nice book, but it's a book for a broad, shallow course in systems programming, and it contains a great deal of material my students don't need. Also, it is just out in a second edition, which will make it expensive. Computer Organization and Design: The Hardware/Software Interface by Dave Patterson and John Hennessy. This is also a very nice book, but it contains way more information about how the hardware works than my students need. Also, the exercises look boring. Finally, it has a show-stopping bug: it is based very heavily on MIPS hardware and the use of a MIPS simulator. My students need to learn how to use DDD, and I can't see getting this to work on a simulator. Not to mention that I can't see them cross-compiling their code for the simulator, and so on and so forth. Another flaw is that the book mentions the x86 architecture only to sneer at it. I am entirely sympathetic to this point of view, but news flash! You guys lost! Write Great Code Vol I: Understanding the Machine by Randall Hyde. I haven't evaluated this book as thoroughly as the other two. It has a lot of what I need, but the translation from high-level language to assembler is deferred to Volume Two, which has mixed reviews. My students will be annoyed if I make them buy a two-volume series, even if the price of those two volumes is smaller than the price of other books. I would really welcome other suggestions of books that would help students in a class where they are to learn how C-language data structures and code are translated to machine-level data structures and code and where they learn how to think about performance, with an emphasis on the cache.

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• How to output JOINed tables?

  - by ilhan

  $id=(int)$_GET["id"]; $result = mysql_query("SELECT questionstable.*, categorytable.name FROM questionstable INNER JOIN categorytable ON categorytable.id = questionstable.category WHERE id=$id"); $row = mysql_fetch_assoc($result); Warning: mysql_fetch_assoc() expects parameter 1 to be resource, boolean given in C:\Program Files\EasyPHP-5.3.4.0\www\scsoru.php on line 33

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• Database time data retrieval, time based queries

  - by Raphael Pineda

  I am new to time manipulation or time arithmetic operations and am currently developing a navigation system with Web server based information and currently I have this Database that contains a table peek hours whose columns are id, start_time, end_time , edge_id, day_of_the_week, edge_weight ------------------------------------------------------------------------ | Peek Hours | ------------------------------------------------------------------------ | | | | | | | | id | start_time | end_time | edge_id | day_of_the_week | edge_weight | | | | | | | | ------------------------------------------------------------------------ I am using PHP as a webservice and so based on the current time i want to get all the records that would fit this equation start_time< current_time < end_time

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• Set theory problem - transform one set to another

  - by mwnorman

  Given 2 sets A & B, is there an algorithm that will generate the insert/update/delete operations required to transform set A into set B?

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• What is the need of collection framework in java?

  - by JavaUser

  Hi, What is the need of Collection framework in Java since all the data operations(sorting/adding/deleting) are possible with Arrays and moreover array is suitable for memory consumption and performance is also better compared with Collections. Can anyone point me a real time data oriented example which shows the difference in both(array/Collections) of these implementations. Thx

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• ROR heroku PostGres issue

  - by oelbrenner

  getting error: ActiveRecord::StatementInvalid (PGError: ERROR: argument of HAVING must be type boolean, not type timestamp without time zone controller code snippet: def inactive @number_days = params[:days].to_i || 90 @clients = Client.find(:all, :include = :appointments, :conditions = ["clients.user_id = ? AND appointments.start_time <= ?", current_user.id, @number_days.days.ago], :group = 'client_id', :having = 'MAX(appointments.start_time)' ) end

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• Are there any implementations of multiset for .Net?

  - by dangph

  I'm looking for a .Net implementation of a multiset. Can anyone recommend a good one? (A multiset, or bag, is a set that can have duplicate values, and on which you can do set operations: intersection, difference, etc. A shopping cart for instance could be thought of as a multiset because you can have multiple occurrences of the same product.)

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• What would be the good name for this operation?

  - by Rogach

  I see that Scala standard library misses the method to get ranges of objects in the collection, that satisfy the predicate: def <???>(p: A => Boolean): List[List[A]] = { val buf = collection.mutable.ListBuffer[List[A]]() var elems = this.dropWhile(e => !p(e)) while (elems.nonEmpty) { buf += elems.takeWhile(p) elems = elems.dropWhile(e => !p(e)) } buf.toList } What would be the good name for such method? And is my implementation good enough?

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• java filenames filter pattern

  - by Sergey

  Hello, I need to implement File[] files = getFiles( String folderName, String ptrn ); Where ptrn is a command prompt style pattern like "*2010*.txt" I'm familar with FilenameFilter class, but can't implement public boolean accept(File dir, String filename) because String.matches() doesn't accept such patterns. Thanks!

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• Built-in precedence for Expression Trees?

  - by jdk

  I'm unable to find the .NET FCL built-in concept of precedence to leverage while constructing Expression Trees. Ref System.Linq.Expressions Namespace. Is this something that must be handled manually in code, or is it somehow implicit and I'm not recognizing it, maybe through helper methods or classes? I want to apply it to math operations to ensure 3 + 5 * 10 results in 53 instead of 80.

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• Getting a specific bit value in a byte string

  - by ignoramus

  There is a byte at a specific index in a byte string which represents eight flags; one flag per bit in the byte. If a flag is set, its corresponding bit is 1, otherwise its 0. For example, if I've got b'\x21' the flags would be 0001 0101 # Three flags are set at indexes 3, 5 and 7 # and the others are not set What would be the best way to get each bit value in that byte, so I know whether a particular flag is set or not? (Preferably using bitwise operations)

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• Android Couchdb - libcouch and IPC Aidl Services

  - by dirtySanchez

  I am working on a native CouchdDB app with android. Now just this week CouchOne released libcouch, described as "Library files needed to interact with CouchDB on Android": couchone_libcouch@Github It is a basic app that installs CouchDB if the CouchDB service (that comes with CouchDB if it was installed previously) can't be bound to. To be more precise, as I understand it: libcouch estimates CouchDb's presence on the device by trying to bind to a IPC Service from CouchDB and through that service wants communicate with CouchDB. Please see the method "attemptLaunch()" at CouchAppLauncher.class for reviewing this: public void attemptLaunch() { Log.i(TAG,"1.) called attemptLaunch"); Intent intent = new Intent(ICouchService.class.getName()); Log.i(TAG,"1.a) setup Intent"); Boolean canStart = bindService(intent, couchServiceConn, Context.BIND_AUTO_CREATE); Log.i(TAG,"1.b bound service. canStart: " + Boolean.toString(canStart)); if (!canStart) { setContentView(R.layout.install_couchdb); TextView label = (TextView) findViewById(R.id.install_couchdb_text); Button btn = (Button) this.findViewById(R.id.install_couchdb_btn); String text = getString(R.string.app_name) + " requires Apache CouchDB to be installed."; label.setText(text); // Launching the market will fail on emulators btn.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { launchMarket(); finish(); } }); } } The question(s) I have about this are: libcouch never is able to "find" a previously installed CouchDB. It always attempts to install CouchDB from the market. This is because it never actually is able to bind to the CouchDBService. As I understand the purpose auf AIDL generated service interfaces, the actual service that intends to offer it's IPC to other applications should make use of AIDL. In this case the AIDL has been moved to the application that is trying to bind to the remote service, which is libcouch in this case. Reviewing the commits the AIDL files have just been moved out of that repository to libcouch. For complete linkage, here's the link to the Android CouchDB sources: github.com/couchone/libcouch-android Now, I could be completely wrong in my findings, it could also be lincouch's Manifest that s missing something, but I am really looking forward to get some answers!

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• Asp.Net Mvc - Html.TextBox - Set Autofocus property

  - by Melursus

  In Html 5, there is an new attribute on textbox call autofocus. The problem is it is a boolean value (there or not there) It should look something like : <input name="a" value="" autofocus> I try : <%= Html.TextBox( "a", null, new { autofocus } ) %> But, it's give me an error because I'm not setting a value to autofocus... I know I can do it manually, but can I do it with Html.TextBox ?

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• Preventing a RichTextBox operation from being added to the control's Undo stack

  - by shadeMe

  Editing a RichTextBox control's text (more specifically, modifying selection font/color) programmatically seems to be tracked in the control's built in undo stack. Is there a way, short of writing my own undo/redo manager, to prevent certain actions/operations from being added to the undo stack ?

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• How to test an iPad app's speed without an iPad when the simulator runs faster?

  - by Tyler

  Title says it all: I have some operations in my iPad app that are CPU-intensive, and I'd really like to be able to test them on the simulator, making sure things will still run smoothly on the actual iPad. Is there any way I can do this?

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• How to discover whether Geo-tagging is enabled with Twitter / MGTwitterEngine?

  - by cannyboy

  Using Matt Gemmell's MGTwitterEngine, how would I find out if the user (that i'm logged in as) has geo tagging enabled? According to the Twitter API, there is a 'geo_enabled' boolean flag, but I can't work out how to interrogate it using MGTwitterEngine. http://apiwiki.twitter.com/Geotagging-API-Best-Practice

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• text search with two parameters

  - by stck777

  The user should input two strings and the script will performe a text search: $sql = "SELECT * FROM table_one WHERE name='%$str1%' AND MATCH (street, city, pin) AGAINST ('$hrtg'IN BOOLEAN MODE)"; somehow the % does not work, but it alwas did actually. please help?

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• High speed matrix manipulation in c#?

  - by Donnie

  I'm working on some image manipulation code in c# and need to do some matrix operations (specifically 2D convolution). I have the code written in matlab which uses the conv2 function ... is there a library for C# / .NET that does good high-speed matrix manipulations? I'd be fine if it requires some specific GPU and does the matrix math on-GPU if that's what it takes.

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• Android HelloGoogleMaps to OSMdroid (Open Street Maps)

  - by birgit

  I am trying to reproduce a working HelloGoogleMaps app in Open Street Maps - but I have trouble including the itemized overlay in OSMdroid. I have looked at several resources but I cannot figure out how to fix the error on OsmItemizedOverlay - I guess I am constructing OsmItemizedOverlay wrongly or have a mixup with OsmItemizedOverlay and ItemizedOverlay? But everything I tried to change just raised more errors... "Implicit super constructor ItemizedOverlay() is undefined. Must explicitly invoke another constructor" "Cannot make a static reference to the non-static method setMarker(Drawable) from the type OverlayItem" - I hope someone can help me getting the class definition straight? Thanks so much! package com.example.osmdroiddemomap; import java.util.ArrayList; import android.app.AlertDialog; import android.content.Context; import android.graphics.Point; import android.graphics.drawable.Drawable; import org.osmdroid.api.IMapView; import org.osmdroid.views.*; import org.osmdroid.views.overlay.*; import org.osmdroid.views.overlay.OverlayItem.HotspotPlace; public class OsmItemizedOverlay extends ItemizedOverlay<OverlayItem> { Context mContext; private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>(); //ERRORS are raised by the following 3 lines: public OsmItemizedOverlay(Drawable defaultMarker, Context context) { OverlayItem.setMarker(defaultMarker); OverlayItem.setMarkerHotspot(HotspotPlace.CENTER); mContext = context; } public void addOverlay(OverlayItem overlay) { mOverlays.add(overlay); populate(); } @Override protected OverlayItem createItem(int i) { return mOverlays.get(i); } @Override public int size() { return mOverlays.size(); } protected boolean onTap(int index) { OverlayItem item = mOverlays.get(index); AlertDialog.Builder dialog = new AlertDialog.Builder(mContext); dialog.setTitle(item.getTitle()); dialog.setMessage(item.getSnippet()); dialog.show(); return true; } @Override public boolean onSnapToItem(int arg0, int arg1, Point arg2, IMapView arg3) { // TODO Auto-generated method stub return false; } }

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• Python vs. Java performance (runtime speed)

  - by Bijan

  Ignoring all the characteristics of each languages and focusing SOLELY on speed, which language is better performance-wise? You'd think this would be a rather simple question to answer, but I haven't found a decent one. I'm aware that some types of operations may be faster with python, and vice-versa, but I cannot find any detailed information on this. Can anyone shed some light on the performance differences?

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• JProgressBar.stringPainted(true); is not working

  - by Mirza Ghalib

  This is a part of my java code, in this code I have written that when I click the button the value of JProgressBar should becomes 0 and stringPainted(); becomes true, but "string painted" is not visible when I click the button, please help. import java.awt.Color; import java.awt.Dimension; import java.awt.FlowLayout; import java.awt.Graphics; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JProgressBar; public class R implements ActionListener { static int y; CustomProgressBar b = new CustomProgressBar(); public static void main(String arg[]) throws Exception { new R(); } public R() throws Exception { JFrame f = new JFrame(); JButton btn = new JButton("Click"); f.setExtendedState(JFrame.MAXIMIZED_BOTH); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.setUndecorated(true); f.setLayout(new FlowLayout()); btn.addActionListener(this); f.add(b); f.add(btn); f.setVisible(true); } class CustomProgressBar extends JProgressBar{ private static final long serialVersionUID = 1L; private boolean isStringToBePainted = false; public CustomProgressBar() { super(JProgressBar.VERTICAL,0,100); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); if(isStringToBePainted ) { Dimension size = CustomProgressBar.this.getSize(); if( CustomProgressBar.this.getPercentComplete()<0.9 ) R.y = (int)( size.height - size.height * CustomProgressBar.this.getPercentComplete() ); String text = getString(); g.setColor(Color.BLACK ); g.drawString(text, 0, R.y); } } @Override public void setStringPainted(boolean b) { isStringToBePainted=b; } } @Override public void actionPerformed(ActionEvent e) { b.setValue(0); b.setStringPainted(true); } }

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• Converting standard mbeans to dynamic mbeans / Code generation

  - by saugata

  I have a bunch of standard MBeans which I need to convert to dynamic MBeans, (main purpose is to add user friendly descriptions to attributes, operations and operation parameters). I was wondering if there is any tool which can make my job easier by generating skeleton code for dynamic MBeans from the existing standard MBeans.

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• How do I use an Entity Framework 4 model without a real database?

  - by Ivan

  I don't need any data to be stored. I'd like an application to start, create an Entity Framework entities container based on the model I've designed but having no data records in it, then generate some data (from user input and other input sources), work with it and discard all the data on close, without propagating any data operations made with EF contect to a real database hosted on server or in a file. How do I implement such a pattern? I use Entity Framework 4 and Visual Studio 2010.

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• Value object or not for 3d points ?

  - by Stefano Borini

  I need to develop a geometry library in python, describing points, lines and planes in 3d space, and various geometry operations. Related to my previous question. The main issue in the design is if these entities should have identity or not. I was wondering if there's a similar library out there (developed in another language) to take inspiration from, what is the chosen design, and in particular the reason for one choice vs. the other.

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• Python vs Bash - In which kind of tasks each one outruns the other performance-wise ?

  - by Doppelganger

  Obviously Python is more user friendly, a quick search on google shows many results that say that, as Python is byte-compiled is usually faster. I even found this that claims that you can see an improvement of over 2000% on dictionary-based operations. What is your experience on this matter? In which kind of task each one is a clear winner?

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