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• Java: ArrayList bottleneck

  - by Jack

  Hello, while profiling a java application that calculates hierarchical clustering of thousands of elements I realized that ArrayList.get occupies like half of the CPU needed in the clusterization part of the execution. The algorithm searches the two more similar elements (so it is O(n*(n+1)/2) ), here's the pseudo code: int currentMax = 0.0f for (int i = 0 to n) for (int j = i to n) get content i-th and j-th if their similarity > currentMax update currentMax merge the two clusters So effectively there are a lot of ArrayList.get involved. Is there a faster way? I though that since ArrayList should be a linear array of references it should be the quickest way and maybe I can't do anything since there are simple too many gets.. but maybe I'm wrong. I don't think using a HashMap could work since I need to get them all on every iteration and map.values() should be backed by an ArrayList anyway.. Otherwise should I try other collection libraries that are more optimized? Like google's one, or apache one.. Thanks

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• Wrapping/warping a CALayer/UIView (or OpenGL) in 3D (iPhone)

  - by jbrennan

  I've got a UIView (and thus a CALayer) which I'm trying to warp or bend slightly in 3D space. That is, imagine my UIView is a flat label which I want to partially wrap around a beer bottle (not 360 degrees around, just on one "side"). I figured this would be possible by applying a transform to the view's layer, but as far as I can tell, this transform is limited to rotation, scale and translation of the layer uniformly. I could be wrong here, as my linear algebra is foggy at this point, to say the least. How can I achieve this?

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• Android: Changing LinearLayout in a widget.

  - by Profete162

  Hello all, I have this really annoying problem: In my widget, i would like to change the background by code. I noticed on the Google doc than I can easily change the background of an Imageview: remoteViews.setImageViewResource(R.id.my_iv, R.drawable.my_bg); Ok, too easy, i want to change now the Linear layout.. What I read about the remoteview id that I can change a Bitmap, Int, Bool, String, etc... but not a drawable. So i guess i cannot use: remoteViews.setBitmap(R.id.my_ll,"setBackgroundDrawable",BitmapFactory.decodeResource(context.getResources(), R.drawablemy_bg)); I am totally disapointed and tried a last idea: views.setInt(R.id.my_ll,"setBackgroundResource",R.drawable.my_bg); But The logcat told me: android.widget.RemoteViews$ActionException:view: android.widget.LinearLayout can't use method with RemoteViews: setBackgroundResource(int) I am totally lost and I really don't know what to do... I would really appreciate any help. Thank a lot!

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• How to get image to pulse with opacity with JQuery

  - by Alex

  I am trying to get an image to change opacity smoothly over a duration of time. Here's the code I have for it. <script type="text/javascript"> pulsem(elementid){ var element = document.getElementById(elementid) jquery(element).pulse({opacity: [0,1]}, { duration: 100, // duration of EACH individual animation times: 3, // Will go three times through the pulse array [0,1] easing: 'linear', // easing function for each individual animation complete: function() { alert("I'm done pulsing!"); } }) </script> <a href="city.htm"><img src="waterloo.png" onmouseover="javascript:pulsem("waterloo")" border="0" class="env" id="waterloo"/></a> Also, is there a way for this to happen automatically without the need of a mouseover? Thanks.

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• Multithreading/Parallel Processing in PHP

  - by manyxcxi

  I have a PHP script that will generate a report using PHPExcel from data queried from a MySQL DB. Currently, it is linear in processing in that it gets the data back from MySQL, reads in the Excel template, writes the data to the template, then outputs it. I have optimized the code to the point that the data is only iterated over once, and there is very little processing done on the PHP side. The query returns hundreds of lines in less than .001 seconds, so it is running fast enough. After some timing I have found my bottlenecks to be (surprise, surprise) reading the template and writing the output. I would like to do this: Spawn a thread/process to read the template Spawn a thread/process to fetch the data Return back to parent thread - Parent thread will wait until both are complete Proceed on as normal My main questions are is this possible, is it worth it? If yes to both, how would you tackle it? Also, it is PHP 5 on CentOS

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• Error when trying to create a faceted plot in ggplot2

  - by John Horton

  I am trying to make a faceted plot in ggplot2 of the coefficients on the regressors from two linear models with the same predictors. The data frame I constructed is this: r.together> reg coef se y 1 (Intercept) 5.068608671 0.6990873 Labels 2 goodTRUE 0.310575129 0.5228815 Labels 3 indiaTRUE -1.196868662 0.5192330 Labels 4 moneyTRUE -0.586451273 0.6011257 Labels 5 maleTRUE -0.157618168 0.5332040 Labels 6 (Intercept) 4.225580743 0.6010509 Bonus 7 goodTRUE 1.272760149 0.4524954 Bonus 8 indiaTRUE -0.829588862 0.4492838 Bonus 9 moneyTRUE -0.003571476 0.5175601 Bonus 10 maleTRUE 0.977011737 0.4602726 Bonus The "y" column is a label for the model, reg are the regressors and coef and se are what you would think. I want to plot: g <- qplot(reg, coef, facets=.~y, data = r.together) + coord_flip() But when I try to display the plot, I get: > print(g) Error in names(df) <- output : 'names' attribute [2] must be the same length as the vector [1] What's strange is that qplot(reg, coef, colour=y, data = r.together) + coord_flip() plots as you would expect.

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• Adding audio channel using ffmpeg

  - by Raj

  Hi all, I am working on ffmpeg and trying to add a audio stream on the fly. I am using AudioQueues and I get raw audio buffer. I am encoding audio with linear PCM and hence the audio I get will be of raw format, which I know ffmpeg does accept it. But I cannot figure out how. I have looked into AVStream, where in we have to create a new stream for this audio channel but how do I encode it to a video which is already initialized in another AVStream structure. Overall, I would like to have an idea of the architecture of ffmpeg. I found it difficult to work since it is least documented. Any pointers or details are appreciated. Thanks and Regards, Raj Pawan G

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• Calculating determinant by hand

  - by ldigas

  Okey, this is only half programming, but let's see how you are on terms with manual calculations. I believe many of you did this on your university's while giving "linear systems" ... the problem is it's been so long I can't remember how to do it any more. I know quite a few algorithms for calculating determinants, and they all work fine ... for large systems, where one would never try to do it manually. Unfortunatelly, I'm soon going on an exam, where I do have to calculate it manually, up to the system of 5. So, I have a K(omega) matrix that looks like this: [2-(omega^2)*c -4 2 0 0] [-2 5-(omega^2)*c -4 1 0] [1 -4 6-(omega^2)*c -4 1] [0 1 -4 5-(omega^2)*c -2] [0 0 2 -4 2-(omega^2)*c] and I need all the omegas which satisfy the det[K(omega)]=0 criteria. What would be a good way to calculate it so it can be repeated in a manual process ?

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• Understanding glm$residuals and resid(glm)

  - by Michael Bishop

  Hi, Can you tell me what is returned by glm$residuals and resid(glm) where glm is a quasipoisson object. e.g. How would I create them using glm$y and glm$linear.predictors. glm$residuals n missing unique Mean .05 .10 .25 .50 .75 .90 .95 37715 10042 2174 -0.2574 -2.7538 -2.2661 -1.4480 -0.4381 0.7542 1.9845 2.7749 lowest : -4.243 -3.552 -3.509 -3.481 -3.464 highest: 8.195 8.319 8.592 9.089 9.416 resid(glm) n missing unique Mean .05 .10 .25 37715 0 2048 -2.727e-10 -1.0000 -1.0000 -0.6276 .50 .75 .90 .95 -0.2080 0.4106 1.1766 1.7333 lowest : -1.0000 -0.8415 -0.8350 -0.8333 -0.8288 highest: 7.2491 7.6110 7.6486 7.9574 10.1932

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• JQuery preventDefault() but still add the fragment path to the URL without navigating to the fragment

  - by jdln

  My question is similar to this one but none of the answers solve my problem: Use JQuery preventDefault(), but still add the path to the URL When a user clicks a fragment link, I need to remove the default behaviour of jumping to the fragment but still add the fragment to the URL. This code (taken from the link) will fire the animation, and then add the fragment to the URL. However the fragment is then navigated to, which im my case breaks my site. $("#login_link").click(function (e) { e.preventDefault(); $("#login").animate({ 'margin-top': 0 }, 600, 'linear', function(){ window.location.hash = $(this).attr('href'); }); });

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• How to sketch out an event-driven system?

  - by Jordan

  I'm trying to design a system in Node.js (an attempt at solving one of my earlier problems, using Node's concurrency) but I'm running into trouble figuring out how to draw a plan of how the thing should operate. I'm getting very tripped up thinking in terms of callbacks instead of returned values. The flow isn't linear, and it's really boggling my ability to draft it. How does one draw out an operational flow for an event-driven system? I need something I can look at and say "Ok, yes, that's how it will work. I'll start it over here, and it will give me back these results over here." Pictures would be very helpful for this one. Thanks. Edit: I'm looking for something more granular than UML, specifically, something that will help me transition from a blocking and object-oriented programming structure, where I'm comfortable, to a non-blocking and event driven structure, where I'm unfamiliar.

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• marquee text view in android

  - by raqz

  i tried various combinations as answered here in SO...but i am still not able to get the text to marquee... combination 1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent"> <TextView android:id="@+id/organizationText" android:layout_height="38px" android:gravity="center_horizontal" android:textColor="#0099CC" android:layout_gravity="center" android:textSize="08pt" android:layout_width="wrap_content" android:maxLines="1" android:ellipsize="marquee" android:fadingEdge="horizontal" android:marqueeRepeatLimit="marquee_forever" android:scrollHorizontally="true" android:focusable="true" android:focusableInTouchMode="true" /> </RelativeLayout> orgText.setSelected(true); orgText.setEllipsize(TruncateAt.MARQUEE); orgText.setText(organization); I tried without using setSelected but it still doesnt work. any help would be appreciated... also, this entire view is a part of Linear layout.

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• How does the linux kernel manage less than 1GB physical memory ?

  - by TheLoneJoker

  I'm learning the linux kernel internals and while reading "Understanding Linux Kernel", quite a few memory related questions struck me. One of them is, how the Linux kernel handles the memory mapping if the physical memory of say only 512 MB is installed on my system. As I read, kernel maps 0(or 16) MB-896MB physical RAM into 0xC0000000 linear address and can directly address it. So, in the above described case where I only have 512 MB: How can the kernel map 896 MB from only 512 MB ? What about user mode processes in this situation? Where are user mode processes in phys RAM? Every article explains only the situation, when you've installed 4 GB of memory and the kernel maps the 1 GB into kernel space and user processes uses the remaining amount of RAM. I would appreciate any help in improving my understanding. Thanks..!

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• tetris rotation

  - by Samuel

  Hey, For university we're supposed to write a game (the language is modula2 little chance you know it). Each tetromino is defined through a central piece and 3 relative pieces, Now when it comes to rotation i just rotate the relative blocks (linear algebra). What i am asking myself is how to handle the rotations a user does when the piece has already "landed" because than the user has a little time left to move his pieve quickly into the desired position but in tetris versions all over the web you can "rotate over" other pieces, but i dont seem to get it with my rotation. Over what piece do i need to rotate? are there guidelines? Thanks

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• How to place a Linearlayout at bottom inside a Relativelayout in android

  - by SANDHYA

  I need to place a linear layout at bottom inside a relativelayout which is the top most parent in xml. How can i do this? Please help me. <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@drawable/background" android:orientation="vertical" > <RelativeLayout ....... <<--- this should occupy total available space </Relativelayout <Linearlayout ....... <<-- this should place at bottom always with height 50dp </LineaLayout> </ReltiveLayout>

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• Send files using Content-Disposition: attachment in parallel

  - by Manos Dilaverakis

  I have a PHP page that sends a file to the browser depending on the request data it receives. getfile.php?get=something sends file A, getfile.php?get=somethingelse sends file B and so on and so forth. This is done like so: header('Content-Disposition: attachment; filename='. urlencode($filename)); readfile($fileURL); It works except it can only send one file at a time. Any other files requested are send in linear fashion. One starts as soon as another finishes. How can I get this to send files in parallel if the user requests another file while one is downloading?

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• Algorithm to generate radial gradient

  - by user146780

  I have this algorithm here: pc = # the point you are coloring now p0 = # start point p1 = # end point v = p1 - p0 d = Length(v) v = Normalize(v) # or Scale(v, 1/d) v0 = pc - p0 t = Dot(v0, v) t = Clamp(t/d, 0, 1) color = (start_color * t) + (end_color * (1 - t)) to generate point to point linear gradients. It works very well for me. I was wondering if there was a similar algorithm to generate radial gradients. By similar, I mean one that solves for color at point P rather than solve for P at a certain color (where P is the coordinate you are painting). Thanks

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• Is the heap actually a heap?

  - by ElectricDialect

  In .NET (and Java as far as I know), the area where objects are dynamically allocated is referred to as the managed heap. However, most documentation that describes how the managed heap works depicts it as a linear data structure, such as a linked list or stack. So, is the managed heap actually a heap, or is it implemented with some other data structure? If it actually does not use a heap data structure, is seems like a significant failure of terminology to overload the meaning of this word. If it is in fact a heap data structure, what is the value that satisfies the heap property: the size of the allocated memory region?

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• Producer/consumer in Grails?

  - by Mulone

  Hi all, I'm trying to implement a Consumer/Producer app in Grails, after several unsuccessful attempts at implementing concurrent threads. Basically I want to store all the events coming from a clients (through separate AJAX calls) in a single queue and then process such a queue in a linear way as soon as new events are added. This looks like a Producer/Consumer problem: http://en.wikipedia.org/wiki/Producer-consumer_problem How can I implement this in Grails (maybe with a timer or even better by generating an event 'process queue')? Basically I'd like to a have a singleton service waiting for new events in the queue and processing them linearly (even if the queue is loaded by several concurrent processes). Any hints? Cheers!

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• CSS3 gradient background set on body doesn't stretch but instead repeats?

  - by John Isaacks

  ok say the content inside the <body> totals 300px high. If I set the background of my <body> using -webkit-gradient or -moz-linear-gradient Then I maximize my window (or just make it taller than 300px) the gradient will be exactly 300px tall (the height of the content) and just repeat to fill the rest of the window. I am assuming this is not a bug since it is the same in both webkit and gecko. But is there a way to make the gradient stretch to fill the window instead of repeat?

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• The speed of .NET in numerical computing

  - by Yin Zhu

  In my experience, .net is 2 to 3 times slower than native code. (I implemented L-BFGS for multivariate optimization). I have traced the ads on stackoverflow to http://www.centerspace.net/products/ the speed is really amazing, the speed is close to native code. How can they do that? They said that: Q. Is NMath "pure" .NET? A. The answer depends somewhat on your definition of "pure .NET". NMath is written in C#, plus a small Managed C++ layer. For better performance of basic linear algebra operations, however, NMath does rely on the native Intel Math Kernel Library (included with NMath). But there are no COM components, no DLLs--just .NET assemblies. Also, all memory allocated in the Managed C++ layer and used by native code is allocated from the managed heap. Can someone explain more to me? Thanks!

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• Help with hash tables and quadratic probing in Java

  - by user313458

  I really need help with inserting into a hash table. I'm just not totally getting it right now. Could someone explain quadratic and linear probing in layman's terms? public void insert(String key) { int homeLocation = 0; int location = 0; int count = 0; if (find(key).getLocation() == -1) // make sure key is not already in the table { //****** ADD YOUR CODE HERE FOR QUADRATIC PROBING ******** } } This is the code I'm working on. I'm not asking anyone to do it, I just really need help with learning the whole concept Any help would be greatly appreciated.

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• How to create a container that holds different types of function pointers in C++?

  - by Alex

  I'm doing a linear genetic programming project, where programs are bred and evolved by means of natural evolution mechanisms. Their "DNA" is basically a container (I've used arrays and vectors successfully) which contain function pointers to a set of functions available. Now, for simple problems, such as mathematical problems, I could use one type-defined function pointer which could point to functions that all return a double and all take as parameters two doubles. Unfortunately this is not very practical. I need to be able to have a container which can have different sorts of function pointers, say a function pointer to a function which takes no arguments, or a function which takes one argument, or a function which returns something, etc (you get the idea)... Is there any way to do this using any kind of container ? Could I do that using a container which contains polymorphic classes, which in their turn have various kinds of function pointers? I hope someone can direct me towards a solution because redesigning everything I've done so far is going to be painful.

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• removing duplicate strings from a massive array in java efficiently?

  - by Preator Darmatheon

  I'm considering the best possible way to remove duplicates from an (Unsorted) array of strings - the array contains millions or tens of millions of stringz..The array is already prepopulated so the optimization goal is only on removing dups and not preventing dups from initially populating!! I was thinking along the lines of doing a sort and then binary search to get a log(n) search instead of n (linear) search. This would give me nlogn + n searches which althout is better than an unsorted (n^2) search = but this still seems slow. (Was also considering along the lines of hashing but not sure about the throughput) Please help! Looking for an efficient solution that addresses both speed and memory since there are millions of strings involved without using Collections API!

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• Spatial Index for Rectangles With Fast Insert

  - by TheCloudlessSky

  Hello, I'm looking for a data structure that provides indexing for Rectangles. I need the insert algorithm to be as fast as possible since the rectangles will be moving around the screen (think of dragging a rectangle with your mouse to a new position). I've looked into R-Trees, R+Trees, kD-Trees, Quad-Trees and B-Trees but from my understanding insert's are usually slow. I'd prefer to have inserts at sub-linear time complexity so maybe someone can prove me wrong about either of the listed data structures. I should be able to query the data structure for what rectangles are at point(x, y) or what rectangles intersect rectangle(x, y, width, height). EDIT: The reason I want insert so fast is because if you think of a rectangle being moved around the screen, they're going to have to be removed and then re-inserted. Thanks!

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