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  • Object Slicing, Is it advantage ?

    - by harigm
    Object slicing is some thing that object looses some of its attributes or functions when a child class is assigned to base class. Some thing like Class A{ } Class B extends A{ } Class SomeClass{ A a = new A(); B b = new B(); // Some where if might happen like this */ a = b; (Object slicing happens) } Do we say Object slicing is any beneficial in any ways? If yes, can any one please tell me how object slicing be a helpful in development and where it might be helpful?

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  • slicing behaviour question of a list of lists

    - by Lex
    I got a function like def f(): ... ... return [list1, list2] this returns a list of lists [[list1.item1,list1.item2,...],[list2.item1,list2.item2,...]] now when I do the following: for i in range(0,2):print f()[i][0:10] it works and print the lists sliced but if i do print f()[0:2][0:10] then it prints the lists ignoring the [0:10] slicing. Is there any way to make the second form work or do I have to loop every time to get the desired result?

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  • Object slicing in Java.

    - by ferrari fan
    Can you take a subclass object and somehow convert it to an object of the same type as the parent class and at the same time slicing all the fields that are not part of the parent class? I know you can do this in C++, but I have no idea how to do it in Java.

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  • Issues with time slicing

    - by user12331
    I was trying to see the effect of time slicing. And how it can consume significant amount of time. Actually, I was trying to divide a certain work into number of threads and see the effect. I have a two core processor. So two threads can run in parallel. I was trying to see if I have a work w that is done by 2 threads, and if I have the same work done by t threads with each thread doing w/t of the work. How much does time slicing play a role in it As time slicing is time consuming process, I was expecting that when I do the same work using a two thread process or by a t thread process, the amount of time taken by the t thread process will be more Any suggestions?

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  • Python: Implementing slicing in __getitem__

    - by nicotine
    I am trying to implement slice functionality for a class I am making that creates a vector representation. I have this code so far, which I believe will properly implement the slice but whenever I do a call like v[4] where v is a vector python returns an error about not having enough parameters. So I am trying to figure out how to define the getitem class to handle both plain indexes and slicing. def __getitem__(self, start, stop, step): indx = start if stop == None: end = start + 1 else: end = stop if step == None: stride = 1 else: stride = step return self.__data[indx:end:stride]

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  • slicing a 2d numpy array

    - by MedicalMath
    The following code: import numpy as p myarr=[[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6],[0,1],[0,6]] copy=p.array(myarr) p.mean(copy)[:,1] Is generating the following error message: Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> p.mean(copy)[:,1] IndexError: 0-d arrays can only use a single () or a list of newaxes (and a single ...) as an index I looked up the syntax at this link and I seem to be using the correct syntax to slice. However, when I type copy[:,1] into the Python shell, it gives me the following output, which is clearly wrong, and is probably what is throwing the error: array([1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6, 1, 6]) Can anyone show me how to fix my code so that I can extract the second column and then take the mean of the second column as intended in the original code above? EDIT: Thank you for your solutions. However, my posting was an oversimplification of my real problem. I used your solutions in my real code, and got a new error. Here is my real code with one of your solutions that I tried: filteredSignalArray=p.array(filteredSignalArray) logical=p.logical_and(EndTime-10.0<=matchingTimeArray,matchingTimeArray<=EndTime) finalStageTime=matchingTimeArray.compress(logical) finalStageFiltered=filteredSignalArray.compress(logical) for j in range(len(finalStageTime)): if j == 0: outputArray=[[finalStageTime[j],finalStageFiltered[j]]] else: outputArray+=[[finalStageTime[j],finalStageFiltered[j]]] print 'outputArray[:,1].mean() is: ',outputArray[:,1].mean() And here is the error message that is now being generated by the new code: File "mypath\myscript.py", line 1545, in WriteToOutput10SecondsBeforeTimeMarker print 'outputArray[:,1].mean() is: ',outputArray[:,1].mean() TypeError: list indices must be integers, not tuple Second EDIT: This is solved now that I added: outputArray=p.array(outputArray) above my code. I have been at this too many hours and need to take a break for a while if I am making these kinds of mistakes.

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  • Python slicing a string using space characters and a maximum length

    - by chrism
    I'd like to slice a string up in a similar way to .split() (so resulting in a list) but in a more intelligent way: I'd like it to split it into chunks that are up to 15 characters, but are not split mid word so: string = 'A string with words' [splitting process takes place] list = ('A string with','words') The string in this example is split between 'with' and 'words' because that's the last place you can split it and the first bit be 15 characters or less.

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  • Slicing a time range into parts

    - by beporter
    First question. Be gentle. I'm working on software that tracks technicians' time spent working on tasks. The software needs to be enhanced to recognize different billable rate multipliers based on the day of the week and the time of day. (For example, "Time and a half after 5 PM on weekdays.") The tech using the software is only required to log the date, his start time and his stop time (in hours and minutes). The software is expected to break the time entry into parts at the boundaries of when the rate multipliers change. A single time entry is not permitted to span multiple days. Here is a partial sample of the rate table. The first-level array keys are the days of the week, obviously. The second-level array keys represent the time of the day when the new multiplier kicks in, and runs until the next sequential entry in the array. The array values are the multiplier for that time range. [rateTable] => Array ( [Monday] => Array ( [00:00:00] => 1.5 [08:00:00] => 1 [17:00:00] => 1.5 [23:59:59] => 1 ) [Tuesday] => Array ( [00:00:00] => 1.5 [08:00:00] => 1 [17:00:00] => 1.5 [23:59:59] => 1 ) ... ) In plain English, this represents a time-and-a-half rate from midnight to 8 am, regular rate from 8 to 5 pm, and time-and-a-half again from 5 till 11:59 pm. The time that these breaks occur may be arbitrary to the second and there can be an arbitrary number of them for each day. (This format is entirely negotiable, but my goal is to make it as easily human-readable as possible.) As an example: a time entry logged on Monday from 15:00:00 (3 PM) to 21:00:00 (9 PM) would consist of 2 hours billed at 1x and 4 hours billed at 1.5x. It is also possible for a single time entry to span multiple breaks. Using the example rateTable above, a time entry from 6 AM to 9 PM would have 3 sub-ranges from 6-8 AM @ 1.5x, 8AM-5PM @ 1x, and 5-9 PM @ 1.5x. By contrast, it's also possible that a time entry may only be from 08:15:00 to 08:30:00 and be entirely encompassed in the range of a single multiplier. I could really use some help coding up some PHP (or at least devising an algorithm) that can take a day of the week, a start time and a stop time and parse into into the required subparts. It would be ideal to have the output be an array that consists of multiple entries for a (start,stop,multiplier) triplet. For the above example, the output would be: [output] => Array ( [0] => Array ( [start] => 15:00:00 [stop] => 17:00:00 [multiplier] => 1 ) [1] => Array ( [start] => 17:00:00 [stop] => 21:00:00 [multiplier] => 1.5 ) ) I just plain can't wrap my head around the logic of splitting a single (start,stop) into (potentially) multiple subparts.

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  • C++ polymorphism and slicing

    - by Draco Ater
    The following code, prints out Derived Base Base But I need every Derived object put into User::items, call its own print function, but not the base class one. Can I achieve that without using pointers? If it is not possible, how should I write the function that deletes User::items one by one and frees memory, so that there should not be any memory leaks? #include <iostream> #include <vector> #include <algorithm> using namespace std; class Base{ public: virtual void print(){ cout << "Base" << endl;} }; class Derived: public Base{ public: void print(){ cout << "Derived" << endl;} }; class User{ public: vector<Base> items; void add_item( Base& item ){ item.print(); items.push_back( item ); items.back().print(); } }; void fill_items( User& u ){ Derived d; u.add_item( d ); } int main(){ User u; fill_items( u ); u.items[0].print(); }

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  • Type Object does not support slicing Unity3D

    - by Vish
    I am getting the following error in my code and I can't seem to understand why. Can anyone help me with it? This is my current code. The line causing the error is marked in a comment near the end. var rows : int = 4; var cols : int = 4; var totalCards : int = cols * rows; var matchesNeedToWin : int = totalCards * 0.5; var matchesMade : int = 0; var cardW : int = 100; var cardH : int = 100; var aCards : Array; var aGrid : Array; // This Array will store the two cards that the player flipped var aCardsFlipped : ArrayList; // To prevent player from clicking buttons when we don't want him to var playerCanClick : boolean; var playerHasWon : boolean = false; class Card extends System.Object { var isFaceUp : boolean = false; var isMatched : boolean = false; var img : String; function Card () { img = "robot"; } } function Start () { var i : int = 0; var j : int = 0; playerCanClick = true; aCards = new Array (); aGrid = new Array (); aCardsFlipped = new ArrayList (); for ( i = 0; i < rows; i++) { aGrid [i] = new Array (); for (j = 0; j < cols; cols++ ) { aGrid [i] [j] = new Card (); // <------ Error over here } } } function Update () { Debug.Log("Game Screen has loaded"); } The error states as follows: Error BCE0048: Type 'Object' does not support slicing. (BCE0048) (Assembly-UnityScript)

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  • Slicing the EDG

    - by Antony Reynolds
    Different SOA Domain Configurations In this blog entry I would like to introduce three different configurations for a SOA environment.  I have omitted load balancers and OTD/OHS as they introduce a whole new round of discussion.  For each possible deployment architecture I have identified some of the advantages. Super Domain This is a single EDG style domain for everything needed for SOA/OSB.   It extends the standard EDG slightly but otherwise assumes a single “super” domain. This is basically the SOA EDG.  I have broken out JMS servers and Coherence servers to improve scalability and reduce dependencies. Key Points Separate JMS allows those servers to be kept up separately from rest of SOA Domain, allowing JMS clients to post messages even if rest of domain is unavailable. JMS servers are only used to host application specific JMS destinations, SOA/OSB JMS destinations remain in relevant SOA/OSB managed servers. Separate Coherence servers allow OSB cache to be offloaded from OSB servers. Use of Coherence by other components as a shared infrastructure data grid service. Coherence cluster may be managed by WLS but more likely run as a standalone Coherence cluster. Benefits Single Administration Point (1 Admin Server) Closely follows EDG with addition of application specific JMS servers and standalone Coherence servers for OSB caching and application specific caches. Coherence grid can be scaled independent of OSB/SOA. JMS queues provide for inter-application communication. Drawbacks Patching is an all or nothing affair. Startup time for SOA may be slow if large number of composites deployed. Multiple Domains This extends the EDG into multiple domains, allowing separate management and update of these domains.  I see this type of configuration quite often with customers, although some don't have OWSM, others don't have separate Coherence etc. SOA & BAM are kept in the same domain as little benefit is obtained by separating them. Key Points Separate JMS allows those servers to be kept up separately from rest of SOA Domain, allowing JMS clients to post messages even if other domains are unavailable. JMS servers are only used to host application specific JMS destinations, SOA/OSB JMS destinations remain in relevant SOA/OSB managed servers. Separate Coherence servers allow OSB cache to be offloaded from OSB servers. Use of Coherence by other components as a shared infrastructure data grid service. Coherence cluster may be managed by WLS but more likely run as a standalone Coherence cluster. Benefits Follows EDG but in separate domains and with addition of application specific JMS servers and standalone Coherence servers for OSB caching and application specific caches. Coherence grid can be scaled independent of OSB/SOA. JMS queues provide for inter-application communication. Patch lifecycle of OSB/SOA/JMS are no longer lock stepped. JMS may be kept running independently of other domains allowing applications to insert messages fro later consumption by SOA/OSB. OSB may be kept running independent of other domains, allowing service virtualization to continue independent of other domains availability. All domains use same OWSM policy store (MDS-WSM). Drawbacks Multiple domains to manage and configure. Multiple Admin servers (single view requires use of Grid Control) Multiple Admin servers/WSM clusters waste resources. Additional homes needed to enjoy benefits of separate patching. Cross domain trust needs setting up to simplify cross domain interactions. Startup time for SOA may be slow if large number of composites deployed. Shared Service Environment This model extends the previous multiple domain arrangement to provide a true shared service environment.This extends the previous model by allowing multiple additional SOA domains and/or other domains to take advantage of the shared services.  Only one non-shared domain is shown, but there could be multiple, allowing groups of applications to share patching independent of other application groups. Key Points Separate JMS allows those servers to be kept up separately from rest of SOA Domain, allowing JMS clients to post messages even if other domains are unavailable. JMS servers are only used to host application specific JMS destinations, SOA/OSB JMS destinations remain in relevant SOA/OSB managed servers. Separate Coherence servers allow OSB cache to be offloaded from OSB servers. Use of Coherence by other components as a shared infrastructure data grid service Coherence cluster may be managed by WLS but more likely run as a standalone Coherence cluster. Shared SOA Domain hosts Human Workflow Tasks BAM Common "utility" composites Single OSB domain provides "Enterprise Service Bus" All domains use same OWSM policy store (MDS-WSM) Benefits Follows EDG but in separate domains and with addition of application specific JMS servers and standalone Coherence servers for OSB caching and application specific caches. Coherence grid can be scaled independent of OSB/SOA. JMS queues provide for inter-application communication. Patch lifecycle of OSB/SOA/JMS are no longer lock stepped. JMS may be kept running independently of other domains allowing applications to insert messages fro later consumption by SOA/OSB. OSB may be kept running independent of other domains, allowing service virtualization to continue independent of other domains availability. All domains use same OWSM policy store (MDS-WSM). Supports large numbers of deployed composites in multiple domains. Single URL for Human Workflow end users. Single URL for BAM end users. Drawbacks Multiple domains to manage and configure. Multiple Admin servers (single view requires use of Grid Control) Multiple Admin servers/WSM clusters waste resources. Additional homes needed to enjoy benefits of separate patching. Cross domain trust needs setting up to simplify cross domain interactions. Human Workflow needs to be specially configured to point to shared services domain. Summary The alternatives in this blog allow for patching to have different impacts, depending on the model chosen.  Each organization must decide the tradeoffs for itself.  One extreme is to go for the shared services model and have one domain per SOA application.  This requires a lot of administration of the multiple domains.  The other extreme is to have a single super domain.  This makes the entire enterprise susceptible to an outage at the same time due to patching or other domain level changes.  Hopefully this blog will help your organization choose the right model for you.

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  • RUN FUNCTION AFTER SOMETIME IN JQUERY & AUTOMATIC SLICING OF IMAGES

    - by user2697032
    I am not being able to start the automatic slicing of images, it is happening only after a click, how should i modify my code so that i get to change the slicing of the images automatically. <!DOCTYPE html> <html lang="en"> <head> <title>Slicebox - 3D Image Slider</title> <meta charset="UTF-8" /> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta name="description" content="Slicebox - 3D Image Slider with Fallback" /> <meta name="keywords" content="jquery, css3, 3d, webkit, fallback, slider, css3, 3d transforms, slices, rotate, box, automatic" /> <meta name="author" content="Pedro Botelho for Codrops" /> <link rel="shortcut icon" href="../favicon.ico"> <link rel="stylesheet" type="text/css" href="css/demo.css" /> <link rel="stylesheet" type="text/css" href="css/slicebox.css" /> <link rel="stylesheet" type="text/css" href="css/custom.css" /> <script type="text/javascript" src="js/modernizr.custom.46884.js"></script> </head> <body onload="funct()"> <div class="container"> <div class="codrops-top clearfix"> <a href="http://tympanus.net/Development/AutomaticImageMontage/"><span>&laquo; Previous Demo: </span>Automatic Image Montage</a> <span class="right"> <a target="_blank" href="http://www.flickr.com/photos/strupler/">Images by <strong>ND Strupler</strong></a> <a href="http://tympanus.net/codrops/?p=5657"><strong>Back to the Codrops Article</strong></a> </span> </div> <h1>Slicebox <span>A fresh 3D image slider with graceful fallback</span></h1> <div class="more"> <ul id="sb-examples"> <li>More examples:</li> <li class="selected"><a href="index.html">Example 1</a></li> <li><a href="index2.html">Example 2</a></li> <li><a href="index3.html">Example 3</a></li> <li><a href="index4.html">Example 4</a></li> </ul> </div> <div class="wrapper" id="checkthis"> <ul id="sb-slider" class="sb-slider"> <li> <a href="http://www.flickr.com/photos/strupler/2969141180" target="_blank"><img src="images/1.jpg" alt="image1"/></a> <div class="sb-description"> <h3>Creative Lifesaver</h3> </div> </li> <li> <a href="http://www.flickr.com/photos/strupler/2968268187" target="_blank"><img src="images/2.jpg" alt="image2"/></a> <div class="sb-description"> <h3>Honest Entertainer</h3> </div> </li> <li> <a href="http://www.flickr.com/photos/strupler/2968114825" target="_blank"><img src="images/3.jpg" alt="image1"/></a> <div class="sb-description"> <h3>Brave Astronaut</h3> </div> </li> <li> <a href="http://www.flickr.com/photos/strupler/2968122059" target="_blank"><img src="images/4.jpg" alt="image1"/></a> <div class="sb-description"> <h3>Affectionate Decision Maker</h3> </div> </li> <li> <a href="http://www.flickr.com/photos/strupler/2969119944" target="_blank"><img src="images/5.jpg" alt="image1"/></a> <div class="sb-description"> <h3>Faithful Investor</h3> </div> </li> <li> <a href="http://www.flickr.com/photos/strupler/2968126177" target="_blank"><img src="images/6.jpg" alt="image1"/></a> <div class="sb-description"> <h3>Groundbreaking Artist</h3> </div> </li> <li> <a href="http://www.flickr.com/photos/strupler/2968945158" target="_blank"><img src="images/7.jpg" alt="image1"/></a> <div class="sb-description"> <h3>Selfless Philantropist</h3> </div> </li> </ul> <div id="shadow" class="shadow"></div> <div id="nav-arrows" class="nav-arrows"> <a href="#x">Next</a> <a href="#y">Previous</a> </div> <div id="nav-dots" class="nav-dots"> <span class="nav-dot-current"></span> <span></span> <span></span> <span></span> <span></span> <span></span> <span></span> </div> </div><!-- /wrapper --> <p class="info"><strong>Example 1:</strong> Default settings</p> </div> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script> <script type="text/javascript" src="js/jquery.slicebox.js"></script> <script type="text/javascript"> $(function() { var Page = (function() { var $navArrows = $( '#nav-arrows' ).hide(), $navDots = $( '#nav-dots' ).hide(), $nav = $navDots.children( 'span' ), $shadow = $( '#shadow' ).hide(), slicebox = $( '#sb-slider' ).slicebox( { onReady : function() { $navArrows.show(); $navDots.show(); $shadow.show(); }, onBeforeChange : function( pos ) { $nav.removeClass( 'nav-dot-current' ); $nav.eq( pos ).addClass( 'nav-dot-current' ); } } ), init = function() { initEvents(); }, initEvents = function() { // add navigation events $navArrows.children( ':first' ).on( 'click', function() { setInterval("callme()", 1000); return false; } ); //$(function(){ //callme(); //}); function callme(){ //$('#checkit').append("callme loaded<br />"); slicebox.next(); setInterval("callme()", 1000); } $navArrows.children( ':last' ).on( 'click', function() { slicebox.previous(); return false; } ); $nav.each( function( i ) { $( this ).on( 'click', function( event ) { var $dot = $( this ); if( !slicebox.isActive() ) { $nav.removeClass( 'nav-dot-current' ); $dot.addClass( 'nav-dot-current' ); } slicebox.jump( i + 1 ); return false; } ); } ); }; return { init : init }; })(); Page.init(); }); </script> <script> // make sure the "myContainer" id in the script is the same id of the div $(document).ready(function() { slicebox.next(); $('#nav-arrows').sbslider(); // this is the piece of code that will do the magic thing }); </script> </body> </html> I am not being able to start the automatic slicing of images, it is happening only after a click, how should i modify my code so that i get to change the slicing of the images automatically.

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  • What means slicing in C++?

    - by George2
    Hello everyone, It is mentioned in C++ FAQ site -- "larger derived class objects get sliced when passed by value as a base class object", what does slicing mean? Any sample to demonstrate? http://www.parashift.com/c++-faq-lite/value-vs-ref-semantics.html#faq-31.8 I am using VSTS 2008 + native C++ as my development environment. thanks in advance, George

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  • What does slicing mean in C++?

    - by George2
    Hello everyone, It is mentioned in C++ FAQ site -- "larger derived class objects get sliced when passed by value as a base class object", what does slicing mean? Any sample to demonstrate? http://www.parashift.com/c++-faq-lite/value-vs-ref-semantics.html#faq-31.8 I am using VSTS 2008 + native C++ as my development environment. thanks in advance, George

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  • java: "downcasting" to new object / opposite of slicing

    - by rhavin
    Sorry, i really dont know how to make a headline for that question; maybe there is a name for what im trying to do that i dont know, but i can explain it with some code: Guess you have a class that unfortunately neither has a copy-constructor nor a public static copy method. class A { private int i; // <- private, cant access String x; // <- even worse: cant access unless in same pkg! /* … other stuff, ctor, etc. … */ public A clone() { A a = new A(); a.i = i; a.x = x; return x; } } Guess further, there is some function that returns an object of that class: public static A someFn(x,y,z); Now the problem: I want to derive from that class to add some functionality. Unfortunately, i neither have a sizeof in java nor a cc or static copy method. So when i do a class B extends A { protected w; public B clone() { /* as usual */ } } then i can clone my B and get a new one, but how can i convert the returned A from someFn() into a B. Is there anyway to do the opposite of slicing in java? if i clone it, it's still an A, and i cant copy it field by field. This is all simple in c++, but how to do this in Java?

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  • Python/numpy tricky slicing problem

    - by daver
    Hi stack overflow, I have a problem with some numpy stuff. I need a numpy array to behave in an unusual manner by returning a slice as a view of the data I have sliced, not a copy. So heres an example of what I want to do: Say we have a simple array like this: a = array([1, 0, 0, 0]) I would like to update consecutive entries in the array (moving left to right) with the previous entry from the array, using syntax like this: a[1:] = a[0:3] This would get the following result: a = array([1, 1, 1, 1]) Or something like this: a[1:] = 2*a[:3] # a = [1,2,4,8] To illustrate further I want the following kind of behaviour: for i in range(len(a)): if i == 0 or i+1 == len(a): continue a[i+1] = a[i] Except I want the speed of numpy. The default behavior of numpy is to take a copy of the slice, so what I actually get is this: a = array([1, 1, 0, 0]) I already have this array as a subclass of the ndarray, so I can make further changes to it if need be, I just need the slice on the right hand side to be continually updated as it updates the slice on the left hand side. Am I dreaming or is this magic possible? Update: This is all because I am trying to use Gauss-Seidel iteration to solve a linear algebra problem, more or less. It is a special case involving harmonic functions, I was trying to avoid going into this because its really not necessary and likely to confuse things further, but here goes. The algorithm is this: while not converged: for i in range(len(u[:,0])): for j in range(len(u[0,:])): # skip over boundary entries, i,j == 0 or len(u) u[i,j] = 0.25*(u[i-1,j] + u[i+1,j] + u[i, j-1] + u[i,j+1]) Right? But you can do this two ways, Jacobi involves updating each element with its neighbours without considering updates you have already made until the while loop cycles, to do it in loops you would copy the array then update one array from the copied array. However Gauss-Seidel uses information you have already updated for each of the i-1 and j-1 entries, thus no need for a copy, the loop should essentially 'know' since the array has been re-evaluated after each single element update. That is to say, every time we call up an entry like u[i-1,j] or u[i,j-1] the information calculated in the previous loop will be there. I want to replace this slow and ugly nested loop situation with one nice clean line of code using numpy slicing: u[1:-1,1:-1] = 0.25(u[:-2,1:-1] + u[2:,1:-1] + u[1:-1,:-2] + u[1:-1,2:]) But the result is Jacobi iteration because when you take a slice: u[:,-2,1:-1] you copy the data, thus the slice is not aware of any updates made. Now numpy still loops right? Its not parallel its just a faster way to loop that looks like a parallel operation in python. I want to exploit this behaviour by sort of hacking numpy to return a pointer instead of a copy when I take a slice. Right? Then every time numpy loops, that slice will 'update' or really just replicate whatever happened in the update. To do this I need slices on both sides of the array to be pointers. Anyway if there is some really really clever person out there that awesome, but I've pretty much resigned myself to believing the only answer is to loop in C.

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  • Python: Slicing a list into n nearly-equal-length partitions

    - by Drew
    I'm looking for a fast, clean, pythonic way to divide a list into exactly n nearly-equal partitions. partition([1,2,3,4,5],5)->[[1],[2],[3],[4],[5]] partition([1,2,3,4,5],2)->[[1,2],[3,4,5]] (or [[1,2,3],[4,5]]) partition([1,2,3,4,5],3)->[[1,2],[3,4],[5]] (there are other ways to slice this one too) There are several answers in here http://stackoverflow.com/questions/1335392/iteration-over-list-slices that run very close to what I want, except they are focused on the size of the list, and I care about the number of the lists (some of them also pad with None). These are trivially converted, obviously, but I'm looking for a best practice. Similarly, people have pointed out great solutions here http://stackoverflow.com/questions/312443/how-do-you-split-a-list-into-evenly-sized-chunks-in-python for a very similar problem, but I'm more interested in the number of partitions than the specific size, as long as it's within 1. Again, this is trivially convertible, but I'm looking for a best practice.

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  • Python: slicing a very large binary file

    - by Duncan Tait
    Say I have a binary file of 12GB and I want to slice 8GB out of the middle of it. I know the position indices I want to cut between. How do I do this? Obviously 12GB won't fit into memory, that's fine, but 8GB won't either... Which I thought was fine, but it appears binary doesn't seem to like it if you do it in chunks! I was appending 10MB at a time to a new binary file and there are discontinuities on the edges of each 10MB chunk in the new file. Is there a Pythonic way of doing this easily?

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  • slicing up a very big jpg map image , 49000* 34300 pixel

    - by sirvan
    hi i want to write a mapviewer, i must to work small tile of big map image file and there is need to tiling the big image, the problem now is to tiling big image to small tiles (250 * 250 pixel or like this size) so on, i used ImageMagic program to do it but there was problem now is any other programing method or application that do tiling? can i do it with JAI in java? how?

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  • slicing up a very big jpg map image , 140000*125000 pixel

    - by sirvan
    hi i want to write a mapviewer, i must to work small tile of big map image file and there is need to tiling the big image, the problem now is to tiling big image to small tiles (250 * 250 pixel or like this size) so on, i used ImageMagic program to do it but there was problem now is any other programing method or application that do tiling? can i do it with JAI in java? how?

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  • Python - List of Lists Slicing Behavior

    - by Dan Dobint
    When I define a list and try to change a single item like this: list_of_lists = [['a', 'a', 'a'], ['a', 'a', 'a'], ['a', 'a', 'a']] list_of_lists[1][1] = 'b' for row in list_of_lists: print row It works as intended. But when I try to use list comprehension to create the list: row = ['a' for range in xrange(3)] list_of_lists = [row for range in xrange(3)] list_of_lists[1][1] = 'b' for row in list_of_lists: print row It results in an entire column of items in the list being changed. Why is this? How can I achieve the desired effect with list comprehension?

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  • slicing 2d numpy array

    - by MedicalMath
    I have a 2d numpy array called FilteredOutput that has 2 columns and 10001 rows, though the number of rows is a variable. I am trying to take the 2nd column of FilteredOutput and use it to populate a new 1d numpy array called timeSeriesArray using the following line of code: timeSeriesArray=p.array(FilteredOutput[:,0]) I got this syntax from the following link. But the problem is that I am getting the following error message: TypeError: list indices must be integers, not tuple Can anyone show me the proper syntax for populating the 1d array timeSeriesArray with the contents of the second column of the 2d array FilteredOutput?

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  • slicing arrays in numpy/scipy

    - by user248237
    I have an array like: a = array([[1,2,3],[3,4,5],[4,5,6]]) what's the most efficient way to slice out a 1x2 array out of this that has only the first two columns of "a"? I.e., array([[2,3],[4,5],[5,6]]) in this case. thanks.

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