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• WRTU54G-TM router with 3rd party firmware; Can custom firmware include stock binary portions?

  - by dlamblin

  I've been doing a lot of reading online about the Linksys WRTU54G-TM router model that I now own. It seems getting a custom firmware onto it is not a problem. But no one is talking about retaining the Voip features (yet). So far they're all disappointed that it's not a SIP machine and used GSM over IPSec. Personally I don't care about using it with non-t-mobile. If I take the original firmware, shouldn't I be able to extract it, and it's SquashFS image, and then move all of the t-mobile specific binaries for enabling the calling features over to a custom firmware installation (maybe OpenWRT)? You might ask why, and the reason is, that if I do this I could retain my calling features, which I do want, and ssh to the router and use it to run additional software, as any OpenWRT router could do. Does anyone know if this can be done, and how the firmware's binaries could be gotten at and installed correctly? Update I have found someone working on 3rd party WRTU54G-TM firmware. I am still interested in my second part of the questions, that is can't the stock firmware images be pulled apart and have the close-source, if any, binary kernel modules moved into another more flexible custom firmware?

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• help in the Donalds B. Johnson's algorithm, i cannot understand the pseudo code

  - by Pitelk

  Hi , does anyone know the Donald B. Johnson's algorithm which enumarates all the elementary circuits (cycles) in a Directed graph? link text I have the paper he had published in 1975 but I cannot understand the pseudo-code. My goal is to implement this algorithm in java. Some questions i have is for example what is the matrix Ak it refers to. In the pseudo code mentions that Ak:=adjacency structure of strong component K with least vertex in subgraph of G induced by {s,s+1,....n}; Does that mean i have to implement another algorithm that finds the Ak matrix? Another question is what the following means? begin logical f; Does also the line "logical procedure CIRCUIT (integer value v);" means that the circuit procedure returns a logical variable. In the pseudo code also has the line "CIRCUIT := f;" . Does this mean? It would be great if someone could translate this 1970's pseudocode to a more modern type of pseudo code so i can understand it in case you are interested to help but you cannot find the paper please email me at [email protected] and i will send you the paper. Thanks in advance

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• Most efficient way of creating tree from adjacency list

  - by Jeff Meatball Yang

  I have an adjacency list of objects (rows loaded from SQL database with the key and it's parent key) that I need to use to build an unordered tree. It's guaranteed to not have cycles. This is taking wayyy too long (processed only ~3K out of 870K nodes in about 5 minutes). Running on my workstation Core 2 Duo with plenty of RAM. Any ideas on how to make this faster? public class StampHierarchy { private StampNode _root; private SortedList<int, StampNode> _keyNodeIndex; // takes a list of nodes and builds a tree // starting at _root private void BuildHierarchy(List<StampNode> nodes) { Stack<StampNode> processor = new Stack<StampNode>(); _keyNodeIndex = new SortedList<int, StampNode>(nodes.Count); // find the root _root = nodes.Find(n => n.Parent == 0); // find children... processor.Push(_root); while (processor.Count != 0) { StampNode current = processor.Pop(); // keep a direct link to the node via the key _keyNodeIndex.Add(current.Key, current); // add children current.Children.AddRange(nodes.Where(n => n.Parent == current.Key)); // queue the children foreach (StampNode child in current.Children) { processor.Push(child); nodes.Remove(child); // thought this might help the Where above } } } } public class StampNode { // properties: int Key, int Parent, string Name, List<StampNode> Children }

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• Replace Temp with Query

  - by student

  The Replace Temp with Query refactoring method is recommended quite widely now but seems to be very inefficient for very little gain. The method from the Martin Fowler's site gives the following example: Extract the expression into a method. Replace all references to the temp with the expression. The new method can then be used in other methods. double basePrice = _quantity * _itemPrice; if (basePrice > 1000) return basePrice * 0.95; else return basePrice * 0.98; becomes if (basePrice() > 1000) return basePrice() * 0.95; else return basePrice() * 0.98; double basePrice() { return _quantity * _itemPrice; } Why is this a good idea? surely it means the calculation is needlessly repeated and you have the overhead of calling a function. I know CPU cycles are cheap but throwing them away like this seems careless? Am I missing something?

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• C# Communication between threads.

  - by GT

  Hi, I am using .NET 3.5 and am trying to wrap my head around a problem (not being a supreme threading expert bear with me). I have a windows service which has a very intensive process that is always running, I have put this process onto a separate thread so that the main thread of my service can handle operational tasks - i.e., service audit cycles, handling configuration changes, etc, etc. I'm starting the thread via the typical ThreadStart to a method which kicks the process off - call it workerthread. On this workerthread I am sending data to another server, as is expected the server reboots every now and again and connection is lost and I need to re-establish the connection (I am notified by the lost of connection via an event). From here I do my reconnect logic and I am back in and running, however what I easily started to notice to happen was that I was creating this worker thread over and over again each time (not what I want). Now I could kill the workerthread when I lose the connection and start a new one but this seems like a waste of resources. What I really want to do, is marshal the call (i.e., my thread start method) back to the thread that is still in memory although not doing anything. Please post any examples or docs you have that would be of use. Thanks.

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• The subsets-sum problem and the solvability of NP-complete problems

  - by G.E.M.

  I was reading about the subset-sums problem when I came up with what appears to be a general-purpose algorithm for solving it: (defun subset-contains-sum (set sum) (let ((subsets) (new-subset) (new-sum)) (dolist (element set) (dolist (subset-sum subsets) (setf new-subset (cons element (car subset-sum))) (setf new-sum (+ element (cdr subset-sum))) (if (= new-sum sum) (return-from subset-contains-sum new-subset)) (setf subsets (cons (cons new-subset new-sum) subsets))) (setf subsets (cons (cons element element) subsets))))) "set" is a list not containing duplicates and "sum" is the sum to search subsets for. "subsets" is a list of cons cells where the "car" is a subset list and the "cdr" is the sum of that subset. New subsets are created from old ones in O(1) time by just cons'ing the element to the front. I am not sure what the runtime complexity of it is, but appears that with each element "sum" grows by, the size of "subsets" doubles, plus one, so it appears to me to at least be quadratic. I am posting this because my impression before was that NP-complete problems tend to be intractable and that the best one can usually hope for is a heuristic, but this appears to be a general-purpose solution that will, assuming you have the CPU cycles, always give you the correct answer. How many other NP-complete problems can be solved like this one?

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• How can I return json from my WCF rest service (.NET 4), using Json.Net, without it being a string,

  - by Samuel Meacham

  The DataContractJsonSerializer is unable to handle many scenarios that Json.Net handles just fine when properly configured (specifically, cycles). A service method can either return a specific object type (in this case a DTO), in which case the DataContractJsonSerializer will be used, or I can have the method return a string, and do the serialization myself with Json.Net. The problem is that when I return a json string as opposed to an object, the json that is sent to the client is wrapped in quotes. Using DataContractJsonSerializer, returning a specific object type, the response is: {"Message":"Hello World"} Using Json.Net to return a json string, the response is: "{\"Message\":\"Hello World\"}" I do not want to have to eval() or JSON.parse() the result on the client, which is what I would have to do if the json comes back as a string, wrapped in quotes. I realize that the behavior is correct; it's just not what I want/need. I need the raw json; the behavior when the service method's return type is an object, not a string. So, how can I have my method return an object type, but not use the DataContractJsonSerializer? How can I tell it to use the Json.Net serializer instead? Or, is there someway to directly write to the response stream? So I can just return the raw json myself? Without the wrapping quotes? Here is my contrived example, for reference: [DataContract] public class SimpleMessage { [DataMember] public string Message { get; set; } } [ServiceContract] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)] public class PersonService { // uses DataContractJsonSerializer // returns {"Message":"Hello World"} [WebGet(UriTemplate = "helloObject")] public SimpleMessage SayHelloObject() { return new SimpleMessage("Hello World"); } // uses Json.Net serialization, to return a json string // returns "{\"Message\":\"Hello World\"}" [WebGet(UriTemplate = "helloString")] public string SayHelloString() { SimpleMessage message = new SimpleMessage() { Message = "Hello World" }; string json = JsonConvert.Serialize(message); return json; } // I need a mix of the two. Return an object type, but use the Json.Net serializer. }

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• SQL select descendants of a row

  - by Joey Adams

  Suppose a tree structure is implemented in SQL like this: CREATE TABLE nodes ( id INTEGER PRIMARY KEY, parent INTEGER -- references nodes(id) ); Although cycles can be created in this representation, let's assume we never let that happen. The table will only store a collection of roots (records where parent is null) and their descendants. The goal is to, given an id of a node on the table, find all nodes that are descendants of it. A is a descendant of B if either A's parent is B or A's parent is a descendant of B. Note the recursive definition. Here is some sample data: INSERT INTO nodes VALUES (1, NULL); INSERT INTO nodes VALUES (2, 1); INSERT INTO nodes VALUES (3, 2); INSERT INTO nodes VALUES (4, 3); INSERT INTO nodes VALUES (5, 3); INSERT INTO nodes VALUES (6, 2); which represents: 1 `-- 2 |-- 3 | |-- 4 | `-- 5 | `-- 6 We can select the (immediate) children of 1 by doing this: SELECT a.* FROM nodes AS a WHERE parent=1; We can select the children and grandchildren of 1 by doing this: SELECT a.* FROM nodes AS a WHERE parent=1 UNION ALL SELECT b.* FROM nodes AS a, nodes AS b WHERE a.parent=1 AND b.parent=a.id; We can select the children, grandchildren, and great grandchildren of 1 by doing this: SELECT a.* FROM nodes AS a WHERE parent=1 UNION ALL SELECT b.* FROM nodes AS a, nodes AS b WHERE a.parent=1 AND b.parent=a.id UNION ALL SELECT c.* FROM nodes AS a, nodes AS b, nodes AS c WHERE a.parent=1 AND b.parent=a.id AND c.parent=b.id; How can a query be constructed that gets all descendants of node 1 rather than those at a finite depth? It seems like I would need to create a recursive query or something. I'd like to know if such a query would be possible using SQLite. However, if this type of query requires features not available in SQLite, I'm curious to know if it can be done in other SQL databases.

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• WRTU54G-TM router with 3rd party firmware; Can custom firmware include stock binary portions?

  - by dlamblin

  I've been doing a lot of reading online about the Linksys WRTU54G-TM router model that I now own. It seems getting a custom firmware onto it is not a problem. But no one is talking about retaining the Voip features (yet). So far they're all disappointed that it's not a SIP machine and used GSM over IPSec. Personally I don't care about using it with non-t-mobile. If I take the original firmware, shouldn't I be able to extract it, and it's SquashFS image, and then move all of the t-mobile specific binaries for enabling the calling features over to a custom firmware installation (maybe OpenWRT)? You might ask why, and the reason is, that if I do this I could retain my calling features, which I do want, and ssh to the router and use it to run additional software, as any OpenWRT router could do. Does anyone know if this can be done, and how the firmware's binaries could be gotten at and installed correctly? Update I have found someone working on 3rd party WRTU54G-TM firmware. I am still interested in my second part of the questions, that is can't the stock firmware images be pulled apart and have the close-source, if any, binary kernel modules moved into another more flexible custom firmware?

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• Convert mp4 video to a format xbox 360 can play

  - by Björn Lindqvist

  Here is a video file my Xbox 360 refuses to play: $ MP4Box -info video.mp4 * Movie Info * Timescale 90000 - Duration 02:18:33.365 Fragmented File no - 2 track(s) File Brand mp42 - version 0 Created: GMT Sat Jul 21 07:08:55 2012 File has root IOD (9 bytes) Scene PL 0xff - Graphics PL 0xff - OD PL 0xff Visual PL: ISO Reserved Profile (0x7f) Audio PL: High Quality Audio Profile @ Level 2 (0x0f) No streams included in root OD iTunes Info: Encoder Software: HandBrake 0.9.6 2012022800 Track # 1 Info - TrackID 1 - TimeScale 90000 - Duration 02:18:33.235 Media Info: Language "Undetermined" - Type "vide:avc1" - 199318 samples Visual Track layout: x=0 y=0 width=1280 height=688 MPEG-4 Config: Visual Stream - ObjectTypeIndication 0x21 AVC/H264 Video - Visual Size 1280 x 688 AVC Info: 1 SPS - 1 PPS - Profile High @ Level 4.1 NAL Unit length bits: 32 Self-synchronized Track # 2 Info - TrackID 2 - TimeScale 48000 - Duration 02:18:33.365 Media Info: Language "English" - Type "soun:mp4a" - 389689 samples MPEG-4 Config: Audio Stream - ObjectTypeIndication 0x40 MPEG-4 Audio MPEG-4 Audio AAC LC - 6 Channel(s) - SampleRate 48000 Synchronized on stream 1 $ avconv -i video.mp4 avconv version 0.8.4-4:0.8.4-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers built on Nov 6 2012 16:51:33 with gcc 4.6.3 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4': Metadata: major_brand : mp42 minor_version : 0 compatible_brands: mp42isomavc1 creation_time : 2012-07-21 07:08:55 encoder : HandBrake 0.9.6 2012022800 Duration: 02:18:33.36, start: 0.000000, bitrate: 2299 kb/s Stream #0.0(und): Video: h264 (High), yuv420p, 1280x688, 1973 kb/s, 23.98 fps, 90k tbr, 90k tbn, 180k tbc Metadata: creation_time : 2012-07-21 07:08:55 Stream #0.1(eng): Audio: aac, 48000 Hz, 5.1, s16, 319 kb/s Metadata: creation_time : 2012-07-21 07:08:55 At least one output file must be specified What tool, such as ffmpeg or mencoder, and what magic command line incantation should I use to transcode this file into a format Xbox 360 can play? I want the transcode process to retain as good video quality as possible.

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• Does GC guarantee that cleared References are enqueued to ReferenceQueue in topological order?

  - by Dimitris Andreou

  Say there are two objects, A and B, and there is a pointer A.x --> B, and we create, say, WeakReferences to both A and B, with an associated ReferenceQueue. Assume that both A and B become unreachable. Intuitively B cannot be considered unreachable before A is. In such a case, do we somehow get a guarantee that the respective references will be enqueued in the intuitive (topological when there are no cycles) order in the ReferenceQueue? I.e. ref(A) before ref(B). I don't know - what if the GC marked a bunch of objects as unreachable, and then enqueued them in no particular order? I was reviewing Finalizer.java of guava, seeing this snippet: private void cleanUp(Reference<?> reference) throws ShutDown { ... if (reference == frqReference) { /* * The client no longer has a reference to the * FinalizableReferenceQueue. We can stop. */ throw new ShutDown(); } frqReference is a PhantomReference to the used ReferenceQueue, so if this is GC'ed, no Finalizable{Weak, Soft, Phantom}References can be alive, since they reference the queue. So they have to be GC'ed before the queue itself can be GC'ed - but still, do we get the guarantee that these references will be enqueued to the ReferenceQueue at the order they get "garbage collected" (as if they get GC'ed one by one)? The code implies that there is some kind of guarantee, otherwise unprocessed references could theoretically remain in the queue. Thanks

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• Linux 2.6.31 Scheduler and Multithreaded Jobs

  - by dsimcha

  I run massively parallel scientific computing jobs on a shared Linux computer with 24 cores. Most of the time my jobs are capable of scaling to 24 cores when nothing else is running on this computer. However, it seems like when even one single-threaded job that isn't mine is running, my 24-thread jobs (which I set for high nice values) only manage to get ~1800% CPU (using Linux notation). Meanwhile, about 500% of the CPU cycles (again, using Linux notation) are idle. Can anyone explain this behavior and what I can do about it to get all of the 23 cores that aren't being used by someone else? Notes: In case it's relevant, I have observed this on slightly different kernel versions, though I can't remember which off the top of my head. The CPU architecture is x64. Is it at all possible that the fact that my 24-core jobs are 32-bit and the other jobs I'm competing w/ are 64-bit is relevant? Edit: One thing I just noticed is that going up to 30 threads seems to alleviate the problem to some degree. It gets me up to ~2100% CPU.

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• Manipulating jQuery to retrieve the onclick function of an item which lies directly below the curren

  - by Stevie Jenowski

  First off, I want to thank you for looking into my question as I really do appreciate your time. I've built a list of items using php by having a foreach loop cycle through an associative array printing the array data as parameters of an onclick function call and gives each item it cycles through an ID of $thecount. All items retrieved have the same parent div and calls the very same onclick function, only with 11 different parameters. My question is how do I go about calling the onClick("function();") of an item directly below the current focus, making it the new focus, only without a physical click? If this is confusing to you whatsoever, I'm essentially building a dynamic playlist, and I've already implemented the listener for when the player's current item has finished playing, Now I'm having trouble grasping how I'd go about having the next item in the list become the new focus while also calling it's specific onClick() function once the player returns that it has finished with the current file. All without any user interaction besides the initial play call. If it helps I'm using the most recent release of Longtails' JW Player and once again thank you very much for your time!

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• Netbook thinks it is a desktop

  - by Narcolapser

  Question: Are, and if so what, there packages for download that I can get netbook to understand it is not a desktop and that it is a netbook. Info: I'm running an Acer Aspire One with ubuntu desktop 9.10. I tried Ubuntu Netbook Remix first but it has graphics issues with the aspire one. So I changed to Ubuntu Desktop. It was the only distro (after debian, centOS, Fedora, and Knoppix all failed me) that I managed to get working. The only thing is that it is having issues doing things that a netbook/laptop should be doing. most notably is that it will run it's battery dead if I close the screen and throw it into my back pack. It seems to just stay fully on and runs it's self to death. also it will lock up some times if I close the screen and come back to it 10 or 20 minutes later. It also won't retain volume settings when I reboot, as well as screen brightness. and just a couple of other things that I can't quite put my finger on, but just seem amiss. like I said, Essentially my netbook thinks it is a desktop, how can I fix this? ~N

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• emacs: x-popup-menu max size constraints?

  - by Cheeso

  I'm working on an intellisense or code-completion capability for C#. So far, so good. Right now I have basic completion working. There are 2 ways to request completion. The first cycles through all the potential matches. The second presents a popup menu of the matches. It works for types: And also for local variables: I'm confronting two problems with x-popup-menu: the popup menu can expand to consume all available screen space, when the number of choices is large. Literally it can obscure the entire screen. The silly thing is, it's scrollable. First it expands to consume all available space, then it also becomes scrollable. Is there a way I can limit the maximum size of x-popup-menu? To specify the position of the popup menu, I pass in a position, and x-popup-menu uses that as the *middle*, not the left, of the top line of the menu. Why middle? who knows. What this means is, if I specify (40 . 60) for the location of the menu, and the menu happens to be 100 pixels wide, the menu will extend beyond the left border of the emacs window. You can see this in the 2nd image above. If I knew how wide the popup would be before specifying the position, I could compensate. But I don't. Is there a workaround? Is there a way to get x-popup-menu to take its position as the LEFT rather than the middle.

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• Why is it assumed that send may return with less than requested data transmitted on a blocking socke

  - by Ernelli

  The standard method to send data on a stream socket has always been to call send with a chunk of data to write, check the return value to see if all data was sent and then keep calling send again until the whole message has been accepted. For example this is a simple example of a common scheme: int send_all(int sock, unsigned char *buffer, int len) { int nsent; while(len 0) { nsent = send(sock, buffer, len, 0); if(nsent == -1) // error return -1; buffer += nsent; len -= nsent; } return 0; // ok, all data sent } Even the BSD manpage mentions that ...If no messages space is available at the socket to hold the message to be transmitted, then send() normally blocks... Which indicates that we should assume that send may return without sending all data. Now I find this rather broken but even W. Richard Stevens assumes this in his standard reference book about network programming, not in the beginning chapters, but the more advanced examples uses his own writen (write all data) function instead of calling write. Now I consider this still to be more or less broken, since if send is not able to transmit all data or accept the data in the underlying buffer and the socket is blocking, then send should block and return when the whole send request has been accepted. I mean, in the code example above, what will happen if send returns with less data sent is that it will be called right again with a new request. What has changed since last call? At max a few hundred CPU cycles have passed so the buffer is still full. If send now accepts the data why could'nt it accept it before? Otherwise we will end upp with an inefficient loop where we are trying to send data on a socket that cannot accept data and keep trying, or else? So it seems like the workaround, if needed, results in heavily inefficient code and in those circumstances blocking sockets should be avoided at all an non blocking sockets together with select should be used instead.

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• MFC Combo-Box Control is not showing the full list of items when I click the drop-down menu...

  - by shan23

  I'm coding an app in MSVS 2008, which has a ComboBox control which I initialize thru the code as below: static char* OptionString[4] = {"Opt1", "Opt2", "Opt3", "Opt4"}; BOOL CMyAppDlg::OnInitDialog() { CDialog::OnInitDialog(); // Set the icon for this dialog. The framework does this automatically // when the application's main window is not a dialog SetIcon(m_hIcon, TRUE); // Set big icon SetIcon(m_hIcon, FALSE); // Set small icon // TODO: Add extra initialization here m_Option.AddString(OptionString[0]); m_Option.AddString(OptionString[1]); m_Option.AddString(OptionString[2]); m_Option.AddString(OptionString[3]); m_Option.SetCurSel(0); return TRUE; // return TRUE unless you set the focus to a control } Now, when I build the app and click the down-arrow, the drop-down box shows the first option ONLY(since I've selected that thru my code). But, if i press down-arrow key on keyboard, it cycles thru the options in the order I've inserted, but never does it show more than 1 option in the box. So, In case an user wants to select option3, he has to cycle through options 1 and 2 !! Though once I select any option using the keyboard, the appropriate event handlers are fired, I'm miffed by this behaviour , as is understandable. I'm listing the properties of the combo-box control as well - only the properties that are true(rest are set to false): Type - Dropdown Vertical Scrollbar Visible Tabstop This has bugged me for weeks now. Can anyone pls enlighten me ?

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• How do I remove a USB drive's write protection?

  - by nate

  I have a SanDisk Cruser Blade USB stick that suddenly seems to be write protected. I tried running DiskPart but after I write the command "attributes disk clear readonly" it displays this: Microsoft DiskPart version 5.1.3565 ADD - Add a mirror to a simple volume. ACTIVE - Marks the current basic partition as an active boot partition. ASSIGN - Assign a drive letter or mount point to the selected volume. BREAK - Break a mirror set. CLEAN - Clear the configuration information, or all information, off the disk. CONVERT - Converts between different disk formats. CREATE - Create a volume or partition. DELETE - Delete an object. DETAIL - Provide details about an object. EXIT - Exit DiskPart EXTEND - Extend a volume. HELP - Prints a list of commands. IMPORT - Imports a disk group. LIST - Prints out a list of objects. INACTIVE - Marks the current basic partition as an inactive partition. ONLINE - Online a disk that is currently marked as offline. REM - Does nothing. Used to comment scripts. REMOVE - Remove a drive letter or mount point assignment. REPAIR - Repair a RAID-5 volume. RESCAN - Rescan the computer looking for disks and volumes. RETAIN - Place a retainer partition under a simple volume. SELECT - Move the focus to an object. It's like when you type help at the DiskPart prompt, so how do I get past this? This problem started when I plugged the stick into a laptop which had viruses, if that's any help.

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• Unexpected performance curve from CPython merge sort

  - by vkazanov

  I have implemented a naive merge sorting algorithm in Python. Algorithm and test code is below: import time import random import matplotlib.pyplot as plt import math from collections import deque def sort(unsorted): if len(unsorted) <= 1: return unsorted to_merge = deque(deque([elem]) for elem in unsorted) while len(to_merge) > 1: left = to_merge.popleft() right = to_merge.popleft() to_merge.append(merge(left, right)) return to_merge.pop() def merge(left, right): result = deque() while left or right: if left and right: elem = left.popleft() if left[0] > right[0] else right.popleft() elif not left and right: elem = right.popleft() elif not right and left: elem = left.popleft() result.append(elem) return result LOOP_COUNT = 100 START_N = 1 END_N = 1000 def test(fun, test_data): start = time.clock() for _ in xrange(LOOP_COUNT): fun(test_data) return time.clock() - start def run_test(): timings, elem_nums = [], [] test_data = random.sample(xrange(100000), END_N) for i in xrange(START_N, END_N): loop_test_data = test_data[:i] elapsed = test(sort, loop_test_data) timings.append(elapsed) elem_nums.append(len(loop_test_data)) print "%f s --- %d elems" % (elapsed, len(loop_test_data)) plt.plot(elem_nums, timings) plt.show() run_test() As much as I can see everything is OK and I should get a nice N*logN curve as a result. But the picture differs a bit: Things I've tried to investigate the issue: PyPy. The curve is ok. Disabled the GC using the gc module. Wrong guess. Debug output showed that it doesn't even run until the end of the test. Memory profiling using meliae - nothing special or suspicious. ` I had another implementation (a recursive one using the same merge function), it acts the similar way. The more full test cycles I create - the more "jumps" there are in the curve. So how can this behaviour be explained and - hopefully - fixed? UPD: changed lists to collections.deque UPD2: added the full test code UPD3: I use Python 2.7.1 on a Ubuntu 11.04 OS, using a quad-core 2Hz notebook. I tried to turn of most of all other processes: the number of spikes went down but at least one of them was still there.

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• jQuery .attr() crashing Internet Explorer

  - by Sunyatasattva

  Hello everyone, This is my first time posting a question here, as I usually try to find solutions myself. This one, though, being an IE issue, just drives me crazy. I use jQuery cycle plug-in on a website I made and, to populate a caption div, I use a little function that is called after the image is loaded, which uses the "alt" attribute of the image. This seems to exasperate Internet Explorer, which, doesn't have the time to fulfill this apparently so-complicated task, and, as the slideshow cycles, it enters in an infinite loop and eventually crashes – the newer the version, the worse the crash: the older IEs just display an error message saying “The webpage cannot be displayed”, while the newer (7 and 8) completely crash the system. I have no idea on how to solve or work around this. Here is the problematic code. function changeCaption() { var caption = $("img", this).attr("alt"); $('#caption').fadeIn("slow").html(caption); } Thanks in advance for any pointer: I am amazed as how something so simple and globally recognized (didn't encounter any other browser who had problem with this), can cause a problem so big. I also read somewhere that being able to crash a browser remotely is a serious issue :) Lucio

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• Fastest way to generate delimited string from 1d numpy array

  - by Abiel

  I have a program which needs to turn many large one-dimensional numpy arrays of floats into delimited strings. I am finding this operation quite slow relative to the mathematical operations in my program and am wondering if there is a way to speed it up. For example, consider the following loop, which takes 100,000 random numbers in a numpy array and joins each array into a comma-delimited string. import numpy as np x = np.random.randn(100000) for i in range(100): ",".join(map(str, x)) This loop takes about 20 seconds to complete (total, not each cycle). In contrast, consider that 100 cycles of something like elementwise multiplication (x*x) would take than one 1/10 of a second to complete. Clearly the string join operation creates a large performance bottleneck; in my actual application it will dominate total runtime. This makes me wonder, is there a faster way than ",".join(map(str, x))? Since map() is where almost all the processing time occurs, this comes down to the question of whether there a faster to way convert a very large number of numbers to strings.

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• Fixed and dynamic IPs in ISC DHPD lead to double lease

  - by GorillaPatch

  I would like to have a small dynamic adress part and the most clients are assigned a fixed IP adress. My dhcpd.conf looks like this: use-host-decl-names on; authoritative; allow client-updates; ddns-updates on; # Einstellungen fuer DHCP leases default-lease-time 3600; max-lease-time 86400; lease-file-name "/var/lib/dhcpd/dhcpd.leases"; subnet 192.168.11.0 netmask 255.255.255.0 { ddns-updates on; pool { # IP range which will be assigned statically range 192.168.11.1 192.168.11.240; deny all clients; } pool { # small dynamic range range 192.168.11.241 192.168.11.254; # used for temporary devices } } group { host pc1 { hardware ethernet xx:xx:xx:xx:xx:xx; fixed-address 192.168.11.11; } } The motivation for the pool declaration with deny all hosts comes from the ISC DHCPD homepage http://www.isc.org/files/auth.html This will allow hosts to be first added to the network, where they will receive a temporary IP from the 241-254 adress range and then later write an explicit host declaration. Upon next connect it will receive the right configuration. The problem is that I am getting error messages that 192.168.11.13 has a dynamic and a static lease. I am a bit confused as I expected the pool declaration with deny all clients would not count as dynamic. Dynamic and static leases present for 192.168.11.13. Remove host declaration pc1 or remove 192.168.11.13 from the dynamic address pool for 192.168.11.0/24 Is there a way to have the DHCP server send an DHCPNA to clients if they have a host statement and retain this dynamic range?

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• XP Pro freezes on welcome screen

  - by Peter B

  I have a problem that sounds much the same as http://superuser.com/questions/83101/how-to-diagnose-a-freeze-on-startup-in-windows-xp About every 2nd or 3rd boot, XP-Pro freezes on the Welcome page (the one showing the user name icons). The mouse moves the cursor OK, but clicking on an icon does nothing, and neither does any keystroke. If you press too many keys there is a beep and after that the mouse won't move the cursor anymore. The work-around is always to reboot into Safe mode and request a CHKDSK /R After this, the next boot is fine. There are no related entries in the Event log when the problem occurs. The only two entries are: "Microsoft (R) Windows (R) 5.01. 2600 Service Pack 3 Multiprocessor Free." "The Event log service was started." Update 1: Many thanks for that but I found no problems with any diagnostics I have run. But, I have managed to locate, and code round, the source of the problem - which is with whatever processing goes on behind the XP Welcome (as opposed to "classic") login screen. Unfortunately, having classic login means you don't get the useful Fast User Switching (FUS) login/switch mode. So, to retain this, my fix is: Add a Windows shutdown script (using gpedit.msc) to force "classic" mode for the first logon after next XP startup, by running: reg add "hklm\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon" /v LogonType /t REG_DWORD /d 0 /f Add a Scheduled Task to run at User Logon that enables Welcome screen (and hence FUS) by running the same command with 1 instead of 0 after the /d flag. The task is run as a privileged user (who can run "reg add").

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• Confused about definition of a 'median' when constructing a kd-Tree

  - by user352636

  Hi there. Im trying to build a kd-tree for searching through a set of points, but am getting confused about the use of 'median' in the wikipedia article. For ease of use, the wikipedia article states the pseudo-code of kd-tree construction as: function kdtree (list of points pointList, int depth) { if pointList is empty return nil; else { // Select axis based on depth so that axis cycles through all valid values var int axis := depth mod k; // Sort point list and choose median as pivot element select median by axis from pointList; // Create node and construct subtrees var tree_node node; node.location := median; node.leftChild := kdtree(points in pointList before median, depth+1); node.rightChild := kdtree(points in pointList after median, depth+1); return node; } } I'm getting confused about the "select median..." line, simply because I'm not quite sure what is the 'right' way to apply a median here. As far as I know, the median of an odd-sized (sorted) list of numbers is the middle element (aka, for a list of 5 things, element number 3, or index 2 in a standard zero-based array), and the median of an even-sized array is the sum of the two 'middle' elements divided by two (aka, for a list of 6 things, the median is the sum of elements 3 and 4 - or 2 and 3, if zero-indexed - divided by 2.). However, surely that definition does not work here as we are working with a distinct set of points? How then does one choose the correct median for an even-sized list of numbers, especially for a length 2 list? I appreciate any and all help, thanks! -Stephen

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• How does jquery display an image received from an ajax request?

  - by Gnee

  I have this working great, but I'd like a deeper understanding of what is actually going on behind the scenes. I am using Jquery's Ajax method to pull 5 blog posts (returning only the title and first photo). A PHP script grabs the blog posts' title and first photo and sticks it in an array and sends it back to my browser as JSON. Upon receiving the JSON object, Jquery grabs the first member of the JSON object and displays it's title and photo. In a gallery I made, using buttons – the user can iterate the 1-5 posts. So the actual AJAX call happens right away, and only once. I am basically using this kind of setup: $('my_div').html(json_obj[i]) and each click does a i++. So jquery is plucking these blog posts from my computers memory, my web browsers cache, or some kind of cache in the Javascript engine? One of the things it's returning is a pretty gnarly animated gif. I just wonder if it constantly running in the background (but not visible), stealing processing cycles...etc. Or Javascript just inserting (say a flash movie) into the DOM, but before hand does nothing but take up a little memory (no processing). Anyway, I'm just curious. If someone is a guru on this, I'd love to hear your take. Thanks!!

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