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  • Converting an input text value to a decimal number

    - by vitto
    Hi, I'm trying to work with decimal data in my PHP and MySql practice and I'm not sure about how can I do for an acceptable level af accuracy. I've wrote a simple function which recives my input text value and converts it to a decimal number ready to be stored in the database. <?php function unit ($value, $decimal_point = 2) { return number_format (str_replace (",", ".", strip_tags (trim ($value))), $decimal_point); } ?> I've resolved something like AbdlBsF5%?nl with some jQuery code for replace and some regex to keep only numbers, dots and commas. In some country, people uses the comma , to send decimal numbers, so a number like 72.08 is wrote like 72,08. I'd like avoid to forcing people to change their usual chars and I've decided to use a jQuery to keep this too. Now every web developer knows the last validation must be handled by the dynamic page for security reasons. So my answer is should I use something like unit (); function to store data or shoul I also check if users inserts invalid chars like letters or something else? If I try this and send letters, the query works without save the invalid data, I think this isn't bad, but I could easily be wrong because I'm a rookie. What kind of method should I use if I want a number like 99999.99 for my query?

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  • What algorithms are suitable for this simple machine learning problem?

    - by user213060
    I have a what I think is a simple machine learning question. Here is the basic problem: I am repeatedly given a new object and a list of descriptions about the object. For example: new_object: 'bob' new_object_descriptions: ['tall','old','funny']. I then have to use some kind of machine learning to find previously handled objects that had similar descriptions, for example, past_similar_objects: ['frank','steve','joe']. Next, I have an algorithm that can directly measure whether these objects are indeed similar to bob, for example, correct_objects: ['steve','joe']. The classifier is then given this feedback training of successful matches. Then this loop repeats with a new object. a Here's the pseudo-code: Classifier=new_classifier() while True: new_object,new_object_descriptions = get_new_object_and_descriptions() past_similar_objects = Classifier.classify(new_object,new_object_descriptions) correct_objects = calc_successful_matches(new_object,past_similar_objects) Classifier.train_successful_matches(object,correct_objects) But, there are some stipulations that may limit what classifier can be used: There will be millions of objects put into this classifier so classification and training needs to scale well to millions of object types and still be fast. I believe this disqualifies something like a spam classifier that is optimal for just two types: spam or not spam. (Update: I could probably narrow this to thousands of objects instead of millions, if that is a problem.) Again, I prefer speed when millions of objects are being classified, over accuracy. What are decent, fast machine learning algorithms for this purpose?

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  • get lattitude and longitude of a place against its zipcode

    - by yunas
    Hello i have used the following code to get the location of the particular place on map using the following piece of code NSString * urlString = [[NSString alloc] initWithFormat:@"http://maps.google.com/maps/geo?key=%@&output=xml&q=%@",GoogleMapsAPIKey,[placeName stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]; result: <?xml version="1.0" encoding="UTF-8" ?> <kml xmlns="http://earth.google.com/kml/2.0"><Response> <name>postdam</name> <Status> <code>200</code> <request>geocode</request> </Status> <Placemark id="p1"> <address>Potsdam, Germany</address> <AddressDetails Accuracy="4" xmlns="urn:oasis:names:tc:ciq:xsdschema:xAL:2.0"><Country><CountryNameCode>DE</CountryNameCode><CountryName>Deutschland</CountryName><AdministrativeArea><AdministrativeAreaName>Brandenburg</AdministrativeAreaName><SubAdministrativeArea><SubAdministrativeAreaName>Potsdam</SubAdministrativeAreaName><Locality><LocalityName>Potsdam</LocalityName></Locality></SubAdministrativeArea></AdministrativeArea></Country></AddressDetails> <ExtendedData> <LatLonBox north="52.4513968" south="52.3424614" east="13.1866602" west="12.9305414" /> </ExtendedData> <Point><coordinates>13.0586008,52.3969627,0</coordinates></Point> </Placemark> </Response></kml> but now i want to get the information agianst the zipcode how to do that using the maps.google.com ???

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  • Testing fault tolerant code

    - by Robert
    I’m currently working on a server application were we have agreed to try and maintain a certain level of service. The level of service we want to guaranty is: if a request is accepted by the server and the server sends on an acknowledgement to the client we want to guaranty that the request will happen, even if the server crashes. As requests can be long running and the acknowledgement time needs be short we implement this by persisting the request, then sending an acknowledgement to the client, then carrying out the various actions to fulfill the request. As actions are carried out they too are persisted, so the server knows the state of a request on start up, and there’s also various reconciliation mechanisms with external systems to check the accuracy of our logs. This all seems to work fairly well, but we have difficult saying this with any conviction as we find it very difficult to test our fault tolerant code. So far we’ve come up with two strategies but neither is entirely satisfactory: Have an external process watch the server code and then try and kill it off at what the external process thinks is an appropriate point in the test Add code the application that will cause it to crash a certain know critical points My problem with the first strategy is the external process cannot know the exact state of the application, so we cannot be sure we’re hitting the most problematic points in the code. My problem with the second strategy, although it gives more control over were the fault takes, is I do not like have code to inject faults within my application, even with optional compilation etc. I fear it would be too easy to over look a fault injection point and have it slip into a production environment.

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  • Calculating bounding box a certain distance away from a lat/long coordinate in Java

    - by Bryce Thomas
    Given a coordinate (lat, long), I am trying to calculate a square bounding box that is a given distance (e.g. 50km) away from the coordinate. So as input I have lat, long and distance and as output I would like two coordinates; one being the south-west (bottom-left) corner and one being the north-east (top-right) corner. I have seen a couple of answers on here that try to address this question in Python, but I am looking for a Java implementation in particular. Just to be clear, I intend on using the algorithm on Earth only and so I don't need to accommodate a variable radius. It doesn't have to be hugely accurate (+/-20% is fine) and it'll only be used to calculate bounding boxes over small distances (no more than 150km). So I'm happy to sacrifice some accuracy for an efficient algorithm. Any help is much appreciated. Edit: I should have been clearer, I really am after a square, not a circle. I understand that the distance between the center of a square and various points along the square's perimeter is not a constant value like it is with a circle. I guess what I mean is a square where if you draw a line from the center to any one of the four points on the perimeter that results in a line perpendicular to a side of the perimeter, then those 4 lines have the same length.

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  • Java SSH2 libraries in depth: Trilead/Ganymed/Orion [/other?]

    - by Bernd Haug
    I have been searching for a pure Java SSH library to use for a project. The single most important needed feature is that it has to be able to work with command-line git, but remote-controlling command-line tools is also important. A pretty common choice, e.g. used in the IntelliJ IDEA git integration (which works very well), seems to be Trilead SSH2. Looking at their website, it's not being maintained any more. Trilead seems to have been a fork of Ganymed SSH2, which was a ETH Zurich project that didn't see releases for a while, but had a recent release by its new owner, Christian Plattner. There is another actively maintained fork from that code base, Orion SSH, that saw an even more recent release, but which seems to get mentioned online much less than the other 2 forks. Has anybody here worked with any of (or, if possible, both) of Ganymed and Orion and could kindly describe the development experience with either/both? Accuracy of documentation [existence of documentation?], stability, buggyness... - all of these would be highly interesting to me. Performance is not so important for my current project. If there is another pure-Java SSH implementation that should be used instead, please feel free to mention it, but please don't just mention a name...describe your judgment from actual experience. Sorry if this question may seem a bit "do my homework"-y, but I've really searched for reviews. Everything out there seems to be either a listing of implementations or short "use this! it's great!" snippets.

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  • Performance of Java matrix math libraries?

    - by dfrankow
    We are computing something whose runtime is bound by matrix operations. (Some details below if interested.) This experience prompted the following question: Do folk have experience with the performance of Java libraries for matrix math (e.g., multiply, inverse, etc.)? For example: JAMA: http://math.nist.gov/javanumerics/jama/ COLT: http://acs.lbl.gov/~hoschek/colt/ Apache commons math: http://commons.apache.org/math/ I searched and found nothing. Details of our speed comparison: We are using Intel FORTRAN (ifort (IFORT) 10.1 20070913). We have reimplemented it in Java (1.6) using Apache commons math 1.2 matrix ops, and it agrees to all of its digits of accuracy. (We have reasons for wanting it in Java.) (Java doubles, Fortran real*8). Fortran: 6 minutes, Java 33 minutes, same machine. jvisualm profiling shows much time spent in RealMatrixImpl.{getEntry,isValidCoordinate} (which appear to be gone in unreleased Apache commons math 2.0, but 2.0 is no faster). Fortran is using Atlas BLAS routines (dpotrf, etc.). Obviously this could depend on our code in each language, but we believe most of the time is in equivalent matrix operations. In several other computations that do not involve libraries, Java has not been much slower, and sometimes much faster.

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  • Android Accessing Accelerometer: Returns always 0 as Value

    - by Rotesmofa
    Hello there, i would like to use the accelerometer in an Android Handset for my Application. The data from the sensor will be saved together with a GPS Point, so the Value is only needed when the GPS Point is updated. If i use the attached Code the values is always zero. API Level 8 Permissions: Internet, Fine Location Testing Device: Galaxy S(i9000), Nexus One Any Suggestions? I am stuck at this point. Best regards from Germany, Pascal import android.app.Activity; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.os.Bundle; public class AccelerometerService extends Activity{ AccelerometerData accelerometerData; private SensorManager mSensorManager; private float x,y,z; private class AccelerometerData implements SensorEventListener{ public void onSensorChanged(SensorEvent event) { x = event.values[0]; y = event.values[1]; z = event.values[2]; } public void onAccuracyChanged(Sensor sensor, int accuracy) {} } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE); mSensorManager.registerListener(accelerometerData, mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_FASTEST); } @Override protected void onResume() { super.onResume(); } @Override protected void onStop() { mSensorManager.unregisterListener(accelerometerData); super.onStop(); } public String getSensorString() { return ("X: " + x+"m/s, Y: "+ y +"m/s, Z: "+ z +"m/s" ); } }

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  • Fast, very lightweight algorithm for camera motion detection?

    - by Ertebolle
    I'm working on an augmented reality app for iPhone that involves a very processor-intensive object recognition algorithm (pushing the CPU at 100% it can get through maybe 5 frames per second), and in an effort to both save battery power and make the whole thing less "jittery" I'm trying to come up with a way to only run that object recognizer when the user is actually moving the camera around. My first thought was to simply use the iPhone's accelerometers / gyroscope, but in testing I found that very often people would move the iPhone at a consistent enough attitude and velocity that there wouldn't be any way to tell that it was still in motion. So that left the option of analyzing the actual video feed and detecting movement in that. I got OpenCV working and tried running their pyramidal Lucas-Kanade optical flow algorithm, which works well but seems to be almost as processor-intensive as my object recognizer - I can get it to an acceptable framerate if I lower the depth levels / downsample the image / track fewer points, but then accuracy suffers and it starts to miss some large movements and trigger on small hand-shaking-y ones. So my question is, is there another optical flow algorithm that's faster than Lucas-Kanade if I just want to detect the overall magnitude of camera movement? I don't need to track individual objects, I don't even need to know which direction the camera is moving, all I really need is a way to feed something two frames of video and have it tell me how far apart they are.

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  • 1k of Program Space, 64 bytes of RAM. Is assembly an absolute must?

    - by Earlz
    (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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  • Are Fortran control characters (carriage control) still implemented in compilers?

    - by CmdrGuard
    In the book Fortran 95/2003 for Scientists and Engineers, there is much talk given to the importance of recognizing that the first column in a format statement is reserved for control characters. I've also seen control characters referred to as carriage control on the internet. To avoid confusion, by control characters, I refer to the characters "1, a blank (i.e. \s), 0, and +" as having an effect on the vertical spacing of output when placed in the first column (character) of a FORMAT statement. Also, see this text-only web page written entirely in fixed-width typeface : Fortran carriage-control (because nothing screams accuracy and antiquity better than prose in monospaced font). I found this page and others like it to be not quite clear. According to Fortran 95/2003 for Scientists and Engineers, failure to recall that the first column is reserved for carriage control can lead to horrible unintended output. Paraphrasing Dave Barry, type the wrong character, and nuclear missiles get fired at Norway. However, when I attempt to adhere to this stern warning, I find that gfortran has no idea what I'm talking about. Allow me to illustrate my point with some example code. I am trying to print out the number Pi: PROGRAM test_format IMPLICIT NONE REAL :: PI = 2 * ACOS(0.0) WRITE (*, 100) PI WRITE (*, 200) PI WRITE (*, 300) PI 100 FORMAT ('1', "New page: ", F11.9) 200 FORMAT (' ', "Single Space: ", F11.9) 300 FORMAT ('0', "Double Space: ", F11.9) END PROGRAM test_format This is the output: 1New page: 3.141592741 Single Space: 3.141592741 0Double Space: 3.141592741 The "1" and "0" are not typos. It appears that gfortran is completely ignoring the control character column. My question, then, is this: Are control characters still implemented in standards compliant compilers or is gfortran simply not standards compliant? For clarity, here is the output of my gfortran -v Using built-in specs. Target: powerpc-apple-darwin9 Configured with: ../gcc-4.4.0/configure --prefix=/sw --prefix=/sw/lib/gcc4.4 --mandir=/sw/share/man --infodir=/sw/share/info --enable-languages=c,c++,fortran,objc,java --with-gmp=/sw --with-libiconv-prefix=/sw --with-ppl=/sw --with-cloog=/sw --with-system-zlib --x-includes=/usr/X11R6/include --x-libraries=/usr/X11R6/lib --disable-libjava-multilib --build=powerpc-apple-darwin9 --host=powerpc-apple-darwin9 --target=powerpc-apple-darwin9 Thread model: posix gcc version 4.4.0 (GCC)

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  • Using Partitions for a large MySQL table

    - by user293594
    An update on my attempts to implement a 505,000,000-row table on MySQL on my MacBook Pro: Following the advice given, I have partitioned my table, tr: i UNSIGNED INT NOT NULL, j UNSIGNED INT NOT NULL, A FLOAT(12,8) NOT NULL, nu BIGINT NOT NULL, KEY (nu), key (A) with a range on nu. nu ought to be a real number, but because I only have 6-d.p. accuracy and the maximum value of nu is 30000. I multiplied it by 10^8 made it a BIGINT - I gather one can't use FLOAT or DOUBLE values to PARTITION a MySQL table. Anyway, I have 15 partitions (p0: nu<25,000,000,000, p1: nu<50,000,000,000, etc.). I was thinking that this should speed up a typical to SELECT: SELECT * FROM tr WHERE nu>95000000000 AND nu<100000000000 AND A.>1. to something of the order of the same query on a table consisting of only the data in the relevant partition (<30 secs). But it's taking 30mins+ to return rows for queries within a partition and double that if the query is for rows spanning two (contiguous) partitions. I realise I could just have 15 different tables, and query them separately, but is there a way to do this 'automatically' with partitions? Has anyone got any suggestions?

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  • How to stop Android GPS using "Mobile data"

    - by prepbgg
    My app requests location updates with "minTime" set to 2 seconds. When "Mobile data" is switched on (in the phone's settings) and GPS is enabled the app uses "mobile data" at between 5 and 10 megabytes per hour. This is recorded in the ICS "Data usage" screen as usage by "Android OS". In an attempt to prevent this I have unticked Settings-"Location services"-"Google's location service". Does this refer to Assisted GPS, or is it something more than that? Whatever it is, it seems to make no difference to my app's internet access. As further confirmation that it is the GPS usage by my app that is causing the mobile data access I have observed that the internet data activity indicator on the status bar shows activity when and only when the GPS indicator is present. The only way to prevent this mobile data usage seems to be to switch "Mobile data" off, and GPS accuracy seems to be almost as good without the support of mobile data. However, it is obviously unsatisfactory to have to switch mobile data off. The only permissions in the Manifest are "android.permission.ACCESS_FINE_LOCATION" (and "android.permission.WRITE_EXTERNAL_STORAGE"), so the app has no explicit permission to use internet data. The LocationManager code is ` criteria.setAccuracy(Criteria.ACCURACY_FINE); criteria.setSpeedRequired(false); criteria.setAltitudeRequired(false); criteria.setBearingRequired(true); criteria.setCostAllowed(false); criteria.setPowerRequirement(Criteria.NO_REQUIREMENT); bestProvider = lm.getBestProvider(criteria, true); if (bestProvider != null) { lm.requestLocationUpdates(bestProvider, gpsMinTime, gpsMinDistance, this); ` The reference for LocationManager.getBestProvider says If no provider meets the criteria, the criteria are loosened ... Note that the requirement on monetary cost is not removed in this process. However, despite setting setCostAllowed to false the app still incurs a potential monetary cost. What else can I do to prevent the app from using mobile data?

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  • 1k of Program Space, 64 bytes of RAM. Is 1 wire communication possible?

    - by Earlz
    (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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  • [jQuery 1.4] move one div over another

    - by Tomasz Zielinski
    I have two div elements that are twins (i.e. their dimensions and contents are identical). I want to move of those div-s over another, so that their corners are at exactly the same coordinates. What I try to do is: var offset = $('div#placeholder').offset(); $('div#overlay').css('position', 'absolute').css('left', offset.left + 'px').css('top', offset.top + 'px') -- but this causes the overlay to be exactly (or almost exactly, taking subpixel accuracy into account) 16px below the placeholder (below, i.e. overlay_top = placeholder_top + 16px). I'm aware that offset() gives position relative to the document, and position: absolute sets position relative to body element, but compensating for body offset() doesn't help much (I'm getting 8px offset, equal to margins): offset.top -= $('body').offset().top; offset.left -= $('body').offset().left; Also, compensating for body margins (in case they were different that offset() didn't help, as they were set to 8px). Does somebody know what I'm doing wrong here? UPDATE: Take a look at here - I'm getting the same result in FireFox 3.6.3 and Opera 10.10.

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  • How to implement Horner's scheme for multivariate polynomials?

    - by gsreynolds
    Background I need to solve polynomials in multiple variables using Horner's scheme in Fortran90/95. The main reason for doing this is the increased efficiency and accuracy that occurs when using Horner's scheme to evaluate polynomials. I currently have an implementation of Horner's scheme for univariate/single variable polynomials. However, developing a function to evaluate multivariate polynomials using Horner's scheme is proving to be beyond me. An example bivariate polynomial would be: 12x^2y^2+8x^2y+6xy^2+4xy+2x+2y which would factorised to x(x(y(12y+8))+y(6y+4)+2)+2y and then evaluated for particular values of x & y. Research I've done my research and found a number of papers such as: staff.ustc.edu.cn/~xinmao/ISSAC05/pages/bulletins/articles/147/hornercorrected.pdf citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.40.8637&rep=rep1&type=pdf www.is.titech.ac.jp/~kojima/articles/B-433.pdf Problem However, I'm not a mathematician or computer scientist, so I'm having trouble with the mathematics used to convey the algorithms and ideas. As far as I can tell the basic strategy is to turn a multivariate polynomial into separate univariate polynomials and compute it that way. Can anyone help me? If anyone could help me turn the algorithms into pseudo-code that I can implement into Fortran myself, I would be very grateful.

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  • Downloading javascript Without Blocking

    - by doug
    The context: My question relates to improving web-page loading performance, and in particular the effect that javascript has on page-loading (resources/elements below the script are blocked from downloading/rendering). This problem is usually avoided/mitigated by placing the scripts at the bottom (eg, just before the tag). The code i am looking at is for web analytics. Placing it at the bottom reduces its accuracy; and because this script has no effect on the page's content, ie, it's not re-writing any part of the page--i want to move it inside the head. Just how to do that without ruining page-loading performance is the crux. From my research, i've found six techniques (w/ support among all or most of the major browsers) for downloading scripts so that they don't block down-page content from loading/rendering: (i) XHR + eval(); (ii) XHR + 'inject'; (iii) download the HTML-wrapped script as in iFrame; (iv) setting the script tag's 'async' flag to 'TRUE' (HTML 5 only); (v) setting the script tag's 'defer' attribute; and (vi) 'Script DOM Element'. It's the last of these i don't understand. The javascript to implement the pattern (vi) is: (function() { var q1 = document.createElement('script'); q1.src = 'http://www.my_site.com/q1.js' document.documentElement.firstChild.appendChild(q1) })(); Seems simple enough: inside this anonymous function, a script element is created, its 'src' element is set to it's location, then the script element is added to the DOM. But while each line is clear, it's still not clear to me how exactly this pattern allows script loading without blocking down-page elements/resources from rendering/loading?

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  • Rounding up milliseconds when printing with Joda Time

    - by RoToRa
    I'm implementing a count-down using Joda Time. I only need a display accuracy of seconds. However when printing the time, the seconds are displayed as full seconds, so when the count down reaches, for example, 900ms, then "0" seconds is printed, but as a count-down it would make more sense to display "1" second, until the time actually reaches 0ms. Example: void printDuration(Duration d) { System.out.println( d.toPeriod(PeriodType.time()).toString( new PeriodFormatterBuilder().printZeroAlways().appendSeconds().toFormatter() ) ); } printDuration(new Duration(5000)); // Prints "5" => OK printDuration(new Duration(4900)); // Prints "4" => need "5" printDuration(new Duration(1000)); // Prints "1" => OK printDuration(new Duration(900)); // Prints "0" => need "1" printDuration(new Duration(0)); // Prints "0" => OK Basically I need to the seconds to be display rounded up from milliseconds and not rounded down. Is there a way to achieve this with Joda without needing to write my own formatter?

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  • cancelPreviousPerformRequestWithTarget is not canceling my previously delayed thread started with pe

    - by jmurphy
    Hello, I've launched a delayed thread using performSelector but the user still has the ability to hit the back button on the current view causing dealloc to be called. When this happens my thread still seems to be called which causes my app to crash because the properties that thread is trying to write to have been released. To solve this I am trying to call cancelPreviousPerformRequestsWithTarget to cancel the previous request but it doesn't seem to be working. Below are some code snippets. - (void) viewDidLoad { [self performSelector:@selector(myStopUpdatingLocation) withObject:nil afterDelay:6]; } (void)viewWillDisappear:(BOOL)animated { [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(myStopUpdatingLocation) object:nil]; } Am I doing something incorrect here? The method myStopUpdatingLocation is defined in the same class that I'm calling the perform requests. A little more background. The function that I'm trying to implement is to find a users location, search google for some locations around that location and display several annotations on the map. On viewDidLoad I start updating the location with CLLocationManager. I've build in a timeout after 6 seconds if I don't get my desired accuracy within the timeout and I'm using a performSelector to do this. What can happen is the user clicks the back button in the view and this thread will still execute even though all my properties have been released causing a crash. Thanks in advance! James

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  • How best to deal with warning c4305 when type could change?

    - by identitycrisisuk
    I'm using both Ogre and NxOgre, which both have a Real typedef that is either float or double depending on a compiler flag. This has resulted in most of our compiler warnings now being: warning C4305: 'argument' : truncation from 'double' to 'Ogre::Real' When initialising variables with 0.1 for example. Normally I would use 0.1f but then if you change the compiler flag to double precision then you would get the reverse warning. I guess it's probably best to pick one and stick with it but I'd like to write these in a way that would work for either configuration if possible. One fix would be to use #pragma warning (disable : 4305) in files where it occurs, I don't know if there are any other more complex problems that can be hidden by not having this warning. I understand I would push and pop these in header files too so that they don't end up spreading across code. Another is to create some macro based on the accuracy compiler flag like: #if OGRE_DOUBLE_PRECISION #define INIT_REAL(x) (x) #else #define INIT_REAL(x) static_cast<float>( x ) #endif which would require changing all the variable initialisation done so far but at least it would be future proof. Any preferences or something I haven't thought of?

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  • Convert long/lat to pixel x/y on a given picure.

    - by Kalinin
    I have a city "map" (for example - Moscow). She in accuracy repeats the contours the given city in google maps (that is it is copied from google maps and it is a little processed, but the sense remained the same). Also I have object co-ordinates in a city (in co-ordinates of google). Problem: how to convert google co-ordinates to the co-ordinates of my picture (that is in pixels on OX and OY on a picture). That is I receive google-co-ordinates and it is necessary for me to draw this point on my picture. The most desired variant of the answer - is based on javascript, but it is possible and on php. I know that on small scales (for example on city scales) it to make simply enough (it is necessary to learn what google-co-ordinates has one of picture corners, then to learn "price" of one pixel in google-co-ordinates on a picture on axes OX and OY separately). But on the big scales (country scale) "price" of one pixel will be not a constant, and will vary strongly enough and the method described above cannot be applied. How to solve a problem on country scales?

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  • Finding What You Need in R: function arguments/parameters from outside the function's package

    - by doug
    Often in R, there are a dozen functions scattered across as many packages--all of which have the same purpose but of course differ in accuracy, performance, theoretical rigor, and so on. How do you gather all of these in one place before you start your task? So for instance: the generic plot function. Setting secondary ticks is much easier (IMHO) using a function outside of the base package, minor.tick(nx=n, ny=n, tick.ratio=n), found in Hmisc. Of course, that doesn't show up in plot's docstring. Likewise, the data-input arguments to 'plot' can be supplied by an object returned from the function 'hexbin', again, from a library outside of the base installation (where 'plot' resides). What would be great obviously is a programmatic way to gather these function arguments from the various libraries and put them in a single namespace. edit: (trying to re-state my example just above more clearly:) the arguments to plot supplied in the base package for, e.g., setting the axis tick frequency are xaxp/yaxp; however, one can also set a/t/f via a function outside of the base package, again, as in the minor.tick function from the Hmisc package--but you wouldn't know that just from looking at the plot method signature. Is there a meta function in R for this? So far, as i come across them, i've been manually gathering them in a TextMate 'snippet' (along with the attendant library imports). This isn't that difficult or time consuming, but i can only update my snippet as i find out about these additional arguments/parameters. Is there a canonical R way to do this, or at least an easier way? Just in case that wasn't clear, i am not talking about the case where multiple packages provide functions directed to the same statistic or view (e.g., 'boxplot' in the base package; 'boxplot.matrix' in gplots; and 'bplots' in Rlab). What i am talking is the case in which the function name is the same across two or more packages.

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  • Long primitive or AtomicLong for a counter?

    - by Rich
    Hi I have a need for a counter of type long with the following requirements/facts: Incrementing the counter should take as little time as possible. The counter will only be written to by one thread. Reading from the counter will be done in another thread. The counter will be incremented regularly (as much as a few thousand times per second), but will only be read once every five seconds. Precise accuracy isn't essential, only a rough idea of the size of the counter is good enough. The counter is never cleared, decremented. Based upon these requirements, how would you choose to implement your counter? As a simple long, as a volatile long or using an AtomicLong? Why? At the moment I have a volatile long but was wondering whether another approach would be better. I am also incrementing my long by doing ++counter as opposed to counter++. Is this really any more efficient (as I have been led to believe elsewhere) because there is no assignment being done? Thanks in advance Rich

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  • Timing issues with playback of the HTML5 Audio API

    - by pat
    I'm using the following code to try to play a sound clip with the HTML5 Audio API: HTMLAudioElement.prototype.playClip = function(startTime, stopTime) { this.stopTime = stopTime; this.currentTime = startTime; this.play(); $(this).bind('timeupdate', function(){ if (this.ended || this.currentTime >= stopTime) { this.pause(); $(this).unbind('timeupdate'); } }); } I utilize this new playClip method as follows. First I have a link with some data attributes: <a href=# data-stop=1.051 data-start=0.000>And then I was thinking,</a> And finally this bit of jQuery which runs on $(document).ready to hook up a click on the link with the playback: $('a').click(function(ev){ $('a').click(function(ev){ var start = $(this).data('start'), stop = $(this).data('stop'), audio = $('audio').get(0), $audio = $(audio); ev.preventDefault(); audio.playClip(start,stop); }) This approach seems to work, but there's a frustrating bug: sometimes, the playback of a given clip plays beyond the correct data-stop time. I suspect it could have something to do with the timing of the timeupdate event, but I'm no JS guru and I don't know how to begin debugging the problem. Here are a few clues I've gathered: The same behavior appears to come up in both FF and Chrome. The playback of a given clip actually seems to vary a bit -- if I play the same clip a couple times in a row, it may over-play a different amount of time on each playing. Is the problem here the inherent accuracy of the Audio API? My app needs milliseconds. Is there a problem with the way I'm using jQuery to bind and unbind the timeupdate event? I tried using the jQuery-less approach with addEventListener but I couldn't get it to work. Thanks in advance, I would really love to know what's going wrong.

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  • Detecting the axis of rotation from a pointcloud

    - by tfinniga
    I'm trying to auto-detect the axis of rotation on a 3d pointcloud. In other words, if I took a small 3d pointcloud, chose a single axis of rotation, and make several copies of the points at different rotation angles, then I get a larger pointcloud. The input to my algorithm is the larger pointcloud, and the desired output is the single axis of symmetry. And eventually I'm going to compute the correspondences between points that are rotations of each other. The size of the larger pointcloud is on the order of 100K points, and the number of rotational copies made is unknown. The rotation angles in my case have constant deltas, but don't necessarily span 360 degrees. For example, I might have 0, 20, 40, 60. Or I might have 0, 90, 180, 270. But I won't have 0, 13, 78, 212 (or if I do, I don't care to detect it). This seems like a computer vision problem, but I'm having trouble figuring out how to precisely find the axis. The input will generally be very clean, close to float accuracy.

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