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  • Guaranteeing ACID properties for InnoDB databases.

    - by plinehan
    What steps must one take to ensure that an otherwise defaultly-configured InnoDB server is truly ACID compliant? The InnoDB configuration page mentions that the hardware itself must be configured to honor fsync calls, i.e. disable any write-back caches. This page mentions some other concerns, but may be conflating the binary log and the InnoDB log, and may be a bit out of date regarding default settings for MySQL 5.x. Upon reading the binary log document page it would seem that the "sync_binlog=1" setting is not required for ACID properties in general, only for ACID properties vis a vis point-in-time recovery and replication. So, is disabling write-back disk caching sufficient, or are there other settings that must be tweaked?

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  • Perl script segfaulting after 64-bit upgrade

    - by Brent
    I recently upgraded a 32-bit Debian server to 64-bit by re-installing, and copying my data into place. After this I have a perl script that repeats the following, and is segfaulting on the tell line: seek(FIN,$ps,0); tell(FIN, $ps); $line=<FIN>; I don't speak perl, so I'm not sure exactly what is going on here. I can get the script to run (apparently successfully) by commenting every occurrence of tell, but this is obviously not the best solution. I suspect that tell is calling a 32-bit binary or something, and that is the cause of the segfault - but I don't know. Can someone explain what tell does, and if it is indeed a separate binary, what package it belongs to (or how it is installed ie. cpan)? Or perhaps I am on the wrong track?

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  • Multidimensional vectors in scheme?

    - by incrediman
    I earlier asked a question about arrays in scheme (turns out they're called vectors but are basically otherwise the same as you'd expect). Is there an easy way to do multidimensional arrays vectors in PLT Scheme though? For my purposes I'd like to have a procedure called make-multid-vector or something. By the way if this doesn't already exist, I don't need a full code example of how to implement it. If I have to roll this myself I'd appreciate some general direction though. The way I'd probably do it is to just iterate through each element of the currently highest dimension of the vector to add another dimension, but I can see that being a bit ugly using scheme's recursive setup. Also, this seems like something I should have been able to find myself so please know that I did actually google it and nothing came up.

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  • c++ casting base class to derived class mess

    - by alan2here
    If I were to create a base class called base and derived classes called derived_1, derived_2 etc... I use a collection of instances of the base class, then when I retrieved an element and tried to use it I would find that C++ thinks it's type is that of the base class, probably because I retrieved it from a std::vector of base. Which is a problem when I want to use features that only exist for the specific derived class who's type I knew this object was when I put it into the vector. So I cast the element into the type it is supposed to be and found this wouldn't work. (derived_3)obj_to_be_fixed; And remembered that it's a pointer thing. After some tweaking this now worked. *((derived_3*)&obj_to_be_fixed); Is this right or is there for example an abc_cast() function that does it with less mess?

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  • CentOS: update a package from a repository safely on a production server

    - by dan
    Hello everybody. I have a CentOS server on a production environment. I need to update the PHP package that I installed using the REMI repository. Quite easy: yum update php But what is it going to happen if something goes wrong during the update? How can I rollback? What's the best technique to make sure not to compromise a production server due to an update? Is it maybe better to compile PHP from the source, rather than using a binary package? EDIT: I am not afraid of incompatibility between my code and the new PHP version (I have well tested that on development). I am more afraid of something going wrong while CentOS updated the binary (power cut, lost connection, unexpected conflit) Thanks, Dan

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  • How to Serialize a WPF Drawing?

    - by Néstor Sánchez A.
    Hi, maybe I'm missing something. I believed that WPF vector-based Drawings (like DrawingGroup, DrawingGeometry, etc.) were ready to be serialized. But they are not. So, should I navigate all these drawing childrens, and store they points, lines, brushes (that also are not serializable) and so on, and then made my custom serialization? Is really that difficult or I'm missing something pretty obvious? I mean, even serializing Bitmap images is easy. I thinked serializing vector-based drawings were easier (no quality loss, just descriptive info, no massive data). Thanks for your practical answers, alternate-way suggestions and comments!

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  • Is there a way to communicate DBMS with raw memory block or binaries

    - by darkcminor
    I am trying to communicate a numerical matrix operations library like LAPACK with any DBMS. Is it possible to send/receive complete matrices as binary or as a direct memory pointers to process them (it will be something like: The Outside library processes data stored in DBMS, then it computes some huge matrix stuff and then via memory block or a binary DBMS get the result from library)? The main purpose is speed and avoid passing through a flat file, and last but not least, use library toefficiently do some operations DBMS are not designed to. * Is it possible that Oracle, SQL Server, MySQL support this technique?.

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  • Find missing birth days in Apple Addressbook

    - by Felix Ogg
    I am trying to clean the holes out of my Mac address book. As a first step I want to ask all my friends for their birth day, to be able to congratulate them with cheesy Hallmark cards. I need a "group" in my address book, to mailmerge personalized messages from. This is the Applescript I came up with: tell application "Address Book" make new group with properties {name:"No Birthday"} set birthdayPeople to (get every person whose birth date is greater than date "Monday, January 1, 1900 12:00:00 AM") repeat with i from 1 to number of items in people set thePerson to item i of people if not (birthdayPeople contains thePerson) then add thePerson to group "No Birthday" end if end repeat save end tell It breaks, but from the error messages I cannot deduce what is wrong: Result: error "Can’t make «class azf4» id \"05F770BA-7492-436B-9B58-E24F494702F8:ABPerson\" of application \"Address Book\" into type vector." number -1700 from «class azf4» id "05F770BA-7492-436B-9B58-E24F494702F8:ABPerson" to vector (BTW: Did I mention this is my first AppleScript code, EVER? So, if this code can be simplified, or made more elegant, that is welcome too.)

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  • Most efficient way to solve system of equations involving the digamma function?

    - by Neil G
    What is the most efficient way to solve system of equations involving the digamma function? I have a vector v and I want to solve for a vector w such that for all i: digamma(sum(w)) - digamma(w_i) = v_i and w_i 0 I found the gsl function gsl_sf_psi, which is the digamma function. Is there an identity I can use to reduce the equations? Is my best bet to use a solver? I am using C++0x; which solver is easiest to use and fast?

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  • What is the most efficient way to solve system of equations containing the digamma function?

    - by Neil G
    What is the most efficient way to solve system of equations involving the digamma function? I have a vector v and I want to solve for a vector w such that for all i: digamma(sum(w)) - digamma(w_i) = v_i and w_i 0 I found the gsl function gsl_sf_psi, which is the digamma function (calculated using some kind of series.) Is there an identity I can use to reduce the equations? Is my best bet to use a solver? I am using C++0x; which solver is easiest to use and fast?

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  • Adding an overlay to Google maps with path taken

    - by user341652
    Hi, I am trying to write a class to track a person's location(s), and to draw the path they've taken on a MapView. This feature of the program is for the user to track their speed, distance, path, etc. while running/cycling (or whatever else) using their Android phone. This is my first Android application, and I am not sure how to do the Overlay object for the MapView. I also wanted to see if anyone had opinions on the GPS-Tracking part I have written (if it would work, if there is a better way of doing it, code examples would be helpful). I currently have this for my GPSTrackerService: package org.drexel.itrain.logic; import java.util.Vector; import org.drexel.itrain.Constants; import android.app.Notification; import android.app.NotificationManager; import android.app.Service; import android.content.Context; import android.content.Intent; import android.content.SharedPreferences; import android.location.GpsSatellite; import android.location.GpsStatus; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.location.GpsStatus.Listener; import android.os.Binder; import android.os.Bundle; import android.os.IBinder; import android.preference.PreferenceManager; public class GPSTrackingService extends Service { private static final int MAX_REASONABLE_SPEED = 60; private static final String TAG = "OGT.TrackingService"; private Context mContext; private LocationManager mLocationManager; private NotificationManager mNotificationManager; private Notification mNotification; private int mSatellites = 0; private int mTrackingState = Constants.GPS_TRACKING_UNKNOWN; private float mCurrentSpeed = 0; private float mTotalDistance = 0; private Location mPreviousLocation; private Vector<Location> mTrackedLocations; private LocationListener mLocationListener = null; private Listener mStatusListener = null; private IBinder binder = null; @Override public void onCreate() { super.onCreate(); this.mContext = getApplicationContext(); this.mLocationManager = (LocationManager) this.mContext.getSystemService( Context.LOCATION_SERVICE ); this.mNotificationManager = (NotificationManager) this.mContext.getSystemService( Context.NOTIFICATION_SERVICE ); this.mTrackedLocations = new Vector<Location>(); this.binder = new Binder(); SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this.mContext); binder = new Binder(); if(mTrackingState != Constants.GPS_TRACKING_UNKNOWN) { createListeners(); } } @Override public void onDestroy() { destroyListeneres(); } @Override public IBinder onBind(Intent intent) { return binder; } @Override public boolean onUnbind(Intent intent) { return true; } public boolean acceptLocation(Location proposedLocation) { if(!(proposedLocation.hasSpeed() || proposedLocation.hasAccuracy())) { return false; } else if(proposedLocation.getSpeed() >= MAX_REASONABLE_SPEED) { return false; } return true; } public void updateNotification() { //TODO Alert that no GPS sattelites are available (or are available) } public void startTracking() { this.mTrackingState = Constants.GPS_TRACKING_STARTED; this.mTotalDistance = 0; this.mCurrentSpeed = 0; this.mTrackedLocations = new Vector<Location>(); this.mPreviousLocation = null; createListeners(); } public void pauseTracking() { this.mTrackingState = Constants.GPS_TRACKING_PAUSED; this.mPreviousLocation = null; this.mCurrentSpeed = 0; } public void resumeTracking() { if(this.mTrackingState == Constants.GPS_TRACKING_STOPPED){ this.startTracking(); } this.mTrackingState = Constants.GPS_TRACKING_STARTED; } public void stopTracking() { this.mTrackingState = Constants.GPS_TRACKING_STOPPED; destroyListeneres(); } private void createListeners() { /** * LocationListener receives locations from */ this.mLocationListener = new LocationListener() { @Override public void onStatusChanged(String provider, int status, Bundle extras) { // TODO Auto-generated method stub } @Override public void onProviderEnabled(String provider) { // TODO Auto-generated method stub } @Override public void onProviderDisabled(String provider) { // TODO Auto-generated method stub } @Override public void onLocationChanged(Location location) { if(mTrackingState == Constants.GPS_TRACKING_STARTED && acceptLocation(location)) { if(mPreviousLocation != null) { //Add the distance between the new location and the previous location mTotalDistance += mPreviousLocation.distanceTo(location); } if(location.hasSpeed()) { mCurrentSpeed = location.getSpeed(); } else { mCurrentSpeed = -1; //-1 means speed N/A } mPreviousLocation = location; mTrackedLocations.add(location); } } }; /** * Receives updates reguarding the GPS Status */ this.mStatusListener = new GpsStatus.Listener() { @Override public synchronized void onGpsStatusChanged(int event) { switch( event ) { case GpsStatus.GPS_EVENT_SATELLITE_STATUS: { GpsStatus status = mLocationManager.getGpsStatus( null ); mSatellites = 0; Iterable<GpsSatellite> list = status.getSatellites(); for( GpsSatellite satellite : list ) { if( satellite.usedInFix() ) { mSatellites++; } } updateNotification(); break; } default: break; } } }; } /** * Destroys the LocationListenere and the GPSStatusListener */ private void destroyListeneres() { this.mLocationListener = null; this.mStatusListener = null; } /** * Gets the total distance traveled by the * * @return the total distance traveled (in meters) */ public float getDistance() { return mTotalDistance; } /** * Gets the current speed of the last good location * * @return the current speed (in meters/second) */ public float getSpeed() { return mCurrentSpeed; } } Any assistance would be much appreciated. This is my group's first Android app, and we are a little pressed for time at the moment. The project is for a class, and is available from SourceForge (currently called iTrain, soon to be renamed). Thanks in Advance, Steve

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  • Adding JTextField to a JPanel and showing them

    - by Davide Gualano
    I'm building a little app using Java and Swing in NetBeans. Using NetBeans design window, I created a JFrame with a JPanel inside. Now I want to dynamically add some jTextFields to the JPanel. I wrote something like that: Vector textFieldsVector = new Vector(); JTextField tf; int i = 0; while (i < 3) { tf = new JTextField(); textFieldVector.add(tf); myPanel.add(tf); //myPanel is the JPanel where I want to put the JTextFields i++; } myPanel.validate(); myPanel.repaint(); But nothing happens: when I run the app, the JFrame shows with the JPanel inside, but the JTextFields don't. I'm a total newbie in writing graphical Java apps, so I'm surely missing something very simple, but I can't see what.

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  • Unique_ptr compiler errors

    - by Godric Seer
    I am designing and entity-component system for a project, and C++ memory management is giving me a few issues. I just want to make sure my design is legitimate. So to start I have an Entity class which stores a vector of Components: class Entity { private: std::vector<std::unique_ptr<Component> > components; public: Entity() { }; void AddComponent(Component* component) { this -> components.push_back(std::unique_ptr<Component>(component)); } ~Entity(); }; Which if I am not mistaken means that when the destructor is called (even the default, compiler created one), the destructor for the Entity, will call ~components, which will call ~std::unique_ptr for each element in the vector, and lead to the destruction of each Component, which is what I want. The component class has virtual methods, but the important part is its constructor: Component::Component(Entity parent) { parent.addComponent(this) // I am not sure if this would work like I expect // Other things here } As long as passing this to the method works, this also does what I want. My confusion is in the factory. What I want to do is something along the lines of: std::shared_ptr<Entity> createEntity() { std::shared_ptr<Entity> entityPtr(new Entity()); new Component(*parent); // Initialize more, and other types of Components return entityPtr; } Now, I believe that this setup will leave the ownership of the Component in the hands of its Parent Entity, which is what I want. First a small question, do I need to pass the entity into the Component constructor by reference or pointer or something? If I understand C++, it would pass by value, which means it gets copied, and the copied entity would die at the end of the constructor. The second, and main question is that code based on this sample will not compile. The complete error is too large to print here, however I think I know somewhat of what is going on. The compiler's error says I can't delete an incomplete type. My Component class has a purely virtual destructor with an implementation: inline Component::~Component() { }; at the end of the header. However since the whole point is that Component is actually an interface. I know from here that a complete type is required for unique_ptr destruction. The question is, how do I work around this? For reference I am using gcc 4.4.6.

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  • String.substring(index) has stoped my thread in debug mode.

    - by Arkaha
    Hello! I work with j2me polish 2.0.7, in eclipse 3.4.2, with wtk2.5.2_01. I create control which draws text: normal, bold, and italic. The code below is parsing raw text, and search for * and _ symbols, if found than add to draw vector the text and the drawer, and it's just stops after getting second time to the line 58: String test = new String(raw_text_buff.substring(iter)); it stops in raw_text_buff.substring(iter), ONLY in debug mode.. raw text is: bla bla bla *1000* bla bla Full code: private String raw_text = "bla bla bla *1000* bla bla"; Vector draw_items = null; private void prepareText() { char open_char = 0; int open_pos = 0; Object []param = null; StringBuffer sb = new StringBuffer(); String raw_text_buff = new String(raw_text); int iter = 0; boolean was_reset = false; while(true) { char c = raw_text_buff.charAt(iter); if(iter == raw_text_buff.length() || c == '*' || c == '_') { if(sb.length() > 0) { BmFont viewer = null; String str = sb.toString(); if(open_char == '*' && null != bm_strong) { viewer = bm_strong.getViewer(str); }else if(open_char == '_' && null != bm_italic) { viewer = bm_italic.getViewer(str); }else if(null != bm_normal) { viewer = bm_normal.getViewer(str); }else { } param = new Object[2]; param[0] = str; param[1] = viewer; if(null == draw_items) draw_items = new Vector(); draw_items.addElement(param); sb = new StringBuffer(); if(open_char == 0 && (c == '*' || c=='_')) open_char = c; else open_char = 0; String test = new String(raw_text_buff.substring(iter)); // stucks here. raw_text_buff = test; iter = 0; was_reset = true; }else { open_char = c; } if(iter == raw_text_buff.length()) break; }else { sb.append(c); } ++iter; } } What I'm doing wrong?

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  • Daemons die with bus error when their binaries live on NFS

    - by mbac32768
    We have some daemons executing on a number of hosts. The daemon executable images are these very large binaries that are hosted on NFS. When the binaries are updated on the NFS server, the previously running daemons sometimes drop dead with a Bus error. I'm assuming what's happening is the NFS server is replacing the binaries in a way that's invisible to the VFS layer on the NFS clients so they end up loading pages from the updated binary, which of course leads to madness. We tried moving the new binaries into place instead of cp, but that doesn't seem to fix it. I'm considering simply mlock()'ing the binary in the daemon startup script, but surely there's magic NFS options or semantics that we should be abusing. Is there a better way to fix this?

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  • How do I classify using SVM Classifier?

    - by Gomathi
    I'm doing a project in liver tumor classification. Actually I initially used Region Growing method for liver segmentation and from that I segmented tumor using FCM. I,then, obtained the texture features using Gray Level Co-occurence Matrix. My output for that was stats = autoc: [1.857855266614132e+000 1.857955341199538e+000] contr: [5.103143332457753e-002 5.030548650257343e-002] corrm: [9.512661919561399e-001 9.519459060378332e-001] corrp: [9.512661919561385e-001 9.519459060378338e-001] cprom: [7.885631654779597e+001 7.905268525471267e+001] Now how should I give this as an input to the SVM program. function [itr] = multisvm( T,C,tst ) %MULTISVM(2.0) classifies the class of given training vector according to the % given group and gives us result that which class it belongs. % We have also to input the testing matrix %Inputs: T=Training Matrix, C=Group, tst=Testing matrix %Outputs: itr=Resultant class(Group,USE ROW VECTOR MATRIX) to which tst set belongs %----------------------------------------------------------------------% % IMPORTANT: DON'T USE THIS PROGRAM FOR CLASS LESS THAN 3, % % OTHERWISE USE svmtrain,svmclassify DIRECTLY or % % add an else condition also for that case in this program. % % Modify required data to use Kernel Functions and Plot also% %----------------------------------------------------------------------% % Date:11-08-2011(DD-MM-YYYY) % % This function for multiclass Support Vector Machine is written by % ANAND MISHRA (Machine Vision Lab. CEERI, Pilani, India) % and this is free to use. email: [email protected] % Updated version 2.0 Date:14-10-2011(DD-MM-YYYY) u=unique(C); N=length(u); c4=[]; c3=[]; j=1; k=1; if(N>2) itr=1; classes=0; cond=max(C)-min(C); while((classes~=1)&&(itr<=length(u))&& size(C,2)>1 && cond>0) %This while loop is the multiclass SVM Trick c1=(C==u(itr)); newClass=c1; svmStruct = svmtrain(T,newClass); classes = svmclassify(svmStruct,tst); % This is the loop for Reduction of Training Set for i=1:size(newClass,2) if newClass(1,i)==0; c3(k,:)=T(i,:); k=k+1; end end T=c3; c3=[]; k=1; % This is the loop for reduction of group for i=1:size(newClass,2) if newClass(1,i)==0; c4(1,j)=C(1,i); j=j+1; end end C=c4; c4=[]; j=1; cond=max(C)-min(C); % Condition for avoiding group %to contain similar type of values %and the reduce them to process % This condition can select the particular value of iteration % base on classes if classes~=1 itr=itr+1; end end end end Kindly guide me. Images:

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  • Dijkstras Algorithm exaplination java

    - by alchemey89
    Hi, I have found an implementation for dijkstras algorithm on the internet and was wondering if someone could help me understand how the code works. Many thanks private int nr_points=0; private int[][]Cost; private int []mask; private void dijkstraTSP() { if(nr_points==0)return; //algorithm=new String("Dijkstra"); nod1=new Vector(); nod2=new Vector(); weight=new Vector(); mask=new int[nr_points]; //initialise mask with zeros (mask[x]=1 means the vertex is marked as used) for(int i=0;i<nr_points;i++)mask[i]=0; //Dijkstra: int []dd=new int[nr_points]; int []pre=new int[nr_points]; int []path=new int[nr_points+1]; int init_vert=0,pos_in_path=0,new_vert=0; //initialise the vectors for(int i=0;i<nr_points;i++) { dd[i]=Cost[init_vert][i]; pre[i]=init_vert; path[i]=-1; } pre[init_vert]=0; path[0]=init_vert; pos_in_path++; mask[init_vert]=1; for(int k=0;k<nr_points-1;k++) { //find min. cost in dd for(int j=0;j<nr_points;j++) if(dd[j]!=0 && mask[j]==0){new_vert=j; break;} for(int j=0;j<nr_points;j++) if(dd[j]<dd[new_vert] && mask[j]==0 && dd[j]!=0)new_vert=j; mask[new_vert]=1; path[pos_in_path]=new_vert; pos_in_path++; for(int j=0;j<nr_points;j++) { if(mask[j]==0) { if(dd[j]>dd[new_vert]+Cost[new_vert][j]) { dd[j]=dd[new_vert]+Cost[new_vert][j]; } } } } //Close the cycle path[nr_points]=init_vert; //Save the solution in 3 vectors (for graphical purposes) for(int i=0;i<nr_points;i++) { nod1.addElement(path[i]); nod2.addElement(path[i+1]); weight.addElement(Cost[path[i]][path[i+1]]); } }

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  • Mysql innoDB corruption after server crash

    - by Ward Loockx
    Yesterday my server died because an outage in the data center. Today it's back up, but having some problems with mysql. First of all my mysql server was not able to start. For this reason I deleted the files ib_logfile0 and ib_logfile1 in /var/lib/mysql folder (I still have the old failing files). After this my server was able to startup again. But now I see a lot of issues in the mysql log file. Sep 1 09:43:55 * mysqld: 120901 9:43:55 InnoDB: Error: page 70944 log sequence number 8 1483471899 Sep 1 09:43:55 * mysqld: InnoDB: is in the future! Current system log sequence number 5 612394935. Sep 1 09:43:55 * mysqld: InnoDB: Your database may be corrupt or you may have copied the InnoDB Sep 1 09:43:55 * mysqld: InnoDB: tablespace but not the InnoDB log files. See Sep 1 09:43:55 * mysqld: InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html When I check the docs on mysql.com, I found that I need to recover my database with backups. I have a backup but not sure what's the good way on importing it. Or is there a way to recover without having to re-import the database again? So if I'm correct I need to put innodb_force_recovery to 4 in mysql and delete all current data and re-import? Is there a way to do this without having downtime? I also have one slave running. This slave has the current status now: Last_Error: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log), the slave's relay log is corrupted (you can check this by running 'mysqlbinlog' on the relay log), a network problem, or a bug in the master's or slave's MySQL code. If you want to check the master's binary log or slave's relay log, you will be able to know their names by issuing 'SHOW SLAVE STATUS' on this slave. How can I totally reset the slave after the new import on the master has happend? Hopefully we can find a solution without not to much downtime. Thanks!

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  • Trackpad Drag lock pissing me off with Windows 7

    - by rockinthesixstring
    This is driving me insane and I've scowered the web for two days trying to fix this. I just picked up an Apple Magic Trackpad to be used exclusively on a Windows 7 PC (not apple with bootcamp). I found a nice driver that got it working right away, but when I'm moving the cursor around the screen, often it will begin "highlighting" text, or picking up and dragging things I don't want it to. I looked in the "regedit" where people are saying there is binary that can be changed, however the driver I installed doesn't use the binary being suggested. Can anyone suggest a better driver for my situation or a way to disable the drag lock that is driving me so nuts? I don't mind not being able to lift my finger when dragging, it's a far better compromise than having the insane feature.

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  • Go - Using a container/heap to implement a priority queue

    - by Seth Hoenig
    In the big picture, I'm trying to implement Dijkstra's algorithm using a priority queue. According to members of golang-nuts, the idiomatic way to do this in Go is to use the heap interface with a custom underlying data structure. So I have created Node.go and PQueue.go like so: //Node.go package pqueue type Node struct { row int col int myVal int sumVal int } func (n *Node) Init(r, c, mv, sv int) { n.row = r n.col = c n.myVal = mv n.sumVal = sv } func (n *Node) Equals(o *Node) bool { return n.row == o.row && n.col == o.col } And PQueue.go: // PQueue.go package pqueue import "container/vector" import "container/heap" type PQueue struct { data vector.Vector size int } func (pq *PQueue) Init() { heap.Init(pq) } func (pq *PQueue) IsEmpty() bool { return pq.size == 0 } func (pq *PQueue) Push(i interface{}) { heap.Push(pq, i) pq.size++ } func (pq *PQueue) Pop() interface{} { pq.size-- return heap.Pop(pq) } func (pq *PQueue) Len() int { return pq.size } func (pq *PQueue) Less(i, j int) bool { I := pq.data.At(i).(Node) J := pq.data.At(j).(Node) return (I.sumVal + I.myVal) < (J.sumVal + J.myVal) } func (pq *PQueue) Swap(i, j int) { temp := pq.data.At(i).(Node) pq.data.Set(i, pq.data.At(j).(Node)) pq.data.Set(j, temp) } And main.go: (the action is in SolveMatrix) // Euler 81 package main import "fmt" import "io/ioutil" import "strings" import "strconv" import "./pqueue" const MATSIZE = 5 const MATNAME = "matrix_small.txt" func main() { var matrix [MATSIZE][MATSIZE]int contents, err := ioutil.ReadFile(MATNAME) if err != nil { panic("FILE IO ERROR!") } inFileStr := string(contents) byrows := strings.Split(inFileStr, "\n", -1) for row := 0; row < MATSIZE; row++ { byrows[row] = (byrows[row])[0 : len(byrows[row])-1] bycols := strings.Split(byrows[row], ",", -1) for col := 0; col < MATSIZE; col++ { matrix[row][col], _ = strconv.Atoi(bycols[col]) } } PrintMatrix(matrix) sum, len := SolveMatrix(matrix) fmt.Printf("len: %d, sum: %d\n", len, sum) } func PrintMatrix(mat [MATSIZE][MATSIZE]int) { for r := 0; r < MATSIZE; r++ { for c := 0; c < MATSIZE; c++ { fmt.Printf("%d ", mat[r][c]) } fmt.Print("\n") } } func SolveMatrix(mat [MATSIZE][MATSIZE]int) (int, int) { var PQ pqueue.PQueue var firstNode pqueue.Node var endNode pqueue.Node msm1 := MATSIZE - 1 firstNode.Init(0, 0, mat[0][0], 0) endNode.Init(msm1, msm1, mat[msm1][msm1], 0) if PQ.IsEmpty() { // make compiler stfu about unused variable fmt.Print("empty") } PQ.Push(firstNode) // problem return 0, 0 } The problem is, upon compiling i get the error message: [~/Code/Euler/81] $ make 6g -o pqueue.6 Node.go PQueue.go 6g main.go main.go:58: implicit assignment of unexported field 'row' of pqueue.Node in function argument make: *** [all] Error 1 And commenting out the line PQ.Push(firstNode) does satisfy the compiler. But I don't understand why I'm getting the error message in the first place. Push doesn't modify the argument in any way.

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  • compare function for upper_bound / lower_bound

    - by Martin Beckett
    I want to find the first item in a sorted vector that has a field less than some value x. I need to supply a compare function that compares 'x' with the internal value in MyClass but I can't work out the function declaration. Can't I simply overload '<' but how do I do this when the args are '&MyClass' and 'float' ? float x; std::vector< MyClass >::iterator last = std::upper_bound(myClass.begin(),myClass.end(),x);

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  • Why does my performance slow to a crawl I move methods into a base class?

    - by Juliet
    I'm writing different implementations of immutable binary trees in C#, and I wanted my trees to inherit some common methods from a base class. However, I find. I have lots of binary tree data structures to implement, and I wanted move some common methods into in a base binary tree class. Unfortunately, classes which derive from the base class are abysmally slow. Non-derived classes perform adequately. Here are two nearly identical implementations of an AVL tree to demonstrate: AvlTree: http://pastebin.com/V4WWUAyT DerivedAvlTree: http://pastebin.com/PussQDmN The two trees have the exact same code, but I've moved the DerivedAvlTree.Insert method in base class. Here's a test app: using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using Juliet.Collections.Immutable; namespace ConsoleApplication1 { class Program { const int VALUE_COUNT = 5000; static void Main(string[] args) { var avlTreeTimes = TimeIt(TestAvlTree); var derivedAvlTreeTimes = TimeIt(TestDerivedAvlTree); Console.WriteLine("avlTreeTimes: {0}, derivedAvlTreeTimes: {1}", avlTreeTimes, derivedAvlTreeTimes); } static double TimeIt(Func<int, int> f) { var seeds = new int[] { 314159265, 271828183, 231406926, 141421356, 161803399, 266514414, 15485867, 122949829, 198491329, 42 }; var times = new List<double>(); foreach (int seed in seeds) { var sw = Stopwatch.StartNew(); f(seed); sw.Stop(); times.Add(sw.Elapsed.TotalMilliseconds); } // throwing away top and bottom results times.Sort(); times.RemoveAt(0); times.RemoveAt(times.Count - 1); return times.Average(); } static int TestAvlTree(int seed) { var rnd = new System.Random(seed); var avlTree = AvlTree<double>.Create((x, y) => x.CompareTo(y)); for (int i = 0; i < VALUE_COUNT; i++) { avlTree = avlTree.Insert(rnd.NextDouble()); } return avlTree.Count; } static int TestDerivedAvlTree(int seed) { var rnd = new System.Random(seed); var avlTree2 = DerivedAvlTree<double>.Create((x, y) => x.CompareTo(y)); for (int i = 0; i < VALUE_COUNT; i++) { avlTree2 = avlTree2.Insert(rnd.NextDouble()); } return avlTree2.Count; } } } AvlTree: inserts 5000 items in 121 ms DerivedAvlTree: inserts 5000 items in 2182 ms My profiler indicates that the program spends an inordinate amount of time in BaseBinaryTree.Insert. Anyone whose interested can see the EQATEC log file I've created with the code above (you'll need EQATEC profiler to make sense of file). I really want to use a common base class for all of my binary trees, but I can't do that if performance will suffer. What causes my DerivedAvlTree to perform so badly, and what can I do to fix it?

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  • Interoperability between two AES algorithms

    - by lpfavreau
    Hello, I'm new to cryptography and I'm building some test applications to try and understand the basics of it. I'm not trying to build the algorithms from scratch but I'm trying to make two different AES-256 implementation talk to each other. I've got a database that was populated with this Javascript implementation stored in Base64. Now, I'm trying to get an Objective-C method to decrypt its content but I'm a little lost as to where the differences in the implementations are. I'm able to encrypt/decrypt in Javascript and I'm able to encrypt/decrypt in Cocoa but cannot make a string encrypted in Javascript decrypted in Cocoa or vice-versa. I'm guessing it's related to the initialization vector, nonce, counter mode of operation or all of these, which quite frankly, doesn't speak to me at the moment. Here's what I'm using in Objective-C, adapted mainly from this and this: @implementation NSString (Crypto) - (NSString *)encryptAES256:(NSString *)key { NSData *input = [self dataUsingEncoding: NSUTF8StringEncoding]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:TRUE]; return [Base64 encode:output]; } - (NSString *)decryptAES256:(NSString *)key { NSData *input = [Base64 decode:self]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:FALSE]; return [[[NSString alloc] initWithData:output encoding:NSUTF8StringEncoding] autorelease]; } + (NSData *)cryptoAES256:(NSData *)input key:(NSString *)key doEncrypt:(BOOL)doEncrypt { // 'key' should be 32 bytes for AES256, will be null-padded otherwise char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused) bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding) // fetch key data [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [input length]; // See the doc: For block ciphers, the output size will always be less than or // equal to the input size plus the size of one block. // That's why we need to add the size of one block here size_t bufferSize = dataLength + kCCBlockSizeAES128; void* buffer = malloc(bufferSize); size_t numBytesCrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(doEncrypt ? kCCEncrypt : kCCDecrypt, kCCAlgorithmAES128, kCCOptionECBMode | kCCOptionPKCS7Padding, keyPtr, kCCKeySizeAES256, nil, // initialization vector (optional) [input bytes], dataLength, // input buffer, bufferSize, // output &numBytesCrypted ); if (cryptStatus == kCCSuccess) { // the returned NSData takes ownership of the buffer and will free it on deallocation return [NSData dataWithBytesNoCopy:buffer length:numBytesCrypted]; } free(buffer); // free the buffer; return nil; } @end Of course, the input is Base64 decoded beforehand. I see that each encryption with the same key and same content in Javascript gives a different encrypted string, which is not the case with the Objective-C implementation that always give the same encrypted string. I've read the answers of this post and it makes me believe I'm right about something along the lines of vector initialization but I'd need your help to pinpoint what's going on exactly. Thank you!

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  • Vectors of Pointers, inheritance

    - by user308553
    Hi I am a C++ beginner just encountered a problem I don't know how to fix I have two class, this is the header file: class A { public: int i; A(int a); }; class B: public A { public: string str; B(int a, string b); }; then I want to create a vector in main which store either class A or class B vector<A*> vec; A objectOne(1); B objectTwo(2, "hi"); vec.push_back(&objectOne); vec.push_back(&objectTwo); cout << vec.at(1)->i; //this is fine cout << vec.at(1)->str; //ERROR here I am really confused, I checked sites and stuff but I just don't know how to fix it, please help thanks in advance

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