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  • How to avoid the "divide by zero" error in SQL?

    - by Henrik Staun Poulsen
    I hate this error message: Msg 8134, Level 16, State 1, Line 1 Divide by zero error encountered. What is the best way to write SQL code, so that I will never see this error message again? I mean, I could add a where clause so that my divisor is never zero. Or I could add a case statement, so that there is a special treatment for zero. Is the best way to use a NullIf clause? Is there better way, or how can this be enforced?

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  • What does msvc 6 throw when an integer divide by zero occurs?

    - by EvilTeach
    I have been doing a bit of experimenting, and have discovered that an exception is being thrown, when an integer divide by zero occurs. #include <iostream> #include <stdexcept> using namespace std; int main ( void ) { try { int x = 3; int y = 0; int z = x / y; cout << "Didn't throw or signal" << endl; } catch (std::exception &e) { cout << "Caught exception " << e.what() << endl; } return 0; } Clearly it is not throwing a std::exception. What else might it be throwing?

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  • Ways to divide the high/low byte from a 16bit address?

    - by Grissiom
    Hello, I'm developing a software on 8051 processor. A frequent job is to divide the high and low byte of a 16bit address. I want to see there are how many ways to achieve it. The ways I come up so far are: (say ptr is a 16bit pointer, and int is 16bit int) ADDH = (unsigned int) ptr >> 8; ADDL = (unsigned int) ptr & 0x00FF; and ADDH = ((unsigned char *)&ptr)[0]; ADDL = ((unsigned char *)&ptr)[1]; Does anyone have any other bright ideas? ;) And anyone can tell me which way is more efficient?

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  • Java MVC - How to divide a done text game into MVC?

    - by Zopyrus
    Been sitting here for hours now trying to figure this out, so a bit sympathy for this large question. :) The Goal: I simply want to divide my done code into MVC (Model View Controller) parts. I have the game logics done and text based - the code works fine. The Problem: Well, I want to implement this code into MVC, but where do explain for the MODEL that it should use text-based? Because the VIEW is only for the layout (graphically) correct? I am having a REALLY hard time figuring out where to begin at all. Any pointers would be so nice! Here is my game logics code: import mind.*; import javax.swing.*; import java.util.*; import java.lang.*; import java.awt.*; public class Drive { String[] mellan; boolean gameEnd, checkempty, checkempty2, enemy, enemy2; String gr,rd,tom; int digits; public Drive() { // Gamepieces in textform gr="G"; rd="R"; tom=" "; mellan = new String[7]; String[] begin = {gr,gr,gr,tom,rd,rd,rd}; String[] end = {rd,rd,rd,tom,gr,gr,gr}; //input Scanner in = new Scanner(System.in); mellan=begin; gameEnd=false; while (gameEnd == false) { for(int i=0; i<mellan.length; i++) { System.out.print(mellan[i]); } System.out.print(" Choose 0-6: "); digits = in.nextInt(); move(); checkWin(); } } void move() { //BOOLEAN for gameruls!!! checkempty = digits<6 && mellan[digits+1]==tom; checkempty2 = digits>0 && mellan[digits-1]==tom; enemy = (mellan[digits]==gr && mellan[digits+1]==rd && mellan[digits+2]==tom); enemy2 = (mellan[digits]==rd && mellan[digits-1]==gr && mellan[digits-2]==tom); if(checkempty) { mellan[digits+1]=mellan[digits]; mellan[digits]=tom; } else if (checkempty2) { mellan[digits-1]=mellan[digits]; mellan[digits]=tom; } else if (enemy) { mellan[digits+2]=mellan[digits]; mellan[digits]=tom; } else if (enemy2) { mellan[digits-2]=mellan[digits]; mellan[digits]=tom; } } void checkWin() { String[] end = {rd,rd,rd,tom,gr,gr,gr}; for (int i=0; i<mellan.length; i++){ } if (Arrays.equals(mellan,end)) { for (int j=0; j<mellan.length; j++) { System.out.print(mellan[j]); } displayWin(); } } void displayWin() { gameEnd = true; System.out.println("\nNicely Done!"); return; } // Kör Drive! public static void main(String args[]) { new Drive(); } } Here is how I defined my DriveView thus far: (just trying to make one button to work) import mind.*; import javax.swing.*; import java.util.*; import java.lang.*; import java.awt.*; import java.awt.event.*; public class DriveView extends JFrame { JButton ruta1 = new JButton("Green"); JButton ruta2 = new JButton("Green"); JButton rutatom = new JButton(""); JButton ruta6 = new JButton("Red"); private DriveModel m_model; public DriveView(DriveModel model) { m_model = model; //Layout for View JPanel myPanel = new JPanel(); myPanel.setLayout(new FlowLayout()); myPanel.add(ruta1); myPanel.add(ruta2); myPanel.add(rutatom); myPanel.add(ruta6); this.setContentPane(myPanel); this.pack(); this.setTitle("Drive"); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } void addMouseListener(ActionListener mol) { ruta2.addActionListener(mol); } } And DriveController which gives me error at compile import mind.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.lang.*; public class DriveController { private DriveModel m_model; private DriveView m_view; public DriveController(DriveModel model, DriveView view) { m_model = model; m_view = view; view.addMouseListener(new MouseListener()); } class MouseListener implements ActionListener { public void actionPerformed(ActionEvent e) { String mening; mening = e.getActionCommand(); if (mening.equals("Green")) { setForeground(Color.red); } } } }

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  • How can I best study a problem to determine whether recursion can/should be used?

    - by user10326
    In some cases, I fail to see that a problem could be solved by the divide and conquer method. To give a specific example, when studying the find max sub-array problem, my first approach is to brute force it by using a double loop to find the max subarray. When I saw the solution using the divide and conquer approach which is recursion-based, I understood it but ok. From my side, though, when I first read the problem statement, I did not think that recursion is applicable. When studying a problem, is there any technique or trick to see that a recursion based (i.e. divide and conquer) approach can be used or not?

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  • How divide a GWT module into some separate javascript files ?

    - by Ehsan Khodarahmi
    Hi, I've a big GWT module which comprised of many java classes (& of course it's impossible to break it down into several modules). My GWT application consists of some forms, but the users usually work only with a few of them, anyway they should be abale to open any form as they need. Now my problem its that gwt generates a big js file that will load each time, but most of its content may never use! Is there any way to break the big js module file into several smaller files(for example, one file for each class) & gwt load them automatically as needed ?

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  • Java - How to avoid loss of precision during divide and cast to int?

    - by David Buckley
    I have a situation where I need to find out how many times an int goes into a decimal, but in certain cases, I'm losing precision. Here is the method: public int test(double decimalAmount, int divisor) { return (int) (decimalAmount/ (1d / divisor)); } The problem with this is if I pass in 1.2 as the decimal amount and 5 as the divisor, I get 5 instead of 6. How can I restrusture this so I know how many times 5 goes into the decimal amount as an int?

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  • help me improve my sse yuv to rgb ssse3 code

    - by David McPaul
    Hello, I am looking to optimise some sse code I wrote for converting yuv to rgb (both planar and packed yuv functions). i am using SSSE3 at the moment but if there are useful functions from later sse versions thats ok. I am mainly interested in how I would work out processor stalls and the like. Anyone know of any tools that do static analysis of sse code? ; ; Copyright (C) 2009-2010 David McPaul ; ; All rights reserved. Distributed under the terms of the MIT License. ; ; A rather unoptimised set of ssse3 yuv to rgb converters ; does 8 pixels per loop ; inputer: ; reads 128 bits of yuv 8 bit data and puts ; the y values converted to 16 bit in xmm0 ; the u values converted to 16 bit and duplicated into xmm1 ; the v values converted to 16 bit and duplicated into xmm2 ; conversion: ; does the yuv to rgb conversion using 16 bit integer and the ; results are placed into the following registers as 8 bit clamped values ; r values in xmm3 ; g values in xmm4 ; b values in xmm5 ; outputer: ; writes out the rgba pixels as 8 bit values with 0 for alpha ; xmm6 used for scratch ; xmm7 used for scratch %macro cglobal 1 global _%1 %define %1 _%1 align 16 %1: %endmacro ; conversion code %macro yuv2rgbsse2 0 ; u = u - 128 ; v = v - 128 ; r = y + v + v >> 2 + v >> 3 + v >> 5 ; g = y - (u >> 2 + u >> 4 + u >> 5) - (v >> 1 + v >> 3 + v >> 4 + v >> 5) ; b = y + u + u >> 1 + u >> 2 + u >> 6 ; subtract 16 from y movdqa xmm7, [Const16] ; loads a constant using data cache (slower on first fetch but then cached) psubsw xmm0,xmm7 ; y = y - 16 ; subtract 128 from u and v movdqa xmm7, [Const128] ; loads a constant using data cache (slower on first fetch but then cached) psubsw xmm1,xmm7 ; u = u - 128 psubsw xmm2,xmm7 ; v = v - 128 ; load r,b with y movdqa xmm3,xmm0 ; r = y pshufd xmm5,xmm0, 0xE4 ; b = y ; r = y + v + v >> 2 + v >> 3 + v >> 5 paddsw xmm3, xmm2 ; add v to r movdqa xmm7, xmm1 ; move u to scratch pshufd xmm6, xmm2, 0xE4 ; move v to scratch psraw xmm6,2 ; divide v by 4 paddsw xmm3, xmm6 ; and add to r psraw xmm6,1 ; divide v by 2 paddsw xmm3, xmm6 ; and add to r psraw xmm6,2 ; divide v by 4 paddsw xmm3, xmm6 ; and add to r ; b = y + u + u >> 1 + u >> 2 + u >> 6 paddsw xmm5, xmm1 ; add u to b psraw xmm7,1 ; divide u by 2 paddsw xmm5, xmm7 ; and add to b psraw xmm7,1 ; divide u by 2 paddsw xmm5, xmm7 ; and add to b psraw xmm7,4 ; divide u by 32 paddsw xmm5, xmm7 ; and add to b ; g = y - u >> 2 - u >> 4 - u >> 5 - v >> 1 - v >> 3 - v >> 4 - v >> 5 movdqa xmm7,xmm2 ; move v to scratch pshufd xmm6,xmm1, 0xE4 ; move u to scratch movdqa xmm4,xmm0 ; g = y psraw xmm6,2 ; divide u by 4 psubsw xmm4,xmm6 ; subtract from g psraw xmm6,2 ; divide u by 4 psubsw xmm4,xmm6 ; subtract from g psraw xmm6,1 ; divide u by 2 psubsw xmm4,xmm6 ; subtract from g psraw xmm7,1 ; divide v by 2 psubsw xmm4,xmm7 ; subtract from g psraw xmm7,2 ; divide v by 4 psubsw xmm4,xmm7 ; subtract from g psraw xmm7,1 ; divide v by 2 psubsw xmm4,xmm7 ; subtract from g psraw xmm7,1 ; divide v by 2 psubsw xmm4,xmm7 ; subtract from g %endmacro ; outputer %macro rgba32sse2output 0 ; clamp values pxor xmm7,xmm7 packuswb xmm3,xmm7 ; clamp to 0,255 and pack R to 8 bit per pixel packuswb xmm4,xmm7 ; clamp to 0,255 and pack G to 8 bit per pixel packuswb xmm5,xmm7 ; clamp to 0,255 and pack B to 8 bit per pixel ; convert to bgra32 packed punpcklbw xmm5,xmm4 ; bgbgbgbgbgbgbgbg movdqa xmm0, xmm5 ; save bg values punpcklbw xmm3,xmm7 ; r0r0r0r0r0r0r0r0 punpcklwd xmm5,xmm3 ; lower half bgr0bgr0bgr0bgr0 punpckhwd xmm0,xmm3 ; upper half bgr0bgr0bgr0bgr0 ; write to output ptr movntdq [edi], xmm5 ; output first 4 pixels bypassing cache movntdq [edi+16], xmm0 ; output second 4 pixels bypassing cache %endmacro SECTION .data align=16 Const16 dw 16 dw 16 dw 16 dw 16 dw 16 dw 16 dw 16 dw 16 Const128 dw 128 dw 128 dw 128 dw 128 dw 128 dw 128 dw 128 dw 128 UMask db 0x01 db 0x80 db 0x01 db 0x80 db 0x05 db 0x80 db 0x05 db 0x80 db 0x09 db 0x80 db 0x09 db 0x80 db 0x0d db 0x80 db 0x0d db 0x80 VMask db 0x03 db 0x80 db 0x03 db 0x80 db 0x07 db 0x80 db 0x07 db 0x80 db 0x0b db 0x80 db 0x0b db 0x80 db 0x0f db 0x80 db 0x0f db 0x80 YMask db 0x00 db 0x80 db 0x02 db 0x80 db 0x04 db 0x80 db 0x06 db 0x80 db 0x08 db 0x80 db 0x0a db 0x80 db 0x0c db 0x80 db 0x0e db 0x80 ; void Convert_YUV422_RGBA32_SSSE3(void *fromPtr, void *toPtr, int width) width equ ebp+16 toPtr equ ebp+12 fromPtr equ ebp+8 ; void Convert_YUV420P_RGBA32_SSSE3(void *fromYPtr, void *fromUPtr, void *fromVPtr, void *toPtr, int width) width1 equ ebp+24 toPtr1 equ ebp+20 fromVPtr equ ebp+16 fromUPtr equ ebp+12 fromYPtr equ ebp+8 SECTION .text align=16 cglobal Convert_YUV422_RGBA32_SSSE3 ; reserve variables push ebp mov ebp, esp push edi push esi push ecx mov esi, [fromPtr] mov edi, [toPtr] mov ecx, [width] ; loop width / 8 times shr ecx,3 test ecx,ecx jng ENDLOOP REPEATLOOP: ; loop over width / 8 ; YUV422 packed inputer movdqa xmm0, [esi] ; should have yuyv yuyv yuyv yuyv pshufd xmm1, xmm0, 0xE4 ; copy to xmm1 movdqa xmm2, xmm0 ; copy to xmm2 ; extract both y giving y0y0 pshufb xmm0, [YMask] ; extract u and duplicate so each u in yuyv becomes u0u0 pshufb xmm1, [UMask] ; extract v and duplicate so each v in yuyv becomes v0v0 pshufb xmm2, [VMask] yuv2rgbsse2 rgba32sse2output ; endloop add edi,32 add esi,16 sub ecx, 1 ; apparently sub is better than dec jnz REPEATLOOP ENDLOOP: ; Cleanup pop ecx pop esi pop edi mov esp, ebp pop ebp ret cglobal Convert_YUV420P_RGBA32_SSSE3 ; reserve variables push ebp mov ebp, esp push edi push esi push ecx push eax push ebx mov esi, [fromYPtr] mov eax, [fromUPtr] mov ebx, [fromVPtr] mov edi, [toPtr1] mov ecx, [width1] ; loop width / 8 times shr ecx,3 test ecx,ecx jng ENDLOOP1 REPEATLOOP1: ; loop over width / 8 ; YUV420 Planar inputer movq xmm0, [esi] ; fetch 8 y values (8 bit) yyyyyyyy00000000 movd xmm1, [eax] ; fetch 4 u values (8 bit) uuuu000000000000 movd xmm2, [ebx] ; fetch 4 v values (8 bit) vvvv000000000000 ; extract y pxor xmm7,xmm7 ; 00000000000000000000000000000000 punpcklbw xmm0,xmm7 ; interleave xmm7 into xmm0 y0y0y0y0y0y0y0y0 ; extract u and duplicate so each becomes 0u0u punpcklbw xmm1,xmm7 ; interleave xmm7 into xmm1 u0u0u0u000000000 punpcklwd xmm1,xmm7 ; interleave again u000u000u000u000 pshuflw xmm1,xmm1, 0xA0 ; copy u values pshufhw xmm1,xmm1, 0xA0 ; to get u0u0 ; extract v punpcklbw xmm2,xmm7 ; interleave xmm7 into xmm1 v0v0v0v000000000 punpcklwd xmm2,xmm7 ; interleave again v000v000v000v000 pshuflw xmm2,xmm2, 0xA0 ; copy v values pshufhw xmm2,xmm2, 0xA0 ; to get v0v0 yuv2rgbsse2 rgba32sse2output ; endloop add edi,32 add esi,8 add eax,4 add ebx,4 sub ecx, 1 ; apparently sub is better than dec jnz REPEATLOOP1 ENDLOOP1: ; Cleanup pop ebx pop eax pop ecx pop esi pop edi mov esp, ebp pop ebp ret SECTION .note.GNU-stack noalloc noexec nowrite progbits

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  • How do I define a template class and divide it into multiple files?

    - by hkBattousai
    I have written a simple template class for test purpose. It compiles without any errors, but when I try to use it in main(), it give some linker errors. main.cpp #include <iostream> #include "MyNumber.h" int wmain(int argc, wchar_t * argv[]) { MyNumber<float> num; num.SetValue(3.14); std::cout << "My number is " << num.GetValue() << "." << std::endl; system("pause"); return 0; } MyNumber.h #pragma once template <class T> class MyNumber { public: MyNumber(); ~MyNumber(); void SetValue(T val); T GetValue(); private: T m_Number; }; MyNumber.cpp #include "MyNumber.h" template <class T> MyNumber<T>::MyNumber() { m_Number = static_cast<T>(0); } template <class T> MyNumber<T>::~MyNumber() { } template <class T> void MyNumber<T>::SetValue(T val) { m_Number = val; } template <class T> T MyNumber<T>::GetValue() { return m_Number; } When I build this code, I get the following linker errors: Error 7 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\X64\Debug\Console Demo.exe 1 error LNK1120: 4 unresolved externals Error 3 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: __cdecl MyNumber::~MyNumber(void)" (??1?$MyNumber@M@@QEAA@XZ) referenced in function wmain Error 6 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: __cdecl MyNumber::MyNumber(void)" (??0?$MyNumber@M@@QEAA@XZ) referenced in function wmain Error 4 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: float __cdecl MyNumber::GetValue(void)" (?GetValue@?$MyNumber@M@@QEAAMXZ) referenced in function wmain Error 5 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: void __cdecl MyNumber::SetValue(float)" (?SetValue@?$MyNumber@M@@QEAAXM@Z) referenced in function wmain But, if I leave main() empty, I don't get any linker errors. What is wrong with my template class? What am I doing wrong?

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  • insert ... select with divide operator in select errors?

    - by Mark
    Hi, the following query CREATE TABLE IF NOT EXISTS XY ( x INT NOT NULL , y FLOAT NULL , PRIMARY KEY(x) ) INSERT INTO XY (x,y) (select 1 as x ,(1/7) as y); errors with Error code 1064, SQL state 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO XY (x,y) (select 1 as x ,(1/7) as y)' at line 7 Line 1, column 1 any ideas?

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  • A new mission statement for my school's algorithms class

    - by Eric Fode
    The teacher at Eastern Washington University that is now teaching the algorithms course is new to eastern and as a result the course has changed drastically mostly in the right direction. That being said I feel that the class could use a more specific, and industry oriented (since that is where most students will go, though suggestions for an academia oriented class are also welcome) direction, having only worked in industry for 2 years I would like the community's (a wider and much more collectively experienced and in the end plausibly more credible) opinion on the quality of this as a statement for the purpose an algorithms class, and if I am completely off target your suggestion for the purpose of a required Jr. level Algorithms class that is standalone (so no other classes focusing specifically on algorithms are required). The statement is as follows: The purpose of the algorithms class is to do three things: Primarily, to teach how to learn, do basic analysis, and implement a given algorithm found outside of the class. Secondly, to teach the student how to model a problem in their mind so that they can find a an existing algorithm or have a direction to start the development of a new algorithm. Third, to overview a variety of algorithms that exist and to deeply understand and analyze one algorithm in each of the basic algorithmic design strategies: Divide and Conquer, Reduce and Conquer, Transform and Conquer, Greedy, Brute Force, Iterative Improvement and Dynamic Programming. The Question in short is: do you agree with this statement of the purpose of an algorithms course, so that it would be useful in the real world, if not what would you suggest?

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  • Why does (360 / 24) / 60 = 0 ... in Java

    - by Ankur
    I am trying to compute (360 / 24) / 60 I keep getting the answer 0.0 when I should get 0.25 In words: I want to divide 360 by 24 and then divide the result by 60 public class Divide { public static void main(String[] args){ float div = ((360 / 24) / 60); System.out.println(div); } } This prints out: 0.0 Why is that? Am I doing something really stupid, or is there a good reason for this

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  • Octree subdivision problem

    - by ChaosDev
    Im creating octree manually and want function for effectively divide all nodes and their subnodes - For example - I press button and subnodes divided - press again - all subnodes divided again. Must be like - 1 - 8 - 64. The problem is - i dont understand how organize recursive loops for that. OctreeNode in my unoptimized implementation contain pointers to subnodes(childs),parent,extra vector(contains dublicates of child),generation info and lots of information for drawing. class gOctreeNode { //necessary fields gOctreeNode* FrontBottomLeftNode; gOctreeNode* FrontBottomRightNode; gOctreeNode* FrontTopLeftNode; gOctreeNode* FrontTopRightNode; gOctreeNode* BackBottomLeftNode; gOctreeNode* BackBottomRightNode; gOctreeNode* BackTopLeftNode; gOctreeNode* BackTopRightNode; gOctreeNode* mParentNode; std::vector<gOctreeNode*> m_ChildsVector; UINT mGeneration; bool mSplitted; bool isSplitted(){return m_Splitted;} .... //unnecessary fields }; DivideNode of Octree class fill these fields, set mSplitted to true, and prepare for correctly drawing. Octree contains basic nodes(m_nodes). Basic node can be divided, but now I want recursivly divide already divided basic node with 8 subnodes. So I write this function. void DivideAllChildCells(int ix,int ih,int id) { std::vector<gOctreeNode*> nlist; std::vector<gOctreeNode*> dlist; int index = (ix * m_Height * m_Depth) + (ih * m_Depth) + (id * 1);//get index of specified node gOctreeNode* baseNode = m_nodes[index].get(); nlist.push_back(baseNode->FrontTopLeftNode); nlist.push_back(baseNode->FrontTopRightNode); nlist.push_back(baseNode->FrontBottomLeftNode); nlist.push_back(baseNode->FrontBottomRightNode); nlist.push_back(baseNode->BackBottomLeftNode); nlist.push_back(baseNode->BackBottomRightNode); nlist.push_back(baseNode->BackTopLeftNode); nlist.push_back(baseNode->BackTopRightNode); bool cont = true; UINT d = 0;//additional recursive loop param (?) UINT g = 0;//additional recursive loop param (?) LoopNodes(d,g,nlist,dlist); //Divide resulting nodes for(UINT i = 0; i < dlist.size(); i++) { DivideNode(dlist[i]); } } And now, back to the main question,I present LoopNodes, which must do all work for giving dlist nodes for splitting. void LoopNodes(UINT& od,UINT& og,std::vector<gOctreeNode*>& nlist,std::vector<gOctreeNode*>& dnodes) { //od++;//recursion depth bool f = false; //pass through childs for(UINT i = 0; i < 8; i++) { if(nlist[i]->isSplitted())//if node splitted and have childs { //pass forward through tree for(UINT j = 0; j < 8; j++) { nlist[j] = nlist[j]->m_ChildsVector[j];//set pointers to these childs } LoopNodes(od,og,nlist,dnodes); } else //if no childs { //add to split vector dnodes.push_back(nlist[i]); } } } This version of loop nodes works correctly for 2(or 1?) generations after - this will not divide neightbours nodes, only some corners. I need correct algorithm. Screenshot All I need - is correct version of LoopNodes, which can add all nodes for DivideNode.

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  • Modular Inverse and BigInteger division

    - by dano82
    I've been working on the problem of calculating the modular inverse of an large integer i.e. a^-1 mod n. and have been using BigInteger's built in function modInverse to check my work. I've coded the algorithm as shown in The Handbook of Applied Cryptography by Menezes, et al. Unfortunately for me, I do not get the correct outcome for all integers. My thinking is that the line q = a.divide(b) is my problem as the divide function is not well documented (IMO)(my code suffers similarly). Does BigInteger.divide(val) round or truncate? My assumption is truncation since the docs say that it mimics int's behavior. Any other insights are appreciated. This is the code that I have been working with: private static BigInteger modInverse(BigInteger a, BigInteger b) throws ArithmeticException { //make sure a >= b if (a.compareTo(b) < 0) { BigInteger temp = a; a = b; b = temp; } //trivial case: b = 0 => a^-1 = 1 if (b.equals(BigInteger.ZERO)) { return BigInteger.ONE; } //all other cases BigInteger x2 = BigInteger.ONE; BigInteger x1 = BigInteger.ZERO; BigInteger y2 = BigInteger.ZERO; BigInteger y1 = BigInteger.ONE; BigInteger x, y, q, r; while (b.compareTo(BigInteger.ZERO) == 1) { q = a.divide(b); r = a.subtract(q.multiply(b)); x = x2.subtract(q.multiply(x1)); y = y2.subtract(q.multiply(y1)); a = b; b = r; x2 = x1; x1 = x; y2 = y1; y1 = y; } if (!a.equals(BigInteger.ONE)) throw new ArithmeticException("a and n are not coprime"); return x2; }

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  • Adding info to an exception

    - by NoozNooz42
    I'd like to add information to a stack trace/exception. Basically I've got something like this as of now, which I really like: Exception in thread "main" java.lang.ArithmeticException: / by zero at com.so.main(SO.java:41) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke However I'd like to catch that exception and add additional info to it, while still having the original stack trace. For example, I'd like to have that: Exception in thread "main" CustomException: / by zero (you tried to divide 42 by 0) at com.so.main(SO.java:41) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke So basically I want to catch the ArithmeticException and rethrow, say, a CustomException (adding "you tried to divide 42 by 0" in this example) while still keeping the stacktrace from the original ArithmeticException. What is the correct way to do this in Java? Is the following correct: try { .... } catch (ArithmeticException e) { throw new CustomException( "You tried to divide " + x + " by " + y, e ); }

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  • Doing a passable 4X game AI

    - by Extrakun
    I am coding a rather "simple" 4X game (if a 4X game can be simple). It's indie in scope, and I am wondering if there's anyway to come up with a passable AI without having me spending months coding on it. The game has three major decision making portions; spending of production points, spending of movement points and spending of tech points (basically there are 3 different 'currency', currency unspent at end of turn is not saved) Spend Production Points Upgrade a planet (increase its tech and production) Build ships (3 types) Move ships from planets to planets (costing Movement Points) Move to attack Move to fortify Research Tech (can partially research a tech i.e, as in Master of Orion) The plan for me right now is a brute force approach. There are basically 4 broad options for the player - Upgrade planet(s) to its his production and tech output Conquer as many planets as possible Secure as many planets as possible Get to a certain tech as soon as possible For each decision, I will iterate through the possible options and come up with a score; and then the AI will choose the decision with the highest score. Right now I have no idea how to 'mix decisions'. That is, for example, the AI wishes to upgrade and conquer planets at the same time. I suppose I can have another logic which do a brute force optimization on a combination of those 4 decisions.... At least, that's my plan if I can't think of anything better. Is there any faster way to make a passable AI? I don't need a very good one, to rival Deep Blue or such, just something that has the illusion of intelligence. This is my first time doing an AI on this scale, so I dare not try something too grand too. So far I have experiences with FSM, DFS, BFS and A*

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  • Why do you need float/double?

    - by acidzombie24
    I was watching http://www.joelonsoftware.com/items/2011/06/27.html and laughed at Jon Skeet joke about 0.3 not being 0.3. I personally never had problems with floats/decimals/doubles but then I remember I learned 6502 very early and never needed floats in most of my programs. The only time I used it was for graphics and math where inaccurate numbers were ok and the output was for the screen and not to be stored (in a db, file) or dependent on. My question is, where are places were you typically use floats/decimals/double? So I know to watch out for these gotchas. With money I use longs and store values by the cent, for speed of an object in a game I add ints and divide (or bitshift) the value to know if I need to move a pixel or not. (I made object move in the 6502 days, we had no divide nor floats but had shifts). So I was mostly curious.

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  • Do I need the 'w' component in my Vector class?

    - by bobobobo
    Assume you're writing matrix code that handles rotation, translation etc for 3d space. Now the transformation matrices have to be 4x4 to fit the translation component in. However, you don't actually need to store a w component in the vector do you? Even in perspective division, you can simply compute and store w outside of the vector, and perspective divide before returning from the method. For example: // post multiply vec2=matrix*vector Vector operator*( const Matrix & a, const Vector& v ) { Vector r ; // do matrix mult r.x = a._11*v.x + a._12*v.y ... real w = a._41*v.x + a._42*v.y ... // perspective divide r /= w ; return r ; } Is there a point in storing w in the Vector class?

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  • Window Management for Mac OS X

    - by Paolo Maffei
    Ok, I feel dumb. I've put many hours into this and found nothing, yet. When I was using Windows I had this little tool called WinSplit Revolution. What it did was letting you divide your screen into how many and of how much size you choose "virtual monitors". You set one time of you want to divide your monitor, then everytime WinSplit is opened the monitor is automatically divided into Virtual Monitors. Screenshots: http://www.google.com/images?hl=en&q=winsplit%20revolution&um=1&ie=UTF-8&source=og&sa=N&tab=wi&biw=1045&bih=499 I'm now using a 30' which i want almost always divided into 4 equal size "virtual monitors" (plus my mbp 13' those will be 5 1280x800 virtual monitors) Now I've switched to Mac OS X and can't find anything that does just this efficiently. I tried Divvy but I found no way to divide my screen into arbitrary "virtual monitors", I need a couple of clicks to select a 3x3 space on a 9x9 grid. Before starting coding something like this can you tell me if you already know of some software that does window management like this?

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  • BigDecimal, division & MathContext - very strange behaviour

    - by blackliteon
    CentOs 5.4, OpenJDK Runtime Environment (build 1.6.0-b09) MathContext context = new MathContext(2, RoundingMode.FLOOR); BigDecimal total = new BigDecimal("200.0", context); BigDecimal goodPrice = total.divide(BigDecimal.valueOf(3), 2, RoundingMode.FLOOR); System.out.println("divided price=" + goodPrice.toPlainString()); // prints 66.66 BigDecimal goodPrice2 = total.divide(BigDecimal.valueOf(3), new MathContext(2, RoundingMode.FLOOR)); System.out.println("divided price2=" + goodPrice2.toPlainString()); // prints 66 BUG ?

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  • Factorising program not working. Help required.

    - by Ender
    I am working on a factorisation problem using Fermat's Factorization and for small numbers it is working well. I've been able to calculate the factors (getting the answers from Wolfram Alpha) for small numbers, like the one on the Wikipedia page (5959). Just when I thought I had the problem licked I soon realised that my program was not working when it came to larger numbers. The program follows through the examples from the Wikipedia page, printing out the values a, b, a2 and b2; the results printed for large numbers are not correct. I've followed the pseudocode provided on the Wikipedia page, but am struggling to understand where to go next. Along with the Wikipedia page I have been following this guide. Once again, as my Math knowledge is pretty poor I cannot follow what I need to do next. The code I am using so far is as follows: import java.math.BigInteger; /** * * @author AlexT */ public class Fermat { private BigInteger a, b; private BigInteger b2; private static final BigInteger TWO = BigInteger.valueOf(2); public void fermat(BigInteger N) { // floor(sqrt(N)) BigInteger tmp = getIntSqrt(N); // a <- ceil(sqrt(N)) a = tmp.add(BigInteger.ONE); // b2 <- a*a-N b2 = (a.multiply(a)).subtract(N); final int bitLength = N.bitLength(); BigInteger root = BigInteger.ONE.shiftLeft(bitLength / 2); root = root.add(b2.divide(root)).divide(TWO); // while b2 not square root while(!(isSqrt(b2, root))) { // a <- a + 1 a = a.add(BigInteger.ONE); // b2 <- (a * a) - N b2 = (a.multiply(a)).subtract(N); root = root.add(b2.divide(root)).divide(TWO); } b = getIntSqrt(b2); BigInteger a2 = a.pow(2); // Wrong BigInteger sum = (a.subtract(b)).multiply((a.add(b))); //if(sum.compareTo(N) == 0) { System.out.println("A: " + a + "\nB: " + b); System.out.println("A^2: " + a2 + "\nB^2: " + b2); //} } /** * Is the number provided a perfect Square Root? * @param n * @param root * @return */ private static boolean isSqrt(BigInteger n, BigInteger root) { final BigInteger lowerBound = root.pow(2); final BigInteger upperBound = root.add(BigInteger.ONE).pow(2); return lowerBound.compareTo(n) <= 0 && n.compareTo(upperBound) < 0; } public BigInteger getIntSqrt(BigInteger x) { // It returns s where s^2 < x < (s+1)^2 BigInteger s; // final result BigInteger currentRes = BigInteger.valueOf(0); // init value is 0 BigInteger currentSum = BigInteger.valueOf(0); // init value is 0 BigInteger sum = BigInteger.valueOf(0); String xS = x.toString(); // change input x to a string xS int lengthOfxS = xS.length(); int currentTwoBits; int i=0; // index if(lengthOfxS % 2 != 0) {// if odd length, add a dummy bit xS = "0".concat(xS); // add 0 to the front of string xS lengthOfxS++; } while(i < lengthOfxS){ // go through xS two by two, left to right currentTwoBits = Integer.valueOf(xS.substring(i,i+2)); i += 2; // sum = currentSum*100 + currentTwoBits sum = currentSum.multiply(BigInteger.valueOf(100)); sum = sum.add(BigInteger.valueOf(currentTwoBits)); // subtraction loop do { currentSum = sum; // remember the value before subtract // in next 3 lines, we work out // currentRes = sum - 2*currentRes - 1 sum = sum.subtract(currentRes); // currentRes++ currentRes = currentRes.add(BigInteger.valueOf(1)); sum = sum.subtract(currentRes); } while(sum.compareTo(BigInteger.valueOf(0)) >= 0); // the loop stops when sum < 0 // go one step back currentRes = currentRes.subtract(BigInteger.valueOf(1)); currentRes = currentRes.multiply(BigInteger.valueOf(10)); } s = currentRes.divide(BigInteger.valueOf(10)); // go one step back return s; } /** * @param args the command line arguments */ public static void main(String[] args) { Fermat fermat = new Fermat(); //Works //fermat.fermat(new BigInteger("5959")); // Doesn't Work fermat.fermat(new BigInteger("90283")); } } If anyone can help me out with this problem I'll be eternally grateful.

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