start c++ implementation
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*.class
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*.class
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README.md
60
README.md
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CS426 - Operating Systems
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# Collatz assignment
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The Collatz conjecture is simple. It says that for every starting number
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the sequence below always eventually gets to a 1.
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f(n) = n/2 if n is even
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f(n+1) = 3n+1 if n is odd
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For example.
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17 -> 52 -> 26 -> 13 -> 40 -> 20 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1
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### Your mission is to find the starting number that is less than 1,000,000 with the longest sequence.
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This might take a long time. To make it faster, you might cache previous
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answers. Suppose you have an array prev[]. Prev[n] is the length of the
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sequence starting at n. If, when computing a sequence, you ever get to a
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number with a value in prev[], you can use that instead of continuing the
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computation.
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If you have multiple threads, you must use good locking.
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### Objectives
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* Can compute the collatz sequence length for a given number.
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* Can find the longest sequence.
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* Uses Java threads
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* Uses C++ Threads
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* Uses the array prev[] above.
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CS426 - Operating Systems
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# Collatz assignment
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The Collatz conjecture is simple. It says that for every starting number
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the sequence below always eventually gets to a 1.
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f(n) = n/2 if n is even
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f(n+1) = 3n+1 if n is odd
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For example.
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17 -> 52 -> 26 -> 13 -> 40 -> 20 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1
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### Your mission is to find the starting number that is less than 1,000,000 with the longest sequence.
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This might take a long time. To make it faster, you might cache previous
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answers. Suppose you have an array prev[]. Prev[n] is the length of the
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sequence starting at n. If, when computing a sequence, you ever get to a
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number with a value in prev[], you can use that instead of continuing the
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computation.
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If you have multiple threads, you must use good locking.
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### Objectives
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* Can compute the collatz sequence length for a given number.
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* Can find the longest sequence.
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* Uses Java threads
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* Uses C++ Threads
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* Uses the array prev[] above.
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* Does better load balancing that simple partitioning.
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CSW = -O3 -Wall
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LSW = -lfd
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all:
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make collatz
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collatz: collatz.o Makefile
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g++ collatz.o -o collatz
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collatz.o: collatz.cc Makefile
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g++ collatz.cc -c -o collatz.o $(CSW)
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collatz.cc: collatz.h Makefile
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touch collatz.cc
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clean:
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touch Makefile; make
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#import <unistd.h>
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int collatz(int start) {
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int cnt = 0;
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while(start != 1) {
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cnt++;
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start = start % 2 == 0 ? start/2 : 3*start + 1;
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}
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return cnt;
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}
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// Ben Harris
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#import <unistd.h>
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#import <cstdlib>
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#import <string>
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#import <iostream>
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#import "collatz.h"
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using namespace std;
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int *prev = new int[1000000];
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int maxcnt = 0, maxsteps = 0;
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int main (int argc, char **argv) {
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cout << "cCollatz" << endl;
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for (int i = 1; i <= 100000; i++) {
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cout << i << "\tnum of steps: " << collatz(i) << endl;
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}
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cout << "Longest path was " << maxsteps << " steps for " << maxcnt << endl;
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}
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int collatz (int start) {
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int cnt = 0;
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int initval = start;
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while(start != 1) {
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cnt++;
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if (start < 1000000 && prev[start] != 0) {
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start = prev[start];
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continue;
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}
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start = start % 2 == 0 ? start/2 : 3*start + 1;
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}
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prev[start] = cnt;
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if (cnt > maxcnt) {
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maxcnt = initval;
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maxsteps = cnt;
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}
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return cnt;
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}
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// Ben Harris
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#ifndef _COLLATZ_h_
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#define _COLLATZ_h_
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// method definitions
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int main(int argc, char **argv);
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int collatz(int start);
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#endif
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class Collatz {
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int prev[] = new int[1000000];
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int max = 0;
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int maxsteps = 0;
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public static void main(String[] args) {
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System.out.println("collatz calc");
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Collatz c = new Collatz();
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for(int i = 1; i <= 100000; i++){
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System.out.println(i + "\tnum of steps: " + c.collatz(i));
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}
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System.out.println("Longest path was at " + c.max + " with " + c.maxsteps + " steps.");
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}
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int collatz(int start) {
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int cnt = 0;
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int initval = start;
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while(start != 1) {
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cnt++;
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if(start < 1000000 && prev[start] != 0) {
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start = prev[start];
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continue;
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}
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start = start % 2 == 0 ? start/2 : 3*start + 1;
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}
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prev[start] = cnt;
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if(cnt > max){
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max = initval;
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maxsteps = cnt;
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}
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return cnt;
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}
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// Ben Harris
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class Collatz {
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int prev[] = new int[1000000];
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int max = 0;
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int maxsteps = 0;
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public static void main(String[] args) {
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System.out.println("javaCollatz");
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Collatz c = new Collatz();
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for(int i = 1; i <= 100000; i++){
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System.out.println(i + "\tnum of steps: " + c.collatz(i));
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}
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System.out.println("Longest path was at " + c.max + " with " + c.maxsteps + " steps.");
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}
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int collatz(int start) {
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int cnt = 0;
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int initval = start;
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while(start != 1) {
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cnt++;
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if(start < 1000000 && prev[start] != 0) {
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start = prev[start];
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continue;
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}
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start = start % 2 == 0 ? start/2 : 3*start + 1;
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}
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prev[start] = cnt;
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if(cnt > max){
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max = initval;
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maxsteps = cnt;
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}
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return cnt;
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}
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}
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