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preperation for distributed
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change variables in solvers from ijkl to ld rd col and startQueensIjklList
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@timmitohnetim
timmitohnetim committed Jan 6, 2022
1 parent 1bd8a77 commit 2fec7d9
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Showing 4 changed files with 175 additions and 91 deletions.
5 changes: 3 additions & 2 deletions src/de/nqueensfaf/SolverTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,8 @@ void tearDown() throws Exception {
// @Test
// void testCpuSolver() {
// CpuSolver s = new CpuSolver();
// s.setN(6);
// s.setN(17);
// s.setThreadcount(4);
// s.addTerminationCallback(() -> {
// System.out.println(s.getSolutions() + " solutions found in " + s.getDuration() + " ms");
// });
Expand All @@ -52,7 +53,7 @@ void testGpuSolver() {
GpuSolver s = new GpuSolver();
s.setDevice(0);
s.setProgressUpdatesEnabled(false);
s.setN(17);
s.setN(18);
new Thread(() -> {
while(true) {
if(s.getGlobalWorkSize() == 0) {
Expand Down
180 changes: 157 additions & 23 deletions src/de/nqueensfaf/compute/CpuSolver.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,24 +19,26 @@ public class CpuSolver extends Solver {

private final int smallestN = 6;
private int threadcount = 1;
private int kbit, lbit, preQueens = 4, L, mask, LD, RD, counter;
private long start, end;
private HashSet<Integer>
startConstellations = new HashSet<Integer>();
private HashSet<Integer> startConstellations = new HashSet<Integer>();
private ArrayList<Integer> ldList = new ArrayList<Integer>(), rdList = new ArrayList<Integer>(), colList = new ArrayList<Integer>();
private ArrayList<Integer> startQueensIjklList = new ArrayList<Integer>();
private ArrayList<CpuSolverThread> threads = new ArrayList<CpuSolverThread>();
private int startConstCount, solvedConstellations;
private long timePassed = 0, pauseStart = 0;
private long solutions;
private boolean restored = false;
private ArrayList<Runnable> pausing = new ArrayList<Runnable>();

// inherited functions
@Override
protected void run() {
// check if run is called without calling reset after a run call had finished
if(start != 0) {
throw new IllegalStateException("You first have to call reset() when calling solve() multiple times on the same object");
}

start = System.currentTimeMillis();
if(N <= smallestN) { // if N is very small, use the simple Solver from the parent class
solutions = solveSmallBoard();
Expand All @@ -50,7 +52,7 @@ protected void run() {
genConstellations();
startConstCount = startConstellations.size();
}

// split starting constellations in [cpu] many lists (splitting the work for the threads)
ArrayList<ArrayDeque<Integer>> threadConstellations = new ArrayList<ArrayDeque<Integer>>(threadcount);
for(int i = 0; i < threadcount; i++) {
Expand All @@ -64,11 +66,11 @@ protected void run() {
// start the threads and wait until they are all finished
ExecutorService executor = Executors.newFixedThreadPool(threadcount);
for(i = 0; i < threadcount; i++) {
CpuSolverThread cpuSolverThread = new CpuSolverThread(N, threadConstellations.get(i), this);
CpuSolverThread cpuSolverThread = new CpuSolverThread(N, threadConstellations.get(i), this, ldList, rdList, colList, startQueensIjklList);
threads.add(cpuSolverThread);
executor.submit(cpuSolverThread);
}

// wait for the threads to finish
executor.shutdown();
try {
Expand All @@ -84,7 +86,7 @@ protected void run() {
}
restored = false;
}

@Override
public void store_(String filepath) throws IOException {
// if Solver was not even started yet, throw exception
Expand All @@ -102,7 +104,7 @@ public void store_(String filepath) throws IOException {
}
long timePassed = getDuration();
RestorationInformation resInfo = new RestorationInformation(N, startConstellations, timePassed, solutions, startConstCount);

FileOutputStream fos = new FileOutputStream(filepath);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(resInfo);
Expand Down Expand Up @@ -132,12 +134,12 @@ public void restore_(String filepath) throws IOException, ClassNotFoundException
solvedConstellations = startConstCount - startConstellations.size();
restored = true;
}

@Override
public boolean isRestored() {
return restored;
}

@Override
public void reset() {
start = 0;
Expand Down Expand Up @@ -189,13 +191,15 @@ public long getSolutions() {
}
return solutions;
}

// own functions
private void genConstellations() {
startConstellations.clear();

// halfN half of N rounded up
final int halfN = (N + 1) / 2;
L = 1 << (N -1);
mask = (1 << N) - 1;

// calculating start constellations with the first Queen on square (0,0)
for(int j = 1; j < N-2; j++) { // j is idx of Queen in last row
Expand All @@ -221,8 +225,92 @@ private void genConstellations() {
}
}
}
HashSet<Integer> startConstellationsJasmin = new HashSet<Integer>();
// rotate and mirror all start constellations, such that the queen in the last row is as close to the right border as possible
for(int startConstellation : startConstellations) {
startConstellationsJasmin.add(jasmin(startConstellation));
}
startConstellations = startConstellationsJasmin;

int i, j, k, l, ld, rd, col, currentSize = 0;
for(int sc : startConstellations) {
i = geti(sc); j = getj(sc); k = getk(sc); l = getl(sc);
// fill up the board with preQueens queens and generate corresponding variables ld, rd, col, start_queens_ijkl for each constellation
// occupy the board corresponding to the queens on the borders of the board
ld = (L >>> (i-1)) | (1 << (N-k));
rd = (L >>> (i+1)) | (1 << (l-1));
col = 1 | L | (L >>> j) | (L >>> i);
// occupy diagonals of the queens j k l in the last row
// later we are going to shift them upwards the board
LD = (L >>> j) | (L >>> l);
RD = (L >>> j) | (1 << k);
// this is the queen in row k and l
// their diagonals have to be occupied later
// we can not do this right now, because in row k, the queen k has to be actually set
kbit = (1 << (N-k-1));
lbit = (1 << l);

// counts all subconstellations
counter = 0;
// generate all subconstellations
setPreQueens(ld, rd, col, k, l, 1, 4);
currentSize = startQueensIjklList.size();
// jkl and sym and start are the same for all subconstellations
for(int a = 0; a < counter; a++) {
startQueensIjklList.set(currentSize-a-1, startQueensIjklList.get(currentSize-a-1) | (preQueens << 20) | toijkl(i, j, k, l));
}
}
}


// generate subconstellations for each starting constellation with 3 or 4 queens
private void setPreQueens(int ld, int rd, int col, int k, int l, int row, int queens) {
// in row k and l just go further
if(row == k || row == l) {
setPreQueens(ld<<1, rd>>>1, col, k, l, row+1, queens);
return;
}
// add queens until we have preQueens queens
// this should be variable for the distributed version and different N
if(queens == preQueens) {
// occupy diagonals from queen k and l, that will end in the left or right border
// the following 2 lines are probably TRASH
ld &= ~(kbit << row);
rd &= ~(lbit >>> row);
// make left and right col free
col &= ~(1 | L);
// if k already came, then occupy it on the board
if(k < row) {
rd |= (L >> (row-k));
col |= L;
}
// same for l
if(l < row) {
ld |= (1 << (row-l));
col |= 1;
}
// add the subconstellations to the list
ldList.add(ld);
rdList.add(rd);
colList.add(col);
startQueensIjklList.add(row << 25);
counter++;
return;
}
// if not done or row k or l, just place queens and occupy the board and go further
else {
int free = ~(ld | rd | col | (LD >>> (N-1-row)) | (RD << (N-1-row))) & mask;
int bit;

while(free > 0) {
bit = free & (-free);
free -= bit;
setPreQueens((ld|bit) << 1, (rd|bit) >>> 1, col|bit, k, l, row+1, queens+1);
}
}
}



// true, if starting constellation rotated by any angle has already been found
private boolean checkRotations(int i, int j, int k, int l) {
// rot90
Expand All @@ -240,10 +328,56 @@ private boolean checkRotations(int i, int j, int k, int l) {
return false;
}

// wrap i, j, k and l to one integer using bitwise movement
// i, j, k, l to ijkl and functions to get specific entry
private int toijkl(int i, int j, int k, int l) {
return (i<<24) + (j<<16) + (k<<8) + l;
}
private int geti(int ijkl) {
return ijkl >> 24;
}
private int getj(int ijkl) {
return (ijkl >> 16) & 255;
}
private int getk(int ijkl) {
return (ijkl >> 8) & 255;
}
private int getl(int ijkl) {
return ijkl & 255;
}
// rotate and mirror board, so that the queen closest to a corner is on the right side of the last row
private int jasmin(int ijkl) {
int min = Math.min(getj(ijkl), N-1 - getj(ijkl)), arg = 0;

if(Math.min(geti(ijkl), N-1 - geti(ijkl)) < min) {
arg = 2;
min = Math.min(geti(ijkl), N-1 - geti(ijkl));
}
if(Math.min(getk(ijkl), N-1 - getk(ijkl)) < min) {
arg = 3;
min = Math.min(getk(ijkl), N-1 - getk(ijkl));
}
if(Math.min(getl(ijkl), N-1 - getl(ijkl)) < min) {
arg = 1;
min = Math.min(getl(ijkl), N-1 - getl(ijkl));
}

for(int i = 0; i < arg; i++) {
ijkl = rot90(ijkl);
}

if(getj(ijkl) < N-1 - getj(ijkl))
ijkl = mirvert(ijkl);

return ijkl;
}
// mirror left-right
private int mirvert(int ijkl) {
return toijkl(N-1-geti(ijkl), N-1-getj(ijkl), getl(ijkl), getk(ijkl));
}
// rotate 90 degrees clockwise
private int rot90(int ijkl) {
return ((N-1-getk(ijkl))<<24) + ((N-1-getl(ijkl))<<16) + (getj(ijkl)<<8) + geti(ijkl);
}

// for user interaction
public void pause() {
Expand All @@ -257,7 +391,7 @@ public void pause() {
t.pauseThread();
}
}

public void cancel() {
if(!isRunning()) {
throw new IllegalStateException("unable to cancel a CpuSolver when it is not running");
Expand All @@ -266,7 +400,7 @@ public void cancel() {
t.cancelThread();
}
}

public void resume() {
if(!isRunning()) {
throw new IllegalStateException("unable to resume a CpuSolver when it is not running");
Expand All @@ -280,7 +414,7 @@ public void resume() {
pauseStart = 0;
}
}

public boolean isPaused() {
if(threads.size() <= 0) {
return false;
Expand All @@ -291,7 +425,7 @@ public boolean isPaused() {
}
return true;
}

public boolean wasCanceled() {
if(isRunning() || N <= smallestN) {
return false;
Expand All @@ -302,14 +436,14 @@ public boolean wasCanceled() {
}
return true;
}

public void addOnPauseCallback(Runnable r) {
if(r == null) {
throw new IllegalArgumentException("pausing callback must not be null");
}
pausing.add(r);
}

// is called from the SolverThreads to measure correct time of the start of the pause
synchronized void onPauseStart() {
if(isPaused() && pauseStart == 0) {
Expand All @@ -321,19 +455,19 @@ synchronized void onPauseStart() {
}
}
}

// getters and setters
public void setThreadcount(int threadcount) {
if(threadcount < 1 || threadcount > Runtime.getRuntime().availableProcessors()) {
throw new IllegalArgumentException("threadcount must be a number between 1 and " + Runtime.getRuntime().availableProcessors() + " (=your CPU's number of logical cores) (inclusive)");
}
this.threadcount = threadcount;
}

public int getThreadcount() {
return threadcount;
}

// for saving and restoring
private record RestorationInformation(int N, HashSet<Integer> startConstellations, long timePassed, long solutions, int startConstCount) implements Serializable {
RestorationInformation(int N, HashSet<Integer> startConstellations, long timePassed, long solutions, int startConstCount) {
Expand Down
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