我有一个返回一组点的方法，我确信这个方法的 for 循环部分可以拆分为一个 RecursiveTask，它为每个线程返回一组点。
我尝试了很多次，但都失败了。那里有 Java 天才吗？
我现有的方法:
private Set<Point3D> getCordinatesAroundCenterPoint(Point3D point, int width) {
Set<Point3D> points = new LinkedHashSet<>();
double maxValue = width;
double minValue = maxValue * -1;
double minX = point.getX() + minValue;
double maxX = point.getX() + maxValue;
double minY = point.getY() + minValue;
double maxY = point.getY() + maxValue;
double minZ = point.getY() + minValue;
double maxZ = point.getZ() + maxValue;
double x = point.getX();
double y = point.getY();
double z = point.getZ();
double numberOfPoints = Math.pow((double) (maxValue * 2) + 1, Double.parseDouble("3"));
for (int i = 1; i <= numberOfPoints; i++) {
if (x > maxX) {
x = minX;
y++;
}
if (y > maxY) {
y = minY;
z++;
}
if (z > maxZ) {
z = minZ;
}
Point3D ppoint = new Point3D();
ppoint.setX(x);
ppoint.setY(y);
ppoint.setZ(z);
points.add(ppoint);
x++;
}
return points;
}
更新#1:
这是我将其拆分为递归任务的尝试，它似乎在范围为 1(应等于 27 点)-1、0、+1、= 3 点、3 立方 = 27 时工作正常。任何范围失败的更大数字，例如范围 2 应该返回 125 点。 -2、-1、0、+1、+2 = 5 点，5 的立方 = 125。
主要.java:
public static void main(String[] args) {
System.out.println("Enter system extent: ");
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
try {
String string = bufferedReader.readLine();
LinkedHashSet<Point3D> set = getStarSystemCordinatesAroundCenterSystem(Integer.parseInt(string));
System.out.println(set.size() + " systems generated.");
} catch (IOException e) {
e.printStackTrace();
}
}
private static LinkedHashSet<Point3D> getStarSystemCordinatesAroundCenterSystem(int extent) {
ForkJoinPool pool = new ForkJoinPool();
double maxValue = extent;
double minValue = maxValue * -1;
ForkPoints task = new ForkPoints(minValue, maxValue);
LinkedHashSet<Point3D> linkedHashSet = (LinkedHashSet<Point3D>) pool.invoke(task);
return linkedHashSet;
}
叉点.java:
public class ForkPoints extends RecursiveTask<Set<Point3D>> {
private static final long serialVersionUID = -5450450150370659468L;
private double minValue;
private double maxValue;
static final double SEQUENTIAL_THRESHHOLD = 2;
public ForkPoints(double minValue, double maxValue) {
this.minValue = minValue;
this.maxValue = maxValue;
}
@Override
protected Set<Point3D> compute() {
if (maxValue - minValue <= SEQUENTIAL_THRESHHOLD) {
return computeValue(minValue, maxValue);
} else {
double midValue = minValue + SEQUENTIAL_THRESHHOLD;
ForkPoints left = new ForkPoints(minValue, midValue);
ForkPoints right = new ForkPoints(midValue, maxValue);
left.fork();
Set<Point3D> rightPoints = right.compute();
Set<Point3D> leftPoints = left.join();
leftPoints.addAll(rightPoints);
return leftPoints;
}
}
private Set<Point3D> computeValue(double minv, double maxv) {
//Assume starting point of 0,0,0
double minX = 0 + minv;
double maxX = 0 + maxv;
double minY = 0 + minv;
double maxY = 0 + maxv;
double minZ = 0 + minv;
double maxZ = 0 + maxv;
double x = minv;
double y = minv;
double z = minv;
Set<Point3D> points = new LinkedHashSet<>();
boolean notFinished = true;
while (notFinished) {
if (x > maxX) {
x = minX;
y++;
}
if (y > maxY) {
y = minY;
z++;
}
if (z > maxZ) {
z = minZ;
}
Point3D ppoint = new Point3D();
ppoint.setX(x);
ppoint.setY(y);
ppoint.setZ(z);
points.add(ppoint);
if (x == maxX && y == maxY && z == maxZ) {
notFinished = false;
}
x++;
}
return points;
}
}
最佳答案
这里的主要问题是您正在尝试拆分 3D 对象，但只在一个方向上拆分。 IE。 ForkPoints.compute() 实际上不应产生 2 个，而是至少 8 个子任务，以防它无法自行执行计算。
下面是它的外观示例 - 代码的最小更改:
public class ForkPoints extends RecursiveTask<Set<Point3D>> {
private static final long serialVersionUID = -5450450150370659468L;
private final Point3D origin;
private final double radius;
static final double SEQUENTIAL_THRESHHOLD = 5;
public ForkPoints(final Point3D origin, final double radius) {
this.origin = origin;
this.radius = radius;
}
@Override
protected Set<Point3D> compute() {
if (radius <= SEQUENTIAL_THRESHHOLD) {
return computeValue();
} else {
final ForkPoints subCubes[] = new ForkPoints[8];
final double newRadius = radius / 2;
Point3D newOrigin = new Point3D();
newOrigin.setX(origin.getX() + newRadius);
newOrigin.setY(origin.getY() + newRadius);
newOrigin.setZ(origin.getZ() + newRadius);
subCubes[0] = new ForkPoints(newOrigin, newRadius);
subCubes[0].fork();
newOrigin = new Point3D();
newOrigin.setX(origin.getX() + newRadius);
newOrigin.setY(origin.getY() + newRadius);
newOrigin.setZ(origin.getZ() - newRadius);
subCubes[1] = new ForkPoints(newOrigin, newRadius);
subCubes[1].fork();
newOrigin = new Point3D();
newOrigin.setX(origin.getX() + newRadius);
newOrigin.setY(origin.getY() - newRadius);
newOrigin.setZ(origin.getZ() + newRadius);
subCubes[2] = new ForkPoints(newOrigin, newRadius);
subCubes[2].fork();
newOrigin = new Point3D();
newOrigin.setX(origin.getX() + newRadius);
newOrigin.setY(origin.getY() - newRadius);
newOrigin.setZ(origin.getZ() - newRadius);
subCubes[3] = new ForkPoints(newOrigin, newRadius);
subCubes[3].fork();
newOrigin = new Point3D();
newOrigin.setX(origin.getX() - newRadius);
newOrigin.setY(origin.getY() + newRadius);
newOrigin.setZ(origin.getZ() + newRadius);
subCubes[4] = new ForkPoints(newOrigin, newRadius);
subCubes[4].fork();
newOrigin = new Point3D();
newOrigin.setX(origin.getX() - newRadius);
newOrigin.setY(origin.getY() + newRadius);
newOrigin.setZ(origin.getZ() - newRadius);
subCubes[5] = new ForkPoints(newOrigin, newRadius);
subCubes[5].fork();
newOrigin = new Point3D();
newOrigin.setX(origin.getX() - newRadius);
newOrigin.setY(origin.getY() - newRadius);
newOrigin.setZ(origin.getZ() + newRadius);
subCubes[6] = new ForkPoints(newOrigin, newRadius);
subCubes[6].fork();
newOrigin = new Point3D();
newOrigin.setX(origin.getX() - newRadius);
newOrigin.setY(origin.getY() - newRadius);
newOrigin.setZ(origin.getZ() - newRadius);
subCubes[7] = new ForkPoints(newOrigin, newRadius);
subCubes[7].fork();
final Set<Point3D> results = new LinkedHashSet<Point3D>();
for(final ForkPoints singleSubCube : subCubes) {
results.addAll(singleSubCube.join());
}
return results;
}
}
private Set<Point3D> computeValue() {
double minX = origin.getX() - radius;
double maxX = origin.getX() + radius;
double minY = origin.getY() - radius;
double maxY = origin.getY() + radius;
double maxZ = origin.getZ() + radius;
double x = minX;
double y = minY;
double z = origin.getZ() - radius;
Set<Point3D> points = new LinkedHashSet<>();
boolean notFinished = true;
while (notFinished) {
if (x > maxX) {
x = minX;
y++;
}
if (y > maxY) {
y = minY;
z++;
}
if (z > maxZ) {
break;
}
Point3D ppoint = new Point3D();
ppoint.setX(x);
ppoint.setY(y);
ppoint.setZ(z);
points.add(ppoint);
x++;
}
return points;
}
}
但请注意，使用此代码还有很多工作要做。例如 - 两个对相邻空间执行计算的子任务都生成位于相互 Pane 上的点；当前代码通过 Set.addAll(..) 调用的 Point3D.equals(..) 排除了这些重复项。在现实生活中，算法甚至不应该生成它们，因为这些重复的点在整个生成的点中占很大一部分，尤其是对于 SEQUENTIAL_THRESHHOLD 的低值。
关于java - 卡在递归 Fork/Join 上，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13609758/