C#两个几乎相同的线程，性能差异很大

Question

我在C#中有一个大的多线程系统，我意识到两个线程之间的性能非常不同。现在，我设计了两个几乎相同的线程，其中一个线程的执行速度快4-5倍(如果你改变它们必须运行的循环数量，它会线性扩展(。区别在哪里？一个笨拙的条件围绕着其中一个的实际重代码。这对我来说毫无意义，如果这样一个小细节能产生如此巨大的影响，我对未来的优化感到无能为力。这在Unity中进行了测试，因此在其他环境中可能会出现不同的结果。

线程A完成时间：2.8秒。线程完成时间：0.6秒

请注意，ThreadB是有条件的(在迭代的第一次迭代时会立即求值为true(。这么愚蠢的代码添加怎么会让实际的有效负载(for循环和数字运算(执行得更快？此外，如果我将"；延迟；带有静态"的变量；0.0"；直接在ThreadB的条件下，它再次像ThreadA一样执行。换句话说：一个双精度，无论它是硬编码值，还是引用变量，都会对性能产生4-5倍的影响。

别管实际的算法，它只是为了让计算机处理一些数字。我知道我正在一次又一次地比较相同的数据，这是无关紧要的。

我不是一个编译迷，我无法探究实际机器/汇编代码中的差异。我只知道差异是巨大的，对我来说毫无意义。我错过了什么？我偶然发现了这一点，在未来我可能无法知道给定线程以20%的可能速度运行，而一个微小的改变就可以解决它

求你了。我需要一个书呆子让它从纯粹的魔法变成"；哦，这就是为什么。。。！现在我知道如何避免它在未来&"；。我知道C#的编译被一层层托管的东西所包围，但这一定是有逻辑原因的。正确的

这里有一些测试代码和一些简单的结构来支持它。如果有人有时间检查他们是否得到了和我一样的结果，我会很高兴的。

using System.Threading;
public class ThreadTest
{
Thread threadA;
Thread threadB;
bool runThreadA = false;
bool runThreadB = false;
System.Diagnostics.Stopwatch stopWatch;
double elapsedTimeA = 0;
double elapsedTimeB = 0;

public ThreadTest()
{
stopWatch = new System.Diagnostics.Stopwatch();
StartThreads();
}
public void StartThreads ()
{
stopWatch.Reset();
stopWatch.Start();
threadA = new Thread(ThreadA);
threadB = new Thread(ThreadB);
runThreadA = true;
runThreadB = true;
elapsedTimeA = 0;
elapsedTimeB = 0;
threadA.Start();
threadB.Start();
}
void ThreadA ()
{
while (runThreadA)
{

runThreadA = false;
double preTicks = stopWatch.ElapsedTicks;
Line3Double lineA = new Line3Double(new Vector3DoublePrecision(10, 20, 30), new Vector3DoublePrecision(100, 140, 180));
Line3Double lineB = new Line3Double(new Vector3DoublePrecision(-10, -20, -30), new Vector3DoublePrecision(-100, -140, -180));
int lines = 1000;
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < lines; j++)
{
double aStartX = lineA.startX;
double aStartY = lineA.startY;
double aStartZ = lineA.startZ;
double aEndX = lineA.endX;
double aEndY = lineA.endY;
double aEndZ = lineA.endZ;
double aDirX = lineA.dirX;
double aDirY = lineA.dirY;
double aDirZ = lineA.dirZ;
double aDotSelf = lineA.dotSelf;
for (int k = 0; k < 8; k++)
{
for (int l = 0; l < lines; l++)
{
double wX = aStartX - lineB.startX;
double wY = aStartY - lineB.startY;
double wZ = aStartZ - lineB.startZ;
double b = aDirX * lineB.dirX + aDirY * lineB.dirY + aDirZ * lineB.dirZ;
double d = aDirX * wX + aDirY * wY + aDirZ * wZ;
double e = lineB.dirX * wX + lineB.dirY * wY + lineB.dirZ * wZ;
double D = aDotSelf * lineB.dotSelf - b * b;
double sc, tc;
if (D < 0.0000001)
{
sc = 0.0f;
tc = (b > lineB.dotSelf ? d / b : e / lineB.dotSelf);
}
else
{
sc = (b * e - lineB.dotSelf * d) / D;
tc = (aDotSelf * e - b * d) / D;
}
double shortestX = wX + (sc * aDirX) - (tc * lineB.dirX);
double shortestY = wY + (sc * aDirY) - (tc * lineB.dirY);
double shortestZ = wZ + (sc * aDirZ) - (tc * lineB.dirZ);
double distance = shortestX * shortestX + shortestY * shortestY + shortestZ * shortestZ;
}
}
}
}
double postTicks = stopWatch.ElapsedTicks;
double time = ((postTicks - preTicks) / System.Diagnostics.Stopwatch.Frequency) * 1000;
elapsedTimeA = time;
}
}
void ThreadB()
{
long startTicks = stopWatch.ElapsedTicks;
double delay = 0;
while (runThreadB)
{
if ((double)(stopWatch.ElapsedTicks - startTicks) / System.Diagnostics.Stopwatch.Frequency >= delay)
{
runThreadB = false;
double preTicks = stopWatch.ElapsedTicks;
Line3Double lineA = new Line3Double(new Vector3DoublePrecision(10, 20, 30), new Vector3DoublePrecision(100, 140, 180));
Line3Double lineB = new Line3Double(new Vector3DoublePrecision(-10, -20, -30), new Vector3DoublePrecision(-100, -140, -180));
int lines = 1000;
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < lines; j++)
{
double aStartX = lineA.startX;
double aStartY = lineA.startY;
double aStartZ = lineA.startZ;
double aEndX = lineA.endX;
double aEndY = lineA.endY;
double aEndZ = lineA.endZ;
double aDirX = lineA.dirX;
double aDirY = lineA.dirY;
double aDirZ = lineA.dirZ;
double aDotSelf = lineA.dotSelf;
for (int k = 0; k < 8; k++)
{
for (int l = 0; l < lines; l++)
{
double wX = aStartX - lineB.startX;
double wY = aStartY - lineB.startY;
double wZ = aStartZ - lineB.startZ;
double b = aDirX * lineB.dirX + aDirY * lineB.dirY + aDirZ * lineB.dirZ;
double d = aDirX * wX + aDirY * wY + aDirZ * wZ;
double e = lineB.dirX * wX + lineB.dirY * wY + lineB.dirZ * wZ;
double D = aDotSelf * lineB.dotSelf - b * b;
double sc, tc;
if (D < 0.0000001)
{
sc = 0.0f;
tc = (b > lineB.dotSelf ? d / b : e / lineB.dotSelf);
}
else
{
sc = (b * e - lineB.dotSelf * d) / D;
tc = (aDotSelf * e - b * d) / D;
}
double shortestX = wX + (sc * aDirX) - (tc * lineB.dirX);
double shortestY = wY + (sc * aDirY) - (tc * lineB.dirY);
double shortestZ = wZ + (sc * aDirZ) - (tc * lineB.dirZ);
double distance = shortestX * shortestX + shortestY * shortestY + shortestZ * shortestZ;
}
}
}
}
double postTicks = stopWatch.ElapsedTicks;
double time = ((postTicks - preTicks) / System.Diagnostics.Stopwatch.Frequency) * 1000;
elapsedTimeB = time;
}
}
}
}
public struct Vector3DoublePrecision
{
public double x;
public double y;
public double z;
public Vector3DoublePrecision(double x, double y, double z)
{
this.x = x;
this.y = y;
this.z = z;
}
}
public struct Line3Double
{
public double startX;
public double startY;
public double startZ;
public double endX;
public double endY;
public double endZ;
public double dirX;
public double dirY;
public double dirZ;
public double dotSelf;
public Line3Double(Vector3DoublePrecision start, Vector3DoublePrecision end)
{
startX = start.x;
startY = start.y;
startZ = start.z;
endX = end.x;
endY = end.y;
endZ = end.z;
dirX = end.x - start.x;
dirY = end.y - start.y;
dirZ = end.z - start.z;
dotSelf = dirX * dirX + dirY * dirY + dirZ * dirZ;
}
}

Answer 1

已解决。。。是Unity特有的编译问题。将Scripting后端从Mono更改为IL2CPP，这不仅使一切都能更好地执行，而且还消除了上述问题。所以JIT编译是罪魁祸首。仍然不确定如此愚蠢地包含一个笨拙的条件是如何使我的线程比没有它时表现得更好的，但现在它工作了。我通过修复它学到了很多。