矢量化 For 循环 Matlab 代码中的错误

Question

我有一个要矢量化的 for 循环代码。下面是初始的 for 循环代码，以及代码的矢量化版本。矢量化代码没有给出与 parfor 循环相同的结果，因此我知道代码有问题。如果有哪位论坛成员能帮我查看矢量化代码，看看能不能给我指出错误，我将不胜感激。提前谢谢你。

% 初始化和预计算 % w 是一个 n x 1 向量 % beta：任何大于 0 的数字。通常设置为 1。这是我需要矢量化的 for 循环代码：

f = zeros(n,1);
x = w;
y = w;
rho = 1;
v = f – (rho*y);
rhow = rho*w;
n = length(w);

parfor i = 1 : n

if w(i) >= 0
    if v(i) < -rhow(i) – beta – 1
        x(i) = (-beta -1 -v(i))/rho;

    elseif (-rhow(i) – beta – 1 <= v(i)) && (v(i) <= -rhow(i) + beta – 1)
        x(i) = w(i);

    elseif (-rhow(i) + beta – 1 < v(i)) && (v(i) < beta – 1)
        x(i) = (beta – 1 -v(i))/rho;

    elseif (beta – 1 <= v(i)) && (v(i) <= beta + 1)
        x(i) = 0;

    else
        x(i) = (beta + 1 – v(i))/rho;
    end

else

    if v(i) < -beta -1
        x(i) = (-beta -1 – v(i))/rho;

    elseif (-beta – 1 <= v(i) )&& (v(i) <= -beta + 1)
        x(i) = 0;

    elseif (-beta + 1 < v(i)) && (v(i) < -rhow(i) – beta + 1)
        x(i) = (-beta + 1 – v(i))/rho;

    elseif (-rhow(i) – beta + 1 <= v(i)) && (v(i) <= -rhow(i) + beta + 1)
        x(i) = w(i);

    else
        x(i) = (beta + 1 – v(i))/rho;
    end

end

结束

============================================= =========================

这是上面代码的矢量化版本：

cond1 = (w >= 0);
cond2 = (w >= 0) & (v < -rhow-beta-1);       
x(cond2) = (-beta-1-v(cond2))/rho; 

cond3 = (w>=0)&(-rhow - beta -1 <= v) & (v <= -rhow + beta - 1);
x(cond3) =  w(cond3);

cond4 = (w>=0) & (-rhow +beta - 1 < v) & (v < beta - 1);
x(cond4) = (beta - 1 - v(cond4))/rho;

cond5 = (w>=0) & (beta - 1 <= v) & (v <= beta + 1);
x(cond5) = 0;

cond6 = (~cond2);
x(cond6) = (beta + 1 - v(cond6))/rho;

cond7 = ((~cond1) & v < -beta -1);
x(cond7) = (-beta -1 - v(cond7))/rho;

cond8 = ((~cond1) & (-beta - 1 <= v) & (v <= -beta + 1));
x(cond8) = 0;

cond9 = ((~cond1) & (-beta + 1 < v) & (v < -rhow - beta + 1));
x(cond9) = (-beta + 1 - v(cond9))/rho;

cond10 = ((~cond1) & (-rhow - beta + 1 <= v) & (v <= -rhow + beta + 1));
x(cond10) = w(cond10);

cond11 = (~cond1);
x(cond11) = (beta + 1 - v(cond11))/rho;

Answer 1

这里有一个错误，cond6不等于原来的第一个else

cond2 = (w >= 0) & (v < -rhow-beta-1);
cond6 = (~cond2);
x(cond6) = (beta + 1 - v(cond6))/rho;

原文是这样的：

if w(i) >= 0
   if v(i) < -rhow(i) – beta – 1
      ...
   else
      x(i) = (beta + 1 – v(i))/rho;  %this should be cond6
   end
end

else应该这样计算（如果我没记错的话）

x(cond1) = (beta + 1 - v(cond6))/rho;

在所有其他人之前直到 cond5。

我没有检查所有代码，所以如果这不能解决您的问题，请告诉我。

Answer 2

我正在添加另一个已检查所有条件的答案：

cond1 = (w >= 0);
cond2 = cond1 & (v < -rhow – beta – 1);
cond3 = cond1 & ((-rhow – beta – 1 <= v) && (v <= -rhow + beta – 1));
cond4 = cond1 & ((-rhow + beta – 1 < v) && (v < beta – 1));
cond5 = cond1 & ((beta – 1 <= v) && (v <= beta + 1));
cond6 = cond1 & (v > beta + 1)

cond7 = ~cond1 & (v < -beta -1);
cond8 = ~cond1 & ((-beta – 1 <= v ) && (v <= -beta + 1));
cond9 = ~cond1 & ((-beta + 1 < v) && (v < -rhow – beta + 1));
cond10 = ~cond1 & ((-rhow – beta + 1 <= v) && (v <= -rhow + beta + 1));
cond11 = ~cond1 & (v > -rhow + beta + 1);

x(cond2)=... 到 x(cond11)=... 保持不变。希望这有效。

矢量化 For 循环 Matlab 代码中的错误

Errors in Vectorized For-loop Matlab Code

matlab

for-loop

if-statement

parfor