C# do/while 和 for 哪个更快？
我有一个 C# .NET 2.0 脚本，我想知道为什么以下代码比同类的 do while 循环更快。
private double getStop(double avgPrice, bool longTrading)
{
double stopS = 0.0;
double stopL = 0.0;
for (int i = 0; i < 13; i++)
{
if (i == 0 || i == 12)
{
stopS = 0.0;
stopL = 0.0;
}
else
{
if ((lines[i] - ((lines[i] - lines[i - 1]) / 2)) < avgPrice && avgPrice < (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2)))
{
if (avgPrice < lines[i])
{
stopL = (lines[i] - ((lines[i] - lines[i - 1]) / 2));
stopS = lines[i];
} else {
stopL = lines[i];
stopS = (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2));
}
}
}
}
if (longTrading)
{
return stopL;
} else {
return stopS;
}
}
另外，直接明确地声明每个 if 语句而不是在 for 循环中执行它们会更快吗？
既然回答得这么快，为什么它的运行速度会比上面的代码慢得多？
private double getStop(double avgPrice, bool longTrading)
{
double stopS = 0.0;
double stopL = 0.0;
for (int i = 0; i < 13; i++)
{
if (i == 0 || i == 12)
{
stopS = 0.0;
stopL = 0.0;
skip = true;
}
if (!skip && (lines[i] - ((lines[i] - lines[i - 1]) / 2)) < avgPrice && avgPrice < (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2)))
{
if (avgPrice < lines[i])
{
stopL = (lines[i] - ((lines[i] - lines[i - 1]) / 2));
stopS = lines[i];
} else {
stopL = lines[i];
stopS = (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2));
}
}
}
skip = false;
}
if (longTrading)
{
return stopL;
} else {
return stopS;
}
}
I have a C# .NET 2.0 script and I want to know why the following code would be faster than a do while loop of the same kind.
private double getStop(double avgPrice, bool longTrading)
{
double stopS = 0.0;
double stopL = 0.0;
for (int i = 0; i < 13; i++)
{
if (i == 0 || i == 12)
{
stopS = 0.0;
stopL = 0.0;
}
else
{
if ((lines[i] - ((lines[i] - lines[i - 1]) / 2)) < avgPrice && avgPrice < (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2)))
{
if (avgPrice < lines[i])
{
stopL = (lines[i] - ((lines[i] - lines[i - 1]) / 2));
stopS = lines[i];
} else {
stopL = lines[i];
stopS = (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2));
}
}
}
}
if (longTrading)
{
return stopL;
} else {
return stopS;
}
}
Also, would it be faster just to explicitly state each if statement instead of doing them inside of a for loop?
Being that this was answered so fast, why would this run far slower than the above code?
private double getStop(double avgPrice, bool longTrading)
{
double stopS = 0.0;
double stopL = 0.0;
for (int i = 0; i < 13; i++)
{
if (i == 0 || i == 12)
{
stopS = 0.0;
stopL = 0.0;
skip = true;
}
if (!skip && (lines[i] - ((lines[i] - lines[i - 1]) / 2)) < avgPrice && avgPrice < (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2)))
{
if (avgPrice < lines[i])
{
stopL = (lines[i] - ((lines[i] - lines[i - 1]) / 2));
stopS = lines[i];
} else {
stopL = lines[i];
stopS = (lines[i + 1] - ((lines[i + 1] - lines[i]) / 2));
}
}
}
skip = false;
}
if (longTrading)
{
return stopL;
} else {
return stopS;
}
}
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评论（3）
性能差异应该可以忽略不计，但 for 循环更清晰，所以我会这样做。
The performance difference should be negligible, but the for loop is clearer so I would go with that.
它们应该本质上是等价的。您的“for”循环被评估为：
They should be essentially equivalent. Your 'for' loop gets evaluated as:
循环的变化并没有太大的不同，它取决于上下文和编程语言。
但我的观点是，
for语句在约束匹配之前不会do，因此它应该比do更快/尽管。loop variations aren't too much different, it depends on the context and the programming language.
But my opinion is,
forstatement don't do until the constaint(s) is/are matched, therefore it should be faster than do/while.