为什么wcschr这么慢??? [英] why is wcschr so slow???
问题描述
我认为我的程序必须被循环捕获，并通过任务管理器的
取消它。在Java中花了大约一秒钟，但在
C中重新实现，它已经运行了一分钟。
我设置了一个调试器来显示每个循环的当前位置，让它运行
。它确实完成了，但花了20分钟。
我用我的程序中的wcschr替换了对这个替代品的调用：
静态WCHAR * altchr（注册WCHAR * s，注册WCHAR c）{
而（TRUE）
{if（* s == c）
返回s;
如果（* s == 0）
返回0;
++ s;
}
}
现在我的程序立即完成，比Java版本更快，因为你可能期望
。 br />
wcschr做什么需要这么长时间???
我在XP上，使用Borland 5.5.1 C ++编译器可以从他们的网站上免费下载
。
Albert Oppenheimer < SP ** @ spam.com>在消息中写道
新闻：e0 ********** @ geraldo.cc.utexas.edu ...我以为我的程序必须是陷入循环，并通过任务管理器取消它。在Java中花了大约一秒钟，但是在
C中重新实现，它已经运行了一分钟。
C？你的意思是C ++，还是你在错误的新闻组？
我设置了一个调试器来显示每个循环的当前位置并让它运行。它确实达到了完成，但花了20分钟。
我在我的程序中调用了wcschr来调用这个
代替：
静态WCHAR * altchr （注册WCHAR * s，注册WCHAR c）{
while（TRUE）
{if（* s == c）
return s;
if（* s == 0 ）
返回0;
++ s;
}
现在我的程序立即完成，比Java版本更快，因为你可能会期待。
wcschr可以做什么需要这么长时间？
我在XP上，使用Borland 5.5.1 C ++编译器可以从他们的网站下载
免费
。
我在这里的参考书中没有看到任何功能。这是对strchr的Borland扩展吗？如果是这样，您可以询问他们（或在Borland
新闻组）关于他们实施
功能的任何性能问题。
也许他们的免费编译器值得每一分钱？ :-)
或许你调用函数的方法（或你正在使用的数据）
与这种方式不能很好地工作他们设计了吗？他们会问的是，
我想。
-Howard
>我在这里的参考书中没有看到这个功能。它是一个对strchr的Borland扩展吗？如果是这样，你可以问他们（或在borland
新闻组）关于他们实现该功能的任何性能问题。
wcschr是strchr的unicode版本。
它处理16位字符而不是8位字节。
上帝知道你使用的参考书。寻找标准的好地方
用于XP的C库函数（是的，我确实说这是在XP上）是在
http://msdn.microsoft.com/ library / de ... nipulation.asp
函数是C ++的基本函数，就像标准C表达式一样。
Albert Oppenheimer写道：
< blockquote class =post_quotes> wcschr是strchr的unicode版本。
它处理16位字符而不是8位字节。
调用这样的功能unicode版本是误导。
（不要责怪你 - 很多文档都有这个问题。但是我责备
你把wchar_t混淆为16位。有时候它更多！）
真正处理Unicode的函数将处理编码，例如
UTF-16，它将正确处理各种Unicode诡计，
如复合字符。
wcs函数不是;他们只是将每个wchar_t元素视为一个假设的字形。 （如果有的话我会很高兴知道，但我知道简单的
那些不是，所以wcschr（）可能有资格。）
如果这个wcschr（）确实正确地处理了Unicode，那么它可能会有点慢b / b
如果只是迭代wchar_t元素，然后它就没有理由让b $ b慢了，原版海报必须在别处查找问题。
-
Phlip
http://www.greencheese.org/ZeekLand < - 不是博客!!!
I thought my program had to be caught in a loop, and cancelled it through
the task manager. It took about one second in Java, but re-implemented in
C, it had already run over one minute.
I set up a debugger to display the current location each loop and let it
run. It did reach completion, but it took 20 minutes.
I replaced the calls to wcschr in my program with calls to this substitute:
static WCHAR* altchr(register WCHAR* s, register WCHAR c) {
while (TRUE)
{ if (*s == c)
return s;
if (*s == 0)
return 0;
++s;
}
}
Now my program finishes instantly, faster than the Java version, as you
might expect.
What could wcschr be doing that takes so long???
I''m on XP, using the Borland 5.5.1 C++ compiler that can be downloaded free
from their web site.
"Albert Oppenheimer" <sp**@spam.com> wrote in message
news:e0**********@geraldo.cc.utexas.edu...I thought my program had to be caught in a loop, and cancelled it through
the task manager. It took about one second in Java, but re-implemented in
C, it had already run over one minute.
C? Did you mean C++, or are you in the wrong newsgroup?
I set up a debugger to display the current location each loop and let it
run. It did reach completion, but it took 20 minutes.
I replaced the calls to wcschr in my program with calls to this
substitute:
static WCHAR* altchr(register WCHAR* s, register WCHAR c) {
while (TRUE)
{ if (*s == c)
return s;
if (*s == 0)
return 0;
++s;
}
}
Now my program finishes instantly, faster than the Java version, as you
might expect.
What could wcschr be doing that takes so long???
I''m on XP, using the Borland 5.5.1 C++ compiler that can be downloaded
free
from their web site.
I don''t see that function anywhere in my reference books here. Is it a
Borland extension to strchr? If so, you could ask them (or on a borland
newsgroup) about any performance issues with their implementation of that
function.
Perhaps their free compiler is worth every penny? :-)
Or perhaps your method of calling the function (or the data you''re using)
doesn''t work well with the way they desigend it? They''d be the ones to ask,
I think.
-Howard
> I don''t see that function anywhere in my reference books here. Is it aBorland extension to strchr? If so, you could ask them (or on a borland
newsgroup) about any performance issues with their implementation of that
function.
wcschr is the unicode version of strchr.
It processes 16-bit characters instead of 8-bit bytes.
God knows what reference books you used. A good place to look for standard
C library functions for XP (yes, I did say this is on XP) is at
http://msdn.microsoft.com/library/de...nipulation.asp
Borland has the same standard C functions as Microsoft. And standard C
functions are basic to C++ just like standard C expressions.
Albert Oppenheimer wrote:
wcschr is the unicode version of strchr.
It processes 16-bit characters instead of 8-bit bytes.
Calling such a function "the unicode version" is misleading.
(Not to blame you - much documentation has this problem. But I _do_ blame
you for confusing wchar_t for 16-bits. Sometimes it''s more!)
A function that truly handles Unicode will handle an encoding, such as
UTF-16, and it will deal correctly with the various Unicode shenanigans,
such as composite characters.
The wcs functions don''t; they just treat each wchar_t element as one
hypothetical glyph. (If any do I''d be glad to know, but I know the simple
ones don''t, so wcschr() probably qualifies.)
If this wcschr() did indeed process Unicode correctly, it might be a little
slow.
If all it does is iterate over wchar_t elements, then it had no reason to be
slow, and the Original Poster must look elsewhere for the problem.
--
Phlip
http://www.greencheese.org/ZeekLand <-- NOT a blog!!!
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