Richard said:
Scott Roberts said:
[...]
Later on, however, one or other of us (I forget which) discovered (I'm not
sure how authoritatively) that, apparently, .Net is not good at heavily
recursive code, and since our code did little else *but* recurse (its
Recursive code doesn't IMHO cause a performance problem in .NET. This is
rather a problem for unexperienced C++ programmers placing large objects
on the stack.
That remembers me of a famous article in a German computer magazine,
stating that Java is multiple times faster than C++.
But the author(s) used std::string objects in C++ like Java string
objects and passed them by value, instead as reference. So the C++
compiler copied always the strings to a temporary object on every
function call. And since the code was heavily recursive .....
Do you see the similarities ? In this case the author stated that the
same code did run several times faster in a managed language, than in
C++. I think you are stating currently the opposite ;-)
And if the author would have done the same as your team, he wouldn't
have touched C++ again, because it's so damn slow.
I think the function in your code, which is called recursively uses a
string parameter in it's arguments.
function was to extract dependency relationships from source code, and
much of this was achieved by parsing the source to look for stuff like
#include "foo.h", <a href="yadayadayada.html">, etc etc - and parsing is
There would have been several other possibilities in .NET:
a) Use regular expressions - provided in .NET directly. You have the
option to use on the fly compiled regular expressions in .NET
b) Use a full fledged parser like ANTLR
c) Compile a mixed mode application in .NET
The native part is still native and the other code, using .NET will
be compiled to IL code.
Has downsides, but sometimes still the fastest solution
d) Convert the Code to the .NET platform, not simply recompiling
E.g. replacing the text "oldtext" by "newtext" in a single text file
named "myfile.txt" could be done in a single line in .NET (C#)
File.WriteAllText(
File.ReadAllText(
"myfile.text".Replace("oldtext",
"newtext")), "myfile.text");
(Despited my newsreader wrapped to single line to 3 lines ;-) )
Perhaps good enough for small files, but not a good idea for large
files. So even in .NET there are multiple solutions, some are
faster to implement, but performance wise not always a good idea.
an inherently recursive process), this may go some way towards explaining
the huge performance disparity between .Net and native code.
What about profiling ? Takes only a few minutes.
All in all just the meaning of a "pointy-clicky" developer ;;;-)
By the way. The same way you've (as I assume) ported your code to .NET
Quake II (IIRC) has been ported - simply by recompiling and has reached
90% of the original speed of the native compiled application.
Andre
