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SubjectRe: [Criticism] On the discussion about C++ modules
"Jeff V. Merkey" wrote:
>
> Eray Ozkural wrote:
> >
> > I don't how you would do such a thing in C++. Allocators and the
> > stuff I talked about make it more efficient and safer to manage
> > memory. They don't throw memory calls all over the place. :P
>
> More routines touching more memory on more cache lines (generating more
> MESI traffic between the cache controllers). Plus the poor schmuck who
> has to maintain the source code will will have to debug his 10
> instruction read and write code (in C) to IO register which now does 4
> copies, and is 500 instrutions long (in C++) (copying memory is
> expensive).

You're assuming that g++ generates code that is much larger and slower.
That's not true. An inexperienced C++ programmer can manage it perhaps.
Can you give an example for this? ;>

C++ programmer has the kind of control over the machine the C
programmer has, and then some. [ See the comments on "const" ]

> Oh, I almost forgot, the processor also will have to
> generate an AGI (address generation interlock) since you will load an
> address then immediately jump to it in all the jump tables that the C++
> compiler will put in for every function you call (and your multiple
> instruction piplines will be reduced to one, since the processor has to
> go serial to handle the AGI correctly). In flat model code, jumps to
> functions within a single 4GB segment (or larger) are just done with
> simple math internally in the processor -- C++ injects one or more
> memory fetches in between each function call, plus they use 2-3 times as
> much stack memory. Eh....

Sorry. These are not relevant, especially the last bit about C++ injecting
one or more memory fetches between function calls. Haven't you studied
any compiler courses? [ Let me guess, you're an EE guy and don't want
to know what an optimizer is :> ]

I don't want to repeat myself, but C++ doesn't force you to use
any bad programming practice that will result in slow code:
* exceptions everywhere
* polymorphism everywhere
* dynamic type checking everywhere
* new/delete everywhere
* huge non-const objects copied everywhere
...


If you think that C++ proggys _have_ to contain such terrible code,
then I'll have to conclude that you haven't learnt coding in C++.

If any of what you said was generally true, then nobody would be able
to write any efficient program in C++. In kernel or userland.
Would you mind checking the blitz++ package for understanding
what I mean? That library happens to be a good example of efficient
use of C++.

Let me look back at that graph partitioning program I did; there must
have been a miracle to make it run that fast. :)

--
Eray (exa) Ozkural
Comp. Sci. Dept., Bilkent University, Ankara
e-mail: erayo@cs.bilkent.edu.tr
www: http://www.cs.bilkent.edu.tr/~erayo
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