Algol vs Fortran was RE: VHDL vs Verilog
derschjo at mail.msu.edu
Tue Feb 9 14:49:41 CST 2010
On Feb 9, 2010, at 12:28 PM, Dave McGuire <mcguire at neurotica.com> wrote:
> On Feb 9, 2010, at 2:19 PM, Josh Dersch wrote:
>>> Ok. Show me a processor that has an "object" data type, that has
>>> subtypes like "member" and "method" and such. There aren't any.
>>> Translating from such incredibly high-level constructs to
>>> registers, stacks, and memory locations is not without a lot of
>>> overhead. Try to envision what happens in the instruction stream
>>> during things like virtual function lookups in C++, for example.
>> Ok, I'm envisioning it. A few instructions to do a vtable lookup
>> and a jump to the correct virtual function. Wow. So those extra
>> instructions are what's making every machine in the world
>> (apparently) very very slow?
> Yes, to a large degree! You're talking about it as if it happens
> ONCE, and you know it doesn't. Would you care to estimate how many
> of those vtable lookup happen when someone simply clicks a mouse in
> a modern OS? I don't know for certain, but I'm willing to bet that
> it's thousands.
I'm not going to speculate on things I have no knowledge of. Even if
it were thousands, that would mean an overhead of tens of thousands
of instructions. On a modern CPU, in a user-interaction scenario,
that doesn't even begin to be noticable to the user. If it's millions
of calls in a tight loop doing some heavy calculation then it will
have an impact; but anyone calling a virtual function in such a
scenario is doing it wrong.
>> In C#, virtual lookups are cached at runtime so the cost of the
>> first virtual call to a function goes through the vtable routine;
>> future calls are very fast.
> That's nice. Now if only C# weren't a proprietary product from one
> company which happens to be obsessed with creating vendor lock-in
> situations. ;)
> (though actually, hmm, that IS rather nice...)
>> Objects in their raw form are not "incredibly high-level." In C++,
>> an object is referenced via a pointer; data fields are accessed via
>> offsets just like in C. There is a small overhead for virtual
>> function dispatch. I fail to see how this overhead is somehow
>> responsible for performance problems in computers today.
> There's a bit of congruity between C's structs and C++/C#/Java/etc
> objects, but..
>> What other overheads/inefficiencies are you thinking of?
> ...what happens when someone uses an Integer instead of an int? A
> whole object gets created when all one likely needed was a memory
Depends greatly on the language. Don't confuse one implementation
with ALL OO programming languages. In C++ an integer maps to a
register. Same in C#. Same in objc. Java does this differently.
> What happens when one adds that Integer to another Integer? Add in
> the address offset calculations to find out where the actual int is
> stored within the Integer object, what would those be on most
> architectures...two or three instructions? So our nice single-
> instruction add turns into at least five instructions.
> So you're arguing that increasing the number of instructions
> required to execute a simple operation by a factor of five doesn't
> involve overhead? Ok, howabout when it happens all the time, which
> additions tend to in most programs?
> In C (for example), there's no motivation at all to wrap a struct
> around an int just for the sake of doing so, so it doesn't happen.
> And howabout template programming. I've never seen executables so
> big as the ones in which templates were overused.
Template programming is another paradigm altogether, it's basically C+
+ specific and it has very little to do with OO. (It's also an
abomination along with most of C++.)
> (yes, here I have to give a nod to your point about bad programmers
> below!) All in the name of "saving programmer time", as if that's
> such a big deal, consequences be damned.
> Note well, however, that I'm talking about more than just the
> number of instructions required to accomplish a given task. Sure,
> that in itself has bad side effects when you think about what it
> does to the instruction cache hit rates...the principal of locality
> of reference is blown out the window. But what about memory
> utilization? How big, in bytes, is an Integer compared to an int?
> Ok, the difference may be only a few bytes, but what about the
> program (which would be "most of them") with tens of thousands of
> them? (I'm typing this on a Mac, into Mail.app, which is currently
> eating 1.73GB of memory)
I beleive tha in Objective C, ints are still registers, no magical
Integer objects here. Sounds like Mail.app is poorly written. I'm
running Outlook here (written in a mix of c and c++) and it's using
100mb (with an inbox size of 10gb...).
>> You keep talking about how OO programming is the reason that
>> software today is so inefficient but you offer no data to back it
>> up other than "it doesn't map to the hardware."
> I'm sorry, but knowing how processors work, it's pretty obvious to
> me. The data that backs it up is lots of programs (some of which
> are operating systems) that I use every day, written in OO
> languages, including (perhaps especially!) OS X, are far slower than
> they should be given the hardware they're running on. YOU know how
> processors work too, I know you do, so I know you see my point.
This is only a valid argument if you have an OS X written in plain C
and an OS X written in OO that you can do a real comparison between.
Anything else is speculation. OO does have its overheads, I disagree
that they are anywhere nearly as bad as you claim them to be.
Speculating that OS foo is far slower than it "should be" based on
anecdotal evidence is not proof.
>>> A modern multi-GHz Linux box running GTK is far less "responsive"-
>>> feeling than my old SPARCstation-IPX running fvwm when just
>>> tooling around the GUI. A little more time spent by the
>>> programmers, ignoring the "easy way out" or heavy OO programming
>>> and it'd be FAR faster.
>> So it finally comes out: it's the *bad progammers* at fault here.
>> I knew it all along! Don't confuse poor programmers with
>> programming languages. There are always efficiency tradeoffs in
>> programming languages and a good programmer knows how to make the
>> right choices.
> Yes, I have to acknowledge this; you'll get no argument from me
> there. But bad programmers are the rule, not the exception. Code
> written by bad programmers constitutes 90% of the code written
> today. It's possible to write fast, compact C++ or Java code; we've
> both seen it. But it's not the norm. KDE, OS X (and several of its
> apps, Mail.app comes to mind) *are* the norm, and they're both
> horribly slow for the hardware they're typically run on.
> In an ideal world, one in which all programmers were competent, OO
> languages wouldn't be such a problem. So I guess what I really mean
> is, "Bad programmers are even more detrimental to computing when
> armed with OO languages".
You really think these same programmers would somehow write better
code if only they would stop using OO?
> Dave McGuire
> Port Charlotte, FL
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