On 25 Apr., 19:30, Mensanator <mensana...@[EMAIL PROTECTED]
> wrote:
> On Apr 25, 7:01 am, thomas.mer...@[EMAIL PROTECTED]
wrote:
> > On 25 Apr., 09:46, Mensanator <mensana...@[EMAIL PROTECTED]
> wrote:
> > > On Apr 25, 1:30 am, thomas.mer...@[EMAIL PROTECTED]
wrote:
> > > > Can you give me an update.
>
> > > Trying to convert Sedgewick algorithm from C
> > > to Seed7.
>
> > > Quick question. I define an empty array using
>
> > > var array cycle: cycle_stats is 0 times cycle.value
>
> > > and then expand it one index at a time as needed by
>
> > > cycle_stats &:= [](attractor_stats)
>
> > This is possible, but it costs time to extend the array.
>
> I expected that. I only do it s****adically and because I
> have no way of predicting how big the array has to be.
> It could be half a dozen or several hundred depending
> on the idiosyncrasies of the Collatz function.
>
> > You can request a bigger array at any time with:
>
> > cycle_stats := number times cycle.value;
>
> Ah, that's what I was looking for, didn't know you could
> do that dynamically.
>
> > where 'number' is an integer variable. But note that
> > such a statement replaces the whole array (The old
> > content of the array is lost). There is also the possibility
> > to increase an array:
>
> > cycle_stats &:= 1000 times cycle.value;
>
> > This way 1000 additional elements are added at the end of
> > the array.
>
> > > For the Sedgewick algorithm, the array gets created
> > > as a fixed size M, but M is passed as a command line
> > > parameter, so I can't do
>
> > > var array cycle: cycle_stats is M times cycle.value
>
> > > because M is unknown at compile time? Is that right?
>
> > To use M in the declaration it must be known at compile
> > time. But you can declare it with:
>
> > var array cycle: cycle_stats is 0 times cycle.value;
>
> > and use the statement
>
> > cycle_stats := M times cycle.value;
>
> Thanks, that's exactly what I need. Apparently, the Sedgewick
> algorithm needs to be tuned for optimum performance. Otherwise
> you'll get a fault if the table is too small or performance
> degradtion if too large.
Why is there a problem when the table is too large?
Does the program start thra****ng?
> So the table size pretty much has to
> be a command line parameter.
>
> > to bring it to bigger size. This way M can be unknown
> > at compile time.
>
> > > Is there a way to create the entire array (M times)
> > > in the program body instead of the variable declaration?
> > > Without doing [](attractor_stats) M times?
>
> > See above: cycle_stats := M times cycle.value;
>
> > > Also, working on my web page to summarize all this,
> > > list the Seed7 programs, do some timing comparisons,
> > > etc.
>
> > > I notice the latest Seed7 seems much improved over
> > > the previous one.
>
> > I improved the built-in bigInteger sup****t (the one
> > without GMP) to use bigdigits of 32 bit size. Before
> > the size of a bigdigit was 16 bits.
>
> > > I _thought_ the Brent algorithm
> > > was rather slow in Seed7, but I didn't log it very
> > > carefully and now it doesn't seem so bad. It may turn
> > > out that Brent & Sedgewick are closer than I thought.
>
> > > Trouble is, I don't have two of the same kind of fruit.
>
> > > I've got attractors.c (naive cycle detection)
> > > efd.py (Brent)
> > > ecd001.sd7 (Brent) old Seed7
> > > ecd001.sd7 (Brent) current Seed7 with GMP
> > > ecd001.sd7 (Brent) current Seed7 without GMP
> > > ccd020.c (Sedgewick)
>
> > > And I'm trying to do testing and decide what to do
> > > next. Nothing can touch the C programs, but Brent
> > > in C isn't as much faster than I thought originally,
> > > 39 sec for Seed7 vs 4.7 sec for C. How much of that
> > > is due to the algorithm vs the language? Should I
> > > make a Brent version in C along with a Sedgewick
> > > version of Seed7?
>
> > IMHO: For a comparison of language implementation speeds
> > the same algorithm needs to be used.
>
> Right. I need to focus on what I'm trying to accomplish and
> that's NOT a language benchmark.
No problem. If you think something in Seed7 is too slow tell
me about it: I can profile compiled Seed7 programs.
> What I want is a do***entary
> on how I solved the problem, part of which will feature Seed7
> (and give me an excuse to list all the sample sources in Seed7).
Great.
> I think when all the tradeoffs are considered, everything will
> come out looking good.
Greetings Thomas Mertes
Seed7 Homepage: http://seed7.sourceforge.net
Seed7 - The extensible programming language: User defined statements
and operators, abstract data types, templates without special
syntax, OO with interfaces and multiple dispatch, statically typed,
interpreted or compiled, ****table, runs under linux/unix/windows.
|
