sand15

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4 years, 326 days

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These are replies submitted by sand15

@Carl Love 

Your redefinition of RGB24toName is a very astute stopgap.

About the ColorTools package : I believe it is fairly powerfull while not very easy to work with.
One of the main criticism I would make is that it is quite difficult to pick "the" good color (or to create its own palette) from existing ones because the GetPalette( NameOfThePalette ) display the colors in a disturbing order (see "Resene" for example).

Thanks for the answer ... and for having pointed out a translation mistake :

(FR) Fonction reciproque  <--> reciprocal inverse function (EN)  ... I will remember this

@acer 

You write

  1. Your XP machine seems to be 4 physical cores without hyperthreading capability
    TRUE : this is a capibility that is disabled by default (here again a company policy)

  2. your new Windows 7 machine seems to be 4 physical cores with hyperthreading capability
    TRUE again : I asked that hyperthreading be enabled on my new "Windows 7" machine.
  3. On the Windows 7 machine it's quite possible that the OS distributes the load  ...
    Very likely indeed
    Here is a table that summarizes the performances I have just obtained (new machine / Windows 7)
    (10000 runs, distributed on N nodes ... or the nearest integer of 10000 that N divides)

    N

    Approx. Mean Load

    (%)

    Execution time

    (s)

    Observation from the task monitor (performance tag) 

    2

    25

    881

    4 active cores

    3

    38

    557

    6 active cores

    4

    50

    409

    8 active cores

    5

    60

    381

    ‘’

    6

    73

    370

    ‘’

    7

    90

    355

    ‘’

    8

    95

    343

    8 active cores, all « flat »


    One can notice that the the execution time with N nodes (TN) varies linearly, or so, between N=2, 3, 4.
    For N larger than 4 the improvement is slighter.
    The rightmost column refers to visual observation of the task monitor (ctrl+alt+suppr, tag "performance"). For N >= 4 the 8 cores exhibit a significant activity while, for N=3 two of them have no load at all, and that for N=2 four cores are inactive (odd nodes are active and even ones inactive).
    The approximated mean load column (from the task monitor) increases inversely to the execution time (which seems normal).

    It seems to me that the table above corroborates what you write in your last paragraph (at least as far as I understand ...)

 

Great thanks to you Acer for this fruitfull answer

@Carl Love 
I agree : the ratio 3.2/3.5 is anything but significative.

But the ratio 4/8 of the number of cores nodes should be :

given that all the cores recieve the same amount of runs to execute (resp 2500 on the 4 cores PC and 1250 on the 8 cores one) and that all the cores are active (I do not use Grid:-Launch plus a Send-Recieve protocol), the expected execution time should (?) divided by 2 on the 8 cores machine ... all other things being equal, and more specifically with the same OS.

 

Now, I agree with your suggestion "so you should run your test using the same number of nodes on each machine"
But two difficulties arise :

  1. Considering the performances I announced beforehand, I would have like to proceed to some extended comparisons. But (company policy oblige) the migration of operating systems is generally an opportunity to upgrade the working station if not to change it. This is what was done for me and I am no longer capable to test my code on my previous machine
    Accordingly, my comparisons are probably biased
  2. I have observed the following behaviour while using Grid-Run as described in my initial post
    Let us suppose I'm working on a 2x2 cores machine and that (1) I distribute 10000 runs over 4 cores and next (2) I distribute these 10000 runs over 2 cores (same proc or not ???)
    Let T(4) and T(2) the corresponding execution times. I can expect that T(2) is twice T(4) .. but, for a reason I don't know,  it is not the case (I'm not a specialist of parallel computing or processors architecture).
    A quick look to the performance tab of the task monitor shows in case (1) that the 4 cores are loaded the same way (saying 95% during the whole computation sequence) ... whereas in case (2) two cores are loaded up to a level of 75% (with large deviations) while the 2 others remain between 10% and 30%.

    Furthermore, the performance history is very chaotic in case (2) whereas quite flat in case (1) ... something I (mis)interpreted as a better task control by the operating system in case (1)

On "my" new Windows-7 machine (4 dual core processors) I have obtained the following results

  • Distribution over 8 cores (nodes) : 343 s
  • Distribution over 4 cores               409 s (?!?!?!)
    These results seem to corroborate your claim "using more nodes will incur a higher percentage of administrative costs" (???)

 

On "my" old Windows-XP machine (2 dual core processors) I had obtained these results

  • Distribution over 4 cores (nodes) : 504 s
  • Distribution over 2 cores               983 s
    The expected 1:2 ratio is realized here, suggesting a higher efficiency in task control (???)

 

So I keep thinking that something "is not going well" (more likely  with Windows-7)

Other point : now that I have 8 nodes avaliable to me, it is perhaps better to use Grid-Launch with a "master" node and to distribute the compuation over the remaining 7 ???
There are a lot of questions and posts here I need to look at : even the distribution of similar computations is not as simple as we think it is

Even if your answer is far from the luminous solution to which I was expecting to, it leads me to ask myself a lot of questions.

 I thank you for that

 

@Stephen Forrest 
for reminiding me the "What's New pages".
I am pleased to contribute to the improvement of Maple but I'm not a bug-buster and my "discovery" was completely fortuitous

Have a good day

@Stephen Forrest 


Huge thanks to you Stephen for this comprehensive explanation which, I'm sure, will be of particular interest to me

PS : Sorry for this rather long response time due to vacations

@Thomas Richard ... I believe I have discovered the source of the problem.

 

My function f depends on x and on many other parameters (the number of them is not known a priori) named `P.1`, `P.2`, ...
So this is a simple example that mimics what happens

f := (x, `P.1`) -> x*`P.1` ;

CodeGeneration[Matlab](f, output=string);

If I use more "conventional" names (here f:=(x,a) -> x*a) all goes perfectly well and Maple does no replacement at all.
As I am not familiar with Matlab, I simply guess that `P.1` is not an authorized syntax for the name of a Matlab variable ... so the need for a translation.

If I am right, please consider the question as over.

In any event, thank you for your answer

 

PS :  I thumb up for the disagreement

 

 

 

@Joe Riel  I have received your message loud and clear and it will be very useful for me.
Thanks a lot

@Kitonum  acer has provided an answer syntactically simpler than yours (no offfense here) which fits me just fine.

Your answer corresponds probably to the code I had expected for ... but as it often appears in Maple a simple workaround (see acer's reply) may exist.

Thanks again  for the work you did

@tomleslie 

Dear Tom,

no offence, but I think we should end this fruitless exchange before unnecessarily hurtful words shall be written.

I appreciate reading your many contributions on mapleprimes and this is what does matter.

As far as I am concerned I turn the page and it is fine.

Looking forward to hearing from you about other topics,

Respectfully.



PS : I have deleted my initial question

@tomleslie 
Dear Tom,
no offence, but  I think we could end this fruitless exchange to avoid that unnecessarily hurtful words will be written.
I appreciate the general quality of your contributions and this does matter.
I propose you to remove personaly the initial question.

Looking forward to hearing from you on other topics.

respectfully

@Joe Riel 
I have a question already discussed here (see "How to handle a very long Module ?"  / January 12 2007 boirac 104 )


To avoid problems with the Java environment when I develop a module with many procedures, I
use to proceed this way :

(Worksheet + Maple notation)


restart:

> proc1 := proc(...)
....
end proc:

> proc2 := proc(...)
....
end proc:
.
.
.
.
.

> MyModule := module():
option package:
export  proc1 := eval(:-proc1),
           proc2 := eval(:-proc2),
           .
           .
           .
           procn := eval(:-procn):
end module:


Is this a "good" way to proceed or do you recommend to write procedures in mpl files and use the
$include <....mpl> syntaxes ?

Thanks for your answer.

@tomleslie   but I'm not sure I was waiting this kind of advice from you.
Maybe I'm not so foolish than you make think ?

Have a good day

@tomleslie  Thank you for your answer Tom, but with all due respect I know perfectly that  Mapleprimes users, including me, are able to upload files with no problems.
And I've never suspected MaplePrimes to suffer of some disfunction on this topic.

By asking this question I hoped that someone else, who would have already encountered this kind of problem, could give me some "solution" to try to fix it (you are probably right : there is some barrier in my site security process)

My browser is very classical (Google, not even Chrome nor Firefox ... but I could do a test with this latter).
Trying to do the same operation in "similarlish" websites is a good suggestion from you.
I already know I can upload files in DropBox or in other cloud facilities

Thanks again

@mmcdara 

You are perfectly right, I made a mistake in copying the formula for S2.

Thanks for your correction.

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