sand15

510 Reputation

10 Badges

4 years, 299 days

MaplePrimes Activity


These are questions asked by sand15

Hi everybody,

Maybe it's more a warning than a true question ?

I have written a rather heavy-duty code in Maple 2015. A few years ago I faced strong problems of increases in memory. After some investigations I found there came from a procedure P in which a loop realizes a few tenth of calls to  fsolve.
This same procedure  P was itself called a large number of times.

To try to  fix them I inserted a forget(fsolve, initialize=true) command after the fsolve command.
At the end this didn't prove to be very efficient and I decided to rewrite some part of the code in a more efficient way. Basically the  procedure  P is now called only a few times but its inner loop is executed about 200 hundred times.
This new version of the code no longer presents memory size problems, while being more efficient from a computational time point of view.

Today procedure  P still contains the forget(fsolve, initialize=true) command (I had forgotten to remove it)

Now I keep developping this same code under Maple 2018.
The Maple 2015 and Maple 2018 versions both return the same results, but the procedure  P runs in about 20 times the time it runs in Maple 2015 (40 seconds instead of 2)
This comes from the 200 forget(fsolve, initialize=true) calls which consumme about  38 seconds.

With Maple 2015 these same 200 calls to forget(fsolve, initialize=true) only consumme 0.5 second:


As a cure I remove the forget(fsolve, initialize=true) command, plain and simple.

But maybe this misadventure could reveal an unseen behaviour of Maple 2018 ?

 

Hi,

Here is a set of simple instructions to illustrate the first problem :

restart:
fichier := TheNameOfSomeFile:
writeto(fichier):
printf("Hello\n"):
writeto(termional):

When executed from Maple 2015 or Maple 2016, the content of TheNameOfSomeFile is

Hello

When executed from Maple 2018 it becomes

> printf("Hello\n"):
Hello
> writeto(terminal):

 

Using interface(echo=0) changes nothing to the result obtained with Maple 2018.

Has anyone ever encountered this problem?
How can I fix it?


Thanks in advance

Hi everybody,

Why f generates the error "... orthopoly is not a module or member"

f := proc(n)
   uses orthopoly;
   H(n,z);
end proc;

as g works correctly ?

g := proc(n)
   orthopoly:-H(n,z);
end proc;


Thanks in advance

Hi everybody,

I want to compare the performances of a set of codes that realize the same operation.
The worksheet I use is organized this way

restart:
Code1 := proc(...) ... end proc:
CodeTools[Usage](Code1(...))

restart:
Code2 := proc(...) ... end proc:
CodeTools[Usage](Code2(...))

and so on.

It appears that the execution of the whole worksheet doesn't always return the same values for the different indicators, which means that the ranking of the codes can be affected

To obtain more precise indicators I thought do do some statistics.
I then replace each bloc by :

restart:
CodeX := proc(...) ... end proc:  # here X stands for 1, 2, ...
N := "some positive integer"
for n from 1 to N do
   CodeTools[Usage](CodeX(...))
   "catch the values of the indicators"
end do:
"compute some statistics on the samples ot these indicator"

The problem is that Usage doesn't return any values but only does a printf.
I investigated two ways to circumvent this problem:

  1. - redirect the printings to file MyFile by using writeto(MyFile)
    - read MyFile
    - extract the numerical values of the indicators
    - compute the desired statistics
      It works well but it is far from being elegant
     
  2. - insert with(CodeTools) after the restart (within a separate block)
    - copy-paste the output of showstat(Usage) to define a new function, let's say MyUsage
    - insert at the correct place some lines like
             Tcpu := CodeTools:-FormatTime(result:-cputime)  (if my time of interest is the cpu time)
                          (this for all the indicators)
    - insert the line  [..., Tcpu, ...]; before the 'end proc' declaration;
      More elegant but it doesn't work
      I get the error   error (in T) DoUsage is not a command of the CodeTools package


Do you have some idea (beyond the first method above) of the way to catch the performance indicators that Usage computes ?

Thanks in advance


 

Hi,

 

I'm working on coding questions and I want to realize a particular addition (sometimes called "Nim addition")
Here is an example in base 3

Let A=11 and B=21 two numbers written inbase 10.
I want to realize the operation "A plus B" defined this way

  1. write A and B in base 3 : A -> a=102  and B -> b=210
  2. do c=a+b just as if a and b were numbers in base 10 : c=312
  3. compute all digits modulo 3 : 312 -> 012 = 12
  4. write this number in base 10 : 12 -> 5

Then 11 plus 21 = 5


In Maple"s syntax :

A := 11:
B := 21:
a := convert(A, base, 3):   # returns [1, 0, 2]
b := convert(B, base, 3):   # returns [0, 1, 2]


# the simplest thing I found to implement operation 2 and 3 above is :
# 1/ convert each list into polynomials (let's say pa and pb)
# 2/ set pc = pa+pb mod 3
# 3/ convert pc into a list
#
# Instead of coding something like pa := add(a[k]*x^(k-1), k=1..numelems(a)),
# I found more astute to use the gfun package

sa := gfun[listtoseries](a, x, 'ogf'):  # returns x^2+2+O(x^3)
sb := gfun[listtoseries](b, x, 'ogf'):  # returns 2*x^2+x+O(x^3)
pc := convert(sa, polynom)+convert(sb, polynom) mod 3; # returns x+2


Unfortunately I can't use now gfun[seriestolist](pc, 'revogf') for pc is obviously not a serie !
Reciprocally sc := sa+sb mod 3 doesn't return x+2+O(x^3)

Then I'm trapped here and I don't know how to go further
(of course I know how to proceed if I build directly the polynoms associated to a and b ... but it is far less elegant)

Does anyone have some idea ?

This problems raise the following question: how can we add tho series ?
For instance sa+sb returns (x^2+2+O(x^3))+(2*x^2+x+O(x^3)) without, apparently, no way to simplify this into  x+2+O(x^3)


Thanks in advance

4 5 6 7 8 9 10 Last Page 6 of 17