Maple Questions and Posts

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I have a Maple code which generates a matrix, saves it to a .txt file and this is then read in to a C++ program. I have hit a snag with these matrices, in that they are generating absolutely enourmous .txt files. I need to get to a 5000*5000 matrix yet a 200*200 is generating a 100MB file.

The matrix elements contain a lot of algebraic terms which I would like to keep general as these are defined in the C++ code. They also contain hypergeometric functions which in the example below I have left unsimplified (although they are simplified before reaching C++). I have tried various operations/combinations to simplify, but the file sizes still come out very large.

From previous experience expanding the expressions and then simplifying allows Maple to "do more" with it, but it does not seem to work in this instance. I have tried map(options,expr), simplify(expr,options), combine(expr,options), convert (expr,options) etc... The script attached only contains a small example 10*10 matrix on its own without the code which generates it due to the size of the code. What is the best way to simplify these matrices to generate the smallest .txt file?

Large_Matrix.mw

Any help is appreciated.


-Yeti
 

I am looking for a numerical solver for a parabolic PDE (up to 2nd order derivatives but no mixed ones) on the spatio-temporal domain [X x Y x T], either as an external package or as MAPLE code.  

I have coded the method of lines on the domain [X x T] and indeed also used pdsolve as a check for that case. However, pdsolve (numerical) cannot solve the PDEs on the domain [X x Y x T].  The run times and memory requirements for the latter case would of course be significantly greater.  

I am about to code up the method of lines (in MAPLE) on the domain [X x Y x T], but am wondering whether there exist external FORTRAN or C code packages that would be faster if called up in MAPLE and whose results would then be post-pocessed in MAPLE.

Does anyone have any suggestions?

MRB

Hello,

when trying to solve my equation I always get this error-message:

Error, (in DEtools/convertsys) invalid input: degree expects 1 or 2 arguments, but received 3

To solve, I use this one:

Anfangsbed := phi(0) = 0,  D(phi)(0) = 10;

Einst :=             range = 0..10,            #Integrationsgrenzen
                     relerr = 1e-3,            #Toleranz zur Bestimmung der Integrationsschrittweite
                     optimize = true,          #Optimierung der DGL
                     maxfun = 0,               #Anzahl der Integrationsschritte -- 0 = keine Obergrenze
                     output = operator,        #Lösungsfunktionausgabe: damit Definition als Funktion möglich 
                     stiff = true:

 

Lösung_Bewgl := dsolve({Bewegungsgl_mit_Para, Anfangsbed}, numeric, Einst);

The equation to solve is this one: http://imgur.com/a/SFxI8

What am I doing wrong?

Edit:

This is the worksheet, problem is the last point.

WS.mw

hello,

I am trying to solve a set of equations using solve but it didn't get me any answer !

> eq1 := x[1]-x[2] = 0;
> eq2 := -x[1]+2*x[2]-x[3] = 0;
> eq3 := -x[2]+2*x[3]-x[4] = 0;
> eq4 := -x[3]+x[4]-t = 0;
> solve({eq1, eq2, eq3, eq4}, {x[1], x[2], x[3], x[4]});

there is no error massage or anything.

any help?

thank you,

Mahdi

 

Hi,

Please help me to solve numerically and visualise the following time-delayed integro-differential equation (see also the file attached)

diff(x(t), t$2) = .8/(x(t)^3*exp((2*0.1e-1)*(int(1/x(t), t = 0 .. t-tau))))-1/x(t)^2 , 

with the initial conditions x(0) = 1, (D(x))(0) = 0, and tau=0.1 (variable parameter).

The expected solution is an oscillatory function.

Thanks for your time and advice!

IDE.mw

 

hi--how i can solve following equation?

thanks

 

Eq.mw


Maple Worksheet - Error

Failed to load the worksheet /maplenet/convert/Eq.mw .
 

Download Eq.mw

 

I've implemented the optimal taxation model proposed in this paper using Maple.

But it never stops running and get stuck in the last line for integral computation. Any idea of what's wrong with that?

This is the last line:

Here is the full code.

How to find infinitesimals of a system of pdes? I can find out for a single pde but not able able to solve for system of pdes with several dependent and independent variables. Can anyone please provide me the code for that or give some clue. Thanks

I have a task. Draw a cylinder of a certain diameter and length. And there is a table of values with points inside this cylinder. How to display the points inside the cylinder (the table of values has 3 parameters - angle (sin (a)), radius (R), length?

I am trying to do fsolve in a range (-7..14), however, it gives no solution.

But when I solve the same equations with solve (after removing all the Imaginary solutions), I get two results, one of them is in the range (-7..14). 

I even expanded the range of fsolve, say (-10..20), but still got no solution...

This is just getting weirder and weirder. Attached kindly find the Maple file, note that the first solve takes about 1 minute (on my laptop: CPU i7 + MEM 8G + SSD).

fsolve_In_Range.mw

Hello,

i have a Problem with maple. I have written this simple procedure

myPi_1:=proc(r)
local i,l;
l:=0;
for i from 1 to floor(r) do
    if isprime(i) and (i mod 4 = 1) then
        l:=l+1;
    end if;
end do;
return l;
end proc:    

 

When i use it like this 

k := myPi_1(80);

it works

But when i triy to plot it

plot(myPi_1(t), t = 0 .. 500, numpoints = 500, thickness = 2, color = black);

i get this message
Warning, expecting only range variable t in expression myPi_1(t) to be plotted but found name myPi_1

And no plot

Thank you for any Help

 

 

 

 

I want to calculate the following integral numerically with required precision.

First, the functions are defined:

G1:=-0.9445379894;
f:= (x) -> 0.9/abs(x-0.4)^(1/3)+0.1/abs(x-0.6)^(1/2);
U1 := unapply(-exp(-x)*(evalf(Int(f(t)*exp(t), t = 0 .. x))+G1)/2-exp(x)*(evalf(Int(f(t)*exp(-t), t = 0 .. x))+G1)/2, x);
U:= unapply(-exp(x)/2*(evalf(Int(f(t)*exp(-t),t=0..x))+G1)+exp(-x)/2*(evalf(Int(f(t)*exp(t),t=0..x))+G1), x);

Next, I calculate the integral in numerical form:

evalf(Int(U1(x)^2+U(x)^2-2*f(x)*U(x), x=0..1, digits=4, method = _Gquad));

If I specify digits=4, Maple return the answer -0.4291

If I use digits=5 or larger, Maple return someting like this

Is it possible to increase precision of calculation?


 

 


Please help me on this :

restart; with(PDETools), with(plots)

n := .3:

Eq1 := (1-n)*(diff(f(x, y), `$`(y, 3)))+(1+x*cot(x))*f(x, y)*(diff(f(x, y), `$`(y, 2)))-(diff(f(x, y), y))/Da+(diff(f(x, y), y))^2+n*We*(diff(f(x, y), `$`(y, 2)))*(diff(f(x, y), `$`(y, 3)))+sin(x)*(theta(x, y)+phi(x, y))/x = x*((diff(f(x, y), y))*(diff(f(x, y), y, x))+(diff(f(x, y), `$`(y, 2)))*(diff(f(x, y), x))):

Eq2 := (diff(theta(x, y), `$`(y, 2)))/Pr+Nt*(diff(theta(x, y), y))^2/Pr+Nb*(diff(phi(x, y), y))*(diff(theta(x, y), y))/Pr+(1+x*cot(x))*f(x, y)*(diff(theta(x, y), y)) = x*((diff(f(x, y), y))*(diff(theta(x, y), x))+(diff(theta(x, y), y))*(diff(f(x, y), x))):

Eq3 := Nb*(diff(phi(x, y), `$`(y, 2)))/(tau*Pr)+Nt*(diff(theta(x, y), `$`(y, 2)))/(tau*Pr)+(1+x*cot(x))*f(x, y)*(diff(phi(x, y), y)) = x*((diff(f(x, y), y))*(diff(phi(x, y), x))+(diff(phi(x, y), y))*(diff(f(x, y), x))):

ValWe := [0, 5, 10]:

bcs := {Nb*(D[2](phi))(x, 0)+Nt*(D[2](theta))(x, 0) = 0, f(0, y) = ((1/12)*y)^2*(6-8*((1/12)*y)+3*((1/12)*y)^2), f(x, 0) = 0, phi(0, y) = -.5*y, phi(x, 12) = 0, theta(0, y) = (1-(1/12)*y)^2, theta(x, 0) = 1, theta(x, 12) = 0, (D[2](f))(x, 0) = Da^(1/2)*(D[2, 2](f))(x, 0)+Da*(D[2, 2, 2](f))(x, 0), (D[2](f))(x, 12) = 0}:

pdsys := {Eq1, Eq2, Eq3}:

p1 := ans[1]:-plot(theta(x, y), x = 1, color = blue):

plots[display]({p1, p2, p3})

 

``


 

Download untitle_2_(1).mw


 

S[1] := .51-.67030*t+.4644645000*t^2-.2542824350*t^3+.1337509523*t^4

S[2] := .29-.37330*t+.2539795000*t^2-.1337383850*t^3+0.6737783824e-1*t^4

S[3] := 0.6e-1-0.6280e-1*t+0.3392700000e-1*t^2-0.7715060000e-2*t^3-0.2012235525e-2*t^4

V[1] := .14+.18480*t-.3482570000*t^2+.2511604200*t^3-.1217312553*t^4

V[2] := .37-0.9810e-1*t-.1638085000*t^2+.1665366350*t^3-0.8847577175e-1*t^4

V[3] := .59-.36870*t+0.126205000e-1*t^2+0.8559214500e-1*t^3-0.5666617885e-1*t^4

Iota[1] := 0.8e-1-.1000*t+0.6280600000e-1*t^2-0.2652762667e-1*t^3+0.8545290360e-2*t^4:

E[1] := 0.2040e-2*t-0.3584600000e-2*t^2+0.3405427000e-2*t^3-0.2270144502e-2*t^4:

R[n] := 0.5e-1+0.715e-1*t-0.1627750000e-1*t^2-0.3034627500e-1*t^3+0.2606816769e-1*t^4:

> Pls let someone help me plot S1;S2,S3 using Maple.

``


 

Download FINAL_RESULT.mw

To select a piece from a list, for example:

lst:=[1,2,3,4,5,6]

I want to get the list piece from second place to fifth place: [2,3,4,5].

Is there a function?

Thanks

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