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Hi everyone,

For my first question, I am looking for some help about the following. I have the opportunity to run a worksheet in parallel on a cluster of sixteen workstations, each one endowed with twelve CPUs, through the GRID Computing Toolbox. However, I have troubles concerning how to do that.

I join the worksheet at issue: The aim is to run large-scale numerical simulations of a dynamic system, depending on the values given to the initial conditions and to the parameters. The worksheet is organized in four execution groups:

  1. The required packages (combinat and LinearAlgebra).
  2. Calibration of the parameters and initial conditions.
  3. The system, which is embedded into a procedure called SIM.
  4. The activation of SIM, whose outputs are nine .mla files, each one being made of a real-number matrix.

The truth is, I do not clearly see how to modify the worksheet with some elements of the GRID package. Besides, the cluster operates under HTCondor so that running the worksheet requires beforehand the creation of a .sub file. This should be done in consistency with the aforesaid modification.

Any help is welcome, thanks a lot.



The following problem works if i = j.   I need help to fix this problem for i ≠ j.  Thanks

A := [1, 2, 3, 4, 5];

B := [a, b, c, d];

seq([A[i], B[j]], i = 1 .. 5, j = 1 .. 4);
Error, invalid input: seq expects its 3rd argument, step, to be of type numeric, but received j = 1 .. 4

Hi guys. I am new to the Maple environment.

Was trying to do some GR calculations when the following problem arose.

restart; with(Physics);
Setup(coordinates = (X = [t, r, theta, phi]), metric = -A(r)^2*(dt^2)+B(r)^2*(dr^2)+r^2*(dtheta^2)+r^2*(sin(theta)^2)*(dphi^2));
Setup(math = true);
g_[line_element]; g_[];
Christoffel[nonzero]; Christoffel[`~mu`, alpha, beta, nonzero];
D_[mu](g_[`~alpha`, `~beta`]);
expand(D_[2](g_[`~2`, `~beta`]));
D_[2](g_[`~2`, `~2`]);

The output for the last 3 lines are:

1. 0

2. Expansion in terms of Christoffel symbols (which does equal zero on substituting various values)

3. Non-zero value.

Obviously the answer must be zero for all cases (covariant derivative of metric). So what have I missed/misunderstood here?



What is the Maple command to simplify  -x^(a)+x^n  to zero under the assumption that a=n?

I have attempted the following command

simplify(-x^(a)+x^n) assuming a=n;

However, it did not produce zero. The following command however produces zero


 How to do this operation using assumptions. How to inform Maple to assume that a=n.


Hi MaplePrimes,


I try again to ask about a procedure I wrote.  Maybee someone can spot my error.

Here is the broken procedure - 

cs := proc (n::integer)::integer;
local count;
description "Find the number of steps for a Collatz sequence to reach 1";
count := 1;
while 1 < n do
if `mod`(n, 2) = 0 then n := (1/2)*n else n := 3*n+1 end if;
count := count+1
end do;
return count
end proc




im a huge fan of using the is boolean function maple has in my studies, and in as much as the CAS is a million times smarter than me, i just wanted to show an example of a situation where i am reluctant to use this feature. (see the uploaded worksheet)


perhaps someone with more  programming ability/experience than me can explain how it works, as so i can have a means of knowing whether or not it is appropriate to use in each

how are iterated functions represented in maple? as in f(f(f(x))) is f^3(x)(x)  in conventional notation where by the reader knows it is refering to the iteration conducted 3 times on the argument x, but what does maple use to differentiate between iteration ,exponentiation and differentiation?


can I get values from combobox?

for exemple: if I select "X" in combobox, it returns me "a:=1".

But, I'd like to put this comand inside the combobox and dont in the worksheet..


thanks a lot

Can Maple determine the value of DthetaZero such that the solution to the ODE, for some specific value of t, simultaneously provides the two values theta(t)=Pi and diff(theta(t),t)=0?

sol:=dsolve({4*sin(theta(t))*cos(theta(t))-9.8100*sin(theta(t))-(diff(theta(t), t, t)) = 0, theta(0) = 2*Pi*(1/3), D(theta)(0) = DthetaZero}, numeric)

odeplot(sol,[t,theta(t),diff(theta(t),t)],t=0..5) for trial values of DthetaZero shows that the desired value is

1.0340*Pi <DthetaZero<1.0345*Pi.


how can I find equilibria points of nonlineay system?





I modelled a telecamera and line follower sensors in Maple in order to calculate the "error" for my PID controller. Know i would like to share this information with the PID in MapleSim but I have no idea how to do it. Is there a way to import maple libraries into MapleSim?





I'm trying to export a plot using the open maple api but it looks like open maple API doesnt support certain specific features.


Eg. "Export(\"images\\\result1.gif\", plot(sin(x), title = \"The sine function\", thickness = 3, gridlines=true));"

Above works fine when executing in actual maple application (i.e. correctly exports with gridlines) however doing the same via open maple api it does export the chart but not the specified gridlines.


Had the same issue when setting axis options to show log instead of linear. 


Did anyone else get this? Is this a known issue with open maple api? Is there workaround available?




I know that whattype() is used to find the basic data type of an expression. Unfortunately that information is rarely useful. How can I dig down deeper and get Maple to tell me more about the expression?

I read somewhere that there is a properties() procedure that does that but I cannot find that procedure.


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