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Hi,

When I execute the command

series(exp(x),x)

and then refer to the equation in a new execution group using a equation label (CTRL-L on Windows), the equation is shown in Maple 18, but in Maple 2015 I get an error message: 'Error, missing operator or ';'. Using the % instead does work for both versions.

Is this intended behaviour or a bug in Maple 2015?

Thanks,

Bart

in LinearAlgebra Eigenvectors calculation.

Maple 2015 Error

 

 

So the above output startled me.  I have used the Maple Linear Algebra Eigenvalues, Eigenvectors commands many times with no problem.  Can any one explain to me what is going on.  The program correctly calculates the eigenvalues for the matrix which are all distinct for a real symmetric matrix, and thus should have three distinct non-zero eigenvectors, yet the eigenvectore command returns only zeros for the eigenvectors.  I calculated an eigenvector by hand corresponding to the eigenvalue of 1 and obtained (1, -sqrt(2)/sqrt(3), -1/sqrt(3).

 

So this is either a serious bug or I am going completely insane. 

Found a strange behaviour in Mapke 2015 of the sqrt-function after loading the GRTensor package:

the square-root of a non-square integer, e.g. sqrt(5), does not terminate. 5^(1/2) instead works fine.

Can be reproduced with Maple 18, but not with Maple 11.

I consider this a serious bug, as it makes any expressions containing such roots useless.

As it worked with Maple 11 I am inclined to see it as your fault.

 

In the running of an example I faced to computation of radical ideal of the following ideal:

<-c*m*u+d*c*n+m*b*v+m*c*t>

 

I used from Radical command in PolynomialIdeals package. But I dno't now why it's computation is very hard and Time-consuming?

What I have to do? I think there is a bug, since this ideal is simple, apparently.

In Maple 2015.1 we have

restart;

solve([sin(2*x)/cos(x+3*Pi/2)=1,  x>-4*Pi, x<-5*Pi/2], x, allsolutions, explicit);

solve([sin(2*x)/cos(x+3*Pi/2)=1, x>0, x<2*Pi], x, allsolutions, explicit);

 

 

In the first example, the error message is not clear (actually there exists a unique root  x=-11*Pi/3), in the second example, one root  (x=5*Pi/3) is lost.

 

Has anyone tried to run the following in Maple command-line mode (i.e. in terminal window, type "maple" to start it without the graphic interface),

"

expr1:=t1+t2+t3+t4+t5+t6+t7+t8+t9+t10+t11+t12+t13+t14+t15+t16+t17+t18+t19+t20+t21+t22+t0-t0+t23;
expr2:=t1+t2+t3+t4+t5+t6+t7+t8+t9+t10+t11+t12+t13+t14+t15+t16+t17+t18+t19+t20+t21+t22+t0-t0+t23;
print(expr1-expr2);

"

Surprisingly, I didn't get "0" with my Maple 17 (under Linux platform) or 18 (under Mac OSX platform). Can anyone help me confirm this?

Hi, 

     I'm trying to solve this PDE, and Maple 2015 gives me a solution quickly. I can test the solution with pdetest() and this verifies that it works. However, when I try to verify this myself I don't get zero. Is there some trick pdetest() is using to that I am missing? Or is pdetest() wrong in this case?

 

restart;

eq := I*exp(-(2*I)*k*t)*k*sin(theta)*r^2*cos(theta)^3+4*exp(-(2*I)*k*t)*r*cos(theta)^3+2*(diff(Vr(t, r, theta), theta, theta))*cos(theta)*exp(-I*k*(sin(theta)*r+t))-6*(diff(Vr(t, r, theta), theta))*sin(theta)*exp(-I*k*(sin(theta)*r+t))-4*Vr(t, r, theta)*cos(theta)*exp(-I*k*(sin(theta)*r+t))-4*exp(-(2*I)*k*t)*r*cos(theta);

I*exp(-(2*I)*k*t)*k*sin(theta)*r^2*cos(theta)^3+4*exp(-(2*I)*k*t)*r*cos(theta)^3+2*(diff(diff(Vr(t, r, theta), theta), theta))*cos(theta)*exp(-I*k*(sin(theta)*r+t))-6*(diff(Vr(t, r, theta), theta))*sin(theta)*exp(-I*k*(sin(theta)*r+t))-4*Vr(t, r, theta)*cos(theta)*exp(-I*k*(sin(theta)*r+t))-4*exp(-(2*I)*k*t)*r*cos(theta)

(1)

sol := pdsolve(eq);

Vt(t, r, theta) = _F2(t, r)/cos(theta)^2+sin(theta)*_F1(t, r)/cos(theta)^2-((1/2)*I)*(cos(theta)^2*k^2*r^2-2)*exp(I*(sin(theta)*r-t)*k)/(k^3*r^2*cos(theta)^2)

(2)

pdetest(sol, eq);

0

(3)

eq2 := eval(eq, Vr(t,r,theta) = rhs(sol)):
eq2 := simplify(%);

-((1/2)*I)*exp(-(2*I)*k*t)*k*r^2*cos(theta)^3+2*exp(-(2*I)*k*t)*r*sin(theta)*cos(theta)-3*(diff(Vt(t, r, theta), theta))*sin(theta)*exp(-I*k*(sin(theta)*r+t))-2*Vt(t, r, theta)*cos(theta)*exp(-I*k*(sin(theta)*r+t))+(diff(diff(Vt(t, r, theta), theta), theta))*cos(theta)*exp(-I*k*(sin(theta)*r+t))

(4)

evalb(eq2 = 0);

false

(5)

 

 

 

Download PDESolving.mw

I think that I found a bug in Maple! Please run the following command:

I need the Generators of above Ideal. What is your idea?!

Hi, 

     I was just curious about the difference between defining tensors as arrays/matricies/TensorArrays vs defining them as algebraic symbols. I found that defining them as an expression lead to the wrong answer, and I was forced to define a tensor (LKh) as an array. I've attached a worksheet demonstrating my problem.

I apologize for the amount of tensors needed to find this problem, but it is the only one I have reproduced the issue. I basically define the metric
Metric = g_
auxillary tensor = h
Killing vector = K
LieDerivative of h, wrt K = LKh (not a tensor array)
LieDerivative of h, wrt K = LKh2 (tensor array)
Then I compare two expressions, rho1 and rho2 computed from LKh and LKh2 and they disagree. 


MapleQuestion.mw

Thanks!

Hi, 

     I'm computing a simple covariant derivative of a tensor field W[a,b] in 3 spacetime dimensions. Unfortuntly, my result in Maple 2015 is disagreeing with those obtained in GRTensorII. I think this could be a bug in D_.

Looking at the first result, W[r t ; t] = mu/r in GRTensor II  but D_[t] W[r t] = -mu/r*(cos(theta)^2 - 2). Some ones are correct (diagonals), and some are off by a factor of 2. Some are completely off though.

ErrorsInD.mw


Thanks,

Hi,

     I was wondering if there is an easy way to define another set of indices in the Physics package. For example, usually greek indices are for all 4 spacetime dimensions. Using Setup(spaceindices = lowercaselatin), we can define 3 of those as space indices. I was hoping there is a more general command, so that I could use only 2 indices as "space indices". For example, X[i] would run over x,y while X[mu] would run over t, z. Is there such a command in the Physics package, or a simple way to implement this personally?

Second thing. I was playing with SumOverRepeatedIndices on an expression that contained both space indices and spacetime indices. Usually this seems to work, but in my attached example it does not. I tried the same thing with just spacetime indices in Maple 18 (newest Physics update) and it gave the same error.


Any help appreciated,

PhysicsBug.mw

When solving a simple assignment problem in Maple 2015.1 the bug occurs:

 

In Maple 2012 there are no problems:

A := Matrix([[1, 7, 1, 3], [1, 6, 4, 6], [17, 1, 5, 1], [1, 6, 10, 4]]):

n:=4:

z:=add(add(A[i,j]*x[i,j], j=1..n), i=1..n):

restr:={seq(add(x[i,j], i=1..n)=1, j=1..n),seq(add(x[i,j], j=1..n)=1, i=1..n)};

sol:=Optimization[LPSolve](z, restr, assume=binary); 

 

 

In Maple 2015, on windows 8.1 64-bit the command
series(2*x*(x-y)/y, y = 0, 3);
gives

which is incorrect. The answer is


You can notice the minus sign in front the the -2x is incorrectly typeset, which makes me wonder if it's a bug in the typsetting program and not series itself.

Please fix asap

Hi all,

 

I think the developers should pay attention to this problem.

 

This simple expression with Threads:-Map executed perfectly on my machine with 8-threaded CPU and 16 GB RAM:

Threads:-Map(proc (i) options operator, arrow; ln(i)/2. end proc, [`$`(1 .. 10^7)]);

 

But the similar expression with Grid:-Map never be executed:

Grid:-Map(proc (i) options operator, arrow; ln(i)/2. end proc, [`$`(1 .. 10^7)]);

Maple or freezed, or crashed every time. Although the consuming of memory is not reached even 50%.

 

The similar problem exist for Grid:-Seq too. With `$`(1 .. 3*10^6) Grid:-Map and Grid:-Seq executed normally. With `$`(1 .. 5*10^6) - 50/50. But not with `$`(1 .. 10^7).

 

Is this a real bug of Grid:-Map and Grid:-Seq ?

Or is exist a way to fix this problem?

 

Thanks.

 

Updated:

I got a new error behavior of Grid:-Map in this case instead crash or freeze:

Grid:-Launch(numnodes = 8);

st := time[real](); Grid:-Map(proc (i) options operator, arrow; ln(i)/2. end proc, [`$`(1 .. 10^7)]);

time[real]()-st;

print(`output redirected...`); # input placeholder

`System error, `, "bad id"
2267.482

 

I hope this helps developers to fix this bug.

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