Hello, everyone. I have some problem with multithreaded calculation. I just need calculate eigenvalues of matrix m at various parameters (and then export to a file) using advantages of the parallelizing. The following code works but in serial way

restart: with(LinearAlgebra):

m:=ImportMatrix(cat(currentdir(),"m.txt")): # here is matrix m.txt

step:=1:

prc:=proc(k1,k2)

local u,i,j,nmc:

u:=Matrix(ceil(1+(k2-k1)/step),5):

u[1,1]:=k1:

for i from 2 to op([1,1],u) do

u[i,1]:=u[i-1,1]+step:

end do:

for i from 1 to op([1,1],u) do

nmc:=sort(Eigenvalues(m*u[i,1], output='list')):

for j from 2 to op([1,2],u) do

u[i,j]:=nmc[j-1]:

end do:

writedata[APPEND](cat(currentdir(),"u_",convert(k2,string),".txt"), [convert(Re(u[i]),list)]):

print(u[i,1]);

end do:

return finished:

end proc:

with(Threads[Task]):

Start(ArrayTools[Concatenate], 2, Task=[prc,1,20], Task=[prc,20+step,40]);

quit:

The Start(ArrayTools[Concatenate], 2, Task=[prc,1,20], Task=[prc,20+step,40]) function makes two tasks of calculation at the parameter ranges of 1-20 and 21-40. But in this case Start spends twice more time than simply prc(20+step,40). How to realize a multithreaded calculation?

By the way I don't need to use a Concatenate function in Start but without any procedure Start doesn't work.

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How can to do it automatically? How to make that Maple knows a path from where Maple...

I have a matrix containing numeric values of functions. Each column corresponds to a function. The first element of each column is a name of a function and following elements are numeric values of this function.

For example:

t      a         b     c         d
0    0.5      38    0       0.9e-5

I solve one task. And as a result I receive a matrix and export it to a textfile. Then I receive another matrix and try to export it to the same textfile. Another words I need to add a last matrix to previous one but when I use exportmatrix command the last matrix overwrites previous one. What can do?

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