Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.soft-sys.math.mathematica > #1742

Re: Another AppendTo replacement problem

Show all headers | View raw

The usual trick is to replace AppendTo[list,elem] with list {list,elem}.

The list is going to look like
{{{{{{elem1},elem2},elem3},elem4},elem5},elem6}

At the end you do a list = Flatten[list] and all is fine;

In this case your elements have a structure which has to be protected
against Flatten.
That can be done by replacing the list that contains them with a dummy
head (fl) like this:

Results= {Results, fl[M[[Nbase]], Total[Eigenvalues[matrA[[k]]]]]}

Right after the loop you Flatten and get rid of the head fl:

Results2 = Flatten[Results] /. fl -> List;

For NumBasis =10000 this version is twice as fast, but for NumBasis
=100,000 the speedup is already a factor of 20!

Cheers -- Sjoerd

Turn to StackOverflow for faster answers to Mathematica questions
http://stackoverflow.com/questions/tagged/mathematica



On Apr 16, 1:37 pm, Iv=E1n Lazaro <gamins...@gmail.com> wrote:
> I made a mistake in the code. Now it's fine. Sorry.
>
> NumBasis = 10000;
> q = matrA = ma = Table[0, {i, 2}];
> M = RandomComplex[{-1 - I, 1 + I}, {NumBasis, 2, 2}];
> M = Map[Orthogonalize, M];
> matr = RandomComplex[{-1 - I, 1 + I}, {2, 2}]
> Results = {};
>
> Do[{ma[[k]] =
>    KroneckerProduct[M[[Nbase, k]], Conjugate[M[[Nbase, k]]]];
>   matrA[[k]] = Chop[matr.ma[[k]]];
>   matrA[[k]] = matrA[[k]]/Tr[matrA[[k]].matrA[[k]]] // Chop;
>   If[k == 2,
>    AppendTo[
>     Results, {M[[Nbase]], Total[Eigenvalues[matrA[[k]]]]}]];
>   }, {Nbase, 1, NumBasis}, {k, 1, 2}];
>
> M = Sort[Results, #1[[2]] < #2[[2]] &][[1, 1]];
>
> Thanks in advance!

Back to comp.soft-sys.math.mathematica | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: Another AppendTo replacement problem Iván Lazaro <gaminster@gmail.com> - 2011-04-16 11:37 +0000
  Re: Another AppendTo replacement problem ADL <alberto.dilullo@tiscali.it> - 2011-04-17 11:51 +0000
  Re: Another AppendTo replacement problem "Sjoerd C. de Vries" <sjoerd.c.devries@gmail.com> - 2011-04-17 11:51 +0000
    Re: Another AppendTo replacement problem Ray Koopman <koopman@sfu.ca> - 2011-04-17 23:15 +0000

csiph-web