gistfile1.txt

Hi,

After trying out GSLL, Clem, also FemLisp, Lisplab managed to get me
the functionality I needed with the least trouble.

I'm trying to get the connectivity of a graph (second smallest eigen value) from eigenvalues.

Given the fully connected 4x4 adjacency matrix:

#md(( 0.000      1.000      1.000      1.000    )
    ( 1.000      0.000      1.000      1.000    )
    ( 1.000      1.000      0.000      1.000    )
    ( 1.000      1.000      1.000      0.000    ))

I compute the diagonal matrix of the vector sum of the adjacency matrix and then
subtract the adjacency matrix from it to get the laplacian matrix.

I'm unable to call (lisplab:eigenvalues) on that matrix, despite being a #md matrix.
I can see that the function calls for LISPLAB::MATRIX-FOREIGN-DGE. However other functions
that call for the same type seem to work when called with #md, namely FFT1.

As a workaround, I'm using this call to get the eigenvalues:

(lisplab::dgeev (laplacian-matrix *adj-matrix* *diag-matrix*) nil nil) and I get:

(
#md(( 4.000    )
    (-1.1102d-16)
    ( 4.000    )
    ( 4.000    ))
 NIL NIL)

Is this appropriate?

I'm curious however about different results I get from Matlab.
I get the same results up until the call to 

>> eig(diag(sum(A)) - A)

which gives me

ans =

    0.0000
    4.0000
    4.0000
    4.0000

Any comment I can get on this would be awsome. Am I going about this right?
What might I be missing? 

Sorry about the lengthy email.

Thanks!

Am I missing something?

CL-USER> (type-of (lisplab:make-matrix-instance 'lisplab::matrix-foreign-dge '(4 4) 0))
LISPLAB::MATRIX-FOREIGN-DGE

CL-USER> (lisplab:eigenvalues (lisplab:make-matrix-instance 'lisplab::matrix-foreign-dge '(4 4) 0))

There is no next method for the generic function
  #<STANDARD-GENERIC-FUNCTION LISPLAB:EIGENVALUES (2)>
when called from method
  #<STANDARD-METHOD
    LISPLAB:EIGENVALUES (LISPLAB::MATRIX-FOREIGN-DGE)
    {1006532CF3}>
with arguments
  (
#md(#1=( 0.000    #2=  0.000    #2# 0.000    #2# 0.000    #3=)
    #1# 0.000    #2# 0.000    #2# 0.000    #2# 0.000    #3#
    #1# 0.000    #2# 0.000    #2# 0.000    #2# 0.000    #3#
    #1# 0.000    #2# 0.000    #2# 0.000    #2# 0.000    #3#)).
   [Condition of type SIMPLE-ERROR]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [*ABORT] Return to SLIME's top level.
 2: [REMOVE-FD-HANDLER] Remove #<SB-IMPL::HANDLER INPUT on descriptor 8: #<CLOSURE (LABELS SWANK-BACKEND::RUN :IN SWANK-BACKEND:ADD-FD-HANDLER) {100301C57B}>>
 3: [ABORT] Exit debugger, returning to top level.

Backtrace:
  0: ((SB-PCL::FAST-METHOD NO-NEXT-METHOD (STANDARD-GENERIC-FUNCTION STANDARD-METHOD)) ..)
  1: (SB-INT:SIMPLE-EVAL-IN-LEXENV (LISPLAB:EIGENVALUES (LISPLAB:MAKE-MATRIX-INSTANCE 'LISPLAB::MATRIX-FOREIGN-DGE '(4 4) 0)) #<NULL-LEXENV>)
  2: (EVAL (LISPLAB:EIGENVALUES (LISPLAB:MAKE-MATRIX-INSTANCE 'LISPLAB::MATRIX-FOREIGN-DGE '(4 4) 0)))
  3: (SWANK::EVAL-REGION "(lisplab:eigenvalues (lisplab:make-matrix-instance 'lisplab::matrix-foreign-dge '(4 4) 0))\n")
  4: ((LAMBDA () :IN SWANK::REPL-EVAL))
...