Sorry I didn't reply earlier.
Implementing an is_symmetric function for matrices sounds like a good idea.
But I think it should go in the base class: something like
def is_symmetric(self):
if self.ncols != self.nrows:
return False
cdef int i, j:
for i from 1 <= i < self.nrows:
for j from 0 <= j < i:
if self[i][j] != self[j][i]:
return False
return True
One can override this in a subclass if desired: if there's some special,
faster way to test for symmetry. I can't think of a better method in
general than this.
David
On 6/28/07, Justin C. Walker <[EMAIL PROTECTED]> wrote:
>
>
> Hi,
>
> I ran into a glitch, using QuaternionAlgebraWithGramMatrix(field,
> matrix):
> - the code verifies that the second argument is a matrix
> with "isinstance(Matrix)", which blows up because 'Matrix'
> is not known. A simple 'import' fixes that.
> - then the code blows up because "is_symmetric" is not an
> attribute of the second arg.
>
> Fixing this is a bit more involved. First, it appears that
> "is_symmetric" is supposed to be a boolean, presumably defined when
> the matrix is created. There are other versions, scattered through
> the code, of a function, but nothing in the Matrix class itself.
>
> Seems to me that this should be a function, not a variable (matrices
> aren't immutable), and defined in the class.
>
> My question: is it reasonable to implement is_symmetric() in the
> class definition?
>
> Some more questions:
>
> The Matrix class is a pyrex module, and checking for equality is then
> probably best done by subclasses. Is that correct? Is it reasonable
> to have a generic "it can be done in Pyrex" version that must be
> overridden by a subclass if that assumption is false?
>
> Is there a better (i.e., faster) way than checking for a square
> matrix and making n(n-1)/2 comparisons?
>
> Is the Matrix class undergoing reconstruction, so the above are all
> irrelevant? :-}
>
> Thanks!
>
> Justin
>
> --
> Justin C. Walker, Curmudgeon at Large
> Institute for the Absorption of Federal Funds
> -----------
> If it weren't for carbon-14, I wouldn't date at all.
> -----------
>
>
>
> >
>
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