read very large integer matrix from file

[John Matrix]

Hi,

I'd like to read a very large integer dense square matrix into sage
from a file, in order to determine its rank. I could not find much
information on what format I should store the matrix in, and what
commands to use to read it. Any help would be appreciated.

Thanks!

[David Joyner]

I guess it depends on what "very large" means.
Do you know any Python? If so, one option is just
read in the file of entries then write a python/sage script
to create the matrix in Sage from that. I think large integer
matrices use linbox, which I think is easily capable of some
matrix computations whose row-dim and column-dim are in the
thousands (according to
http://www.sagemath.org/doc/ref/module-sage.matrix.matrix-integer-dense.html,
they must be <2^64-1 on a 64 bit machine).

[John Matrix]

Hi David and Minh,

Thanks for your comments!
@David
In the worst case, the matrix will have roughly 17000 rows and
columns. I could reduce it with some effort, but I'll first
try to figure out if it's worth it. I don't know Python very
well, but I could probably learn that much. Alternatively,
I'm now considering calling linbox directly from c++.

@Minh
Thant looks very helpful, except that the matrix must
first be generated by some other c++ application.
Is any format that the "load" command can handle
somewhere documented?

Thanks again,
John

[Fabio Tonti]

What about http://groups.google.com/group/sage-devel/browse_thread/thread/90ae1dcee213a9c7?pli=1 ?

Fabio

[John Matrix]

Thanks, Fabio, that seems to solve my problem indeed!