gf_spmat

Purpose

General constructor for getfem sparse matrices (i.e. sparse matrices which are stored in the getfem workspace, not the Matlab sparse matrices). Note however that gf_spmat_get, gf_linsolve and gf_precond can be used directly with Matlab sparse matrices.

Synopsis

M=gf_spmat('empty', int m [, int n])
M=gf_spmat('identity', int n)
M=gf_spmat('copy', spmat K [,ivec I [, ivec J]])
M=gf_spmat('mult',  spmat A,  spmat B)
M=gf_spmat('add', spmat A, spmat B)
M=gf_spmat('harwell-boeing', string filename)M=gf_spmat('matrix-market', string filename)

Description

The sparse matrix can be stored as CSC (compressed column sparse), which is the format used by Matlab, or they can be stored as WSC (internal format to getfem). The CSC matrices are not writable (it would be very inefficient), but they are optimized for multiplication with vectors, and memory usage. The WSC are writable, they are very fast with respect to random read/write operation. However their memory overhead is higher than CSC matrices, and they are a little bit slower for matrix-vector multiplications. By default, all newly created matrices are build as WSC matrices. This can be changed later with gf_spmat_set(sm,'to_csc'), or may be changed automatically by getfem (for example gf_linsolve() converts the matrices to CSC). The matrices may store REAL or COMPLEX values.

M=gf_spmat('empty', m, n) : create a new empty (i.e. full of zeros) sparse matrix, of dimensions m×n. If n is ommited, the matrix dimension is m×m.

M=gf_spmat('identity', n) : create a n×n identity matrix.

M=gf_spmat('copy', K [, I [, J]]) : duplicate a matrix K (which might be a gfSpmat or a native matlab sparse matrix). If I and/or J are given, the matrix M will be a submatrix of K. For example M = gf_spmat('copy', sprand(50,50,.1), 1:40, [6 7 8 3 10]) will return a 40x5 matrix.

M=gf_spmat('mult', A, B) : create a sparse matrix as the product of the sparse matrices A and B. It requires that A and B be both real or both complex, you may have to use gf_spmat_set(..,'to_complex')

M=gf_spmat('add', @spmat A, @spmat B) : create a sparse matrix as the sum of the sparse matrices A and B. Adding a real matrix with a complex matrix is possible.

M=gf_spmat('hb', filename) or gf_spmat('harwell-boeing', filename) read a sparse matrix from an Harwell-Boeing file.

M=gf_spmat('mm', filename) or gf_spmat('matrix-market', filename) read a sparse matrix from a Matrix-Market file.

See Also

gf_util