dge.cwp.lib

su 的源代码库

DGE - Double precision Gaussian Elimination matrix subroutines  adapted
	from LINPACK FORTRAN:

dgefa	Gaussian elimination to obtain the LU factorization of a matrix.
dgeco	Gaussian elimination to obtain the LU factorization and condition
		number of a matrix.
dgesl	Solve linear system Ax = b or A'x = b after LU factorization.

Function Prototypes:
void dgefa (double **a, int n, int *ipvt, int *info);
void dgeco (double **a, int n, int *ipvt, double *rcond, double *z);
void dgesl (double **a, int n, int *ipvt, double *b, int job);

dgfa:
Input:
a		matrix[n][n] to be factored (see notes below)
n		dimension of a

Output:
a		matrix[n][n] factored (see notes below)
ipvt		indices of pivot permutations (see notes below)
info		index of last zero pivot (or -1 if no zero pivots)

dgeco:
Input:
a		matrix[n][n] to be factored (see notes below)
n		dimension of a

Output:
a		matrix[n][n] factored (see notes below)
ipvt		indices of pivot permutations (see notes below)
rcond		reciprocal of condition number (see notes below)

Workspace:
z		array[n]

dgesl:
Input:
a		matrix[n][n] that has been LU factored (see notes below)
n		dimension of a
ipvt		indices of pivot permutations (see notes below)
b		right-hand-side vector[n]
job		=0 to solve Ax = b
		=1 to solve A'x = b

Output:
b		solution vector[n]

Notes:
These functions were adapted from LINPACK FORTRAN.  Because two-dimensional 
arrays cannot be declared with variable dimensions in C, the matrix a
is actually a pointer to an array of pointers to floats, as declared
above and used below.

Elements of a are stored as follows:
a[0][0]    a[1][0]    a[2][0]   ... a[n-1][0]
a[0][1]    a[1][1]    a[2][1]   ... a[n-1][1]
a[0][2]    a[1][2]    a[2][2]   ... a[n-1][2]
.                                       .
.             .                         .
.                        .              .
.                                       .
a[0][n-1]  a[1][n-1]  a[2][n-1] ... a[n-1][n-1]

Both the factored matrix a and the pivot indices ipvt are required
to solve linear systems of equations via dgesl.


dgeco:
Given the reciprocal of the condition number, rcond, and the double
epsilon, DBL_EPSILON, the number of significant decimal digits, nsdd,
in the solution of a linear system of equations may be estimated by:
	nsdd = (int)log10(rcond/DBL_EPSILON)

Author:  Dave Hale, Colorado School of Mines, 1989