ASA006
Cholesky Factor of a Positive Definite Symmetric Matrix

ASA006 is a FORTRAN90 library which computes the Cholesky factor of a positive definite symmetric matrix.

ASA006 is Applied Statistics Algorithm 6.

If A is a positive definite symmetric matrix, then there is an upper triangular matrix U with the property that

A = U' * U

The algorithm implemented here uses a compressed storage for both the matrix A and the factor U. This saves some storage, but can make computations a little awkward.

Languages:

ASA006 is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

ASA007, a FORTRAN90 library which computes the inverse of a symmetric positive definite matrix, and uses a version of ASA006 for for Cholesky factorization.

ASA047, a FORTRAN90 library which implements the Nelder-Mead minimization algorithm, and uses a version of ASA006 for Cholesky factorization.

LAPACK_EXAMPLES, a FORTRAN90 program which demonstrates the use of the LAPACK linear algebra library.

LINPACK, a FORTRAN90 library which includes routines for Cholesky factorization.

PPPACK, a FORTRAN90 library which computes piecewise polynomial functions, including cubic splines.

TOEPLITZ_CHOLESKY, a FORTRAN90 library which computes the Cholesky factorization of a nonnegative definite symmetric Toeplitz matrix.

Reference:

1. PR Freeman,
   Remark AS R44: A Remark on AS 6 and AS7: Triangular decomposition of a symmetric matrix and Inversion of a positive semi-definite symmetric matrix,
   Applied Statistics,
   Volume 31, Number 3, 1982, pages 336-339.
2. Michael Healy,
   Algorithm AS 6: Triangular decomposition of a symmetric matrix,
   Applied Statistics,
   Volume 17, Number 2, 1968, pages 195-197.

Source Code:

• asa006.f90, the source code.

Examples and Tests:

• asa006_test.f90, a sample calling program.
• asa006_test.txt, the output file.

List of Routines:

• CHOLESKY computes the Cholesky factorization of a PDS matrix.
• SUBCHL computes the Cholesky factorization of a (subset of a ) PDS matrix.
• TIMESTAMP prints out the current YMDHMS date as a timestamp.

You can go up one level to the FORTRAN90 source codes.