= Linear Algebra Package (LAPACK) =
[http://www.netlib.org/lapack/ LAPACK website] [http://www.netlib.org/lapack/lapackqref.ps List of subroutine]

Many routines for linear algebra. Typical name: XYYZZZ 

* X is precision 
* YY is type of matrix, 
  * e.g. GE (general), GB (general banded), GT (general tridiagonal)

* ZZZ is type of operation, 
  * e.g. SV (solve system), SVX (solve system expert), EV (eigenvalues, vectors), SVD (singularvalues, vectors)

==== General Dense Matrix System Solver ====
Ex: DGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO ) 

[[Image(Lapack_DGESV.png)]]

DGESV computes the solution to a real system of linear equations A * X = B, where A is an N-by-N matrix and X and B are N-by-NRHS matrices.  The LU decomposition with partial pivoting and row interchanges is used to factor A as A = P * L * U, where P is a permutation matrix, L is unit lower triangular, and U is upper triangular. The factored form of A is then used to solve the system of equations A * X = B.

[[Example Codes]]

==== Tri-diagonal Matrix System Solver ====
Ex:DGTSV( N, NRHS, DL, D, DU, B, LDB, INFO ) 

[[Image(Lapack_DGTSV.png)]]

DGTSV solves the equation A*X = B, where A is an n by n tridiagonal matrix, by Gaussian elimination with partial pivoting. Note that the equation A'*X = B may be solved by interchanging the order of the arguments DU and DL. 

[[Example Codes]]

==== Band Matrix System Solver ====
Ex: DGBSV( N, KL, KU, NRHS, AB, LDAB, IPIV, B, LDB, INFO ) 

[[Image(Lapack_DGBSV.png)]]

DGBSV computes the solution to a real system of linear equations A * X = B, where A is a band matrix of order N with KL subdiagonals and KU superdiagonals, and X and B are N-by-NRHS matrices. The LU decomposition with partial pivoting and row interchanges is used to factor A as A = L * U, where L is a product of permutation and unit lower triangular matrices with KL subdiagonals, and U is upper triangular with KL+KU superdiagonals. The factored form of A is then used to solve the system of equations A * X = B. 

[[Band Storage Scheme]]

[[Example Codes]]