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## org.netlib.lapack
Class Dsptrf

    java.lang.Object
      org.netlib.lapack.Dsptrf

    public class Dsptrf

extends java.lang.Object

    Following is the description from the original
    Fortran source.  For each array argument, the Java
    version will include an integer offset parameter, so
    the arguments may not match the description exactly.
    Contact seymour@cs.utk.edu with any questions.

     *     ..
     *
     *  Purpose
     *  =======
     *
     *  DSPTRF computes the factorization of a real symmetric matrix A stored
     *  in packed format using the Bunch-Kaufman diagonal pivoting method:
     *
     *     A = U*D*U**T  or  A = L*D*L**T
     *
     *  where U (or L) is a product of permutation and unit upper (lower)
     *  triangular matrices, and D is symmetric and block diagonal with
     *  1-by-1 and 2-by-2 diagonal blocks.
     *
     *  Arguments
     *  =========
     *
     *  UPLO    (input) CHARACTER*1
     *          = 'U':  Upper triangle of A is stored;
     *          = 'L':  Lower triangle of A is stored.
     *
     *  N       (input) INTEGER
     *          The order of the matrix A.  N >= 0.
     *
     *  AP      (input/output) DOUBLE PRECISION array, dimension (N*(N+1)/2)

     *          On entry, the upper or lower triangle of the symmetric matrix
     *          A, packed columnwise in a linear array.  The j-th column of A
     *          is stored in the array AP as follows:
     *          if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
     *          if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
     *
     *          On exit, the block diagonal matrix D and the multipliers used
     *          to obtain the factor U or L, stored as a packed triangular
     *          matrix overwriting A (see below for further details).
     *
     *  IPIV    (output) INTEGER array, dimension (N)
     *          Details of the interchanges and the block structure of D.
     *          If IPIV(k) > 0, then rows and columns k and IPIV(k) were
     *          interchanged and D(k,k) is a 1-by-1 diagonal block.
     *          If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and
     *          columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k)
     *          is a 2-by-2 diagonal block.  If UPLO = 'L' and IPIV(k) =
     *          IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were
     *          interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
     *
     *  INFO    (output) INTEGER
     *          = 0: successful exit
     *          < 0: if INFO = -i, the i-th argument had an illegal value
     *          > 0: if INFO = i, D(i,i) is exactly zero.  The factorization

     *               has been completed, but the block diagonal matrix D is
     *               exactly singular, and division by zero will occur if it

     *               is used to solve a system of equations.
     *
     *  Further Details
     *  ===============
     *
     *  5-96 - Based on modifications by J. Lewis, Boeing Computer Services
     *         Company
     *
     *  If UPLO = 'U', then A = U*D*U', where
     *     U = P(n)*U(n)* ... *P(k)U(k)* ...,
     *  i.e., U is a product of terms P(k)*U(k), where k decreases from n to

     *  1 in steps of 1 or 2, and D is a block diagonal matrix with 1-by-1
     *  and 2-by-2 diagonal blocks D(k).  P(k) is a permutation matrix as
     *  defined by IPIV(k), and U(k) is a unit upper triangular matrix, such

     *  that if the diagonal block D(k) is of order s (s = 1 or 2), then
     *
     *             (   I    v    0   )   k-s
     *     U(k) =  (   0    I    0   )   s
     *             (   0    0    I   )   n-k
     *                k-s   s   n-k
     *
     *  If s = 1, D(k) overwrites A(k,k), and v overwrites A(1:k-1,k).
     *  If s = 2, the upper triangle of D(k) overwrites A(k-1,k-1), A(k-1,k),
     *  and A(k,k), and v overwrites A(1:k-2,k-1:k).
     *
     *  If UPLO = 'L', then A = L*D*L', where
     *     L = P(1)*L(1)* ... *P(k)*L(k)* ...,
     *  i.e., L is a product of terms P(k)*L(k), where k increases from 1 to

     *  n in steps of 1 or 2, and D is a block diagonal matrix with 1-by-1
     *  and 2-by-2 diagonal blocks D(k).  P(k) is a permutation matrix as
     *  defined by IPIV(k), and L(k) is a unit lower triangular matrix, such

     *  that if the diagonal block D(k) is of order s (s = 1 or 2), then
     *
     *             (   I    0     0   )  k-1
     *     L(k) =  (   0    I     0   )  s
     *             (   0    v     I   )  n-k-s+1
     *                k-1   s  n-k-s+1
     *
     *  If s = 1, D(k) overwrites A(k,k), and v overwrites A(k+1:n,k).
     *  If s = 2, the lower triangle of D(k) overwrites A(k,k), A(k+1,k),
     *  and A(k+1,k+1), and v overwrites A(k+2:n,k:k+1).
     *
     *  =====================================================================
     *
     *     .. Parameters ..

Constructor Summary
`Dsptrf()`

Method Summary
`static void` | `dsptrf(java.lang.String uplo, int n, double[] ap, int _ap_offset, int[] ipiv, int _ipiv_offset, intW info)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### Dsptrf

    public Dsptrf()

Method Detail

### dsptrf

    public static void dsptrf(java.lang.String uplo,
                              int n,
                              double[] ap,
                              int _ap_offset,
                              int[] ipiv,
                              int _ipiv_offset,
                              intW info)

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