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Class org.netlib.lapack.DSPTRD

java.lang.Object
   |
   +----org.netlib.lapack.DSPTRD

public class DSPTRD

extends Object

DSPTRD is a simplified interface to the JLAPACK routine dsptrd.
This interface converts Java-style 2D row-major arrays into
the 1D column-major linearized arrays expected by the lower
level JLAPACK routines.  Using this interface also allows you
to omit offset and leading dimension arguments.  However, because
of these conversions, these routines will be slower than the low
level ones.  Following is the description from the original Fortran
source.  Contact seymour@cs.utk.edu with any questions.

 *     ..
 *
 *  Purpose
 *  =======
 *
 *  DSPTRD reduces a real symmetric matrix A stored in packed form to
 *  symmetric tridiagonal form T by an orthogonal similarity
 *  transformation: Q**T * A * Q = T.
 *
 *  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)*(2*n-j)/2) = A(i,j) for j<=i<=n.
 *          On exit, if UPLO = 'U', the diagonal and first superdiagonal
 *          of A are overwritten by the corresponding elements of the
 *          tridiagonal matrix T, and the elements above the first
 *          superdiagonal, with the array TAU, represent the orthogonal
 *          matrix Q as a product of elementary reflectors; if UPLO
 *          = 'L', the diagonal and first subdiagonal of A are over-
 *          written by the corresponding elements of the tridiagonal
 *          matrix T, and the elements below the first subdiagonal, with
 *          the array TAU, represent the orthogonal matrix Q as a product
 *          of elementary reflectors. See Further Details.
 *
 *  D       (output) DOUBLE PRECISION array, dimension (N)
 *          The diagonal elements of the tridiagonal matrix T:
 *          D(i) = A(i,i).
 *
 *  E       (output) DOUBLE PRECISION array, dimension (N-1)
 *          The off-diagonal elements of the tridiagonal matrix T:
 *          E(i) = A(i,i+1) if UPLO = 'U', E(i) = A(i+1,i) if UPLO = 'L'.
 *
 *  TAU     (output) DOUBLE PRECISION array, dimension (N-1)
 *          The scalar factors of the elementary reflectors (see Further
 *          Details).
 *
 *  INFO    (output) INTEGER
 *          = 0:  successful exit
 *          < 0:  if INFO = -i, the i-th argument had an illegal value
 *
 *  Further Details
 *  ===============
 *
 *  If UPLO = 'U', the matrix Q is represented as a product of elementary
 *  reflectors
 *
 *     Q = H(n-1) . . . H(2) H(1).
 *
 *  Each H(i) has the form
 *
 *     H(i) = I - tau * v * v'
 *
 *  where tau is a real scalar, and v is a real vector with
 *  v(i+1:n) = 0 and v(i) = 1; v(1:i-1) is stored on exit in AP,
 *  overwriting A(1:i-1,i+1), and tau is stored in TAU(i).
 *
 *  If UPLO = 'L', the matrix Q is represented as a product of elementary
 *  reflectors
 *
 *     Q = H(1) H(2) . . . H(n-1).
 *
 *  Each H(i) has the form
 *
 *     H(i) = I - tau * v * v'
 *
 *  where tau is a real scalar, and v is a real vector with
 *  v(1:i) = 0 and v(i+1) = 1; v(i+2:n) is stored on exit in AP,
 *  overwriting A(i+2:n,i), and tau is stored in TAU(i).
 *
 *  =====================================================================
 *
 *     .. Parameters ..

DSPTRD()

DSPTRD(String, int, double[], double[], double[], double[], intW)

 public DSPTRD()

 public static void DSPTRD(String uplo,
                           int n,
                           double ap[],
                           double d[],
                           double e[],
                           double tau[],
                           intW info)

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