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ssbtrd.f(3)				      LAPACK				      ssbtrd.f(3)

       ssbtrd.f -

       subroutine ssbtrd (VECT, UPLO, N, KD, AB, LDAB, D, E, Q, LDQ, WORK, INFO)

Function/Subroutine Documentation
   subroutine ssbtrd (characterVECT, characterUPLO, integerN, integerKD, real, dimension( ldab, *
       )AB, integerLDAB, real, dimension( * )D, real, dimension( * )E, real, dimension( ldq, *
       )Q, integerLDQ, real, dimension( * )WORK, integerINFO)


	    SSBTRD reduces a real symmetric band matrix A to symmetric
	    tridiagonal form T by an orthogonal similarity transformation:
	    Q**T * A * Q = T.


		     VECT is CHARACTER*1
		     = 'N':  do not form Q;
		     = 'V':  form Q;
		     = 'U':  update a matrix X, by forming X*Q.


		     UPLO is CHARACTER*1
		     = 'U':  Upper triangle of A is stored;
		     = 'L':  Lower triangle of A is stored.


		     N is INTEGER
		     The order of the matrix A.  N >= 0.


		     KD is INTEGER
		     The number of superdiagonals of the matrix A if UPLO = 'U',
		     or the number of subdiagonals if UPLO = 'L'.  KD >= 0.


		     AB is REAL array, dimension (LDAB,N)
		     On entry, the upper or lower triangle of the symmetric band
		     matrix A, stored in the first KD+1 rows of the array.  The
		     j-th column of A is stored in the j-th column of the array AB
		     as follows:
		     if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;
		     if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd).
		     On exit, the diagonal elements of AB are overwritten by the
		     diagonal elements of the tridiagonal matrix T; if KD > 0, the
		     elements on the first superdiagonal (if UPLO = 'U') or the
		     first subdiagonal (if UPLO = 'L') are overwritten by the
		     off-diagonal elements of T; the rest of AB is overwritten by
		     values generated during the reduction.


		     LDAB is INTEGER
		     The leading dimension of the array AB.  LDAB >= KD+1.


		     D is REAL array, dimension (N)
		     The diagonal elements of the tridiagonal matrix T.


		     E is REAL array, dimension (N-1)
		     The off-diagonal elements of the tridiagonal matrix T:
		     E(i) = T(i,i+1) if UPLO = 'U'; E(i) = T(i+1,i) if UPLO = 'L'.


		     Q is REAL array, dimension (LDQ,N)
		     On entry, if VECT = 'U', then Q must contain an N-by-N
		     matrix X; if VECT = 'N' or 'V', then Q need not be set.

		     On exit:
		     if VECT = 'V', Q contains the N-by-N orthogonal matrix Q;
		     if VECT = 'U', Q contains the product X*Q;
		     if VECT = 'N', the array Q is not referenced.


		     LDQ is INTEGER
		     The leading dimension of the array Q.
		     LDQ >= 1, and LDQ >= N if VECT = 'V' or 'U'.


		     WORK is REAL array, dimension (N)


		     INFO is INTEGER
		     = 0:  successful exit
		     < 0:  if INFO = -i, the i-th argument had an illegal value

	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

	   November 2011

       Further Details:

	     Modified by Linda Kaufman, Bell Labs.

       Definition at line 163 of file ssbtrd.f.

       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      ssbtrd.f(3)
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