ssptrd
ssptrd - reduce a real symmetric matrix A stored in packed form to symmetric tridiagonal form T by an orthogonal similarity transformation
SUBROUTINE SSPTRD( UPLO, N, AP, D, E, TAU, INFO)
CHARACTER * 1 UPLO
INTEGER N, INFO
REAL AP(*), D(*), E(*), TAU(*)
SUBROUTINE SSPTRD_64( UPLO, N, AP, D, E, TAU, INFO)
CHARACTER * 1 UPLO
INTEGER*8 N, INFO
REAL AP(*), D(*), E(*), TAU(*)
SUBROUTINE SPTRD( UPLO, N, AP, D, E, TAU, [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER :: N, INFO
REAL, DIMENSION(:) :: AP, D, E, TAU
SUBROUTINE SPTRD_64( UPLO, N, AP, D, E, TAU, [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: N, INFO
REAL, DIMENSION(:) :: AP, D, E, TAU
#include <sunperf.h>
void ssptrd(char uplo, int n, float *ap, float *d, float *e, float *tau, int *info);
void ssptrd_64(char uplo, long n, float *ap, float *d, float *e, float *tau, long *info);
ssptrd 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.
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* UPLO (input)
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* N (input)
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The order of the matrix A. N >= 0.
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* AP (input)
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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
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* D (output)
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The diagonal elements of the tridiagonal matrix T:
D(i) = A(i,i).
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* E (output)
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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'.
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* TAU (output)
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The scalar factors of the elementary reflectors (see Further
Details).
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* INFO (output)
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