stev - stev: eig, QR iteration

Generated automatically by Doxygen for LAPACK from the source code. Version 3.12.0 Sun Jul 20 2025 01:40:05 stev(3)

subroutinedstev(characterjobz,integern,doubleprecision,dimension(*)d,doubleprecision,dimension(*)e,doubleprecision,dimension(ldz,*)z,integerldz,doubleprecision,dimension(*)work,integerinfo)DSTEVcomputestheeigenvaluesand,optionally,theleftand/orrighteigenvectorsforOTHERmatricesPurpose: DSTEV computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A. ParametersJOBZ JOBZ is CHARACTER*1 = 'N': Compute eigenvalues only; = 'V': Compute eigenvalues and eigenvectors. N N is INTEGER The order of the matrix. N >= 0. D D is DOUBLE PRECISION array, dimension (N) On entry, the n diagonal elements of the tridiagonal matrix A. On exit, if INFO = 0, the eigenvalues in ascending order. E E is DOUBLE PRECISION array, dimension (N-1) On entry, the (n-1) subdiagonal elements of the tridiagonal matrix A, stored in elements 1 to N-1 of E. On exit, the contents of E are destroyed. Z Z is DOUBLE PRECISION array, dimension (LDZ, N) If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal eigenvectors of the matrix A, with the i-th column of Z holding the eigenvector associated with D(i). If JOBZ = 'N', then Z is not referenced. LDZ LDZ is INTEGER The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N). WORK WORK is DOUBLE PRECISION array, dimension (max(1,2*N-2)) If JOBZ = 'N', WORK is not referenced. INFO INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of E did not converge to zero. Author Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd. subroutinesstev(characterjobz,integern,real,dimension(*)d,real,dimension(*)e,real,dimension(ldz,*)z,integerldz,real,dimension(*)work,integerinfo)SSTEVcomputestheeigenvaluesand,optionally,theleftand/orrighteigenvectorsforOTHERmatricesPurpose: SSTEV computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A. ParametersJOBZ JOBZ is CHARACTER*1 = 'N': Compute eigenvalues only; = 'V': Compute eigenvalues and eigenvectors. N N is INTEGER The order of the matrix. N >= 0. D D is REAL array, dimension (N) On entry, the n diagonal elements of the tridiagonal matrix A. On exit, if INFO = 0, the eigenvalues in ascending order. E E is REAL array, dimension (N-1) On entry, the (n-1) subdiagonal elements of the tridiagonal matrix A, stored in elements 1 to N-1 of E. On exit, the contents of E are destroyed. Z Z is REAL array, dimension (LDZ, N) If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal eigenvectors of the matrix A, with the i-th column of Z holding the eigenvector associated with D(i). If JOBZ = 'N', then Z is not referenced. LDZ LDZ is INTEGER The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N). WORK WORK is REAL array, dimension (max(1,2*N-2)) If JOBZ = 'N', WORK is not referenced. INFO INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of E did not converge to zero. Author Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd.

stev - stev: eig, QR iteration

Functions subroutine dstev (jobz, n, d, e, z, ldz, work, info) DSTEVcomputestheeigenvaluesand,optionally,theleftand/orrighteigenvectorsforOTHERmatrices subroutine sstev (jobz, n, d, e, z, ldz, work, info) SSTEVcomputestheeigenvaluesand,optionally,theleftand/orrighteigenvectorsforOTHERmatrices