#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int dsbgv_(char *jobz, char *uplo, integer *n, integer *ka, integer *kb, doublereal *ab, integer *ldab, doublereal *bb, integer * ldbb, doublereal *w, doublereal *z__, integer *ldz, doublereal *work, integer *info) { /* -- LAPACK driver routine (version 3.0) -- Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., Courant Institute, Argonne National Lab, and Rice University September 30, 1994 Purpose ======= DSBGV computes all the eigenvalues, and optionally, the eigenvectors of a real generalized symmetric-definite banded eigenproblem, of the form A*x=(lambda)*B*x. Here A and B are assumed to be symmetric and banded, and B is also positive definite. Arguments ========= JOBZ (input) CHARACTER*1 = 'N': Compute eigenvalues only; = 'V': Compute eigenvalues and eigenvectors. UPLO (input) CHARACTER*1 = 'U': Upper triangles of A and B are stored; = 'L': Lower triangles of A and B are stored. N (input) INTEGER The order of the matrices A and B. N >= 0. KA (input) INTEGER The number of superdiagonals of the matrix A if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. KA >= 0. KB (input) INTEGER The number of superdiagonals of the matrix B if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. KB >= 0. AB (input/output) DOUBLE PRECISION array, dimension (LDAB, N) On entry, the upper or lower triangle of the symmetric band matrix A, stored in the first ka+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(ka+1+i-j,j) = A(i,j) for max(1,j-ka)<=i<=j; if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+ka). On exit, the contents of AB are destroyed. LDAB (input) INTEGER The leading dimension of the array AB. LDAB >= KA+1. BB (input/output) DOUBLE PRECISION array, dimension (LDBB, N) On entry, the upper or lower triangle of the symmetric band matrix B, stored in the first kb+1 rows of the array. The j-th column of B is stored in the j-th column of the array BB as follows: if UPLO = 'U', BB(kb+1+i-j,j) = B(i,j) for max(1,j-kb)<=i<=j; if UPLO = 'L', BB(1+i-j,j) = B(i,j) for j<=i<=min(n,j+kb). On exit, the factor S from the split Cholesky factorization B = S**T*S, as returned by DPBSTF. LDBB (input) INTEGER The leading dimension of the array BB. LDBB >= KB+1. W (output) DOUBLE PRECISION array, dimension (N) If INFO = 0, the eigenvalues in ascending order. Z (output) DOUBLE PRECISION array, dimension (LDZ, N) If JOBZ = 'V', then if INFO = 0, Z contains the matrix Z of eigenvectors, with the i-th column of Z holding the eigenvector associated with W(i). The eigenvectors are normalized so that Z**T*B*Z = I. If JOBZ = 'N', then Z is not referenced. LDZ (input) INTEGER The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= N. WORK (workspace) DOUBLE PRECISION array, dimension (3*N) INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, and i is: <= N: the algorithm failed to converge: i off-diagonal elements of an intermediate tridiagonal form did not converge to zero; > N: if INFO = N + i, for 1 <= i <= N, then DPBSTF returned INFO = i: B is not positive definite. The factorization of B could not be completed and no eigenvalues or eigenvectors were computed. ===================================================================== Test the input parameters. Parameter adjustments */ /* System generated locals */ integer ab_dim1, ab_offset, bb_dim1, bb_offset, z_dim1, z_offset, i__1; /* Local variables */ static integer inde; static char vect[1]; extern logical lsame_(char *, char *); static integer iinfo; static logical upper, wantz; extern /* Subroutine */ int xerbla_(char *, integer *), dpbstf_( char *, integer *, integer *, doublereal *, integer *, integer *), dsbtrd_(char *, char *, integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, doublereal *, integer *, doublereal *, integer *), dsbgst_(char *, char *, integer *, integer *, integer *, doublereal *, integer *, doublereal *, integer *, doublereal *, integer *, doublereal *, integer *), dsterf_(integer *, doublereal *, doublereal *, integer *); static integer indwrk; extern /* Subroutine */ int dsteqr_(char *, integer *, doublereal *, doublereal *, doublereal *, integer *, doublereal *, integer *); ab_dim1 = *ldab; ab_offset = 1 + ab_dim1 * 1; ab -= ab_offset; bb_dim1 = *ldbb; bb_offset = 1 + bb_dim1 * 1; bb -= bb_offset; --w; z_dim1 = *ldz; z_offset = 1 + z_dim1 * 1; z__ -= z_offset; --work; /* Function Body */ wantz = lsame_(jobz, "V"); upper = lsame_(uplo, "U"); *info = 0; if (! (wantz || lsame_(jobz, "N"))) { *info = -1; } else if (! (upper || lsame_(uplo, "L"))) { *info = -2; } else if (*n < 0) { *info = -3; } else if (*ka < 0) { *info = -4; } else if (*kb < 0 || *kb > *ka) { *info = -5; } else if (*ldab < *ka + 1) { *info = -7; } else if (*ldbb < *kb + 1) { *info = -9; } else if (*ldz < 1 || wantz && *ldz < *n) { *info = -12; } if (*info != 0) { i__1 = -(*info); xerbla_("DSBGV ", &i__1); return 0; } /* Quick return if possible */ if (*n == 0) { return 0; } /* Form a split Cholesky factorization of B. */ dpbstf_(uplo, n, kb, &bb[bb_offset], ldbb, info); if (*info != 0) { *info = *n + *info; return 0; } /* Transform problem to standard eigenvalue problem. */ inde = 1; indwrk = inde + *n; dsbgst_(jobz, uplo, n, ka, kb, &ab[ab_offset], ldab, &bb[bb_offset], ldbb, &z__[z_offset], ldz, &work[indwrk], &iinfo) ; /* Reduce to tridiagonal form. */ if (wantz) { *(unsigned char *)vect = 'U'; } else { *(unsigned char *)vect = 'N'; } dsbtrd_(vect, uplo, n, ka, &ab[ab_offset], ldab, &w[1], &work[inde], &z__[ z_offset], ldz, &work[indwrk], &iinfo); /* For eigenvalues only, call DSTERF. For eigenvectors, call SSTEQR. */ if (! wantz) { dsterf_(n, &w[1], &work[inde], info); } else { dsteqr_(jobz, n, &w[1], &work[inde], &z__[z_offset], ldz, &work[ indwrk], info); } return 0; /* End of DSBGV */ } /* dsbgv_ */