#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int sgghrd_(char *compq, char *compz, integer *n, integer * ilo, integer *ihi, real *a, integer *lda, real *b, integer *ldb, real *q, integer *ldq, real *z__, integer *ldz, integer *info) { /* -- LAPACK 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 ======= SGGHRD reduces a pair of real matrices (A,B) to generalized upper Hessenberg form using orthogonal transformations, where A is a general matrix and B is upper triangular: Q' * A * Z = H and Q' * B * Z = T, where H is upper Hessenberg, T is upper triangular, and Q and Z are orthogonal, and ' means transpose. The orthogonal matrices Q and Z are determined as products of Givens rotations. They may either be formed explicitly, or they may be postmultiplied into input matrices Q1 and Z1, so that Q1 * A * Z1' = (Q1*Q) * H * (Z1*Z)' Q1 * B * Z1' = (Q1*Q) * T * (Z1*Z)' Arguments ========= COMPQ (input) CHARACTER*1 = 'N': do not compute Q; = 'I': Q is initialized to the unit matrix, and the orthogonal matrix Q is returned; = 'V': Q must contain an orthogonal matrix Q1 on entry, and the product Q1*Q is returned. COMPZ (input) CHARACTER*1 = 'N': do not compute Z; = 'I': Z is initialized to the unit matrix, and the orthogonal matrix Z is returned; = 'V': Z must contain an orthogonal matrix Z1 on entry, and the product Z1*Z is returned. N (input) INTEGER The order of the matrices A and B. N >= 0. ILO (input) INTEGER IHI (input) INTEGER It is assumed that A is already upper triangular in rows and columns 1:ILO-1 and IHI+1:N. ILO and IHI are normally set by a previous call to SGGBAL; otherwise they should be set to 1 and N respectively. 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0. A (input/output) REAL array, dimension (LDA, N) On entry, the N-by-N general matrix to be reduced. On exit, the upper triangle and the first subdiagonal of A are overwritten with the upper Hessenberg matrix H, and the rest is set to zero. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(1,N). B (input/output) REAL array, dimension (LDB, N) On entry, the N-by-N upper triangular matrix B. On exit, the upper triangular matrix T = Q' B Z. The elements below the diagonal are set to zero. LDB (input) INTEGER The leading dimension of the array B. LDB >= max(1,N). Q (input/output) REAL array, dimension (LDQ, N) If COMPQ='N': Q is not referenced. If COMPQ='I': on entry, Q need not be set, and on exit it contains the orthogonal matrix Q, where Q' is the product of the Givens transformations which are applied to A and B on the left. If COMPQ='V': on entry, Q must contain an orthogonal matrix Q1, and on exit this is overwritten by Q1*Q. LDQ (input) INTEGER The leading dimension of the array Q. LDQ >= N if COMPQ='V' or 'I'; LDQ >= 1 otherwise. Z (input/output) REAL array, dimension (LDZ, N) If COMPZ='N': Z is not referenced. If COMPZ='I': on entry, Z need not be set, and on exit it contains the orthogonal matrix Z, which is the product of the Givens transformations which are applied to A and B on the right. If COMPZ='V': on entry, Z must contain an orthogonal matrix Z1, and on exit this is overwritten by Z1*Z. LDZ (input) INTEGER The leading dimension of the array Z. LDZ >= N if COMPZ='V' or 'I'; LDZ >= 1 otherwise. INFO (output) INTEGER = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. Further Details =============== This routine reduces A to Hessenberg and B to triangular form by an unblocked reduction, as described in _Matrix_Computations_, by Golub and Van Loan (Johns Hopkins Press.) ===================================================================== Decode COMPQ Parameter adjustments */ /* Table of constant values */ static real c_b10 = 0.f; static real c_b11 = 1.f; static integer c__1 = 1; /* System generated locals */ integer a_dim1, a_offset, b_dim1, b_offset, q_dim1, q_offset, z_dim1, z_offset, i__1, i__2, i__3; /* Local variables */ static integer jcol; static real temp; static integer jrow; extern /* Subroutine */ int srot_(integer *, real *, integer *, real *, integer *, real *, real *); static real c__, s; extern logical lsame_(char *, char *); extern /* Subroutine */ int xerbla_(char *, integer *); static integer icompq; extern /* Subroutine */ int slaset_(char *, integer *, integer *, real *, real *, real *, integer *), slartg_(real *, real *, real * , real *, real *); static integer icompz; static logical ilq, ilz; #define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1] #define b_ref(a_1,a_2) b[(a_2)*b_dim1 + a_1] #define q_ref(a_1,a_2) q[(a_2)*q_dim1 + a_1] #define z___ref(a_1,a_2) z__[(a_2)*z_dim1 + a_1] a_dim1 = *lda; a_offset = 1 + a_dim1 * 1; a -= a_offset; b_dim1 = *ldb; b_offset = 1 + b_dim1 * 1; b -= b_offset; q_dim1 = *ldq; q_offset = 1 + q_dim1 * 1; q -= q_offset; z_dim1 = *ldz; z_offset = 1 + z_dim1 * 1; z__ -= z_offset; /* Function Body */ if (lsame_(compq, "N")) { ilq = FALSE_; icompq = 1; } else if (lsame_(compq, "V")) { ilq = TRUE_; icompq = 2; } else if (lsame_(compq, "I")) { ilq = TRUE_; icompq = 3; } else { icompq = 0; } /* Decode COMPZ */ if (lsame_(compz, "N")) { ilz = FALSE_; icompz = 1; } else if (lsame_(compz, "V")) { ilz = TRUE_; icompz = 2; } else if (lsame_(compz, "I")) { ilz = TRUE_; icompz = 3; } else { icompz = 0; } /* Test the input parameters. */ *info = 0; if (icompq <= 0) { *info = -1; } else if (icompz <= 0) { *info = -2; } else if (*n < 0) { *info = -3; } else if (*ilo < 1) { *info = -4; } else if (*ihi > *n || *ihi < *ilo - 1) { *info = -5; } else if (*lda < max(1,*n)) { *info = -7; } else if (*ldb < max(1,*n)) { *info = -9; } else if (ilq && *ldq < *n || *ldq < 1) { *info = -11; } else if (ilz && *ldz < *n || *ldz < 1) { *info = -13; } if (*info != 0) { i__1 = -(*info); xerbla_("SGGHRD", &i__1); return 0; } /* Initialize Q and Z if desired. */ if (icompq == 3) { slaset_("Full", n, n, &c_b10, &c_b11, &q[q_offset], ldq); } if (icompz == 3) { slaset_("Full", n, n, &c_b10, &c_b11, &z__[z_offset], ldz); } /* Quick return if possible */ if (*n <= 1) { return 0; } /* Zero out lower triangle of B */ i__1 = *n - 1; for (jcol = 1; jcol <= i__1; ++jcol) { i__2 = *n; for (jrow = jcol + 1; jrow <= i__2; ++jrow) { b_ref(jrow, jcol) = 0.f; /* L10: */ } /* L20: */ } /* Reduce A and B */ i__1 = *ihi - 2; for (jcol = *ilo; jcol <= i__1; ++jcol) { i__2 = jcol + 2; for (jrow = *ihi; jrow >= i__2; --jrow) { /* Step 1: rotate rows JROW-1, JROW to kill A(JROW,JCOL) */ temp = a_ref(jrow - 1, jcol); slartg_(&temp, &a_ref(jrow, jcol), &c__, &s, &a_ref(jrow - 1, jcol)); a_ref(jrow, jcol) = 0.f; i__3 = *n - jcol; srot_(&i__3, &a_ref(jrow - 1, jcol + 1), lda, &a_ref(jrow, jcol + 1), lda, &c__, &s); i__3 = *n + 2 - jrow; srot_(&i__3, &b_ref(jrow - 1, jrow - 1), ldb, &b_ref(jrow, jrow - 1), ldb, &c__, &s); if (ilq) { srot_(n, &q_ref(1, jrow - 1), &c__1, &q_ref(1, jrow), &c__1, & c__, &s); } /* Step 2: rotate columns JROW, JROW-1 to kill B(JROW,JROW-1) */ temp = b_ref(jrow, jrow); slartg_(&temp, &b_ref(jrow, jrow - 1), &c__, &s, &b_ref(jrow, jrow)); b_ref(jrow, jrow - 1) = 0.f; srot_(ihi, &a_ref(1, jrow), &c__1, &a_ref(1, jrow - 1), &c__1, & c__, &s); i__3 = jrow - 1; srot_(&i__3, &b_ref(1, jrow), &c__1, &b_ref(1, jrow - 1), &c__1, & c__, &s); if (ilz) { srot_(n, &z___ref(1, jrow), &c__1, &z___ref(1, jrow - 1), & c__1, &c__, &s); } /* L30: */ } /* L40: */ } return 0; /* End of SGGHRD */ } /* sgghrd_ */ #undef z___ref #undef q_ref #undef b_ref #undef a_ref