3 /* Table of constant values */
5 static integer c__1 = 1;
6 static doublereal c_b8 = 0.;
8 /* Subroutine */ int dlarft_(char *direct, char *storev, integer *n, integer *
9 k, doublereal *v, integer *ldv, doublereal *tau, doublereal *t,
12 /* System generated locals */
13 integer t_dim1, t_offset, v_dim1, v_offset, i__1, i__2, i__3;
19 extern logical lsame_(char *, char *);
20 extern /* Subroutine */ int dgemv_(char *, integer *, integer *,
21 doublereal *, doublereal *, integer *, doublereal *, integer *,
22 doublereal *, doublereal *, integer *), dtrmv_(char *,
23 char *, char *, integer *, doublereal *, integer *, doublereal *,
27 /* -- LAPACK auxiliary routine (version 3.1) -- */
28 /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
31 /* .. Scalar Arguments .. */
33 /* .. Array Arguments .. */
39 /* DLARFT forms the triangular factor T of a real block reflector H */
40 /* of order n, which is defined as a product of k elementary reflectors. */
42 /* If DIRECT = 'F', H = H(1) H(2) . . . H(k) and T is upper triangular; */
44 /* If DIRECT = 'B', H = H(k) . . . H(2) H(1) and T is lower triangular. */
46 /* If STOREV = 'C', the vector which defines the elementary reflector */
47 /* H(i) is stored in the i-th column of the array V, and */
49 /* H = I - V * T * V' */
51 /* If STOREV = 'R', the vector which defines the elementary reflector */
52 /* H(i) is stored in the i-th row of the array V, and */
54 /* H = I - V' * T * V */
59 /* DIRECT (input) CHARACTER*1 */
60 /* Specifies the order in which the elementary reflectors are */
61 /* multiplied to form the block reflector: */
62 /* = 'F': H = H(1) H(2) . . . H(k) (Forward) */
63 /* = 'B': H = H(k) . . . H(2) H(1) (Backward) */
65 /* STOREV (input) CHARACTER*1 */
66 /* Specifies how the vectors which define the elementary */
67 /* reflectors are stored (see also Further Details): */
68 /* = 'C': columnwise */
71 /* N (input) INTEGER */
72 /* The order of the block reflector H. N >= 0. */
74 /* K (input) INTEGER */
75 /* The order of the triangular factor T (= the number of */
76 /* elementary reflectors). K >= 1. */
78 /* V (input/output) DOUBLE PRECISION array, dimension */
79 /* (LDV,K) if STOREV = 'C' */
80 /* (LDV,N) if STOREV = 'R' */
81 /* The matrix V. See further details. */
83 /* LDV (input) INTEGER */
84 /* The leading dimension of the array V. */
85 /* If STOREV = 'C', LDV >= max(1,N); if STOREV = 'R', LDV >= K. */
87 /* TAU (input) DOUBLE PRECISION array, dimension (K) */
88 /* TAU(i) must contain the scalar factor of the elementary */
91 /* T (output) DOUBLE PRECISION array, dimension (LDT,K) */
92 /* The k by k triangular factor T of the block reflector. */
93 /* If DIRECT = 'F', T is upper triangular; if DIRECT = 'B', T is */
94 /* lower triangular. The rest of the array is not used. */
96 /* LDT (input) INTEGER */
97 /* The leading dimension of the array T. LDT >= K. */
100 /* =============== */
102 /* The shape of the matrix V and the storage of the vectors which define */
103 /* the H(i) is best illustrated by the following example with n = 5 and */
104 /* k = 3. The elements equal to 1 are not stored; the corresponding */
105 /* array elements are modified but restored on exit. The rest of the */
106 /* array is not used. */
108 /* DIRECT = 'F' and STOREV = 'C': DIRECT = 'F' and STOREV = 'R': */
110 /* V = ( 1 ) V = ( 1 v1 v1 v1 v1 ) */
111 /* ( v1 1 ) ( 1 v2 v2 v2 ) */
112 /* ( v1 v2 1 ) ( 1 v3 v3 ) */
116 /* DIRECT = 'B' and STOREV = 'C': DIRECT = 'B' and STOREV = 'R': */
118 /* V = ( v1 v2 v3 ) V = ( v1 v1 1 ) */
119 /* ( v1 v2 v3 ) ( v2 v2 v2 1 ) */
120 /* ( 1 v2 v3 ) ( v3 v3 v3 v3 1 ) */
124 /* ===================================================================== */
126 /* .. Parameters .. */
128 /* .. Local Scalars .. */
130 /* .. External Subroutines .. */
132 /* .. External Functions .. */
134 /* .. Executable Statements .. */
136 /* Quick return if possible */
138 /* Parameter adjustments */
140 v_offset = 1 + v_dim1;
144 t_offset = 1 + t_dim1;
152 if (lsame_(direct, "F")) {
154 for (i__ = 1; i__ <= i__1; ++i__) {
155 if (tau[i__] == 0.) {
160 for (j = 1; j <= i__2; ++j) {
161 t[j + i__ * t_dim1] = 0.;
168 vii = v[i__ + i__ * v_dim1];
169 v[i__ + i__ * v_dim1] = 1.;
170 if (lsame_(storev, "C")) {
172 /* T(1:i-1,i) := - tau(i) * V(i:n,1:i-1)' * V(i:n,i) */
177 dgemv_("Transpose", &i__2, &i__3, &d__1, &v[i__ + v_dim1],
178 ldv, &v[i__ + i__ * v_dim1], &c__1, &c_b8, &t[
179 i__ * t_dim1 + 1], &c__1);
182 /* T(1:i-1,i) := - tau(i) * V(1:i-1,i:n) * V(i,i:n)' */
187 dgemv_("No transpose", &i__2, &i__3, &d__1, &v[i__ *
188 v_dim1 + 1], ldv, &v[i__ + i__ * v_dim1], ldv, &
189 c_b8, &t[i__ * t_dim1 + 1], &c__1);
191 v[i__ + i__ * v_dim1] = vii;
193 /* T(1:i-1,i) := T(1:i-1,1:i-1) * T(1:i-1,i) */
196 dtrmv_("Upper", "No transpose", "Non-unit", &i__2, &t[
197 t_offset], ldt, &t[i__ * t_dim1 + 1], &c__1);
198 t[i__ + i__ * t_dim1] = tau[i__];
203 for (i__ = *k; i__ >= 1; --i__) {
204 if (tau[i__] == 0.) {
209 for (j = i__; j <= i__1; ++j) {
210 t[j + i__ * t_dim1] = 0.;
218 if (lsame_(storev, "C")) {
219 vii = v[*n - *k + i__ + i__ * v_dim1];
220 v[*n - *k + i__ + i__ * v_dim1] = 1.;
223 /* - tau(i) * V(1:n-k+i,i+1:k)' * V(1:n-k+i,i) */
225 i__1 = *n - *k + i__;
228 dgemv_("Transpose", &i__1, &i__2, &d__1, &v[(i__ + 1)
229 * v_dim1 + 1], ldv, &v[i__ * v_dim1 + 1], &
230 c__1, &c_b8, &t[i__ + 1 + i__ * t_dim1], &
232 v[*n - *k + i__ + i__ * v_dim1] = vii;
234 vii = v[i__ + (*n - *k + i__) * v_dim1];
235 v[i__ + (*n - *k + i__) * v_dim1] = 1.;
238 /* - tau(i) * V(i+1:k,1:n-k+i) * V(i,1:n-k+i)' */
241 i__2 = *n - *k + i__;
243 dgemv_("No transpose", &i__1, &i__2, &d__1, &v[i__ +
244 1 + v_dim1], ldv, &v[i__ + v_dim1], ldv, &
245 c_b8, &t[i__ + 1 + i__ * t_dim1], &c__1);
246 v[i__ + (*n - *k + i__) * v_dim1] = vii;
249 /* T(i+1:k,i) := T(i+1:k,i+1:k) * T(i+1:k,i) */
252 dtrmv_("Lower", "No transpose", "Non-unit", &i__1, &t[i__
253 + 1 + (i__ + 1) * t_dim1], ldt, &t[i__ + 1 + i__ *
257 t[i__ + i__ * t_dim1] = tau[i__];