#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int slarz_(char *side, integer *m, integer *n, integer *l, real *v, integer *incv, real *tau, real *c__, integer *ldc, real * work) { /* -- LAPACK routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= SLARZ applies a real elementary reflector H to a real M-by-N matrix C, from either the left or the right. H is represented in the form H = I - tau * v * v' where tau is a real scalar and v is a real vector. If tau = 0, then H is taken to be the unit matrix. H is a product of k elementary reflectors as returned by STZRZF. Arguments ========= SIDE (input) CHARACTER*1 = 'L': form H * C = 'R': form C * H M (input) INTEGER The number of rows of the matrix C. N (input) INTEGER The number of columns of the matrix C. L (input) INTEGER The number of entries of the vector V containing the meaningful part of the Householder vectors. If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0. V (input) REAL array, dimension (1+(L-1)*abs(INCV)) The vector v in the representation of H as returned by STZRZF. V is not used if TAU = 0. INCV (input) INTEGER The increment between elements of v. INCV <> 0. TAU (input) REAL The value tau in the representation of H. C (input/output) REAL array, dimension (LDC,N) On entry, the M-by-N matrix C. On exit, C is overwritten by the matrix H * C if SIDE = 'L', or C * H if SIDE = 'R'. LDC (input) INTEGER The leading dimension of the array C. LDC >= max(1,M). WORK (workspace) REAL array, dimension (N) if SIDE = 'L' or (M) if SIDE = 'R' Further Details =============== Based on contributions by A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA ===================================================================== Parameter adjustments */ /* Table of constant values */ static integer c__1 = 1; static real c_b5 = 1.f; /* System generated locals */ integer c_dim1, c_offset; real r__1; /* Local variables */ extern /* Subroutine */ int sger_(integer *, integer *, real *, real *, integer *, real *, integer *, real *, integer *); extern logical lsame_(char *, char *); extern /* Subroutine */ int sgemv_(char *, integer *, integer *, real *, real *, integer *, real *, integer *, real *, real *, integer *), scopy_(integer *, real *, integer *, real *, integer *), saxpy_(integer *, real *, real *, integer *, real *, integer *); --v; c_dim1 = *ldc; c_offset = 1 + c_dim1; c__ -= c_offset; --work; /* Function Body */ if (lsame_(side, "L")) { /* Form H * C */ if (*tau != 0.f) { /* w( 1:n ) = C( 1, 1:n ) */ scopy_(n, &c__[c_offset], ldc, &work[1], &c__1); /* w( 1:n ) = w( 1:n ) + C( m-l+1:m, 1:n )' * v( 1:l ) */ sgemv_("Transpose", l, n, &c_b5, &c__[*m - *l + 1 + c_dim1], ldc, &v[1], incv, &c_b5, &work[1], &c__1); /* C( 1, 1:n ) = C( 1, 1:n ) - tau * w( 1:n ) */ r__1 = -(*tau); saxpy_(n, &r__1, &work[1], &c__1, &c__[c_offset], ldc); /* C( m-l+1:m, 1:n ) = C( m-l+1:m, 1:n ) - ... tau * v( 1:l ) * w( 1:n )' */ r__1 = -(*tau); sger_(l, n, &r__1, &v[1], incv, &work[1], &c__1, &c__[*m - *l + 1 + c_dim1], ldc); } } else { /* Form C * H */ if (*tau != 0.f) { /* w( 1:m ) = C( 1:m, 1 ) */ scopy_(m, &c__[c_offset], &c__1, &work[1], &c__1); /* w( 1:m ) = w( 1:m ) + C( 1:m, n-l+1:n, 1:n ) * v( 1:l ) */ sgemv_("No transpose", m, l, &c_b5, &c__[(*n - *l + 1) * c_dim1 + 1], ldc, &v[1], incv, &c_b5, &work[1], &c__1); /* C( 1:m, 1 ) = C( 1:m, 1 ) - tau * w( 1:m ) */ r__1 = -(*tau); saxpy_(m, &r__1, &work[1], &c__1, &c__[c_offset], &c__1); /* C( 1:m, n-l+1:n ) = C( 1:m, n-l+1:n ) - ... tau * w( 1:m ) * v( 1:l )' */ r__1 = -(*tau); sger_(m, l, &r__1, &work[1], &c__1, &v[1], incv, &c__[(*n - *l + 1) * c_dim1 + 1], ldc); } } return 0; /* End of SLARZ */ } /* slarz_ */