text: /* lapack/double/dorgr2.f -- translated by f2c (version 20050501).
     You must link the resulting object file with libf2c:
          on Microsoft Windows system, link with libf2c.lib;
          on Linux or Unix systems, link with .../path/to/libf2c.a -lm
          or, if you install libf2c.a in a standard place, with -lf2c -lm
          -- in that order, at the end of the command line, as in
                  cc *.o -lf2c -lm
          Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
  
                  http://www.netlib.org/f2c/libf2c.zip
  */
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  #include "v3p_netlib.h"
  
  /*<       SUBROUTINE DORGR2( M, N, K, A, LDA, TAU, WORK, INFO ) >*/
  /* Subroutine */ int dorgr2_(integer *m, integer *n, integer *k, doublereal *
          a, integer *lda, doublereal *tau, doublereal *work, integer *info)
  {
      /* System generated locals */
      integer a_dim1, a_offset, i__1, i__2, i__3;
      doublereal d__1;
  
      /* Local variables */
      integer i__, j, l, ii;
      extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *, 
              integer *), dlarf_(char *, integer *, integer *, doublereal *, 
              integer *, doublereal *, doublereal *, integer *, doublereal *, 
              ftnlen), xerbla_(char *, integer *, ftnlen);
  
  
  /*  -- LAPACK routine (version 3.0) -- */
  /*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
  /*     Courant Institute, Argonne National Lab, and Rice University */
  /*     February 29, 1992 */
  
  /*     .. Scalar Arguments .. */
  /*<       INTEGER            INFO, K, LDA, M, N >*/
  /*     .. */
  /*     .. Array Arguments .. */
  /*<       DOUBLE PRECISION   A( LDA, * ), TAU( * ), WORK( * ) >*/
  /*     .. */
  
  /*  Purpose */
  /*  ======= */
  
  /*  DORGR2 generates an m by n real matrix Q with orthonormal rows, */
  /*  which is defined as the last m rows of a product of k elementary */
  /*  reflectors of order n */
  
  /*        Q  =  H(1) H(2) . . . H(k) */
  
  /*  as returned by DGERQF. */
  
  /*  Arguments */
  /*  ========= */
  
  /*  M       (input) INTEGER */
  /*          The number of rows of the matrix Q. M >= 0. */
  
  /*  N       (input) INTEGER */
  /*          The number of columns of the matrix Q. N >= M. */
  
  /*  K       (input) INTEGER */
  /*          The number of elementary reflectors whose product defines the */
  /*          matrix Q. M >= K >= 0. */
  
  /*  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
  /*          On entry, the (m-k+i)-th row must contain the vector which */
  /*          defines the elementary reflector H(i), for i = 1,2,...,k, as */
  /*          returned by DGERQF in the last k rows of its array argument */
  /*          A. */
  /*          On exit, the m by n matrix Q. */
  
  /*  LDA     (input) INTEGER */
  /*          The first dimension of the array A. LDA >= max(1,M). */
  
  /*  TAU     (input) DOUBLE PRECISION array, dimension (K) */
  /*          TAU(i) must contain the scalar factor of the elementary */
  /*          reflector H(i), as returned by DGERQF. */
  
  /*  WORK    (workspace) DOUBLE PRECISION array, dimension (M) */
  
  /*  INFO    (output) INTEGER */
  /*          = 0: successful exit */
  /*          < 0: if INFO = -i, the i-th argument has an illegal value */
  
  /*  ===================================================================== */
  
  /*     .. Parameters .. */
  /*<       DOUBLE PRECISION   ONE, ZERO >*/
  /*<       PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 ) >*/
  /*     .. */
  /*     .. Local Scalars .. */
  /*<       INTEGER            I, II, J, L >*/
  /*     .. */
  /*     .. External Subroutines .. */
  /*<       EXTERNAL           DLARF, DSCAL, XERBLA >*/
  /*     .. */
  /*     .. Intrinsic Functions .. */
  /*<       INTRINSIC          MAX >*/
  /*     .. */
  /*     .. Executable Statements .. */
  
  /*     Test the input arguments */
  
  /*<       INFO = 0 >*/
      /* Parameter adjustments */
      a_dim1 = *lda;
      a_offset = 1 + a_dim1;
      a -= a_offset;
      --tau;
      --work;
  
      /* Function Body */
      *info = 0;
  /*<       IF( M.LT.0 ) THEN >*/
      if (*m < 0) {
  /*<          INFO = -1 >*/
          *info = -1;
  /*<       ELSE IF( N.LT.M ) THEN >*/
      } else if (*n < *m) {
  /*<          INFO = -2 >*/
          *info = -2;
  /*<       ELSE IF( K.LT.0 .OR. K.GT.M ) THEN >*/
      } else if (*k < 0 || *k > *m) {
  /*<          INFO = -3 >*/
          *info = -3;
  /*<       ELSE IF( LDA.LT.MAX( 1, M ) ) THEN >*/
      } else if (*lda < max(1,*m)) {
  /*<          INFO = -5 >*/
          *info = -5;
  /*<       END IF >*/
      }
  /*<       IF( INFO.NE.0 ) THEN >*/
      if (*info != 0) {
  /*<          CALL XERBLA( 'DORGR2', -INFO ) >*/
          i__1 = -(*info);
          xerbla_("DORGR2", &i__1, (ftnlen)6);
  /*<          RETURN >*/
          return 0;
  /*<       END IF >*/
      }
  
  /*     Quick return if possible */
  
  /*<    >*/
      if (*m <= 0) {
          return 0;
      }
  
  /*<       IF( K.LT.M ) THEN >*/
      if (*k < *m) {
  
  /*        Initialise rows 1:m-k to rows of the unit matrix */
  
  /*<          DO 20 J = 1, N >*/
          i__1 = *n;
          for (j = 1; j <= i__1; ++j) {
  /*<             DO 10 L = 1, M - K >*/
              i__2 = *m - *k;
              for (l = 1; l <= i__2; ++l) {
  /*<                A( L, J ) = ZERO >*/
                  a[l + j * a_dim1] = 0.;
  /*<    10       CONTINUE >*/
  /* L10: */
              }
  /*<    >*/
              if (j > *n - *m && j <= *n - *k) {
                  a[*m - *n + j + j * a_dim1] = 1.;
              }
  /*<    20    CONTINUE >*/
  /* L20: */
          }
  /*<       END IF >*/
      }
  
  /*<       DO 40 I = 1, K >*/
      i__1 = *k;
      for (i__ = 1; i__ <= i__1; ++i__) {
  /*<          II = M - K + I >*/
          ii = *m - *k + i__;
  
  /*        Apply H(i) to A(1:m-k+i,1:n-k+i) from the right */
  
  /*<          A( II, N-M+II ) = ONE >*/
          a[ii + (*n - *m + ii) * a_dim1] = 1.;
  /*<    >*/
          i__2 = ii - 1;
          i__3 = *n - *m + ii;
          dlarf_("Right", &i__2, &i__3, &a[ii + a_dim1], lda, &tau[i__], &a[
                  a_offset], lda, &work[1], (ftnlen)5);
  /*<          CALL DSCAL( N-M+II-1, -TAU( I ), A( II, 1 ), LDA ) >*/
          i__2 = *n - *m + ii - 1;
          d__1 = -tau[i__];
          dscal_(&i__2, &d__1, &a[ii + a_dim1], lda);
  /*<          A( II, N-M+II ) = ONE - TAU( I ) >*/
          a[ii + (*n - *m + ii) * a_dim1] = 1. - tau[i__];
  
  /*        Set A(m-k+i,n-k+i+1:n) to zero */
  
  /*<          DO 30 L = N - M + II + 1, N >*/
          i__2 = *n;
          for (l = *n - *m + ii + 1; l <= i__2; ++l) {
  /*<             A( II, L ) = ZERO >*/
              a[ii + l * a_dim1] = 0.;
  /*<    30    CONTINUE >*/
  /* L30: */
          }
  /*<    40 CONTINUE >*/
  /* L40: */
      }
  /*<       RETURN >*/
      return 0;
  
  /*     End of DORGR2 */
  
  /*<       END >*/
  } /* dorgr2_ */
  
  #ifdef __cplusplus
          }
  #endif
  