File: claqr1

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--- 
:name: claqr1
:md5sum: 3f19c2453a865a3b2236f6174de113ff
:category: :subroutine
:arguments: 
- n: 
    :type: integer
    :intent: input
- h: 
    :type: complex
    :intent: input
    :dims: 
    - ldh
    - n
- ldh: 
    :type: integer
    :intent: input
- s1: 
    :type: complex
    :intent: input
- s2: 
    :type: complex
    :intent: input
- v: 
    :type: complex
    :intent: output
    :dims: 
    - n
:substitutions: {}

:fortran_help: "      SUBROUTINE CLAQR1( N, H, LDH, S1, S2, V )\n\n\
  *       Given a 2-by-2 or 3-by-3 matrix H, CLAQR1 sets v to a\n\
  *       scalar multiple of the first column of the product\n\
  *\n\
  *       (*)  K = (H - s1*I)*(H - s2*I)\n\
  *\n\
  *       scaling to avoid overflows and most underflows.\n\
  *\n\
  *       This is useful for starting double implicit shift bulges\n\
  *       in the QR algorithm.\n\
  *\n\
  *\n\n\
  *       N      (input) integer\n\
  *              Order of the matrix H. N must be either 2 or 3.\n\
  *\n\
  *       H      (input) COMPLEX array of dimension (LDH,N)\n\
  *              The 2-by-2 or 3-by-3 matrix H in (*).\n\
  *\n\
  *       LDH    (input) integer\n\
  *              The leading dimension of H as declared in\n\
  *              the calling procedure.  LDH.GE.N\n\
  *\n\
  *       S1     (input) COMPLEX\n\
  *       S2     S1 and S2 are the shifts defining K in (*) above.\n\
  *\n\
  *       V      (output) COMPLEX array of dimension N\n\
  *              A scalar multiple of the first column of the\n\
  *              matrix K in (*).\n\
  *\n\n\
  *     ================================================================\n\
  *     Based on contributions by\n\
  *        Karen Braman and Ralph Byers, Department of Mathematics,\n\
  *        University of Kansas, USA\n\
  *\n\
  *     ================================================================\n\
  *\n"