FLA_QR_UT_unb_var2.c File Reference

(r)

Functions
FLA_Error	FLA_QR_UT_unb_var2 (FLA_Obj A, FLA_Obj T)

---

Function Documentation

FLA_Error FLA_QR_UT_unb_var2	(	FLA_Obj	A,
		FLA_Obj	T
	)

References FLA_Apply_H2_UT(), FLA_Cont_with_3x3_to_2x2(), FLA_Copyt_external(), FLA_Gemv_external(), FLA_Househ2_UT(), FLA_Obj_min_dim(), FLA_ONE, FLA_Part_2x2(), and FLA_Repart_2x2_to_3x3().

Referenced by FLA_QR_UT_internal().

{
  FLA_Obj ATL,   ATR,      A00,  a01,     A02, 
          ABL,   ABR,      a10t, alpha11, a12t,
                           A20,  a21,     A22;

  FLA_Obj TTL,   TTR,      T00,  t01,   T02, 
          TBL,   TBR,      t10t, tau11, t12t,
                           T20,  t21,   T22;


  FLA_Part_2x2( A,    &ATL, &ATR,
                      &ABL, &ABR,     0, 0, FLA_TL );

  FLA_Part_2x2( T,    &TTL, &TTR,
                      &TBL, &TBR,     0, 0, FLA_TL );

  while ( FLA_Obj_min_dim( ABR ) > 0 ){

    FLA_Repart_2x2_to_3x3( ATL, /**/ ATR,       &A00,  /**/ &a01,     &A02,
                        /* ************* */   /* ************************** */
                                                &a10t, /**/ &alpha11, &a12t,
                           ABL, /**/ ABR,       &A20,  /**/ &a21,     &A22,
                           1, 1, FLA_BR );

    FLA_Repart_2x2_to_3x3( TTL, /**/ TTR,       &T00,  /**/ &t01,   &T02,
                        /* ************* */   /* ************************ */
                                                &t10t, /**/ &tau11, &t12t,
                           TBL, /**/ TBR,       &T20,  /**/ &t21,   &T22,
                           1, 1, FLA_BR );

    /*------------------------------------------------------------*/

    // Compute tau11 and u21 from alpha11 and a21 such that tau11 and u21
    // determine a Householder transform H such that applying H from the
    // left to the column vector consisting of alpha11 and a21 annihilates
    // the entries in a21 (and updates alpha11).
    FLA_Househ2_UT( FLA_LEFT,
                    alpha11,
                    a21, tau11 );

    // / a12t \ =  H / a12t \
    // \ A22  /      \ A22  /
    //
    // where H is formed from tau11 and u21.
    FLA_Apply_H2_UT( FLA_LEFT, tau11, a21, a12t,
                                           A22 );

    // t01 = a10t' + A20' * u21;
    FLA_Copyt_external( FLA_CONJ_TRANSPOSE, a10t, t01 );
    FLA_Gemv_external( FLA_CONJ_TRANSPOSE, FLA_ONE, A20, a21, FLA_ONE, t01 );

    /*------------------------------------------------------------*/

    FLA_Cont_with_3x3_to_2x2( &ATL, /**/ &ATR,       A00,  a01,     /**/ A02,
                                                     a10t, alpha11, /**/ a12t,
                            /* ************** */  /* ************************ */
                              &ABL, /**/ &ABR,       A20,  a21,     /**/ A22,
                              FLA_TL );

    FLA_Cont_with_3x3_to_2x2( &TTL, /**/ &TTR,       T00,  t01,   /**/ T02,
                                                     t10t, tau11, /**/ t12t,
                            /* ************** */  /* ********************** */
                              &TBL, /**/ &TBR,       T20,  t21,   /**/ T22,
                              FLA_TL );

  }

  return FLA_SUCCESS;
}