sgegs.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 463 行 · 第 1/3 页

</span><span class="comment">*</span><span class="comment">                                                iteration)
</span><span class="comment">*</span><span class="comment">                =N+7: error return from <a name="SGGBAK.138"></a><a href="sggbak.f.html#SGGBAK.1">SGGBAK</a> (computing VSL)
</span><span class="comment">*</span><span class="comment">                =N+8: error return from <a name="SGGBAK.139"></a><a href="sggbak.f.html#SGGBAK.1">SGGBAK</a> (computing VSR)
</span><span class="comment">*</span><span class="comment">                =N+9: error return from <a name="SLASCL.140"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a> (various places)
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Parameters ..
</span>      REAL               ZERO, ONE
      PARAMETER          ( ZERO = 0.0E0, ONE = 1.0E0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            ILASCL, ILBSCL, ILVSL, ILVSR, LQUERY
      INTEGER            ICOLS, IHI, IINFO, IJOBVL, IJOBVR, ILEFT,
     $                   ILO, IRIGHT, IROWS, ITAU, IWORK, LOPT, LWKMIN,
     $                   LWKOPT, NB, NB1, NB2, NB3
      REAL               ANRM, ANRMTO, BIGNUM, BNRM, BNRMTO, EPS,
     $                   SAFMIN, SMLNUM
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           <a name="SGEQRF.157"></a><a href="sgeqrf.f.html#SGEQRF.1">SGEQRF</a>, <a name="SGGBAK.157"></a><a href="sggbak.f.html#SGGBAK.1">SGGBAK</a>, <a name="SGGBAL.157"></a><a href="sggbal.f.html#SGGBAL.1">SGGBAL</a>, <a name="SGGHRD.157"></a><a href="sgghrd.f.html#SGGHRD.1">SGGHRD</a>, <a name="SHGEQZ.157"></a><a href="shgeqz.f.html#SHGEQZ.1">SHGEQZ</a>, <a name="SLACPY.157"></a><a href="slacpy.f.html#SLACPY.1">SLACPY</a>,
     $                   <a name="SLASCL.158"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>, <a name="SLASET.158"></a><a href="slaset.f.html#SLASET.1">SLASET</a>, <a name="SORGQR.158"></a><a href="sorgqr.f.html#SORGQR.1">SORGQR</a>, <a name="SORMQR.158"></a><a href="sormqr.f.html#SORMQR.1">SORMQR</a>, <a name="XERBLA.158"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      LOGICAL            <a name="LSAME.161"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
      INTEGER            <a name="ILAENV.162"></a><a href="hfy-index.html#ILAENV">ILAENV</a>
      REAL               <a name="SLAMCH.163"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>, <a name="SLANGE.163"></a><a href="slange.f.html#SLANGE.1">SLANGE</a>
      EXTERNAL           <a name="ILAENV.164"></a><a href="hfy-index.html#ILAENV">ILAENV</a>, <a name="LSAME.164"></a><a href="lsame.f.html#LSAME.1">LSAME</a>, <a name="SLAMCH.164"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>, <a name="SLANGE.164"></a><a href="slange.f.html#SLANGE.1">SLANGE</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          INT, MAX
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Executable Statements ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Decode the input arguments
</span><span class="comment">*</span><span class="comment">
</span>      IF( <a name="LSAME.173"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBVSL, <span class="string">'N'</span> ) ) THEN
         IJOBVL = 1
         ILVSL = .FALSE.
      ELSE IF( <a name="LSAME.176"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBVSL, <span class="string">'V'</span> ) ) THEN
         IJOBVL = 2
         ILVSL = .TRUE.
      ELSE
         IJOBVL = -1
         ILVSL = .FALSE.
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( <a name="LSAME.184"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBVSR, <span class="string">'N'</span> ) ) THEN
         IJOBVR = 1
         ILVSR = .FALSE.
      ELSE IF( <a name="LSAME.187"></a><a href="lsame.f.html#LSAME.1">LSAME</a>( JOBVSR, <span class="string">'V'</span> ) ) THEN
         IJOBVR = 2
         ILVSR = .TRUE.
      ELSE
         IJOBVR = -1
         ILVSR = .FALSE.
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Test the input arguments
</span><span class="comment">*</span><span class="comment">
</span>      LWKMIN = MAX( 4*N, 1 )
      LWKOPT = LWKMIN
      WORK( 1 ) = LWKOPT
      LQUERY = ( LWORK.EQ.-1 )
      INFO = 0
      IF( IJOBVL.LE.0 ) THEN
         INFO = -1
      ELSE IF( IJOBVR.LE.0 ) THEN
         INFO = -2
      ELSE IF( N.LT.0 ) THEN
         INFO = -3
      ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
         INFO = -5
      ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
         INFO = -7
      ELSE IF( LDVSL.LT.1 .OR. ( ILVSL .AND. LDVSL.LT.N ) ) THEN
         INFO = -12
      ELSE IF( LDVSR.LT.1 .OR. ( ILVSR .AND. LDVSR.LT.N ) ) THEN
         INFO = -14
      ELSE IF( LWORK.LT.LWKMIN .AND. .NOT.LQUERY ) THEN
         INFO = -16
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.EQ.0 ) THEN
         NB1 = <a name="ILAENV.221"></a><a href="hfy-index.html#ILAENV">ILAENV</a>( 1, <span class="string">'<a name="SGEQRF.221"></a><a href="sgeqrf.f.html#SGEQRF.1">SGEQRF</a>'</span>, <span class="string">' '</span>, N, N, -1, -1 )
         NB2 = <a name="ILAENV.222"></a><a href="hfy-index.html#ILAENV">ILAENV</a>( 1, <span class="string">'<a name="SORMQR.222"></a><a href="sormqr.f.html#SORMQR.1">SORMQR</a>'</span>, <span class="string">' '</span>, N, N, N, -1 )
         NB3 = <a name="ILAENV.223"></a><a href="hfy-index.html#ILAENV">ILAENV</a>( 1, <span class="string">'<a name="SORGQR.223"></a><a href="sorgqr.f.html#SORGQR.1">SORGQR</a>'</span>, <span class="string">' '</span>, N, N, N, -1 )
         NB = MAX( NB1, NB2, NB3 )
         LOPT = 2*N+N*(NB+1)
         WORK( 1 ) = LOPT
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( INFO.NE.0 ) THEN
         CALL <a name="XERBLA.230"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>( <span class="string">'<a name="SGEGS.230"></a><a href="sgegs.f.html#SGEGS.1">SGEGS</a> '</span>, -INFO )
         RETURN
      ELSE IF( LQUERY ) THEN
         RETURN
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Quick return if possible
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.EQ.0 )
     $   RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Get machine constants
</span><span class="comment">*</span><span class="comment">
</span>      EPS = <a name="SLAMCH.243"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>( <span class="string">'E'</span> )*<a name="SLAMCH.243"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>( <span class="string">'B'</span> )
      SAFMIN = <a name="SLAMCH.244"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>( <span class="string">'S'</span> )
      SMLNUM = N*SAFMIN / EPS
      BIGNUM = ONE / SMLNUM
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Scale A if max element outside range [SMLNUM,BIGNUM]
</span><span class="comment">*</span><span class="comment">
</span>      ANRM = <a name="SLANGE.250"></a><a href="slange.f.html#SLANGE.1">SLANGE</a>( <span class="string">'M'</span>, N, N, A, LDA, WORK )
      ILASCL = .FALSE.
      IF( ANRM.GT.ZERO .AND. ANRM.LT.SMLNUM ) THEN
         ANRMTO = SMLNUM
         ILASCL = .TRUE.
      ELSE IF( ANRM.GT.BIGNUM ) THEN
         ANRMTO = BIGNUM
         ILASCL = .TRUE.
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( ILASCL ) THEN
         CALL <a name="SLASCL.261"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>( <span class="string">'G'</span>, -1, -1, ANRM, ANRMTO, N, N, A, LDA, IINFO )
         IF( IINFO.NE.0 ) THEN
            INFO = N + 9
            RETURN
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Scale B if max element outside range [SMLNUM,BIGNUM]
</span><span class="comment">*</span><span class="comment">
</span>      BNRM = <a name="SLANGE.270"></a><a href="slange.f.html#SLANGE.1">SLANGE</a>( <span class="string">'M'</span>, N, N, B, LDB, WORK )
      ILBSCL = .FALSE.
      IF( BNRM.GT.ZERO .AND. BNRM.LT.SMLNUM ) THEN
         BNRMTO = SMLNUM
         ILBSCL = .TRUE.
      ELSE IF( BNRM.GT.BIGNUM ) THEN
         BNRMTO = BIGNUM
         ILBSCL = .TRUE.
      END IF
<span class="comment">*</span><span class="comment">
</span>      IF( ILBSCL ) THEN
         CALL <a name="SLASCL.281"></a><a href="slascl.f.html#SLASCL.1">SLASCL</a>( <span class="string">'G'</span>, -1, -1, BNRM, BNRMTO, N, N, B, LDB, IINFO )
         IF( IINFO.NE.0 ) THEN
            INFO = N + 9
            RETURN
         END IF
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Permute the matrix to make it more nearly triangular
</span><span class="comment">*</span><span class="comment">     Workspace layout:  (2*N words -- &quot;work...&quot; not actually used)
</span><span class="comment">*</span><span class="comment">        left_permutation, right_permutation, work...
</span><span class="comment">*</span><span class="comment">