csrscl.f.html

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      SUBROUTINE <a name="CSRSCL.1"></a><a href="csrscl.f.html#CSRSCL.1">CSRSCL</a>( N, SA, SX, INCX )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  -- LAPACK auxiliary routine (version 3.1) --
</span><span class="comment">*</span><span class="comment">     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
</span><span class="comment">*</span><span class="comment">     November 2006
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     .. Scalar Arguments ..
</span>      INTEGER            INCX, N
      REAL               SA
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Array Arguments ..
</span>      COMPLEX            SX( * )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Purpose
</span><span class="comment">*</span><span class="comment">  =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  <a name="CSRSCL.18"></a><a href="csrscl.f.html#CSRSCL.1">CSRSCL</a> multiplies an n-element complex vector x by the real scalar
</span><span class="comment">*</span><span class="comment">  1/a.  This is done without overflow or underflow as long as
</span><span class="comment">*</span><span class="comment">  the final result x/a does not overflow or underflow.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  Arguments
</span><span class="comment">*</span><span class="comment">  =========
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  N       (input) INTEGER
</span><span class="comment">*</span><span class="comment">          The number of components of the vector x.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  SA      (input) REAL
</span><span class="comment">*</span><span class="comment">          The scalar a which is used to divide each component of x.
</span><span class="comment">*</span><span class="comment">          SA must be &gt;= 0, or the subroutine will divide by zero.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  SX      (input/output) COMPLEX array, dimension
</span><span class="comment">*</span><span class="comment">                         (1+(N-1)*abs(INCX))
</span><span class="comment">*</span><span class="comment">          The n-element vector x.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">  INCX    (input) INTEGER
</span><span class="comment">*</span><span class="comment">          The increment between successive values of the vector SX.
</span><span class="comment">*</span><span class="comment">          &gt; 0:  SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i),     1&lt; i&lt;= n
</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 = 0.0E+0, ONE = 1.0E+0 )
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Local Scalars ..
</span>      LOGICAL            DONE
      REAL               BIGNUM, CDEN, CDEN1, CNUM, CNUM1, MUL, SMLNUM
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Functions ..
</span>      REAL               <a name="SLAMCH.51"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>
      EXTERNAL           <a name="SLAMCH.52"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. External Subroutines ..
</span>      EXTERNAL           CSSCAL, <a name="SLABAD.55"></a><a href="slabad.f.html#SLABAD.1">SLABAD</a>
<span class="comment">*</span><span class="comment">     ..
</span><span class="comment">*</span><span class="comment">     .. Intrinsic Functions ..
</span>      INTRINSIC          ABS
<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">     Quick return if possible
</span><span class="comment">*</span><span class="comment">
</span>      IF( N.LE.0 )
     $   RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Get machine parameters
</span><span class="comment">*</span><span class="comment">
</span>      SMLNUM = <a name="SLAMCH.69"></a><a href="slamch.f.html#SLAMCH.1">SLAMCH</a>( <span class="string">'S'</span> )
      BIGNUM = ONE / SMLNUM
      CALL <a name="SLABAD.71"></a><a href="slabad.f.html#SLABAD.1">SLABAD</a>( SMLNUM, BIGNUM )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Initialize the denominator to SA and the numerator to 1.
</span><span class="comment">*</span><span class="comment">
</span>      CDEN = SA
      CNUM = ONE
<span class="comment">*</span><span class="comment">
</span>   10 CONTINUE
      CDEN1 = CDEN*SMLNUM
      CNUM1 = CNUM / BIGNUM
      IF( ABS( CDEN1 ).GT.ABS( CNUM ) .AND. CNUM.NE.ZERO ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Pre-multiply X by SMLNUM if CDEN is large compared to CNUM.
</span><span class="comment">*</span><span class="comment">
</span>         MUL = SMLNUM
         DONE = .FALSE.
         CDEN = CDEN1
      ELSE IF( ABS( CNUM1 ).GT.ABS( CDEN ) ) THEN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Pre-multiply X by BIGNUM if CDEN is small compared to CNUM.
</span><span class="comment">*</span><span class="comment">
</span>         MUL = BIGNUM
         DONE = .FALSE.
         CNUM = CNUM1
      ELSE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">        Multiply X by CNUM / CDEN and return.
</span><span class="comment">*</span><span class="comment">
</span>         MUL = CNUM / CDEN
         DONE = .TRUE.
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Scale the vector X by MUL
</span><span class="comment">*</span><span class="comment">
</span>      CALL CSSCAL( N, MUL, SX, INCX )
<span class="comment">*</span><span class="comment">
</span>      IF( .NOT.DONE )
     $   GO TO 10
<span class="comment">*</span><span class="comment">
</span>      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="CSRSCL.112"></a><a href="csrscl.f.html#CSRSCL.1">CSRSCL</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

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