dlamc4()

subroutine dlamc4	(	integer	emin,
		double precision	start,
		integer	base
	)

Definition at line 623 of file tools.f.

*
*  -- LAPACK auxiliary routine (version 2.0) --
*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
*     Courant Institute, Argonne National Lab, and Rice University
*     October 31, 1992
*
*     .. Scalar Arguments ..
      INTEGER            BASE, EMIN
      DOUBLE PRECISION   START
*     ..
*
*  Purpose
*  =======
*
*  DLAMC4 is a service routine for DLAMC2.
*
*  Arguments
*  =========
*
*  EMIN    (output) EMIN
*          The minimum exponent before (gradual) underflow, computed by
*          setting A = START and dividing by BASE until the previous A
*          can not be recovered.
*
*  START   (input) DOUBLE PRECISION
*          The starting point for determining EMIN.
*
*  BASE    (input) INTEGER
*          The base of the machine.
*
* =====================================================================
*
*     .. Local Scalars ..
      INTEGER            I
      DOUBLE PRECISION   A, B1, B2, C1, C2, D1, D2, ONE, RBASE, ZERO
*     ..
*     .. External Functions ..
      DOUBLE PRECISION   DLAMC3
      EXTERNAL           dlamc3
*     ..
*     .. Executable Statements ..
*
      a = start
      one = 1
      rbase = one / base
      zero = 0
      emin = 1
      b1 = dlamc3( a*rbase, zero )
      c1 = a
      c2 = a
      d1 = a
      d2 = a
*+    WHILE( ( C1.EQ.A ).AND.( C2.EQ.A ).AND.
*    $       ( D1.EQ.A ).AND.( D2.EQ.A )      )LOOP
   10 CONTINUE
      IF( ( c1.EQ.a ) .AND. ( c2.EQ.a ) .AND. ( d1.EQ.a ) .AND.
     $    ( d2.EQ.a ) ) THEN
         emin = emin - 1
         a = b1
         b1 = dlamc3( a / base, zero )
         c1 = dlamc3( b1*base, zero )
         d1 = zero
         DO 20 i = 1, base
            d1 = d1 + b1
   20    CONTINUE
         b2 = dlamc3( a*rbase, zero )
         c2 = dlamc3( b2 / rbase, zero )
         d2 = zero
         DO 30 i = 1, base
            d2 = d2 + b2
   30    CONTINUE
         GO TO 10
      END IF
*+    END WHILE
*
      RETURN
*
*     End of DLAMC4
*

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