slamc4()

subroutine slamc4	(	integer	EMIN,
		real	START,
		integer	BASE
	)

SLAMC4

Purpose:

 SLAMC4 is a service routine for SLAMC2.

Parameters

[out]	EMIN	The minimum exponent before (gradual) underflow, computed by setting A = START and dividing by BASE until the previous A can not be recovered.
[in]	START	The starting point for determining EMIN.
[in]	BASE	The base of the machine.

Definition at line 694 of file slamchf77.f.

*
*  -- LAPACK auxiliary routine (version 3.7.0) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2010
*
*     .. Scalar Arguments ..
      INTEGER            BASE
      INTEGER            EMIN
      REAL               START
*     ..
* =====================================================================
*
*     .. Local Scalars ..
      INTEGER            I
      REAL               A, B1, B2, C1, C2, D1, D2, ONE, RBASE, ZERO
*     ..
*     .. External Functions ..
      REAL               SLAMC3
      EXTERNAL           slamc3
*     ..
*     .. Executable Statements ..
*
      a = start
      one = 1
      rbase = one / base
      zero = 0
      emin = 1
      b1 = slamc3( 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 = slamc3( a / base, zero )
         c1 = slamc3( b1*base, zero )
         d1 = zero
         DO 20 i = 1, base
            d1 = d1 + b1
   20    CONTINUE
         b2 = slamc3( a*rbase, zero )
         c2 = slamc3( 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 SLAMC4
*

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