MA01BD - SLICOT Library Routine Documentation

## MA01BD

### Safely computing the general product of K real scalars

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

      To compute the general product of K real scalars without over-
      or underflow.

Specification

          SUBROUTINE MA01BD( BASE, LGBAS, K, S, A, INCA, ALPHA, BETA, SCAL )
    C     .. Scalar Arguments ..
          INTEGER           INCA, K, SCAL
          DOUBLE PRECISION  ALPHA, BASE, BETA, LGBAS
    C     .. Array Arguments ..
          INTEGER           S(*)
          DOUBLE PRECISION  A(*)

Arguments

Input/Output Parameters

      BASE    (input)  DOUBLE PRECISION
              Machine base.

      LGBAS   (input)  DOUBLE PRECISION
              Logarithm of BASE.

      K       (input)  INTEGER
              The number of scalars.  K >= 1.

      S       (input)  INTEGER array, dimension (K)
              The signature array. Each entry of S must be 1 or -1.

      A       (input)  DOUBLE PRECISION array, dimension (K)
              Vector of real scalars.

      INCA    (input)  INTEGER
              Increment for the array A. INCA <> 0.

      ALPHA   (output)  DOUBLE PRECISION
              ALPHA is a real scalar such that

                 ALPHA / BETA * BASE**(SCAL)

              is the general product of the scalars in the array A.

      BETA    (output)  DOUBLE PRECISION
              BETA is either 0.0 or 1.0.
              See also the description of ALPHA.

      SCAL    (output)  INTEGER
              Scaling factor exponent, see ALPHA.

Further Comments

      None

Example

Program Text

      None

Program Data

      None

Program Results

      None

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