Laboratoire de l'Informatique et du Parallélisme » Pobyso

TODO::

def slz_compute_binade_bounds(number, emin):

    """

    For given "real number", compute the bounds of the binade it belongs to.

    TODO::

        Deal with the emax exponent.

    """

    RF = number.parent()

    precision = RF.precision()

    RRF = RealField(2 * precision)

    if number == 0:

        return (RF(0),RF(2^(emin)) - RF(2^(emin-precision)))

    l2 = RRF(number).abs().log2()

    offset = int(l2)

    if l2 >= 0:

        if number >= 0:

            lb = RF(2^offset)

            ub = RF(2^(offset + 1) - 2^(-precision+offset+1))

        else: #number < 0

            lb = -RF(2^(offset + 1) - 2^(-precision+offset+1))

            ub = -RF(2^offset)

    else: # log2 < 0

        if l2 < emin: # Denormal

            print "Denormal:", l2

            if number >= 0:

                lb = RF(0)

                ub = RF(2^(emin)) - RF(2^(emin-precision))

            else: # number <= 0

                lb = - RF(2^(emin)) + RF(2^(emin-precision))

                ub = RF(0)

        elif l2 > emin: # Normal number other than +/-2^emin.

            if number >= 0:

                lb = RF(2^(offset-1))

                ub = RF(2^(offset)) - RF(2^(-precision+offset))

            else: # number < 0

                lb = -RF(2^(offset) - 2^(-precision+offset))

                ub = -RF(2^(offset-1))

        else: # +/-2^emin

            if number >= 0:

                lb = RF(2^(offset))

                ub = RF(2^(offset+1)) - RF(2^(-precision+offset+1))

            else: # number < 0

                lb = -RF(2^(offset+1) - 2^(-precision+offset+1))

                ub = -RF(2^(offset))

    return (lb, ub)

# End slz_compute_binade_bounds

#