Examples of ptolemy.math.Precision

ptolemy.math.Precision

This class defines the precision of a signed or unsigned fixed point value. The precision of a fixed point value is represented as internally as three fields: the number of bits (n), the binary exponent (e), and a sign bit (s). The number of bits (n) defines the dynamic range of the format (2ⁿ). The exponent (e) determines the placement of the binary point for all values of this format. This binary point placement is "fixed" and is specified within the precision format rather than within individual Fixed point values. The mantissa bits of all fixed point values using this this precision format are multiplied by 2^m. Note that m can take on a positive, negative, or zero value. This allows the binary point to be placed anywhere necessary and even beyond the bounds of the mantissa (i.e. to the right of the lsb or to the left of the msb). The sign value s is used to indicate whether the fixed point precision value is treated as signed (s = 1) or unsigned (s = 0).

Signed fixed point formats are represented in a 2's complement format. As a consequence, a single bit is used to represent the sign of the number. The value of a multi-bit signed number is:

Signed(B) = 2^m x (- b_{n-1} x 2^{n-1} + \sum_{i=0}^{n-2} b_i x 2^i), where b_i is the value of bit i of the bit vector.

Unsigned fixed formats are represented as unsigned binary values. No bits are used to represent the sign and all values are positive. The actual value of a multi-bit unsigned fixed point number is:

Unsigned(B) = 2^m x (\sum_{i=0}^{n-1} b_i x 2^i)

This class supports several different String formats for specifying and displaying the Precision. These String formats are supported by several classes that extend the {@link PrecisionFormat} class. Several such classeshave been created. Any given precision string format can be represented in any of the valid precision string formats. The four supported Precision String formats are shown in the table below. A static singleton object of each of these formats is provided in this class. Each String Representation column of the table represent equivalent Precision formats:

Format Name	Format Spec	String Representation
{@link IntegerFractionPrecisionFormat}	[integer bits].[fraction bits]	3.2	0.7	-2.12	12.-4	32.0	U1.7
{@link LengthIntegerPrecisionFormat}	[total bits]/[integer bits]	5/3	7/0	10/-2	8/12	32/32	U8/1
{@link VHDLPrecisionFormat}	[MSb position]:[LSb position]	2:-2	-1:-7	-3:-12	11:4	31:0	U0:-7
{@link LengthExponentPrecisionFormat}	[total bits]e[binary point position]	5e-2	7e-7	10e-12	8e4	32e0	U8e-7

An instance of the class is immutable, meaning that its value is set in the constructor and cannot then be modified. @author Bart Kienhuis, Contributor: Mike Wirthlin @version $Id: Precision.java,v 1.73 2007/12/06 21:57:08 cxh Exp $ @since Ptolemy II 0.4 @Pt.ProposedRating Yellow (kienhuis) @Pt.AcceptedRating Red (kienhuis) @see FixPoint

     *  fractional part.
     */
    public FixMatrixToken() {
        _rowCount = 1;
        _columnCount = 1;
        _precision = new Precision(32, 32);
        _value = new FixPoint[1][1];
        _value[0][0] = Quantizer.round(0.0, _precision);
    }

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     *   is invalid.
     */
    public FixToken(double value, int numberOfBits, int integerBits)
            throws IllegalArgumentException {
        try {
            Precision precision = new Precision(numberOfBits, integerBits);
            FixPointQuantization q = new FixPointQuantization(precision,
                    Overflow.SATURATE, Rounding.NEAREST);
            _value = new FixPoint(value, q);
        } catch (NumberFormatException e) {
            throw new IllegalArgumentException(e.getMessage());

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        if (!_isUnitless()) {
            unitString = " * " + unitsString();
        }


        Precision precision = _value.getPrecision();
        return "fix(" + _value.toString() + "," + precision.getNumberOfBits()
                + "," + precision.getIntegerBitLength() + ")" + unitString;
    }

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    /** Construct a new fix type, with no integer bits and no
     * fractional bits.  This (rather useless) type represents the
     * bottom of the FixPoint type lattice.
     */
    public FixType() {
        _precision = new Precision(0, 0);
    }

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     *  @return A new type, or BaseType.GENERAL, if the operation does
     *  not make sense for the given types.
     */
    public Type add(Type rightArgumentType) {
        if (rightArgumentType instanceof FixType) {
            Precision rPrecision = ((FixType) rightArgumentType).getPrecision();
            Precision newPrecision = FixPoint.addPrecision(rPrecision,
                    _precision);
            FixType returnType = new FixType(newPrecision);
            return returnType;
        } else {
            return TypeLattice.leastUpperBound(this, rightArgumentType);

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     *  not make sense for the given types.
     */
    public Type divide(Type rightArgumentType) {
        if (rightArgumentType instanceof FixType) {
            if (rightArgumentType instanceof FixType) {
                Precision rPrecision = ((FixType) rightArgumentType)
                        .getPrecision();
                Precision newPrecision = FixPoint.dividePrecision(rPrecision,
                        _precision);
                FixType returnType = new FixType(newPrecision);
                return returnType;
            } else {
                return TypeLattice.leastUpperBound(this, rightArgumentType);

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     */
    public boolean equals(Object object) {
        if (!(object instanceof FixType)) {
            return false;
        }
        Precision precision = ((FixType) object).getPrecision();
        if (!(precision.equals(_precision))) {
            return false;
        }


        return true;
    }

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     *  @return A new type, or BaseType.GENERAL, if the operation does
     *  not make sense for the given types.
     */
    public Type multiply(Type rightArgumentType) {
        if (rightArgumentType instanceof FixType) {
            Precision rPrecision = ((FixType) rightArgumentType).getPrecision();
            Precision newPrecision = FixPoint.multiplyPrecision(rPrecision,
                    _precision);
            FixType returnType = new FixType(newPrecision);
            return returnType;
        } else {
            return TypeLattice.leastUpperBound(this, rightArgumentType);

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     *  @return A new type, or BaseType.GENERAL, if the operation does
     *  not make sense for the given types.
     */
    public Type subtract(Type rightArgumentType) {
        if (rightArgumentType instanceof FixType) {
            Precision rPrecision = ((FixType) rightArgumentType).getPrecision();
            Precision newPrecision = FixPoint.subtractPrecision(rPrecision,
                    _precision);
            FixType returnType = new FixType(newPrecision);
            return returnType;
        } else {
            return TypeLattice.leastUpperBound(this, rightArgumentType);

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        if (!(type instanceof FixType)) {
            throw new IllegalArgumentException("FixType._compare: "
                    + "The argument is not a FixType.");
        }


        Precision precision = ((FixType) type).getPrecision();


        int fractionBits1 = _precision.getFractionBitLength();
        int fractionBits2 = precision.getFractionBitLength();
        int integerBits1 = _precision.getFractionBitLength();
        int integerBits2 = precision.getFractionBitLength();
        boolean signBit1 = _precision.isSigned();
        boolean signBit2 = precision.isSigned();
        int compareBits1, compareBits2;


        if (_precision.equals(precision)) {
            return CPO.SAME;
        } else if (signBit1 == signBit2) {

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Related Classes of ptolemy.math.Precision

ptolemy.actor.lib.conversions.DoubleToFix

ptolemy.actor.lib.conversions.FixToFix

ptolemy.actor.lib.vhdl.Concat

ptolemy.actor.lib.vhdl.FixComparator

ptolemy.actor.lib.vhdl.FixConst

ptolemy.actor.lib.vhdl.FixSequence

ptolemy.actor.lib.vhdl.FixTransformer

ptolemy.actor.lib.vhdl.LogicalNot

ptolemy.actor.lib.vhdl.LogicFunction

ptolemy.actor.lib.vhdl.Memory

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