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

    protected StructuredType _greatestLowerBound(StructuredType type) {
        if (!(type instanceof FixType)) {
            throw new IllegalArgumentException("FixType._greatestLowerBound: "
                    + "The argument is not a FixType.");
        }
        Precision precision = ((FixType) type).getPrecision();
        int fractionBits = Math.min(precision.getFractionBitLength(),
                _precision.getFractionBitLength());
        int integerBits = Math.min(precision.getIntegerBitLength(), _precision
                .getIntegerBitLength());
        return new FixType(new Precision(fractionBits + integerBits,
                integerBits));
    }

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    protected StructuredType _leastUpperBound(StructuredType type) {
        if (!(type instanceof FixType)) {
            throw new IllegalArgumentException("FixType._greatestLowerBound: "
                    + "The argument is not a FixType.");
        }
        Precision precision = ((FixType) type).getPrecision();
        int fractionBits = Math.max(precision.getFractionBitLength(),
                _precision.getFractionBitLength());
        int integerBits = Math.max(precision.getIntegerBitLength(), _precision
                .getIntegerBitLength());
        FixType returnType = new FixType(new Precision(fractionBits
                + integerBits, integerBits));
        returnType._checkPrecision();
        return returnType;
    }

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            _capacity = ((ScalarToken) capacity.getToken()).intValue();


            _addressWidth = (int) Math.floor(Math.log(_capacity) / Math.log(2));


        } else if (attribute.getName().equals("outputPrecision")) {
            _dataWidth = new Precision(getPortPrecision(output))
                    .getNumberOfBits();
        }
    }

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     *  @exception IllegalActionException If there is no director.
     */
    public void fire() throws IllegalActionException {
        super.fire();
        FixToken result = null;
        Precision precision = new Precision(0, 1, 0);


        if (A.isKnown() && B.isKnown()) {
            result = new FixToken(0, precision);
            FixToken inputA = new FixToken();
            FixToken inputB = new FixToken();

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     * @exception NoRoomException If there is no room in the receiver.
     */
    public void sendOutput(TypedIOPort port, int channel, Token token)
            throws NoRoomException, IllegalActionException {
        if (port.getType() == BaseType.FIX && token instanceof FixToken) {
            Precision precision = new Precision(((Parameter) getAttribute(port
                    .getName()
                    + "Precision")).getExpression());


            Overflow overflow = Overflow.getName(((Parameter) getAttribute(port
                    .getName()

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     *  @exception IllegalActionException If there is no director.
     */
    public void fire() throws IllegalActionException {
        super.fire();


        Precision precision = new Precision(getPortPrecision(output));


        Overflow overflow = Overflow
                .getName(((Parameter) getAttribute("outputOverflow"))
                        .getExpression().toLowerCase());

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                || (enable.hasToken(0) && ((BooleanToken) enable.get(0))
                        .booleanValue())) {
            ArrayToken valuesArray = (ArrayToken) values.getToken();


            if (_currentIndex < valuesArray.length()) {
                Precision precision = new Precision(
                        ((Parameter) getAttribute("outputPrecision"))
                                .getExpression());


                Overflow overflow = Overflow
                        .getName(((Parameter) getAttribute("outputOverflow"))

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                _checkFixTokenWidth(channel, 1);


                _channel = channel.fixValue().getUnscaledValue().intValue();
            }


            Precision outputPrecision = new Precision(
                    ((Parameter) getAttribute("outputPrecision"))
                            .getExpression());


            FixToken tokenA = null;
            FixToken tokenB = null;


            if (A.hasToken(0)) {
                tokenA = (FixToken) A.get(0);
                if (tokenA.fixValue().getPrecision().getNumberOfBits() != outputPrecision
                        .getNumberOfBits()) {


                    throw new IllegalActionException(this,
                            "Input A has different width than the output port");
                }
            }
            if (B.hasToken(0)) {
                tokenB = (FixToken) B.get(0);
                if (tokenB.fixValue().getPrecision().getNumberOfBits() != outputPrecision
                        .getNumberOfBits()) {


                    throw new IllegalActionException(this,
                            "Input B has different width than the output port");
                }

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    public void fire() throws IllegalActionException {
        super.fire();


        if (A.isKnown() && B.isKnown()) {
            BigInteger intResult = null;
            Precision precision = new Precision(
                    ((Parameter) getAttribute("outputPrecision"))
                            .getExpression());
            if (A.hasToken(0) && B.hasToken(0)) {
                FixPoint valueA = ((FixToken) A.get(0)).fixValue();
                FixPoint valueB = ((FixToken) B.get(0)).fixValue();
                if (valueA.getPrecision().getNumberOfBits() != precision
                        .getNumberOfBits()) {
                    throw new IllegalActionException(this,
                            "Input A has different width than the output port");
                }
                if (valueB.getPrecision().getNumberOfBits() != precision
                        .getNumberOfBits()) {
                    throw new IllegalActionException(this,
                            "Input B has different width than the output port");
                }
                BigInteger bigIntA = valueA.getUnscaledValue();

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     *  @param numberOfBits The total number of bits.
     *  @param integerBits The number of bits used for the integer part.
     *  @return A fixed point representation of the value.
     */
    public static FixPoint fix(int value, int numberOfBits, int integerBits) {
        Precision precision = new Precision(numberOfBits, integerBits);
        return Quantizer.round(value, precision);
    }

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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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