Class SubMultiplication

Implements binary multiplication for two numbers a, b stored in the same chain.

Computes a new binary number c := a * b. If the binary representation of c does not fit into the chain, only the lowermost bits are computed and an overflow is detected.

This procedure requires at least 2 pins and it always uses the 2 "outermost / leftmost" pins when traversing the chain. If an amoebot occurs on the chain multiple times, its predecessor and successor directions must be different for all occurrences.

Usage:

Establish a chain of amoebots such that each amoebot knows its predecessor and successor (except the start and end amoebots). Each amoebot should store a bit a and a bit b. The highest-value 1-bit of a must be marked.
Initialize using the Init(bool, bool, bool, Direction, Direction) method. You must pass the bits a and b, the marked MSB of a and the two directions. The start should have no predecessor and the end should have no successor.
Call SetupPinConfig(PinConfiguration) to modify the pin configuration.
Call ActivateSend() in the same round to start the procedure.
After this, call ActivateReceive(), SetupPinConfig(PinConfiguration), and ActivateSend() in this order in every round.
The procedure can be paused after each ActivateReceive() call and resumed by continuing with SetupPinConfig(PinConfiguration) in some future round.
Call IsFinished() after ActivateReceive() to check whether the multiplication is finished.
You can read the result bit c using Bit_C(). After each iteration, you can also read the bit a and the shifted bit b using Bit_A() and Bit_C().
If an overflow has occurred, HaveOverflow() will return true after the procedure has finished.

Inheritance

object

Subroutine

SubMultiplication

Namespace: AS2.Subroutines.BinaryOps

Assembly: .dll

Syntax

public class SubMultiplication : Subroutine

Constructors

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SubMultiplication(Particle, ParticleAttribute<int>)

Declaration

public SubMultiplication(Particle p, ParticleAttribute<int> stateAttr = null)

Parameters

Type	Name	Description
Particle	p
ParticleAttribute<int>	stateAttr

Fields

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bit_A

Declaration

private const int bit_A = 2

Field Value

Type	Description
int

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bit_Add

Declaration

private const int bit_Add = 14

Field Value

Type	Description
int

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bit_B

Declaration

private const int bit_B = 3

Field Value

Type	Description
int

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bit_C

Declaration

private const int bit_C = 4

Field Value

Type	Description
int

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bit_Finished

Declaration

private const int bit_Finished = 13

Field Value

Type	Description
int

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bit_MSB_A

Declaration

private const int bit_MSB_A = 6

Field Value

Type	Description
int

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bit_Overflow

Declaration

private const int bit_Overflow = 15

Field Value

Type	Description
int

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bit_ShiftError

Declaration

private const int bit_ShiftError = 16

Field Value

Type	Description
int

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bit_Token

Declaration

private const int bit_Token = 5

Field Value

Type	Description
int

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state

Declaration

private ParticleAttribute<int> state

Field Value

Type	Description
ParticleAttribute<int>

Methods

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ActivateReceive()

Activation during ActivateBeep() to receive the beeps sent in the last round. Should always be called before SetupPinConfig(PinConfiguration) and ActivateSend(), except in the very first activation, where it should not be called.

Declaration

public void ActivateReceive()

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ActivateSend()

Activation during ActivateBeep() to send the beeps required for this step. Must be called after ActivateReceive() and SetupPinConfig(PinConfiguration).

Declaration

public void ActivateSend()

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Bit_A()

This amoebot's bit of a.

Declaration

public bool Bit_A()

Returns

Type	Description
bool	Whether this amoebot's bit of `a` is equal to `1`.

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Bit_B()

This amoebot's bit of b. Note that b will be shifted along the chain during the procedure, one step per iteration.

Declaration

public bool Bit_B()

Returns

Type	Description
bool	Whether this amoebot's bit of `b` is equal to `1`.

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Bit_C()

This amoebot's bit of c, the result of multiplying a and b.

Declaration

public bool Bit_C()

Returns

Type	Description
bool	Whether this amoebot's bit of `c` is equal to `1`.

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GetStateBit(int)

Helper for reading a single bit from the state integer.

Declaration

private bool GetStateBit(int bit)

Parameters

Type	Name	Description
int	bit	The position of the bit.

Returns

Type	Description
bool	The value of the state bit at position `bit`.

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HaveOverflow()

Checks whether an overflow occurred during the multiplication. Should only be called once the procedure has finished.

Declaration

public bool HaveOverflow()

Returns

Type	Description
bool	`true` if and only if a 1-bit of `b` was shifted or a carry bit was sent beyond the end of the chain.

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Init(bool, bool, bool, Direction, Direction)

Initializes the subroutine. Must be called by each amoebot on the chain that stores a and b.

Declaration

public void Init(bool a, bool b, bool msbA, Direction predDir, Direction succDir)

Parameters

Type	Name	Description
bool	a	This amoebot's bit of `a`.
bool	b	This amoebot's bit of `b`.
bool	msbA	Whether this amoebot is the highest-value 1-bit of `a`.
Direction	predDir	The direction of the predecessor. Should be NONE only at the start of the chain.
Direction	succDir	The direction of the successor. Should be NONE only at the end of the chain.

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IsFinished()

Checks whether the procedure is finished. Should be called after ActivateReceive().

Declaration

public bool IsFinished()

Returns

Type	Description
bool	`true` if and only if the multiplication procedure has finished.

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PredDir()

Helper for reading the predecessor direction from the state integer.

Declaration

private Direction PredDir()

Returns

Type	Description
Direction	The direction of the chain predecessor.

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Round()

Helper for reading the round number from the state integer.

Declaration

private int Round()

Returns

Type	Description
int	The current round number.

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SetRound(int)

Helper for setting the round counter.

Declaration

private void SetRound(int round)

Parameters

Type	Name	Description
int	round	The new value of the round counter.

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SetStateBit(int, bool)

Helper for setting a single bit from the state integer.

Declaration

private void SetStateBit(int bit, bool value)

Parameters

Type	Name	Description
int	bit	The position of the bit.
bool	value	The new value of the bit.

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SetupPinConfig(PinConfiguration)

Sets up the required circuits for the next step in the given pin configuration. This must be called after ActivateReceive() and before ActivateSend().

Declaration

public void SetupPinConfig(PinConfiguration pc)

Parameters

Type	Name	Description
PinConfiguration	pc	The pin configuration to set up. Partition set IDs will always equal one of the IDs of the contained pins.

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SuccDir()

Helper for reading the successor direction from the state integer.

Declaration

private Direction SuccDir()

Returns

Type	Description
Direction	The direction of the chain successor.