Basic streaming blocks
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package scientifik.kmath.sequential
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import kotlinx.atomicfu.atomic
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import kotlinx.atomicfu.getAndUpdate
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import kotlinx.coroutines.channels.ReceiveChannel
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import scientifik.kmath.operations.Space
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/**
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* An object with a state that accumulates incoming elements
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*/
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interface Accumulator<in T> {
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/**
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* Push a value to accumulator. Blocks if [Accumulator] can't access any more elements at that time
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*/
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fun push(value: T)
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/**
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* Does the same as [push], but suspends instead of blocking if accumulator is full
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*/
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suspend fun send(value: T) = push(value)
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}
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/**
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* Push all elements to accumulator
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*/
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fun <T> Accumulator<T>.pushAll(values: Iterable<T>) {
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for (value in values) {
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push(value)
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}
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}
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/**
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* Offer all elements from channel to accumulator
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*/
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suspend fun <T> Accumulator<T>.offerAll(channel: ReceiveChannel<T>) {
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for (value in channel) {
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send(value)
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}
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}
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/**
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* Generic thread-safe average
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*/
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class GenericMean<T : Any>(val context: Space<T>) : Accumulator<T> {
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//TODO add guard against overflow
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private val counter = atomic(0)
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val sum = atomic(context.zero)
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val value get() = with(context) { sum.value / counter.value }
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override fun push(value: T) {
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with(context) {
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counter.incrementAndGet()
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sum.getAndUpdate { it + value }
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}
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}
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}
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package scientifik.kmath.sequential
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import scientifik.kmath.operations.Space
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typealias Reducer<T, C, R> = (C, Iterable<T>) -> R
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inline fun <T, C, R> Iterable<T>.reduce(context: C, crossinline reducer: Reducer<T, C, R>) =
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reducer(context, this@reduce)
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inline fun <T, C, R> Sequence<T>.reduce(context: C, crossinline reducer: Reducer<T, C, R>) =
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asIterable().reduce(context, reducer)
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inline fun <T, C, R> Array<T>.reduce(context: C, crossinline reducer: Reducer<T, C, R>) =
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asIterable().reduce(context, reducer)
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object Reducers {
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fun <T : Any> mean(): Reducer<T, Space<T>, T> = { context, data ->
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data.fold(GenericMean(context)) { sum, value -> sum.apply { push(value) } }.value
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}
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}
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@ -0,0 +1,170 @@
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package scientifik.kmath.sequential
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import kotlinx.atomicfu.atomic
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import kotlinx.atomicfu.update
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import kotlinx.coroutines.CoroutineScope
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import kotlinx.coroutines.channels.*
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import kotlinx.coroutines.launch
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import kotlinx.coroutines.sync.Mutex
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import kotlinx.coroutines.sync.withLock
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/**
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* Initial chain block. Could produce an element sequence and be connected to single [Consumer]
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*
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* The general rule is that channel is created on first call. Also each element is responsible for its connection so
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* while the connections are symmetric, the scope, used for making the connection is responsible for cancelation.
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*
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* Also connections are not reversible. Once connected block stays faithful until it finishes processing.
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* Manually putting elements to connected block could lead to undetermined behavior and must be avoided.
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*/
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interface Producer<T> {
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val output: ReceiveChannel<T>
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fun connect(consumer: Consumer<T>)
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val consumer: Consumer<T>?
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val outputIsConnected: Boolean get() = consumer != null
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}
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/**
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* Terminal chain block. Could consume an element sequence and be connected to signle [Producer]
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*/
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interface Consumer<T> {
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val input: SendChannel<T>
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fun connect(producer: Producer<T>)
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val producer: Producer<T>?
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val inputIsConnected: Boolean get() = producer != null
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}
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interface Processor<T, R> : Consumer<T>, Producer<R>
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abstract class AbstractProducer<T>(protected val scope: CoroutineScope) : Producer<T> {
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override var consumer: Consumer<T>? = null
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protected set
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override fun connect(consumer: Consumer<T>) {
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//Ignore if already connected to specific consumer
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if (consumer != this.consumer) {
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if (outputIsConnected) error("The output slot of producer is occupied")
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if (consumer.inputIsConnected) error("The input slot of consumer is occupied")
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this.consumer = consumer
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if (consumer.producer != null) {
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//No need to save the job, it will be canceled on scope cancel
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scope.launch {
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output.toChannel(consumer.input)
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}
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// connect back, consumer is already set so no circular reference
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consumer.connect(this)
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} else error("Unreachable statement")
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}
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}
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}
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abstract class AbstractConsumer<T>(protected val scope: CoroutineScope) : Consumer<T> {
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override var producer: Producer<T>? = null
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protected set
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override fun connect(producer: Producer<T>) {
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//Ignore if already connected to specific consumer
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if (producer != this.producer) {
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if (inputIsConnected) error("The input slot of consumer is occupied")
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if (producer.outputIsConnected) error("The input slot of producer is occupied")
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this.producer = producer
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//No need to save the job, it will be canceled on scope cancel
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if (producer.consumer != null) {
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scope.launch {
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producer.output.toChannel(input)
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}
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// connect back
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producer.connect(this)
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} else error("Unreachable statement")
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}
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}
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}
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abstract class AbstracProcessor<T, R>(scope: CoroutineScope) : Processor<T, R>, AbstractProducer<R>(scope) {
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override var producer: Producer<T>? = null
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protected set
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override fun connect(producer: Producer<T>) {
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//Ignore if already connected to specific consumer
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if (producer != this.producer) {
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if (inputIsConnected) error("The input slot of consumer is occupied")
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if (producer.outputIsConnected) error("The input slot of producer is occupied")
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this.producer = producer
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//No need to save the job, it will be canceled on scope cancel
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if (producer.consumer != null) {
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scope.launch {
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producer.output.toChannel(input)
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}
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// connect back
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producer.connect(this)
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} else error("Unreachable statement")
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}
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}
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}
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/**
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* A simple [produce]-based producer
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*/
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class GenericProducer<T>(
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scope: CoroutineScope,
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capacity: Int = Channel.UNLIMITED,
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block: suspend ProducerScope<T>.() -> Unit
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) : AbstractProducer<T>(scope) {
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//The generation begins on first request to output
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override val output: ReceiveChannel<T> by lazy { scope.produce(capacity = capacity, block = block) }
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}
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/**
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* Thread-safe aggregator of values from input. The aggregator does not store all incoming values, it uses fold procedure
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* to incorporate them into state on-arrival.
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* The current aggregated state could be accessed by [value]. The input channel is inactive unless requested
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* @param T - the type of the input element
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* @param S - the type of the aggregator
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*/
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class Reducer<T, S>(
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scope: CoroutineScope,
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initialState: S,
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fold: suspend (S, T) -> S
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) : AbstractConsumer<T>(scope) {
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private val state = atomic(initialState)
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val value: S = state.value
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override val input: SendChannel<T> by lazy {
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//create a channel and start process of reading all elements into aggregator
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Channel<T>(capacity = Channel.RENDEZVOUS).also {
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scope.launch {
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it.consumeEach { value -> state.update { fold(it, value) } }
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}
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}
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}
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}
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/**
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* Collector that accumulates all values in a list. List could be accessed from non-suspending environment via [list] value.
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*/
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class Collector<T>(scope: CoroutineScope) : AbstractConsumer<T>(scope) {
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private val _list = ArrayList<T>()
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private val mutex = Mutex()
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val list: List<T> get() = _list
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override val input: SendChannel<T> by lazy {
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//create a channel and start process of reading all elements into aggregator
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Channel<T>(capacity = Channel.RENDEZVOUS).also {
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scope.launch {
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it.consumeEach { value ->
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mutex.withLock {
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_list.add(value)
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}
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}
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}
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}
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}
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}
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