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Basic streaming blocks

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This commit is contained in:
Alexander Nozik 2019-02-05 22:31:41 +03:00
parent 3413d21385
commit 1fe786c90f
3 changed files with 170 additions and 78 deletions
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57
kmath-sequential/src/commonMain/kotlin/scientifik/kmath/sequential/Accumulators.kt
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@ -1,57 +0,0 @@
package scientifik.kmath.sequential
import kotlinx.atomicfu.atomic
import kotlinx.atomicfu.getAndUpdate
import kotlinx.coroutines.channels.ReceiveChannel
import scientifik.kmath.operations.Space
/**
* An object with a state that accumulates incoming elements
*/
interface Accumulator<in T> {
/**
* Push a value to accumulator. Blocks if [Accumulator] can't access any more elements at that time
*/
fun push(value: T)
/**
* Does the same as [push], but suspends instead of blocking if accumulator is full
*/
suspend fun send(value: T) = push(value)
}
/**
* Push all elements to accumulator
*/
fun <T> Accumulator<T>.pushAll(values: Iterable<T>) {
for (value in values) {
push(value)
}
}
/**
* Offer all elements from channel to accumulator
*/
suspend fun <T> Accumulator<T>.offerAll(channel: ReceiveChannel<T>) {
for (value in channel) {
send(value)
}
}
/**
* Generic thread-safe average
*/
class GenericMean<T : Any>(val context: Space<T>) : Accumulator<T> {
//TODO add guard against overflow
private val counter = atomic(0)
val sum = atomic(context.zero)
val value get() = with(context) { sum.value / counter.value }
override fun push(value: T) {
with(context) {
counter.incrementAndGet()
sum.getAndUpdate { it + value }
}
}
}

21
kmath-sequential/src/commonMain/kotlin/scientifik/kmath/sequential/Reducers.kt
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package scientifik.kmath.sequential
import scientifik.kmath.operations.Space
typealias Reducer<T, C, R> = (C, Iterable<T>) -> R
inline fun <T, C, R> Iterable<T>.reduce(context: C, crossinline reducer: Reducer<T, C, R>) =
reducer(context, this@reduce)
inline fun <T, C, R> Sequence<T>.reduce(context: C, crossinline reducer: Reducer<T, C, R>) =
asIterable().reduce(context, reducer)
inline fun <T, C, R> Array<T>.reduce(context: C, crossinline reducer: Reducer<T, C, R>) =
asIterable().reduce(context, reducer)
object Reducers {
fun <T : Any> mean(): Reducer<T, Space<T>, T> = { context, data ->
data.fold(GenericMean(context)) { sum, value -> sum.apply { push(value) } }.value
}
}

170
kmath-sequential/src/commonMain/kotlin/scientifik/kmath/sequential/StreamingBlocks.kt Normal file
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package scientifik.kmath.sequential
import kotlinx.atomicfu.atomic
import kotlinx.atomicfu.update
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.channels.*
import kotlinx.coroutines.launch
import kotlinx.coroutines.sync.Mutex
import kotlinx.coroutines.sync.withLock
/**
* Initial chain block. Could produce an element sequence and be connected to single [Consumer]
*
* The general rule is that channel is created on first call. Also each element is responsible for its connection so
* while the connections are symmetric, the scope, used for making the connection is responsible for cancelation.
*
* Also connections are not reversible. Once connected block stays faithful until it finishes processing.
* Manually putting elements to connected block could lead to undetermined behavior and must be avoided.
*/
interface Producer<T> {
val output: ReceiveChannel<T>
fun connect(consumer: Consumer<T>)
val consumer: Consumer<T>?
val outputIsConnected: Boolean get() = consumer != null
}
/**
* Terminal chain block. Could consume an element sequence and be connected to signle [Producer]
*/
interface Consumer<T> {
val input: SendChannel<T>
fun connect(producer: Producer<T>)
val producer: Producer<T>?
val inputIsConnected: Boolean get() = producer != null
}
interface Processor<T, R> : Consumer<T>, Producer<R>
abstract class AbstractProducer<T>(protected val scope: CoroutineScope) : Producer<T> {
override var consumer: Consumer<T>? = null
protected set
override fun connect(consumer: Consumer<T>) {
//Ignore if already connected to specific consumer
if (consumer != this.consumer) {
if (outputIsConnected) error("The output slot of producer is occupied")
if (consumer.inputIsConnected) error("The input slot of consumer is occupied")
this.consumer = consumer
if (consumer.producer != null) {
//No need to save the job, it will be canceled on scope cancel
scope.launch {
output.toChannel(consumer.input)
}
// connect back, consumer is already set so no circular reference
consumer.connect(this)
} else error("Unreachable statement")
}
}
}
abstract class AbstractConsumer<T>(protected val scope: CoroutineScope) : Consumer<T> {
override var producer: Producer<T>? = null
protected set
override fun connect(producer: Producer<T>) {
//Ignore if already connected to specific consumer
if (producer != this.producer) {
if (inputIsConnected) error("The input slot of consumer is occupied")
if (producer.outputIsConnected) error("The input slot of producer is occupied")
this.producer = producer
//No need to save the job, it will be canceled on scope cancel
if (producer.consumer != null) {
scope.launch {
producer.output.toChannel(input)
}
// connect back
producer.connect(this)
} else error("Unreachable statement")
}
}
}
abstract class AbstracProcessor<T, R>(scope: CoroutineScope) : Processor<T, R>, AbstractProducer<R>(scope) {
override var producer: Producer<T>? = null
protected set
override fun connect(producer: Producer<T>) {
//Ignore if already connected to specific consumer
if (producer != this.producer) {
if (inputIsConnected) error("The input slot of consumer is occupied")
if (producer.outputIsConnected) error("The input slot of producer is occupied")
this.producer = producer
//No need to save the job, it will be canceled on scope cancel
if (producer.consumer != null) {
scope.launch {
producer.output.toChannel(input)
}
// connect back
producer.connect(this)
} else error("Unreachable statement")
}
}
}
/**
* A simple [produce]-based producer
*/
class GenericProducer<T>(
scope: CoroutineScope,
capacity: Int = Channel.UNLIMITED,
block: suspend ProducerScope<T>.() -> Unit
) : AbstractProducer<T>(scope) {
//The generation begins on first request to output
override val output: ReceiveChannel<T> by lazy { scope.produce(capacity = capacity, block = block) }
}
/**
* Thread-safe aggregator of values from input. The aggregator does not store all incoming values, it uses fold procedure
* to incorporate them into state on-arrival.
* The current aggregated state could be accessed by [value]. The input channel is inactive unless requested
* @param T - the type of the input element
* @param S - the type of the aggregator
*/
class Reducer<T, S>(
scope: CoroutineScope,
initialState: S,
fold: suspend (S, T) -> S
) : AbstractConsumer<T>(scope) {
private val state = atomic(initialState)
val value: S = state.value
override val input: SendChannel<T> by lazy {
//create a channel and start process of reading all elements into aggregator
Channel<T>(capacity = Channel.RENDEZVOUS).also {
scope.launch {
it.consumeEach { value -> state.update { fold(it, value) } }
}
}
}
}
/**
* Collector that accumulates all values in a list. List could be accessed from non-suspending environment via [list] value.
*/
class Collector<T>(scope: CoroutineScope) : AbstractConsumer<T>(scope) {
private val _list = ArrayList<T>()
private val mutex = Mutex()
val list: List<T> get() = _list
override val input: SendChannel<T> by lazy {
//create a channel and start process of reading all elements into aggregator
Channel<T>(capacity = Channel.RENDEZVOUS).also {
scope.launch {
it.consumeEach { value ->
mutex.withLock {
_list.add(value)
}
}
}
}
}
}