Fixes in flow transformations

kmath-commons/src/main/kotlin/scientifik/kmath/transform/Transformations.kt

@@ -5,6 +5,8 @@ import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 import org.apache.commons.math3.transform.*
 import scientifik.kmath.operations.Complex
+import scientifik.kmath.streaming.chunked
+import scientifik.kmath.streaming.spread
 import scientifik.kmath.structures.*
 
 
@@ -33,40 +35,40 @@ object Transformations {
     fun fourier(
         normalization: DftNormalization = DftNormalization.STANDARD,
         direction: TransformType = TransformType.FORWARD
-    ): BufferTransform<Complex, Complex> = {
+    ): SuspendBufferTransform<Complex, Complex> = {
         FastFourierTransformer(normalization).transform(it.toArray(), direction).asBuffer()
     }
 
     fun realFourier(
         normalization: DftNormalization = DftNormalization.STANDARD,
         direction: TransformType = TransformType.FORWARD
-    ): BufferTransform<Double, Complex> = {
+    ): SuspendBufferTransform<Double, Complex> = {
         FastFourierTransformer(normalization).transform(it.asArray(), direction).asBuffer()
     }
 
     fun sine(
         normalization: DstNormalization = DstNormalization.STANDARD_DST_I,
         direction: TransformType = TransformType.FORWARD
-    ): BufferTransform<Double, Double> = {
+    ): SuspendBufferTransform<Double, Double> = {
         FastSineTransformer(normalization).transform(it.asArray(), direction).asBuffer()
     }
 
     fun cosine(
         normalization: DctNormalization = DctNormalization.STANDARD_DCT_I,
         direction: TransformType = TransformType.FORWARD
-    ): BufferTransform<Double, Double> = {
+    ): SuspendBufferTransform<Double, Double> = {
         FastCosineTransformer(normalization).transform(it.asArray(), direction).asBuffer()
     }
 
     fun hadamard(
         direction: TransformType = TransformType.FORWARD
-    ): BufferTransform<Double, Double> = {
+    ): SuspendBufferTransform<Double, Double> = {
         FastHadamardTransformer().transform(it.asArray(), direction).asBuffer()
     }
 }
 
 /**
- * Process given [Producer] with commons-math fft transformation
+ * Process given [Flow] with commons-math fft transformation
  */
 @FlowPreview
 fun Flow<Buffer<Complex>>.FFT(
@@ -84,5 +86,24 @@ fun Flow<Buffer<Double>>.FFT(
     direction: TransformType = TransformType.FORWARD
 ): Flow<Buffer<Complex>> {
     val transform = Transformations.realFourier(normalization, direction)
-    return map { transform(it) }
+    return map(transform)
 }
+
+/**
+ * Process a continous flow of real numbers in FFT splitting it in chunks of [bufferSize].
+ */
+@FlowPreview
+@JvmName("realFFT")
+fun Flow<Double>.FFT(
+    bufferSize: Int = Int.MAX_VALUE,
+    normalization: DftNormalization = DftNormalization.STANDARD,
+    direction: TransformType = TransformType.FORWARD
+): Flow<Complex> {
+    return chunked(bufferSize).FFT(normalization,direction).spread()
+}
+
+/**
+ * Map a complex flow into real flow by taking real part of each number
+ */
+@FlowPreview
+fun Flow<Complex>.real(): Flow<Double> = map{it.re}

kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Buffers.kt

@@ -278,3 +278,5 @@ fun <T> Buffer<T>.asReadOnly(): Buffer<T> = if (this is MutableBuffer) {
  * Typealias for buffer transformations
  */
 typealias BufferTransform<T, R> = (Buffer<T>) -> Buffer<R>
+
+typealias SuspendBufferTransform<T, R> = suspend (Buffer<T>) -> Buffer<R>

kmath-coroutines/src/commonMain/kotlin/scientifik/kmath/streaming/BufferFlow.kt

@@ -37,6 +37,9 @@ fun <T> Flow<T>.chunked(bufferSize: Int, bufferFactory: BufferFactory<T>) = flow
             counter = 0
         }
     }
+    if (counter > 0) {
+        emit(bufferFactory(counter) { list[it] })
+    }
 }
 
 /**
@@ -54,8 +57,12 @@ fun Flow<Double>.chunked(bufferSize: Int) = flow {
         if (counter == bufferSize) {
             val buffer = DoubleBuffer(array)
             emit(buffer)
+            counter = 0
         }
     }
+    if (counter > 0) {
+        emit(DoubleBuffer(counter) { array[it] })
+    }
 }
 
 /**