From 14f05eb1e1d57e7e555a3a7e0e624785249e307c Mon Sep 17 00:00:00 2001
From: Alexander Nozik <altavir@gmail.com>
Date: Sun, 7 Apr 2019 12:27:49 +0300
Subject: [PATCH] Matrix refactoring

---
 .../kmath/linear/LinearAlgebraBenchmark.kt    |  3 +-
 .../kmath/linear/MultiplicationBenchmark.kt   |  1 +
 build.gradle.kts                              |  1 +
 .../scientifik/kmath/linear/CMMatrix.kt       | 39 ++++-----
 kmath-core/build.gradle.kts                   | 28 -------
 .../scientifik/kmath/linear/BufferMatrix.kt   |  3 +-
 .../linear/{Matrix.kt => FeaturedMatrix.kt}   | 79 ++++++++-----------
 .../kmath/linear/LUPDecomposition.kt          | 18 +++--
 .../scientifik/kmath/linear/LinearAlgrebra.kt | 17 ++--
 .../scientifik/kmath/linear/MatrixFeatures.kt |  8 +-
 .../scientifik/kmath/linear/VirtualMatrix.kt  | 11 ++-
 .../kmath/structures/NDStructure.kt           |  3 +-
 ...pecializedStructures.kt => Structure1D.kt} | 60 ++++----------
 .../kmath/structures/Structure2D.kt           | 79 +++++++++++++++++++
 .../scientifik/kmath/linear/MatrixTest.kt     |  2 +-
 .../kmath/linear/RealLUSolverTest.kt          |  4 +-
 .../scientifik.kmath.linear/KomaMatrix.kt     | 14 ++--
 kmath-memory/build.gradle.kts                 | 36 +--------
 18 files changed, 196 insertions(+), 210 deletions(-)
 rename kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/{Matrix.kt => FeaturedMatrix.kt} (75%)
 rename kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/{SpecializedStructures.kt => Structure1D.kt} (59%)
 create mode 100644 kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Structure2D.kt

diff --git a/benchmarks/src/main/kotlin/scientifik/kmath/linear/LinearAlgebraBenchmark.kt b/benchmarks/src/main/kotlin/scientifik/kmath/linear/LinearAlgebraBenchmark.kt
index 45a6a774e..fda31b01e 100644
--- a/benchmarks/src/main/kotlin/scientifik/kmath/linear/LinearAlgebraBenchmark.kt
+++ b/benchmarks/src/main/kotlin/scientifik/kmath/linear/LinearAlgebraBenchmark.kt
@@ -1,6 +1,7 @@
 package scientifik.kmath.linear
 
 import koma.matrix.ejml.EJMLMatrixFactory
+import scientifik.kmath.structures.Matrix
 import kotlin.random.Random
 import kotlin.system.measureTimeMillis
 
@@ -30,7 +31,7 @@ fun main() {
 
     //commons-math
 
-    val cmContext = CMMatrixContext
+    val cmContext = CMLUPSolver
 
     val commonsTime = measureTimeMillis {
         cmContext.run {
diff --git a/benchmarks/src/main/kotlin/scientifik/kmath/linear/MultiplicationBenchmark.kt b/benchmarks/src/main/kotlin/scientifik/kmath/linear/MultiplicationBenchmark.kt
index 0b3b7c275..7b1bd9e7e 100644
--- a/benchmarks/src/main/kotlin/scientifik/kmath/linear/MultiplicationBenchmark.kt
+++ b/benchmarks/src/main/kotlin/scientifik/kmath/linear/MultiplicationBenchmark.kt
@@ -1,6 +1,7 @@
 package scientifik.kmath.linear
 
 import koma.matrix.ejml.EJMLMatrixFactory
+import scientifik.kmath.structures.Matrix
 import kotlin.random.Random
 import kotlin.system.measureTimeMillis
 
diff --git a/build.gradle.kts b/build.gradle.kts
index 5ad331c48..964eb4998 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -193,6 +193,7 @@ subprojects {
             targets.all {
                 sourceSets.all {
                     languageSettings.progressiveMode = true
+                    languageSettings.enableLanguageFeature("InlineClasses")
                 }
             }
 
diff --git a/kmath-commons/src/main/kotlin/scientifik/kmath/linear/CMMatrix.kt b/kmath-commons/src/main/kotlin/scientifik/kmath/linear/CMMatrix.kt
index 808b2768b..513dfe517 100644
--- a/kmath-commons/src/main/kotlin/scientifik/kmath/linear/CMMatrix.kt
+++ b/kmath-commons/src/main/kotlin/scientifik/kmath/linear/CMMatrix.kt
@@ -3,13 +3,14 @@ package scientifik.kmath.linear
 import org.apache.commons.math3.linear.*
 import org.apache.commons.math3.linear.RealMatrix
 import org.apache.commons.math3.linear.RealVector
+import scientifik.kmath.structures.Matrix
 
-class CMMatrix(val origin: RealMatrix, features: Set<MatrixFeature>? = null) : Matrix<Double> {
+class CMMatrix(val origin: RealMatrix, features: Set<MatrixFeature>? = null) : FeaturedMatrix<Double> {
     override val rowNum: Int get() = origin.rowDimension
     override val colNum: Int get() = origin.columnDimension
 
     override val features: Set<MatrixFeature> = features ?: sequence<MatrixFeature> {
-        if(origin is DiagonalMatrix) yield(DiagonalFeature)
+        if (origin is DiagonalMatrix) yield(DiagonalFeature)
     }.toSet()
 
     override fun suggestFeature(vararg features: MatrixFeature) =
@@ -45,28 +46,13 @@ fun Point<Double>.toCM(): CMVector = if (this is CMVector) {
 
 fun RealVector.toPoint() = CMVector(this)
 
-object CMMatrixContext : MatrixContext<Double>, LinearSolver<Double> {
+object CMMatrixContext : MatrixContext<Double> {
 
     override fun produce(rows: Int, columns: Int, initializer: (i: Int, j: Int) -> Double): CMMatrix {
         val array = Array(rows) { i -> DoubleArray(columns) { j -> initializer(i, j) } }
         return CMMatrix(Array2DRowRealMatrix(array))
     }
 
-    override fun solve(a: Matrix<Double>, b: Matrix<Double>): CMMatrix {
-        val decomposition = LUDecomposition(a.toCM().origin)
-        return decomposition.solver.solve(b.toCM().origin).toMatrix()
-    }
-
-    override fun solve(a: Matrix<Double>, b: Point<Double>): CMVector {
-        val decomposition = LUDecomposition(a.toCM().origin)
-        return decomposition.solver.solve(b.toCM().origin).toPoint()
-    }
-
-    override fun inverse(a: Matrix<Double>): CMMatrix {
-        val decomposition = LUDecomposition(a.toCM().origin)
-        return decomposition.solver.inverse.toMatrix()
-    }
-
     override fun Matrix<Double>.dot(other: Matrix<Double>) =
         CMMatrix(this.toCM().origin.multiply(other.toCM().origin))
 
@@ -87,6 +73,23 @@ object CMMatrixContext : MatrixContext<Double>, LinearSolver<Double> {
         CMMatrix(this.toCM().origin.scalarMultiply(value.toDouble()))
 }
 
+object CMLUPSolver: LinearSolver<Double>{
+    override fun solve(a: Matrix<Double>, b: Matrix<Double>): CMMatrix {
+        val decomposition = LUDecomposition(a.toCM().origin)
+        return decomposition.solver.solve(b.toCM().origin).toMatrix()
+    }
+
+    override fun solve(a: Matrix<Double>, b: Point<Double>): CMVector {
+        val decomposition = LUDecomposition(a.toCM().origin)
+        return decomposition.solver.solve(b.toCM().origin).toPoint()
+    }
+
+    override fun inverse(a: Matrix<Double>): CMMatrix {
+        val decomposition = LUDecomposition(a.toCM().origin)
+        return decomposition.solver.inverse.toMatrix()
+    }
+}
+
 operator fun CMMatrix.plus(other: CMMatrix): CMMatrix = CMMatrix(this.origin.add(other.origin))
 operator fun CMMatrix.minus(other: CMMatrix): CMMatrix = CMMatrix(this.origin.subtract(other.origin))
 
diff --git a/kmath-core/build.gradle.kts b/kmath-core/build.gradle.kts
index bd125b373..ab6ae7822 100644
--- a/kmath-core/build.gradle.kts
+++ b/kmath-core/build.gradle.kts
@@ -13,34 +13,6 @@ kotlin {
         val commonMain by getting {
             dependencies {
                 api(project(":kmath-memory"))
-                api(kotlin("stdlib"))
-            }
-        }
-        val commonTest by getting {
-            dependencies {
-                implementation(kotlin("test-common"))
-                implementation(kotlin("test-annotations-common"))
-            }
-        }
-        val jvmMain by getting {
-            dependencies {
-                api(kotlin("stdlib-jdk8"))
-            }
-        }
-        val jvmTest by getting {
-            dependencies {
-                implementation(kotlin("test"))
-                implementation(kotlin("test-junit"))
-            }
-        }
-        val jsMain by getting {
-            dependencies {
-                api(kotlin("stdlib-js"))
-            }
-        }
-        val jsTest by getting {
-            dependencies {
-                implementation(kotlin("test-js"))
             }
         }
 //        mingwMain {
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/BufferMatrix.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/BufferMatrix.kt
index dbffea8f3..5d116358d 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/BufferMatrix.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/BufferMatrix.kt
@@ -2,7 +2,6 @@ package scientifik.kmath.linear
 
 import scientifik.kmath.operations.Ring
 import scientifik.kmath.structures.*
-import kotlin.jvm.JvmSynthetic
 
 /**
  * Basic implementation of Matrix space based on [NDStructure]
@@ -25,7 +24,7 @@ class BufferMatrix<T : Any>(
     override val colNum: Int,
     val buffer: Buffer<out T>,
     override val features: Set<MatrixFeature> = emptySet()
-) : Matrix<T> {
+) : FeaturedMatrix<T> {
 
     init {
         if (buffer.size != rowNum * colNum) {
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/Matrix.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/FeaturedMatrix.kt
similarity index 75%
rename from kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/Matrix.kt
rename to kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/FeaturedMatrix.kt
index 329933019..62c360f26 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/Matrix.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/FeaturedMatrix.kt
@@ -8,6 +8,9 @@ import scientifik.kmath.structures.Buffer.Companion.boxing
 import kotlin.math.sqrt
 
 
+/**
+ * Basic operations on matrices. Operates on [Matrix]
+ */
 interface MatrixContext<T : Any> {
     /**
      * Produce a matrix with this context and given dimensions
@@ -101,18 +104,18 @@ interface GenericMatrixContext<T : Any, R : Ring<T>> : MatrixContext<T> {
     operator fun Matrix<T>.times(number: Number): Matrix<T> =
         produce(rowNum, colNum) { i, j -> elementContext.run { get(i, j) * number } }
 
-    operator fun Number.times(matrix: Matrix<T>): Matrix<T> = matrix * this
+    operator fun Number.times(matrix: FeaturedMatrix<T>): Matrix<T> = matrix * this
 
     override fun Matrix<T>.times(value: T): Matrix<T> =
         produce(rowNum, colNum) { i, j -> elementContext.run { get(i, j) * value } }
 }
 
 /**
- * Specialized 2-d structure
+ * A 2d structure plus optional matrix-specific features
  */
-interface Matrix<T : Any> : Structure2D<T> {
-    val rowNum: Int
-    val colNum: Int
+interface FeaturedMatrix<T : Any> : Matrix<T> {
+
+    override val shape: IntArray get() = intArrayOf(rowNum, colNum)
 
     val features: Set<MatrixFeature>
 
@@ -122,70 +125,54 @@ interface Matrix<T : Any> : Structure2D<T> {
      * The implementation does not guarantee to check that matrix actually have the feature, so one should be careful to
      * add only those features that are valid.
      */
-    fun suggestFeature(vararg features: MatrixFeature): Matrix<T>
-
-    override fun get(index: IntArray): T = get(index[0], index[1])
-
-    override val shape: IntArray get() = intArrayOf(rowNum, colNum)
-
-    val rows: Point<Point<T>>
-        get() = VirtualBuffer(rowNum) { i ->
-            VirtualBuffer(colNum) { j -> get(i, j) }
-        }
-
-    val columns: Point<Point<T>>
-        get() = VirtualBuffer(colNum) { j ->
-            VirtualBuffer(rowNum) { i -> get(i, j) }
-        }
-
-    override fun elements(): Sequence<Pair<IntArray, T>> = sequence {
-        for (i in (0 until rowNum)) {
-            for (j in (0 until colNum)) {
-                yield(intArrayOf(i, j) to get(i, j))
-            }
-        }
-    }
+    fun suggestFeature(vararg features: MatrixFeature): FeaturedMatrix<T>
 
     companion object {
-        fun real(rows: Int, columns: Int, initializer: (Int, Int) -> Double) =
-            MatrixContext.real.produce(rows, columns, initializer)
 
-        /**
-         * Build a square matrix from given elements.
-         */
-        fun <T : Any> square(vararg elements: T): Matrix<T> {
-            val size: Int = sqrt(elements.size.toDouble()).toInt()
-            if (size * size != elements.size) error("The number of elements ${elements.size} is not a full square")
-            val buffer = elements.asBuffer()
-            return BufferMatrix(size, size, buffer)
-        }
-
-        fun <T : Any> build(rows: Int, columns: Int): MatrixBuilder<T> = MatrixBuilder(rows, columns)
     }
 }
 
+fun Structure2D.Companion.real(rows: Int, columns: Int, initializer: (Int, Int) -> Double) =
+    MatrixContext.real.produce(rows, columns, initializer)
+
+/**
+ * Build a square matrix from given elements.
+ */
+fun <T : Any> Structure2D.Companion.square(vararg elements: T): FeaturedMatrix<T> {
+    val size: Int = sqrt(elements.size.toDouble()).toInt()
+    if (size * size != elements.size) error("The number of elements ${elements.size} is not a full square")
+    val buffer = elements.asBuffer()
+    return BufferMatrix(size, size, buffer)
+}
+
+fun <T : Any> Structure2D.Companion.build(rows: Int, columns: Int): MatrixBuilder<T> = MatrixBuilder(rows, columns)
+
 class MatrixBuilder<T : Any>(val rows: Int, val columns: Int) {
-    operator fun invoke(vararg elements: T): Matrix<T> {
+    operator fun invoke(vararg elements: T): FeaturedMatrix<T> {
         if (rows * columns != elements.size) error("The number of elements ${elements.size} is not equal $rows * $columns")
         val buffer = elements.asBuffer()
         return BufferMatrix(rows, columns, buffer)
     }
 }
 
+val Matrix<*>.features get() = (this as? FeaturedMatrix)?.features?: emptySet()
+
 /**
  * Check if matrix has the given feature class
  */
-inline fun <reified T : Any> Matrix<*>.hasFeature(): Boolean = features.find { it is T } != null
+inline fun <reified T : Any> Matrix<*>.hasFeature(): Boolean =
+    features.find { it is T } != null
 
 /**
  * Get the first feature matching given class. Does not guarantee that matrix has only one feature matching the criteria
  */
-inline fun <reified T : Any> Matrix<*>.getFeature(): T? = features.filterIsInstance<T>().firstOrNull()
+inline fun <reified T : Any> Matrix<*>.getFeature(): T? =
+    features.filterIsInstance<T>().firstOrNull()
 
 /**
  * Diagonal matrix of ones. The matrix is virtual no actual matrix is created
  */
-fun <T : Any, R : Ring<T>> GenericMatrixContext<T, R>.one(rows: Int, columns: Int): Matrix<T> =
+fun <T : Any, R : Ring<T>> GenericMatrixContext<T, R>.one(rows: Int, columns: Int): FeaturedMatrix<T> =
     VirtualMatrix<T>(rows, columns) { i, j ->
         if (i == j) elementContext.one else elementContext.zero
     }
@@ -194,7 +181,7 @@ fun <T : Any, R : Ring<T>> GenericMatrixContext<T, R>.one(rows: Int, columns: In
 /**
  * A virtual matrix of zeroes
  */
-fun <T : Any, R : Ring<T>> GenericMatrixContext<T, R>.zero(rows: Int, columns: Int): Matrix<T> =
+fun <T : Any, R : Ring<T>> GenericMatrixContext<T, R>.zero(rows: Int, columns: Int): FeaturedMatrix<T> =
     VirtualMatrix<T>(rows, columns) { _, _ -> elementContext.zero }
 
 class TransposedFeature<T : Any>(val original: Matrix<T>) : MatrixFeature
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LUPDecomposition.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LUPDecomposition.kt
index 85ddb8786..94ce8ed97 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LUPDecomposition.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LUPDecomposition.kt
@@ -2,12 +2,12 @@ package scientifik.kmath.linear
 
 import scientifik.kmath.operations.Field
 import scientifik.kmath.operations.Ring
-import scientifik.kmath.structures.MutableBuffer
+import scientifik.kmath.structures.*
 import scientifik.kmath.structures.MutableBuffer.Companion.boxing
-import scientifik.kmath.structures.MutableBufferFactory
-import scientifik.kmath.structures.NDStructure
-import scientifik.kmath.structures.get
 
+/**
+ * Common implementation of [LUPDecompositionFeature]
+ */
 class LUPDecomposition<T : Comparable<T>>(
     private val elementContext: Ring<T>,
     internal val lu: NDStructure<T>,
@@ -20,7 +20,7 @@ class LUPDecomposition<T : Comparable<T>>(
      *
      * L is a lower-triangular matrix with [Ring.one] in diagonal
      */
-    override val l: Matrix<T> = VirtualMatrix(lu.shape[0], lu.shape[1], setOf(LFeature)) { i, j ->
+    override val l: FeaturedMatrix<T> = VirtualMatrix(lu.shape[0], lu.shape[1], setOf(LFeature)) { i, j ->
         when {
             j < i -> lu[i, j]
             j == i -> elementContext.one
@@ -34,7 +34,7 @@ class LUPDecomposition<T : Comparable<T>>(
      *
      * U is an upper-triangular matrix including the diagonal
      */
-    override val u: Matrix<T> = VirtualMatrix(lu.shape[0], lu.shape[1], setOf(UFeature)) { i, j ->
+    override val u: FeaturedMatrix<T> = VirtualMatrix(lu.shape[0], lu.shape[1], setOf(UFeature)) { i, j ->
         if (j >= i) lu[i, j] else elementContext.zero
     }
 
@@ -45,7 +45,7 @@ class LUPDecomposition<T : Comparable<T>>(
      * P is a sparse matrix with exactly one element set to [Ring.one] in
      * each row and each column, all other elements being set to [Ring.zero].
      */
-    override val p: Matrix<T> = VirtualMatrix(lu.shape[0], lu.shape[1]) { i, j ->
+    override val p: FeaturedMatrix<T> = VirtualMatrix(lu.shape[0], lu.shape[1]) { i, j ->
         if (j == pivot[i]) elementContext.one else elementContext.zero
     }
 
@@ -62,7 +62,9 @@ class LUPDecomposition<T : Comparable<T>>(
 
 }
 
-
+/**
+ * Common implementation of LUP [LinearSolver] based on commons-math code
+ */
 class LUSolver<T : Comparable<T>, F : Field<T>>(
     val context: GenericMatrixContext<T, F>,
     val bufferFactory: MutableBufferFactory<T> = ::boxing,
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LinearAlgrebra.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LinearAlgrebra.kt
index 51f61e030..4254fd7ea 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LinearAlgrebra.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/LinearAlgrebra.kt
@@ -3,6 +3,7 @@ package scientifik.kmath.linear
 import scientifik.kmath.operations.Field
 import scientifik.kmath.operations.Norm
 import scientifik.kmath.operations.RealField
+import scientifik.kmath.structures.Matrix
 import scientifik.kmath.structures.VirtualBuffer
 import scientifik.kmath.structures.asSequence
 
@@ -10,9 +11,9 @@ import scientifik.kmath.structures.asSequence
 /**
  * A group of methods to resolve equation A dot X = B, where A and B are matrices or vectors
  */
-interface LinearSolver<T : Any>  {
+interface LinearSolver<T : Any> {
     fun solve(a: Matrix<T>, b: Matrix<T>): Matrix<T>
-    fun solve(a: Matrix<T>, b: Point<T>): Point<T> = solve(a, b.toMatrix()).toVector()
+    fun solve(a: Matrix<T>, b: Point<T>): Point<T> = solve(a, b.toMatrix()).asPoint()
     fun inverse(a: Matrix<T>): Matrix<T>
 }
 
@@ -32,14 +33,14 @@ object VectorL2Norm : Norm<Point<out Number>, Double> {
 typealias RealVector = Vector<Double, RealField>
 typealias RealMatrix = Matrix<Double>
 
-
-
 /**
  * Convert matrix to vector if it is possible
  */
-fun <T: Any> Matrix<T>.toVector(): Point<T> =
+fun <T : Any> Matrix<T>.asPoint(): Point<T> =
     if (this.colNum == 1) {
-        VirtualBuffer(rowNum){ get(it, 0) }
-    } else error("Can't convert matrix with more than one column to vector")
+        VirtualBuffer(rowNum) { get(it, 0) }
+    } else {
+        error("Can't convert matrix with more than one column to vector")
+    }
 
-fun <T: Any> Point<T>.toMatrix(): Matrix<T> = VirtualMatrix(size, 1) { i, _ -> get(i) }
\ No newline at end of file
+fun <T : Any> Point<T>.toMatrix() = VirtualMatrix(size, 1) { i, _ -> get(i) }
\ No newline at end of file
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/MatrixFeatures.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/MatrixFeatures.kt
index 6b45a14b1..de315071f 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/MatrixFeatures.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/MatrixFeatures.kt
@@ -25,7 +25,7 @@ object UnitFeature : MatrixFeature
  * Inverted matrix feature
  */
 interface InverseMatrixFeature<T : Any> : MatrixFeature {
-    val inverse: Matrix<T>
+    val inverse: FeaturedMatrix<T>
 }
 
 /**
@@ -54,9 +54,9 @@ object UFeature: MatrixFeature
  * TODO add documentation
  */
 interface LUPDecompositionFeature<T : Any> : MatrixFeature {
-    val l: Matrix<T>
-    val u: Matrix<T>
-    val p: Matrix<T>
+    val l: FeaturedMatrix<T>
+    val u: FeaturedMatrix<T>
+    val p: FeaturedMatrix<T>
 }
 
 //TODO add sparse matrix feature
\ No newline at end of file
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/VirtualMatrix.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/VirtualMatrix.kt
index 1bab52902..951471a07 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/VirtualMatrix.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/linear/VirtualMatrix.kt
@@ -1,11 +1,16 @@
 package scientifik.kmath.linear
 
+import scientifik.kmath.structures.Matrix
+
 class VirtualMatrix<T : Any>(
     override val rowNum: Int,
     override val colNum: Int,
     override val features: Set<MatrixFeature> = emptySet(),
     val generator: (i: Int, j: Int) -> T
-) : Matrix<T> {
+) : FeaturedMatrix<T> {
+
+    override val shape: IntArray get() = intArrayOf(rowNum, colNum)
+
     override fun get(i: Int, j: Int): T = generator(i, j)
 
     override fun suggestFeature(vararg features: MatrixFeature) =
@@ -13,7 +18,7 @@ class VirtualMatrix<T : Any>(
 
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
-        if (other !is Matrix<*>) return false
+        if (other !is FeaturedMatrix<*>) return false
 
         if (rowNum != other.rowNum) return false
         if (colNum != other.colNum) return false
@@ -34,7 +39,7 @@ class VirtualMatrix<T : Any>(
         /**
          * Wrap a matrix adding additional features to it
          */
-        fun <T : Any> wrap(matrix: Matrix<T>, vararg features: MatrixFeature): Matrix<T> {
+        fun <T : Any> wrap(matrix: Matrix<T>, vararg features: MatrixFeature): FeaturedMatrix<T> {
             return if (matrix is VirtualMatrix) {
                 VirtualMatrix(matrix.rowNum, matrix.colNum, matrix.features + features, matrix.generator)
             } else {
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/NDStructure.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/NDStructure.kt
index 2cf9af6fb..5895251e8 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/NDStructure.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/NDStructure.kt
@@ -5,8 +5,7 @@ interface NDStructure<T> {
 
     val shape: IntArray
 
-    val dimension
-        get() = shape.size
+    val dimension get() = shape.size
 
     operator fun get(index: IntArray): T
 
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/SpecializedStructures.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Structure1D.kt
similarity index 59%
rename from kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/SpecializedStructures.kt
rename to kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Structure1D.kt
index 734aba5ac..df56017a3 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/SpecializedStructures.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Structure1D.kt
@@ -27,20 +27,6 @@ private inline class Structure1DWrapper<T>(val structure: NDStructure<T>) : Stru
     override fun elements(): Sequence<Pair<IntArray, T>> = structure.elements()
 }
 
-/**
- * Represent a [NDStructure] as [Structure1D]. Throw error in case of dimension mismatch
- */
-fun <T> NDStructure<T>.as1D(): Structure1D<T> = if (shape.size == 1) {
-    Structure1DWrapper(this)
-} else {
-    error("Can't create 1d-structure from ${shape.size}d-structure")
-}
-
-fun <T> NDBuffer<T>.as1D(): Structure1D<T> = if (shape.size == 1) {
-    Buffer1DWrapper(this.buffer)
-} else {
-    error("Can't create 1d-structure from ${shape.size}d-structure")
-}
 
 /**
  * A structure wrapper for buffer
@@ -56,39 +42,21 @@ private inline class Buffer1DWrapper<T>(val buffer: Buffer<T>) : Structure1D<T>
     override fun get(index: Int): T = buffer.get(index)
 }
 
-/**
- * Represent this buffer as 1D structure
- */
-fun <T> Buffer<T>.asND(): Structure1D<T> = Buffer1DWrapper(this)
-
-/**
- * A structure that is guaranteed to be two-dimensional
- */
-interface Structure2D<T> : NDStructure<T> {
-    operator fun get(i: Int, j: Int): T
-
-    override fun get(index: IntArray): T {
-        if (index.size != 2) error("Index dimension mismatch. Expected 2 but found ${index.size}")
-        return get(index[0], index[1])
-    }
-}
-
-/**
- * A 2D wrapper for nd-structure
- */
-private inline class Structure2DWrapper<T>(val structure: NDStructure<T>) : Structure2D<T> {
-    override fun get(i: Int, j: Int): T = structure[i, j]
-
-    override val shape: IntArray get() = structure.shape
-
-    override fun elements(): Sequence<Pair<IntArray, T>> = structure.elements()
-}
-
 /**
  * Represent a [NDStructure] as [Structure1D]. Throw error in case of dimension mismatch
  */
-fun <T> NDStructure<T>.as2D(): Structure2D<T> = if (shape.size == 2) {
-    Structure2DWrapper(this)
+fun <T> NDStructure<T>.as1D(): Structure1D<T> = if (shape.size == 1) {
+    if( this is NDBuffer){
+        Buffer1DWrapper(this.buffer)
+    } else {
+        Structure1DWrapper(this)
+    }
 } else {
-    error("Can't create 2d-structure from ${shape.size}d-structure")
-}
\ No newline at end of file
+    error("Can't create 1d-structure from ${shape.size}d-structure")
+}
+
+
+/**
+ * Represent this buffer as 1D structure
+ */
+fun <T> Buffer<T>.asND(): Structure1D<T> = Buffer1DWrapper(this)
\ No newline at end of file
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Structure2D.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Structure2D.kt
new file mode 100644
index 000000000..e736f84a0
--- /dev/null
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/Structure2D.kt
@@ -0,0 +1,79 @@
+package scientifik.kmath.structures
+
+/**
+ * A structure that is guaranteed to be two-dimensional
+ */
+interface Structure2D<T> : NDStructure<T> {
+    val rowNum: Int get() = shape[0]
+    val colNum: Int get() = shape[1]
+
+    operator fun get(i: Int, j: Int): T
+
+    override fun get(index: IntArray): T {
+        if (index.size != 2) error("Index dimension mismatch. Expected 2 but found ${index.size}")
+        return get(index[0], index[1])
+    }
+
+
+    val rows: Buffer<Buffer<T>>
+        get() = VirtualBuffer(rowNum) { i ->
+            VirtualBuffer(colNum) { j -> get(i, j) }
+        }
+
+    val columns: Buffer<Buffer<T>>
+        get() = VirtualBuffer(colNum) { j ->
+            VirtualBuffer(rowNum) { i -> get(i, j) }
+        }
+
+    override fun elements(): Sequence<Pair<IntArray, T>> = sequence {
+        for (i in (0 until rowNum)) {
+            for (j in (0 until colNum)) {
+                yield(intArrayOf(i, j) to get(i, j))
+            }
+        }
+    }
+
+    companion object {
+
+    }
+}
+
+/**
+ * A 2D wrapper for nd-structure
+ */
+private inline class Structure2DWrapper<T>(val structure: NDStructure<T>) : Structure2D<T> {
+    override fun get(i: Int, j: Int): T = structure[i, j]
+
+    override val shape: IntArray get() = structure.shape
+
+    override fun elements(): Sequence<Pair<IntArray, T>> = structure.elements()
+}
+
+/**
+ * Represent a [NDStructure] as [Structure1D]. Throw error in case of dimension mismatch
+ */
+fun <T> NDStructure<T>.as2D(): Structure2D<T> = if (shape.size == 2) {
+    Structure2DWrapper(this)
+} else {
+    error("Can't create 2d-structure from ${shape.size}d-structure")
+}
+
+/**
+ * Represent this 2D structure as 1D if it has exactly one column. Throw error otherwise.
+ */
+fun <T> Structure2D<T>.as1D() = if (colNum == 1) {
+    object : Structure1D<T> {
+        override fun get(index: Int): T = get(index, 0)
+
+        override val shape: IntArray get() = intArrayOf(rowNum)
+
+        override fun elements(): Sequence<Pair<IntArray, T>> = elements()
+
+        override val size: Int get() = rowNum
+    }
+} else {
+    error("Can't convert matrix with more than one column to vector")
+}
+
+
+typealias Matrix<T> = Structure2D<T>
\ No newline at end of file
diff --git a/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/MatrixTest.kt b/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/MatrixTest.kt
index 61aa506c4..8d09b6d7b 100644
--- a/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/MatrixTest.kt
+++ b/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/MatrixTest.kt
@@ -44,7 +44,7 @@ class MatrixTest {
 
     @Test
     fun testBuilder() {
-        val matrix = Matrix.build<Double>(2, 3)(
+        val matrix = FeaturedMatrix.build<Double>(2, 3)(
             1.0, 0.0, 0.0,
             0.0, 1.0, 2.0
         )
diff --git a/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/RealLUSolverTest.kt b/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/RealLUSolverTest.kt
index bfa720369..8887d3a32 100644
--- a/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/RealLUSolverTest.kt
+++ b/kmath-core/src/commonTest/kotlin/scientifik/kmath/linear/RealLUSolverTest.kt
@@ -13,7 +13,7 @@ class RealLUSolverTest {
 
     @Test
     fun testInvert() {
-        val matrix = Matrix.square(
+        val matrix = FeaturedMatrix.square(
             3.0, 1.0,
             1.0, 3.0
         )
@@ -31,7 +31,7 @@ class RealLUSolverTest {
 
         val inverted = LUSolver.real.inverse(decomposed)
 
-        val expected = Matrix.square(
+        val expected = FeaturedMatrix.square(
             0.375, -0.125,
             -0.125, 0.375
         )
diff --git a/kmath-koma/src/commonMain/kotlin/scientifik.kmath.linear/KomaMatrix.kt b/kmath-koma/src/commonMain/kotlin/scientifik.kmath.linear/KomaMatrix.kt
index 343d5b8b9..b95f04887 100644
--- a/kmath-koma/src/commonMain/kotlin/scientifik.kmath.linear/KomaMatrix.kt
+++ b/kmath-koma/src/commonMain/kotlin/scientifik.kmath.linear/KomaMatrix.kt
@@ -2,6 +2,7 @@ package scientifik.kmath.linear
 
 import koma.extensions.fill
 import koma.matrix.MatrixFactory
+import scientifik.kmath.structures.Matrix
 
 class KomaMatrixContext<T : Any>(val factory: MatrixFactory<koma.matrix.Matrix<T>>) : MatrixContext<T>,
     LinearSolver<T> {
@@ -48,24 +49,25 @@ class KomaMatrixContext<T : Any>(val factory: MatrixFactory<koma.matrix.Matrix<T
         KomaMatrix(a.toKoma().origin.inv())
 }
 
-class KomaMatrix<T : Any>(val origin: koma.matrix.Matrix<T>, features: Set<MatrixFeature>? = null) :
-    Matrix<T> {
+class KomaMatrix<T : Any>(val origin: koma.matrix.Matrix<T>, features: Set<MatrixFeature>? = null) : FeaturedMatrix<T> {
     override val rowNum: Int get() = origin.numRows()
     override val colNum: Int get() = origin.numCols()
 
+    override val shape: IntArray get() = intArrayOf(origin.numRows(),origin.numCols())
+
     override val features: Set<MatrixFeature> = features ?: setOf(
         object : DeterminantFeature<T> {
             override val determinant: T get() = origin.det()
         },
         object : LUPDecompositionFeature<T> {
             private val lup by lazy { origin.LU() }
-            override val l: Matrix<T> get() = KomaMatrix(lup.second)
-            override val u: Matrix<T> get() = KomaMatrix(lup.third)
-            override val p: Matrix<T> get() = KomaMatrix(lup.first)
+            override val l: FeaturedMatrix<T> get() = KomaMatrix(lup.second)
+            override val u: FeaturedMatrix<T> get() = KomaMatrix(lup.third)
+            override val p: FeaturedMatrix<T> get() = KomaMatrix(lup.first)
         }
     )
 
-    override fun suggestFeature(vararg features: MatrixFeature): Matrix<T> =
+    override fun suggestFeature(vararg features: MatrixFeature): FeaturedMatrix<T> =
         KomaMatrix(this.origin, this.features + features)
 
     override fun get(i: Int, j: Int): T = origin.getGeneric(i, j)
diff --git a/kmath-memory/build.gradle.kts b/kmath-memory/build.gradle.kts
index f6d10875c..03a05c9fe 100644
--- a/kmath-memory/build.gradle.kts
+++ b/kmath-memory/build.gradle.kts
@@ -8,43 +8,9 @@ val ioVersion: String by rootProject.extra
 kotlin {
     jvm()
     js()
-
-    sourceSets {
-        val commonMain by getting {
-            dependencies {
-                api(kotlin("stdlib"))
-            }
-        }
-        val commonTest by getting {
-            dependencies {
-                implementation(kotlin("test-common"))
-                implementation(kotlin("test-annotations-common"))
-            }
-        }
-        val jvmMain by getting {
-            dependencies {
-                api(kotlin("stdlib-jdk8"))
-            }
-        }
-        val jvmTest by getting {
-            dependencies {
-                implementation(kotlin("test"))
-                implementation(kotlin("test-junit"))
-            }
-        }
-        val jsMain by getting {
-            dependencies {
-                api(kotlin("stdlib-js"))
-            }
-        }
-        val jsTest by getting {
-            dependencies {
-                implementation(kotlin("test-js"))
-            }
-        }
 //        mingwMain {
 //        }
 //        mingwTest {
 //        }
-    }
+    
 }
\ No newline at end of file