Slight adjustment to tensor internals

kmath-tensors/src/commonMain/kotlin/space/kscience/kmath/tensors/core/DoubleTensorAlgebra.kt

@@ -5,8 +5,10 @@
 
 package space.kscience.kmath.tensors.core
 
+import space.kscience.kmath.nd.MutableStructure2D
 import space.kscience.kmath.nd.as1D
 import space.kscience.kmath.nd.as2D
+import space.kscience.kmath.structures.indices
 import space.kscience.kmath.tensors.api.AnalyticTensorAlgebra
 import space.kscience.kmath.tensors.api.LinearOpsTensorAlgebra
 import space.kscience.kmath.tensors.api.Tensor
@@ -813,28 +815,32 @@ public open class DoubleTensorAlgebra :
         val sTensor = zeros(commonShape + intArrayOf(min(n, m)))
         val vTensor = zeros(commonShape + intArrayOf(min(n, m), m))
 
-        tensor.matrixSequence()
+        val matrices = tensor.matrices
-            .zip(
+        val uTensors = uTensor.matrices
-                uTensor.matrixSequence()
+        val sTensorVectors = sTensor.vectors
-                    .zip(
+        val vTensors = vTensor.matrices
-                        sTensor.vectorSequence()
+
-                            .zip(vTensor.matrixSequence())
+        for (index in matrices.indices) {
+            val matrix = matrices[index]
+            val usv = Triple(
+                uTensors[index],
+                sTensorVectors[index],
+                vTensors[index]
             )
-            ).forEach { (matrix, USV) ->
             val matrixSize = matrix.shape.reduce { acc, i -> acc * i }
             val curMatrix = DoubleTensor(
                 matrix.shape,
-                    matrix.mutableBuffer.array().slice(matrix.bufferStart until matrix.bufferStart + matrixSize)
+                matrix.mutableBuffer.array()
+                    .slice(matrix.bufferStart until matrix.bufferStart + matrixSize)
                     .toDoubleArray()
             )
-                svdHelper(curMatrix, USV, m, n, epsilon)
+            svdHelper(curMatrix, usv, m, n, epsilon)
         }
 
         return Triple(uTensor.transpose(), sTensor, vTensor.transpose())
     }
 
-    override fun Tensor<Double>.symEig(): Pair<DoubleTensor, DoubleTensor> =
+    override fun Tensor<Double>.symEig(): Pair<DoubleTensor, DoubleTensor> = symEig(epsilon = 1e-15)
-        symEig(epsilon = 1e-15)
 
     /**
      * Returns eigenvalues and eigenvectors of a real symmetric matrix input or a batch of real symmetric matrices,
@@ -846,12 +852,26 @@ public open class DoubleTensorAlgebra :
      */
     public fun Tensor<Double>.symEig(epsilon: Double): Pair<DoubleTensor, DoubleTensor> {
         checkSymmetric(tensor, epsilon)
+
+        fun MutableStructure2D<Double>.cleanSym(n: Int) {
+            for (i in 0 until n) {
+                for (j in 0 until n) {
+                    if (i == j) {
+                        this[i, j] = sign(this[i, j])
+                    } else {
+                        this[i, j] = 0.0
+                    }
+                }
+            }
+        }
+
         val (u, s, v) = tensor.svd(epsilon)
         val shp = s.shape + intArrayOf(1)
         val utv = u.transpose() dot v
         val n = s.shape.last()
-        for (matrix in utv.matrixSequence())
+        for (matrix in utv.matrixSequence()) {
-            cleanSymHelper(matrix.as2D(), n)
+            matrix.as2D().cleanSym(n)
+        }
 
         val eig = (utv dot s.view(shp)).view(s.shape)
         return eig to v

kmath-tensors/src/commonMain/kotlin/space/kscience/kmath/tensors/core/internal/linUtils.kt

@@ -10,41 +10,54 @@ import space.kscience.kmath.nd.MutableStructure2D
 import space.kscience.kmath.nd.as1D
 import space.kscience.kmath.nd.as2D
 import space.kscience.kmath.operations.invoke
-import space.kscience.kmath.tensors.core.*
+import space.kscience.kmath.structures.VirtualBuffer
+import space.kscience.kmath.structures.asSequence
+import space.kscience.kmath.tensors.core.BufferedTensor
+import space.kscience.kmath.tensors.core.DoubleTensor
 import space.kscience.kmath.tensors.core.DoubleTensorAlgebra
-import space.kscience.kmath.tensors.core.DoubleTensorAlgebra.Companion.valueOrNull
+import space.kscience.kmath.tensors.core.IntTensor
 import kotlin.math.abs
 import kotlin.math.min
-import kotlin.math.sign
 import kotlin.math.sqrt
 
-
+internal val <T> BufferedTensor<T>.vectors: VirtualBuffer<BufferedTensor<T>>
-internal fun <T> BufferedTensor<T>.vectorSequence(): Sequence<BufferedTensor<T>> = sequence {
+    get() {
         val n = shape.size
         val vectorOffset = shape[n - 1]
         val vectorShape = intArrayOf(shape.last())
-    for (offset in 0 until numElements step vectorOffset) {
+
-        val vector = BufferedTensor(vectorShape, mutableBuffer, bufferStart + offset)
+        return VirtualBuffer(numElements / vectorOffset) { index ->
-        yield(vector)
+            val offset = index * vectorOffset
+            BufferedTensor(vectorShape, mutableBuffer, bufferStart + offset)
         }
     }
 
-internal fun <T> BufferedTensor<T>.matrixSequence(): Sequence<BufferedTensor<T>> = sequence {
+
+internal fun <T> BufferedTensor<T>.vectorSequence(): Sequence<BufferedTensor<T>> = vectors.asSequence()
+
+/**
+ * A random access alternative to [matrixSequence]
+ */
+internal val <T> BufferedTensor<T>.matrices: VirtualBuffer<BufferedTensor<T>>
+    get() {
         val n = shape.size
         check(n >= 2) { "Expected tensor with 2 or more dimensions, got size $n" }
         val matrixOffset = shape[n - 1] * shape[n - 2]
         val matrixShape = intArrayOf(shape[n - 2], shape[n - 1])
-    for (offset in 0 until numElements step matrixOffset) {
+
-        val matrix = BufferedTensor(matrixShape, mutableBuffer, bufferStart + offset)
+        return VirtualBuffer(numElements / matrixOffset) { index ->
-        yield(matrix)
+            val offset = index * matrixOffset
+            BufferedTensor(matrixShape, mutableBuffer, bufferStart + offset)
         }
     }
 
+internal fun <T> BufferedTensor<T>.matrixSequence(): Sequence<BufferedTensor<T>> = matrices.asSequence()
+
 internal fun dotHelper(
     a: MutableStructure2D<Double>,
     b: MutableStructure2D<Double>,
     res: MutableStructure2D<Double>,
-    l: Int, m: Int, n: Int
+    l: Int, m: Int, n: Int,
 ) {
     for (i in 0 until l) {
         for (j in 0 until n) {
@@ -60,7 +73,7 @@ internal fun dotHelper(
 internal fun luHelper(
     lu: MutableStructure2D<Double>,
     pivots: MutableStructure1D<Int>,
-    epsilon: Double
+    epsilon: Double,
 ): Boolean {
 
     val m = lu.rowNum
@@ -122,7 +135,7 @@ internal fun <T> BufferedTensor<T>.setUpPivots(): IntTensor {
 
 internal fun DoubleTensorAlgebra.computeLU(
     tensor: DoubleTensor,
-    epsilon: Double
+    epsilon: Double,
 ): Pair<DoubleTensor, IntTensor>? {
 
     checkSquareMatrix(tensor.shape)
@@ -139,7 +152,7 @@ internal fun DoubleTensorAlgebra.computeLU(
 internal fun pivInit(
     p: MutableStructure2D<Double>,
     pivot: MutableStructure1D<Int>,
-    n: Int
+    n: Int,
 ) {
     for (i in 0 until n) {
         p[i, pivot[i]] = 1.0
@@ -150,7 +163,7 @@ internal fun luPivotHelper(
     l: MutableStructure2D<Double>,
     u: MutableStructure2D<Double>,
     lu: MutableStructure2D<Double>,
-    n: Int
+    n: Int,
 ) {
     for (i in 0 until n) {
         for (j in 0 until n) {
@@ -170,7 +183,7 @@ internal fun luPivotHelper(
 internal fun choleskyHelper(
     a: MutableStructure2D<Double>,
     l: MutableStructure2D<Double>,
-    n: Int
+    n: Int,
 ) {
     for (i in 0 until n) {
         for (j in 0 until i) {
@@ -200,7 +213,7 @@ internal fun luMatrixDet(lu: MutableStructure2D<Double>, pivots: MutableStructur
 internal fun luMatrixInv(
     lu: MutableStructure2D<Double>,
     pivots: MutableStructure1D<Int>,
-    invMatrix: MutableStructure2D<Double>
+    invMatrix: MutableStructure2D<Double>,
 ) {
     val m = lu.shape[0]
 
@@ -227,7 +240,7 @@ internal fun luMatrixInv(
 internal fun DoubleTensorAlgebra.qrHelper(
     matrix: DoubleTensor,
     q: DoubleTensor,
-    r: MutableStructure2D<Double>
+    r: MutableStructure2D<Double>,
 ) {
     checkSquareMatrix(matrix.shape)
     val n = matrix.shape[0]
@@ -280,12 +293,11 @@ internal fun DoubleTensorAlgebra.svd1d(a: DoubleTensor, epsilon: Double = 1e-10)
 
 internal fun DoubleTensorAlgebra.svdHelper(
     matrix: DoubleTensor,
-    USV: Pair<BufferedTensor<Double>, Pair<BufferedTensor<Double>, BufferedTensor<Double>>>,
+    USV: Triple<BufferedTensor<Double>, BufferedTensor<Double>, BufferedTensor<Double>>,
-    m: Int, n: Int, epsilon: Double
+    m: Int, n: Int, epsilon: Double,
 ) {
     val res = ArrayList<Triple<Double, DoubleTensor, DoubleTensor>>(0)
-    val (matrixU, SV) = USV
+    val (matrixU, matrixS, matrixV) = USV
-    val (matrixS, matrixV) = SV
 
     for (k in 0 until min(n, m)) {
         var a = matrix.copy()
@@ -329,14 +341,3 @@ internal fun DoubleTensorAlgebra.svdHelper(
         matrixV.mutableBuffer.array()[matrixV.bufferStart + i] = vBuffer[i]
     }
 }
-
-internal fun cleanSymHelper(matrix: MutableStructure2D<Double>, n: Int) {
-    for (i in 0 until n)
-        for (j in 0 until n) {
-            if (i == j) {
-                matrix[i, j] = sign(matrix[i, j])
-            } else {
-                matrix[i, j] = 0.0
-            }
-        }
-}