qr fix

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

@@ -14,7 +14,7 @@ public interface LinearOpsTensorAlgebra<T, TensorType : TensorStructure<T>, Inde
     public fun TensorType.cholesky(): TensorType
 
     //https://pytorch.org/docs/stable/linalg.html#torch.linalg.qr
-    public fun TensorType.qr(): TensorType
+    public fun TensorType.qr(): Pair<TensorType, TensorType>
 
     //https://pytorch.org/docs/stable/generated/torch.lu.html
     public fun TensorType.lu(): Pair<TensorType, IndexTensorType>

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

@@ -1,8 +1,10 @@
 package space.kscience.kmath.tensors.core
 
+import space.kscience.kmath.linear.Matrix
 import space.kscience.kmath.nd.MutableStructure2D
 import space.kscience.kmath.nd.Structure1D
 import space.kscience.kmath.nd.Structure2D
+import space.kscience.kmath.nd.asND
 import space.kscience.kmath.tensors.LinearOpsTensorAlgebra
 import kotlin.math.sqrt
 
@@ -141,7 +143,15 @@ public class DoubleLinearOpsTensorAlgebra :
         return lTensor
     }
 
-    override fun DoubleTensor.qr(): DoubleTensor {
+    private fun matrixQR(
+        matrix: Structure2D<Double>,
+        q: MutableStructure2D<Double>,
+        r: MutableStructure2D<Double>
+    ) {
+
+    }
+
+    override fun DoubleTensor.qr(): Pair<DoubleTensor, DoubleTensor> {
         TODO("ANDREI")
     }
 
@@ -154,6 +164,7 @@ public class DoubleLinearOpsTensorAlgebra :
     }
 
     private fun luMatrixDet(lu: Structure2D<Double>, pivots: Structure1D<Int>): Double {
+        // todo check
         val m = lu.shape[0]
         val sign = if((pivots[m] - m) % 2 == 0) 1.0 else -1.0
         return (0 until m).asSequence().map { lu[it, it] }.fold(sign) { left, right -> left * right }
@@ -184,6 +195,7 @@ public class DoubleLinearOpsTensorAlgebra :
         pivots: Structure1D<Int>,
         invMatrix : MutableStructure2D<Double>
     ): Unit {
+        //todo check
         val m = lu.shape[0]
 
         for (j in 0 until m) {