diff --git a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/BufferedTensor.kt b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/BufferedTensor.kt
index 264692d0c..c9a401ad5 100644
--- a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/BufferedTensor.kt
+++ b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/BufferedTensor.kt
@@ -12,6 +12,9 @@ public open class BufferedTensor<T>(
     public val strides: TensorStrides
         get() = TensorStrides(shape)
 
+    public val numel: Int
+        get() = strides.linearSize
+
     override fun get(index: IntArray): T = buffer[bufferStart + strides.offset(index)]
 
     override fun set(index: IntArray, value: T) {
diff --git a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/DoubleLinearOpsTensorAlgebra.kt b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/DoubleLinearOpsTensorAlgebra.kt
index d6b202556..689eda9e0 100644
--- a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/DoubleLinearOpsTensorAlgebra.kt
+++ b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/DoubleLinearOpsTensorAlgebra.kt
@@ -1,7 +1,7 @@
 package space.kscience.kmath.tensors
 
 public class DoubleLinearOpsTensorAlgebra :
-    LinearOpsTensorAlgebra<Double, DoubleTensor>,
+    LinearOpsTensorAlgebra<Double, DoubleTensor, IntTensor>,
     DoubleTensorAlgebra() {
 
     override fun DoubleTensor.inv(): DoubleTensor {
diff --git a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/LinearOpsTensorAlgebra.kt b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/LinearOpsTensorAlgebra.kt
index 7450c09c1..2e1c4a92c 100644
--- a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/LinearOpsTensorAlgebra.kt
+++ b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/tensors/LinearOpsTensorAlgebra.kt
@@ -1,7 +1,7 @@
 package space.kscience.kmath.tensors
 
 
-public interface LinearOpsTensorAlgebra<T, TensorType : TensorStructure<T>> :
+public interface LinearOpsTensorAlgebra<T, TensorType : TensorStructure<T>, IndexTensorType: TensorStructure<Int>> :
     TensorPartialDivisionAlgebra<T, TensorType> {
 
     //https://pytorch.org/docs/stable/linalg.html#torch.linalg.inv
@@ -14,7 +14,7 @@ public interface LinearOpsTensorAlgebra<T, TensorType : TensorStructure<T>> :
     public fun TensorType.qr(): TensorType
 
     //https://pytorch.org/docs/stable/generated/torch.lu.html
-    public fun TensorType.lu(): Pair<TensorType, IntTensor>
+    public fun TensorType.lu(): Pair<TensorType, IndexTensorType>
 
     //https://pytorch.org/docs/stable/generated/torch.lu_unpack.html
     public fun luPivot(lu: TensorType, pivots: IntTensor): Triple<TensorType, TensorType, TensorType>