Improve RaggedTensor

src/TensorFlowNET.Core/Operations/array_ops.cs

@@ -1139,5 +1139,18 @@ public static Tensor placeholder(TF_DataType dtype, Shape shape = null, string n
             var _op = tf.OpDefLib._apply_op_helper("Placeholder", name: name, args: new { dtype, shape });
             return _op.output;
         }
+
+        public static int get_positive_axis(int axis, int ndims=-100, string axis_name="axis", string ndims_name= "ndims")
+        {
+            if(ndims != -100)
+            {
+                if (axis >= 0 && axis < ndims) return axis;
+                else if (-ndims <= axis && axis < 0) return axis + ndims;
+                else throw new ValueError($"{axis_name}={axis} out of bounds:expected {-ndims}<={axis_name}<{ndims}");
+
+            } else if(axis < 0) throw new ValueError($"{axis_name}={axis} may only be negative if {ndims_name} is statically known.");
+            return axis;
+        }
+
     }
 }

src/TensorFlowNET.Core/Tensors/Ragged/RaggedTensor.cs

@@ -163,5 +163,38 @@ public static implicit operator RaggedTensor(Tensor tensor)
         {
             return tensor.Tag as RaggedTensor;
         }
+        public Tensor nrows(TF_DataType out_type, string name = null)
+        {
+            tf_with(ops.name_scope(name, "RaggedNRows"), scope =>
+            {
+                return math_ops.cast(this._row_partition.nrows(), dtype: out_type);
+            });
+            return null;
+        }
+        public RaggedTensor row_lengths(int axis=-1, string name=null)
+        {
+            if (axis == 0) return this._row_partition.nrows();
+            if (axis == 1) return this._row_partition.row_lengths();
+            var values = (RaggedTensor)this._values;
+            axis = array_ops.get_positive_axis(
+                axis, this.shape.rank, ndims_name: "rank(this)");
+            if (axis == 0) return this.nrows(this._row_partition.GetDataType());
+            else if (axis == 1)
+            {
+                var splits = this._row_partition.row_splits;
+                return splits[new Slice(start: 1)] - splits[new Slice(stop: -1)];
+
+            }
+            else if (this._values is RaggedTensor)
+            {
+                return values.row_lengths(axis - 1);
+            }
+            else
+            {
+                var shape = array_ops.shape(values, out_type: this._row_partition.GetDataType());
+                return array_ops.ones(shape[new Slice(stop:axis - 1)], this._row_partition.GetDataType()) *
+                            shape[axis - 1];
+            }
+        }
     }
 }

src/TensorFlowNET.Core/Tensors/Ragged/RowPartition.cs

@@ -14,10 +14,15 @@ You may obtain a copy of the License at
    limitations under the License.
 ******************************************************************************/
 
+using Serilog.Debugging;
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
+//using System.ComponentModel.DataAnnotations;
 using System.Text;
+using System.Xml.Linq;
 using Tensorflow.Framework;
+using Tensorflow.NumPy;
 using static Tensorflow.Binding;
 
 namespace Tensorflow
@@ -99,5 +104,55 @@ public static RowPartition from_row_splits(Tensor row_splits,
                 return new RowPartition(row_splits);
             });
         }
+
+        public static RowPartition from_row_lengths(Tensor row_lengths,
+                       bool validate=true,
+                       TF_DataType dtype = TF_DataType.TF_INT32,
+                       TF_DataType dtype_hint= TF_DataType.TF_INT32)
+        {
+            row_lengths = _convert_row_partition(
+                row_lengths, "row_lengths", dtype_hint: dtype_hint, dtype: dtype);
+            Tensor row_limits = math_ops.cumsum<Tensor>(row_lengths, tf.constant(-1));
+            Tensor row_splits = array_ops.concat(new Tensor[] { tf.convert_to_tensor(np.array(new int[] { 0 }, TF_DataType.TF_INT64)), row_limits }, axis:0);
+            return new RowPartition(row_splits: row_splits, row_lengths: row_lengths);
+        }
+
+        public static Tensor _convert_row_partition(Tensor partition, string name, TF_DataType dtype, 
+            TF_DataType dtype_hint= TF_DataType.TF_INT64)
+        {
+            if (partition is NDArray && partition.GetDataType() == np.int32) partition = ops.convert_to_tensor(partition, name: name);
+            if (partition.GetDataType() != np.int32 && partition.GetDataType() != np.int64) throw new ValueError($"{name} must have dtype int32 or int64");
+            return partition;
+        }
+
+        public Tensor nrows()
+        {
+            /*Returns the number of rows created by this `RowPartition*/
+            if (this._nrows != null) return this._nrows;
+            var nsplits = tensor_shape.dimension_at_index(this._row_splits.shape, 0);
+            if (nsplits == null) return array_ops.shape(this._row_splits, out_type: this.row_splits.dtype)[0] - 1;
+            else return constant_op.constant(nsplits.value - 1, dtype: this.row_splits.dtype);
+        }
+
+        public Tensor row_lengths()
+        {
+
+            if (this._row_splits != null)
+            {
+                int nrows_plus_one = tensor_shape.dimension_value(this._row_splits.shape[0]);
+                return tf.constant(nrows_plus_one - 1);
+
+            }
+            if (this._row_lengths != null)
+            {
+                var nrows = tensor_shape.dimension_value(this._row_lengths.shape[0]);
+                return tf.constant(nrows);
+            }
+            if(this._nrows != null)
+            {
+                return tensor_util.constant_value(this._nrows);
+            }
+            return tf.constant(-1);
+        }
     }
 }

test/TensorFlowNET.UnitTest/ManagedAPI/RaggedTensorTest.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Tensorflow;
+using Tensorflow.NumPy;
+using static Tensorflow.Binding;
+
+namespace TensorFlowNET.UnitTest.ManagedAPI
+{
+    public class RaggedTensorTest :EagerModeTestBase
+    {
+        [TestMethod]
+        public void Test_from_row_lengths()
+        {
+            var row_lengths = tf.convert_to_tensor(np.array(new int[] { 2, 0, 3, 1, 1 }, TF_DataType.TF_INT64));
+            var rp = RowPartition.from_row_lengths(row_lengths, validate: false);
+            var rp_row_lengths = rp.row_lengths();
+            var rp_nrows = rp.nrows();
+            Assert.IsTrue(rp_nrows.ToArray<long>()[0] == rp.nrows().ToArray<long>()[0]);
+
+        }
+    }
+}