Merge pull request #1182 from lingbai-kong/imdbfix

fix: adjust imdb dataset loader for faster loading speed

Author: Oceania2018

src/TensorFlowNET.Keras/Datasets/Imdb.cs

@@ -112,35 +112,39 @@ public DatasetPass load_data(
 
             if (start_char != null)
             {
-                int[,] new_x_train_array = new int[x_train_array.GetLength(0), x_train_array.GetLength(1) + 1];
-                for (var i = 0; i < x_train_array.GetLength(0); i++)
+                var (d1, d2) = (x_train_array.GetLength(0), x_train_array.GetLength(1));
+                int[,] new_x_train_array = new int[d1, d2 + 1];
+                for (var i = 0; i < d1; i++)
                 {
                     new_x_train_array[i, 0] = (int)start_char;
-                    Array.Copy(x_train_array, i * x_train_array.GetLength(1), new_x_train_array, i * new_x_train_array.GetLength(1) + 1, x_train_array.GetLength(1));
+                    Array.Copy(x_train_array, i * d2, new_x_train_array, i * (d2 + 1) + 1, d2);
                 }
-                int[,] new_x_test_array = new int[x_test_array.GetLength(0), x_test_array.GetLength(1) + 1];
-                for (var i = 0; i < x_test_array.GetLength(0); i++)
+                (d1, d2) = (x_test_array.GetLength(0), x_test_array.GetLength(1));
+                int[,] new_x_test_array = new int[d1, d2 + 1];
+                for (var i = 0; i < d1; i++)
                 {
                     new_x_test_array[i, 0] = (int)start_char;
-                    Array.Copy(x_test_array, i * x_test_array.GetLength(1), new_x_test_array, i * new_x_test_array.GetLength(1) + 1, x_test_array.GetLength(1));
+                    Array.Copy(x_test_array, i * d2, new_x_test_array, i * (d2 + 1) + 1, d2);
                 }
                 x_train_array = new_x_train_array;
                 x_test_array = new_x_test_array;
             }
             else if (index_from != 0)
             {
-                for (var i = 0; i < x_train_array.GetLength(0); i++)
+                var (d1, d2) = (x_train_array.GetLength(0), x_train_array.GetLength(1));
+                for (var i = 0; i < d1; i++)
                 {
-                    for (var j = 0; j < x_train_array.GetLength(1); j++)
+                    for (var j = 0; j < d2; j++)
                     {
                         if (x_train_array[i, j] == 0)
                             break;
                         x_train_array[i, j] += index_from;
                     }
                 }
-                for (var i = 0; i < x_test_array.GetLength(0); i++)
+                (d1, d2) = (x_test_array.GetLength(0), x_test_array.GetLength(1));
+                for (var i = 0; i < d1; i++)
                 {
-                    for (var j = 0; j < x_test_array.GetLength(1); j++)
+                    for (var j = 0; j < d2; j++)
                     {
                         if (x_test_array[i, j] == 0)
                             break;
@@ -169,9 +173,10 @@ public DatasetPass load_data(
 
             if (num_words == null)
             {
+                var (d1, d2) = (xs_array.GetLength(0), xs_array.GetLength(1));
                 num_words = 0;
-                for (var i = 0; i < xs_array.GetLength(0); i++)
-                    for (var j = 0; j < xs_array.GetLength(1); j++)
+                for (var i = 0; i < d1; i++)
+                    for (var j = 0; j < d2; j++)
                         num_words = max((int)num_words, (int)xs_array[i, j]);
             }
 

src/TensorFlowNET.Keras/Utils/data_utils.cs

@@ -53,15 +53,17 @@ public static (int[,], long[]) _remove_long_seq(int maxlen, int[,] seq, long[] l
                     new_seq, new_label: shortened lists for `seq` and `label`.
 
             */
+            var nRow = seq.GetLength(0);
+            var nCol = seq.GetLength(1);
             List<int[]> new_seq = new List<int[]>();
             List<long> new_label = new List<long>();
 
-            for (var i = 0; i < seq.GetLength(0); i++)
+            for (var i = 0; i < nRow; i++)
             {
-                if (maxlen < seq.GetLength(1) && seq[i, maxlen] != 0)
+                if (maxlen < nCol && seq[i, maxlen] != 0)
                     continue;
                 int[] sentence = new int[maxlen];
-                for (var j = 0; j < maxlen && j < seq.GetLength(1); j++)
+                for (var j = 0; j < maxlen && j < nCol; j++)
                 {
                     sentence[j] = seq[i, j];
                 }