Do not save number of deleted elements

Author: Dmitry Yashunin

hnswlib/hnswalg.h

@@ -592,7 +592,6 @@ namespace hnswlib {
             writeBinaryPOD(output, offsetLevel0_);
             writeBinaryPOD(output, max_elements_);
             writeBinaryPOD(output, cur_element_count);
-            writeBinaryPOD(output, num_deleted_);
             writeBinaryPOD(output, size_data_per_element_);
             writeBinaryPOD(output, label_offset_);
             writeBinaryPOD(output, offsetData_);
@@ -630,7 +629,6 @@ namespace hnswlib {
             readBinaryPOD(input, offsetLevel0_);
             readBinaryPOD(input, max_elements_);
             readBinaryPOD(input, cur_element_count);
-            readBinaryPOD(input, num_deleted_);
 
             size_t max_elements = max_elements_i;
             if(max_elements < cur_element_count)
@@ -717,6 +715,11 @@ namespace hnswlib {
                 }
             }
 
+            for (size_t i = 0; i < cur_element_count; i++) {
+                if(isMarkedDeleted(i))
+                    num_deleted_ += 1;
+            }
+
             input.close();
 
             return;