revert mutex test

partitioning/fast_clustering_t.cpp

@@ -127,8 +127,7 @@ void process_file_part(const std::string& input_filename, int part_id, int start
         }
 
         // lock the mutex for this output file until the end of this loop iteration
-        //std::lock_guard<std::mutex> lock(output_mutexes[cluster_id]);
-        output_mutexes[cluster_id].lock();
+        std::lock_guard<std::mutex> lock(output_mutexes[cluster_id]);
         // write the sequence and its id to a cluster file corresponding to the bases found after the primer
         std::ofstream output_file(output_dir + "/" + cluster_id + ".fasta", std::ios::app); // ios app is to append to the file
         if (!output_file.is_open()) {
@@ -138,7 +137,6 @@ void process_file_part(const std::string& input_filename, int part_id, int start
         }
         output_file << ">" << read_name << "\n" << sequence << "\n"; // output format is fasta
         output_file.close();
-        output_mutexes[cluster_id].unlock();
 
     }
     input_read_file.close();