Avoid reading the input file twice for InitializableLookupTable in combination with HashTable.

Before this cl, TextFileLineIterator::total_size() was called for HashTable::DoPrepare, even though HashTable::DoPrepare ignores the size parameter.
In order to have a result ready for TextFileLineIterator::total_size(), Init() called GetNumLinesInTextFile(), which read the whole file. Just to throw away the result :-/

This cl:
- adds a DoLazyPrepare, that gets a functor to get the size, only if needed.
- add HashTable::DoLazyPrepare which does not call this functor.
- modify TextFileLineIterator::Init() to not call GetNumLinesInTextFile() anymore, when vocab_size was given as -1.
- modify TextFileLineIterator::total_size() to call GetNumLinesInTextFile() lazily on the first call, if vocab_size_ was passed as -1.

PiperOrigin-RevId: 190593744

1 files changed, 1 insertions, 1 deletions

diff --git a/tensorflow/core/kernels/initializable_lookup_table.cc b/tensorflow/core/kernels/initializable_lookup_table.cc
index 9c428cdedc..06d53eba30 100644
--- a/tensorflow/core/kernels/initializable_lookup_table.cc
+++ b/tensorflow/core/kernels/initializable_lookup_table.cc
@@ -44,7 +44,7 @@ Status InitializableLookupTable::Initialize(InitTableIterator& iter) {
     return errors::FailedPrecondition("Table already initialized.");
   }
 
-  TF_RETURN_IF_ERROR(DoPrepare(iter.total_size()));
+  TF_RETURN_IF_ERROR(DoLazyPrepare([&iter]() { return iter.total_size(); }));
   while (iter.Valid()) {
     TF_RETURN_IF_ERROR(DoInsert(iter.keys(), iter.values()));
     iter.Next();