employed initialise_with_0 flag to reduce unnecessary 0-fill

src/buildblock/ProjDataInMemory.cxx

@@ -73,12 +73,18 @@ ProjDataInMemory::ProjDataInMemory(shared_ptr<const ExamInfo> const& exam_info_s
 void
 ProjDataInMemory::create_buffer(const bool initialise_with_0)
 {
+  if (!initialise_with_0) {
+    this->buffer.set_initialise_with_zeros(false);
+    this->buffer.grow(0, this->size_all());
+    return;
+  }
 #if 0  
   float *b = new float[this->size_all()];
   if (initialise_with_0)
     memset(b, 0, this->size_all()*sizeof(float));
   return b;
 #else
+  this->buffer.set_initialise_with_zeros(true);
   this->buffer = Array<1, float>(static_cast<int>(this->size_all()));
 #endif
 }

src/include/stir/Array.h

@@ -569,6 +569,15 @@ class Array<1, elemT> : public NumericVectorWithOffset<elemT, elemT>
   inline const elemT& at(const BasicCoordinate<1, int>& c) const;
   //@}
 
+  void set_initialise_with_zeros(bool iwz)
+  {
+    init_with_zeros_ = iwz;
+  }
+  bool get_initialise_with_zeros() const
+  {
+    return init_with_zeros_;
+  }
+
 private:
   // Make sure we can call init() recursively.
   template <int num_dimensions2, class elemT2>
@@ -579,6 +588,8 @@ class Array<1, elemT> : public NumericVectorWithOffset<elemT, elemT>
     \arg data_ptr should start to a contiguous block of correct size
   */
   inline void init(const IndexRange<1>& range, elemT* const data_ptr, bool copy_data);
+
+  bool init_with_zeros_= 0;
 };
 
 END_NAMESPACE_STIR

src/include/stir/Array.inl

@@ -583,6 +583,12 @@ Array<1, elemT>::resize(const int min_index, const int max_index)
   const size_type oldlength = this->size();
 
   base_type::resize(min_index, max_index);
+
+  if (!get_initialise_with_zeros()) {
+    this->check_state();
+    return;
+  }
+
   if (oldlength == 0)
     {
       for (int i = this->get_min_index(); i <= this->get_max_index(); i++)