Tensor pool

include/ambit/tensor.h

@@ -214,7 +214,7 @@ class Tensor
      *
      * Example successful use case:
      *  Tensor A = Tensor::build(CoreTensor, "A3", {4,5,6});
-     *  A.at({0,0,0}) = 1.0; // Fill element 
+     *  A.at({0,0,0}) = 1.0; // Fill element
      *
      * Results:
      *  @return reference to the element, if tensor object supports it
@@ -517,6 +517,8 @@ class Tensor
   public:
     void reshape(const Dimension &dims);
 
+    void resize(const Dimension &dims);
+
     // => Operator Overloading API <= //
 
     LabeledTensor operator()(const string &indices) const;

include/ambit/tensor_pool.h

@@ -0,0 +1,108 @@
+/*
+ * @BEGIN LICENSE
+ *
+ * ambit: C++ library for the implementation of tensor product calculations
+ *        through a clean, concise user interface.
+ *
+ * Copyright (c) 2014-2017 Ambit developers.
+ *
+ * The copyrights for code used from other parties are included in
+ * the corresponding files.
+ *
+ * This file is part of ambit.
+ *
+ * Ambit is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * Ambit is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with ambit; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * @END LICENSE
+ */
+
+#if !defined(TENSOR_POOL_H)
+#define TENSOR_POOL_H
+
+#include <vector>
+
+#include <ambit/tensor.h>
+
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-parameter"
+#endif
+
+namespace ambit
+{
+
+class TempTensor;
+
+class TensorPool
+{
+  public:
+    // => Constructors <= //
+
+    /**
+     * Returns a temporary Core tensor. This function is thread safe.
+     *
+     * Results:
+     *  @return a TempTensor object that will automatically make the
+     *  tensor available to the pool upon destruction.
+     **/
+    TempTensor get_tensor();
+
+    /**
+     * Release a temporary Tensor
+     *
+     * Parameters:
+     *  @param id the id of the Tensor
+     *
+     * Results:
+     *  release a temporary tensor and make it available for a new call from
+     *  get_tensor
+     **/
+    void release_tensor(size_t id);
+
+    /**
+     * Frees the TensorPool's internal memory allocation.
+     */
+    void reset();
+
+  private:
+    std::vector<std::pair<bool, Tensor>> tensor_pool_;
+};
+
+class TempTensor
+{
+  public:
+    // => Constructor <= //
+    TempTensor(size_t id, Tensor t, TensorPool *tp) : id_(id), t_(t), tp_(tp) {}
+    ~TempTensor() { tp_->release_tensor(id_); }
+    Tensor tensor() { return t_; }
+
+  private:
+    size_t id_;
+    Tensor t_;
+    TensorPool *tp_;
+};
+
+namespace tensor_pool
+{
+void initialize();
+void finalize();
+TempTensor get_tensor();
+} // namespace tensor_pool
+} // namespace ambit
+
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
+#endif

src/CMakeLists.txt

@@ -58,6 +58,7 @@ set(TENSOR_SOURCES
         tensor/slice.cc
         tensor/sliced_tensor.cc
         tensor/tensor.cc
+        tensor/tensor_pool.cc
         tensor/tensorimpl.cc
         tensor/timer.cc
 

src/tensor/core/core.cc

@@ -55,6 +55,21 @@ void CoreTensorImpl::reshape(const Dimension &dims)
     TensorImpl::reshape(dims);
 }
 
+void CoreTensorImpl::resize(const Dimension &dims, bool trim)
+{
+    TensorImpl::reshape(dims);
+    // Requests that the vector capacity be at least enough to contain numel
+    // elements. If numel is greater than the current vector capacity, the
+    // function causes the container to reallocate its storage increasing its
+    // capacity to numel (or greater).
+
+    if (numel() > data_.size())
+    {
+        // TODO: implement trimming
+        data_.reserve(numel());
+    }
+}
+
 double CoreTensorImpl::norm(int type) const
 {
     double val = 0.0;

src/tensor/core/core.h

@@ -45,6 +45,8 @@ class CoreTensorImpl : public TensorImpl
     // the strides in the slice codes.
     void reshape(const Dimension &dims);
 
+    void resize(const Dimension &dims, bool trim = true);
+
     vector<double> &data() { return data_; }
     const vector<double> &data() const { return data_; }