// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
// SPDX-FileCopyrightText: Bradley M. Bell <bradbell@seanet.com>
// SPDX-FileContributor: 2003-22 Bradley M. Bell
// ----------------------------------------------------------------------------

/*
{xrst_begin capacity_order.cpp}

Controlling Taylor Coefficient Memory Allocation: Example and Test
##################################################################

{xrst_literal
   // BEGIN C++
   // END C++
}

{xrst_end capacity_order.cpp}
*/
// BEGIN C++
# include <cppad/cppad.hpp>

namespace {
   bool test(void)
   {  bool ok = true;
      using CppAD::AD;
      using CppAD::NearEqual;
      using CppAD::thread_alloc;

      // domain space vector
      size_t n(1), m(1);
      CPPAD_TESTVECTOR(AD<double>) ax(n), ay(n);

      // declare independent variables and start tape recording
      ax[0]  = 1.0;
      CppAD::Independent(ax);

      // Set y = x^3, use enough variables so more that the minimal amount
      // of memory is allocated for Taylor coefficients
      ay[0] = 0.;
      for( size_t i = 0; i < 10; i++)
         ay[0] += ax[0] * ax[0] * ax[0];
      ay[0] = ay[0] / 10.;

      // create f: x -> y and stop tape recording
      // (without running zero order forward mode).
      CppAD::ADFun<double> f;
      f.Dependent(ax, ay);

      // check that this is master thread
      size_t thread = thread_alloc::thread_num();
      ok           &= thread == 0; // this should be master thread

      // The highest order forward mode calculation below is first order.
      // This corresponds to two Taylor coefficient per variable,direction
      // (orders zero and one). Preallocate memory for speed.
      size_t inuse  = thread_alloc::inuse(thread);
      f.capacity_order(2);
      ok &= thread_alloc::inuse(thread) > inuse;

      // zero order forward mode
      CPPAD_TESTVECTOR(double) x(n), y(m);
      x[0] = 0.5;
      y    = f.Forward(0, x);
      double eps = 10. * CppAD::numeric_limits<double>::epsilon();
      ok  &= NearEqual(y[0], x[0] * x[0] * x[0], eps, eps);

      // forward computation of partials w.r.t. x
      CPPAD_TESTVECTOR(double) dx(n), dy(m);
      dx[0] = 1.;
      dy    = f.Forward(1, dx);
      ok   &= NearEqual(dy[0], 3. * x[0] * x[0], eps, eps);

      // Suppose we no longer need the first order Taylor coefficients.
      inuse = thread_alloc::inuse(thread);
      f.capacity_order(1); // just keep zero order coefficients
      ok   &= thread_alloc::inuse(thread) < inuse;

      // Suppose we no longer need the zero order Taylor coefficients
      // (could have done this first and not used f.capacity_order(1)).
      inuse = thread_alloc::inuse(thread);
      f.capacity_order(0);
      ok   &= thread_alloc::inuse(thread) < inuse;

      // turn off memory holding
      thread_alloc::hold_memory(false);

      return ok;
   }
}
bool capacity_order(void)
{  bool ok = true;
   using CppAD::thread_alloc;

   // original amount of memory inuse
   size_t thread = thread_alloc::thread_num();
   ok           &= thread == 0; // this should be master thread
   size_t inuse  = thread_alloc::inuse(thread);

   // do test in separate routine so all objects are destroyed
   ok &= test();

   // check that the amount of memory inuse has not changed
   ok &= thread_alloc::inuse(thread) == inuse;

   // Test above uses hold_memory, so return available memory
   thread_alloc::free_available(thread);

   return ok;
}

// END C++
