Controlling Taylor Coefficient Memory Allocation: Example and Test
Keywords: controlling taylor coefficient memory allocation: example test capacity_order

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Controlling Taylor Coefficient Memory Allocation: Example and Test
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    # 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 memroy 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;
    }

`

Input File: example/capacity_order.cpp