// 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
// ----------------------------------------------------------------------------


/*
Two old Sub examples now used just for valiadation testing
*/
# include <cppad/cppad.hpp>

namespace { // BEGIN empty namespace

bool One(void)
{  bool ok = true;

   using namespace CppAD;


   // independent variable vector, indices, values, and declaration
   CPPAD_TESTVECTOR(AD<double>) U(2);
   size_t s = 0;
   size_t t = 1;
   U[s] = 3.;
   U[t] = 2.;
   Independent(U);

   // dependent variable vector and indices
   CPPAD_TESTVECTOR(AD<double>) Z(3);
   size_t x = 0;
   size_t y = 1;
   size_t z = 2;

   // dependent variable values
   Z[x] = U[s]  - U[t];   // AD<double> - AD<double>
   Z[y] = Z[x]  - 1.;     // AD<double> - double
   Z[z] = 1.    - Z[y];   // double - AD<double>

   // create f: U -> Z and vectors used for derivative calculations
   ADFun<double> f(U, Z);
   CPPAD_TESTVECTOR(double) v( f.Domain() );
   CPPAD_TESTVECTOR(double) w( f.Range() );

   // check function values
   ok &= ( Z[x] == 3. - 2. );
   ok &= ( Z[y] == 3. - 2. - 1. );
   ok &= ( Z[z] == 1. - 3. + 2. + 1. );

   // forward computation of partials w.r.t. s
   v[s] = 1.;
   v[t] = 0.;
   w = f.Forward(1, v);
   ok &= ( w[x] == 1. );   // dx/ds
   ok &= ( w[y] == 1. );   // dy/ds
   ok &= ( w[z] == -1. );   // dz/ds

   // reverse computation of second partials of z
   CPPAD_TESTVECTOR(double) r( f.Domain() * 2 );
   w[x] = 0.;
   w[y] = 0.;
   w[z] = 1.;
   r = f.Reverse(2, w);
   ok &= ( r[2 * s + 1] == 0. );  // d^2 z / (ds ds)
   ok &= ( r[2 * t + 1] == 0. );  // d^2 z / (ds dt)

   return ok;

}

bool Two(void)
{  bool ok = true;
   using namespace CppAD;
   double eps99 = 99.0 * std::numeric_limits<double>::epsilon();

   // independent variable vector
   double u0 = .5;
   CPPAD_TESTVECTOR(AD<double>) U(1);
   U[0]      = u0;
   Independent(U);

   AD<double> a = 2. * U[0] - 1.; // AD<double> - double
   AD<double> b = a  - 2;         // AD<double> - int
   AD<double> c = 3. - b;         // double     - AD<double>
   AD<double> d = 4  - c;         // int        - AD<double>

   // dependent variable vector
   CPPAD_TESTVECTOR(AD<double>) Z(1);
   Z[0] = U[0] - d;          // AD<double> - AD<double>

   // create f: U -> Z and vectors used for derivative calculations
   ADFun<double> f(U, Z);
   CPPAD_TESTVECTOR(double) v(1);
   CPPAD_TESTVECTOR(double) w(1);

   // check value
   ok &= NearEqual(Value(Z[0]) , u0-4+3-2*u0+1+2,  eps99 , eps99);

   // forward computation of partials w.r.t. u
   size_t j;
   size_t p     = 5;
   double jfac  = 1.;
   double value = -1.;
   v[0]         = 1.;
   for(j = 1; j < p; j++)
   {  jfac *= double(j);
      w     = f.Forward(j, v);
      ok &= NearEqual(w[0], value/jfac, eps99, eps99); // d^jz/du^j
      v[0]  = 0.;
      value = 0.;
   }

   // reverse computation of partials of Taylor coefficients
   CPPAD_TESTVECTOR(double) r(p);
   w[0]  = 1.;
   r     = f.Reverse(p, w);
   jfac  = 1.;
   value = -1.;
   for(j = 0; j < p; j++)
   {  ok &= NearEqual(r[j], value/jfac, eps99, eps99); // d^jz/du^j
      jfac *= double(j + 1);
      value = 0.;
   }

   return ok;
}

bool Three(void)
{  bool ok = true;
   using namespace CppAD;

   // special cases where tests above check OK and SubpvOp
   // implementation is known to be wrong.
   // Probably two minuses make a plus.
   size_t n = 1;
   CPPAD_TESTVECTOR(AD<double>) X(n);
   X[0] = 1.;
   Independent(X);
   size_t m = 1;
   CPPAD_TESTVECTOR(AD<double>) Y(m);
   Y[0] = 1. - X[0];
   ADFun<double> f(X, Y);

   CPPAD_TESTVECTOR(double) w(m), dw(n);
   w[0] = 1.;
   dw = f.Reverse(1, w);
   ok &= (dw[0] == -1.);

   return ok;
}

bool Four(void)
{  bool ok = true;
   using namespace CppAD;

   // special cases where parameter number is equal to
   // variable index in result.
   size_t n = 1;
   CPPAD_TESTVECTOR(AD<double>) X(n);
   X[0] = 1.;
   Independent(X);
   size_t m = 1;
   CPPAD_TESTVECTOR(AD<double>) Y(m);
   if( 0. < X[0] && X[0] < 10. )
      Y[0] = X[0] - 2.;
   else
      Y[0] = X[0] - 2.;
   ADFun<double> f(X, Y);

   CPPAD_TESTVECTOR(double) y(m), x(n);
   x[0] = 1.;
   y    = f.Forward(0, x);
   ok  &= (y[0] == -1.);

   CPPAD_TESTVECTOR(double) dy(m), dx(n);
   dx[0] = 1.;
   dy    = f.Forward(1, dx);
   ok  &= (dy[0] == 1.);

   return ok;
}


} // END empty namespace

bool Sub(void)
{  bool ok = true;
   ok &= One();
   ok &= Two();
   ok &= Three();
   ok &= Four();
   return ok;
}
