exp_2: Verify First Order Reverse Sweep
Keywords: exp_2: verify first order reverse sweep exp_2 mode

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exp_2: Verify First Order Reverse Sweep
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    # include <cstddef>                 // define size_t
    # include <cmath>                   // prototype for fabs
    extern bool exp_2_for0(double *v0); // computes zero order forward sweep
    bool exp_2_rev1(void)
    {    bool ok = true;

         // set the value of v0[j] for j = 1 , ... , 5
         double v0[6];
         ok &= exp_2_for0(v0);

         // initial all partial derivatives as zero
         double f_v[6];
         size_t j;
         for(j = 0; j < 6; j++)
              f_v[j] = 0.;

         // set partial derivative for f5
         f_v[5] = 1.;
         ok &= std::fabs( f_v[5] - 1. ) <= 1e-10; // f5_v5

         // f4 = f5( v1 , v2 , v3 , v4 , v2 + v4 )
         f_v[2] += f_v[5] * 1.;
         f_v[4] += f_v[5] * 1.;
         ok &= std::fabs( f_v[2] - 1. ) <= 1e-10; // f4_v2
         ok &= std::fabs( f_v[4] - 1. ) <= 1e-10; // f4_v4

         // f3 = f4( v1 , v2 , v3 , v3 / 2 )
         f_v[3] += f_v[4] / 2.;
         ok &= std::fabs( f_v[3] - 0.5) <= 1e-10; // f3_v3

         // f2 = f3( v1 , v2 , v1 * v1 )
         f_v[1] += f_v[3] * 2. * v0[1];
         ok &= std::fabs( f_v[1] - 0.5) <= 1e-10; // f2_v1

         // f1 = f2( v1 , 1 + v1 )
         f_v[1] += f_v[2] * 1.;
         ok &= std::fabs( f_v[1] - 1.5) <= 1e-10; // f1_v1

         return ok;
    }

`

Input File: introduction/exp_apx/exp_2_rev1.cpp