412       const PetscScalar epsilon = x[i].T * PETSC_SQRT_MACHINE_EPSILON;  in RDIJacobian_FD()  local
418       n1.T = x[i].T + epsilon;  in RDIJacobian_FD()
423       Em_TT = (dEm1.T - dEm.T) / epsilon;  in RDIJacobian_FD()
871   PetscScalar epsilon;  in RDTestDifferentiation()  local
875   epsilon = 1e-8;  in RDTestDifferentiation()
878     PetscScalar T0 = 1000., T1 = T0 * (1. + epsilon), Em0, Em1;  in RDTestDifferentiation()
882     n.E = 1. + epsilon;  in RDTestDifferentiation()
885     fdEm.E = (Em1 - Em0) / epsilon;  in RDTestDifferentiation()
889     fdEm.T = (Em1 - Em0) / (T0 * epsilon);  in RDTestDifferentiation()
901     n.E  = 1. + epsilon;  in RDTestDifferentiation()
906     fdD.E = (D - D0) / epsilon;  in RDTestDifferentiation()
908     n.T   = 1. + epsilon;  in RDTestDifferentiation()
912     fdD.T = (D - D0) / epsilon;  in RDTestDifferentiation()
915     nx.E  = 1. + epsilon;  in RDTestDifferentiation()
918     fdxD.E = (D - D0) / epsilon;  in RDTestDifferentiation()
922     n.T    = 1. + epsilon;  in RDTestDifferentiation()
924     fdxD.T = (D - D0) / epsilon;  in RDTestDifferentiation()
945       n1[i].E += epsilon;  in RDTestDifferentiation()
946       fd[i].E = (RDDiffusion(rd, hx, n1, 1, 0) - a0) / epsilon;  in RDTestDifferentiation()
948       n1[i].T += epsilon;  in RDTestDifferentiation()
949       fd[i].T = (RDDiffusion(rd, hx, n1, 1, 0) - a0) / epsilon;  in RDTestDifferentiation()
960     n.E     = 1. + epsilon;  in RDTestDifferentiation()
963     fdrad.E = (rad - rad0) / epsilon;  in RDTestDifferentiation()
965     n.T     = 1. + epsilon;  in RDTestDifferentiation()
967     fdrad.T = (rad - rad0) / epsilon;  in RDTestDifferentiation()