void BackwardEulerOperator::Mult(const Vector &k, Vector &y) const
{
// compute: y = H(x + dt*(v + dt*k)) + M*k + S*(v + dt*k)
add(*v, dt, k, w);
add(*x, dt, w, z);
H->Mult(z, y);
M->TrueAddMult(k, y);
S->TrueAddMult(w, y);
}
void HyperelasticOperator::Mult(const Vector &vx, Vector &dvx_dt) const
{
// Create views to the sub-vectors v, x of vx, and dv_dt, dx_dt of dvx_dt
int sc = height/2;
Vector v(vx.GetData() + 0, sc);
Vector x(vx.GetData() + sc, sc);
Vector dv_dt(dvx_dt.GetData() + 0, sc);
Vector dx_dt(dvx_dt.GetData() + sc, sc);
H.Mult(x, z);
if (viscosity != 0.0)
S.TrueAddMult(v, z);
z.Neg(); // z = -z
M_solver.Mult(z, dv_dt);
dx_dt = v;
}