30 March 2023 10:39:37.514 AM legendre_exactness(): FORTRAN90 version Investigate the polynomial exactness of a Gauss-Legendre quadrature rule by integrating monomials up to a given degree over the [-1,+1] interval. LEGENDRE_EXACTNESS: User input: Quadrature rule X file = "leg_o4_x.txt". Quadrature rule W file = "leg_o4_w.txt". Quadrature rule R file = "leg_o4_r.txt". Maximum degree to check = 10 Spatial dimension = 1 Number of points = 4 The quadrature rule to be tested is a Gauss-Legendre rule ORDER = 4 Standard rule: Integral ( -1 <= x <= +1 ) f(x) dx is to be approximated by sum ( 1 <= I <= ORDER ) w(i) * f(x(i)). Weights W: w( 1) = 0.3478548451374539 w( 2) = 0.6521451548625459 w( 3) = 0.6521451548625459 w( 4) = 0.3478548451374539 Abscissas X: x( 1) = -0.8611363115940526 x( 2) = -0.3399810435848563 x( 3) = 0.3399810435848563 x( 4) = 0.8611363115940526 Region R: r( 1) = -1.000000000000000 r( 2) = 1.000000000000000 A Gauss-Legendre rule would be able to exactly integrate monomials up to and including degree = 7 Error Error Degree (This rule) (Trapezoid) 0.0000000000000002 0.0000000000000001 0 0.0000000000000000 0.0000000000000001 1 0.0000000000000000 0.2222222222222222 2 0.0000000000000000 0.0000000000000000 3 0.0000000000000000 0.7078189300411522 4 0.0000000000000000 0.0000000000000000 5 0.0000000000000000 1.3397347965249200 6 0.0000000000000000 0.0000000000000000 7 0.0522448979591835 2.0009144947416555 8 0.0000000000000000 0.0000000000000000 9 0.1418075801749270 2.6667908573105947 10 LEGENDRE_EXACTNESS: Normal end of execution. 30 March 2023 10:39:37.515 AM