# NCC_TETRAHEDRON Newton-Cotes Closed Quadrature for the Tetrahedron

NCC_TETRAHEDRON is a FORTRAN90 library which defines the weights and abscisass for a sequence of 7 Newton-Cotes closed quadrature rules for the tetrahedron.

Newton-Cotes rules have the characteristic that the abscissas are equally spaced. For a tetrahedron, this refers to spacing in the unit reference tetrahedron, or in the barycentric coordinate system. These rules may be mapped to an arbitrary tetrahedron, and will still be valid.

The rules are said to be "closed" when they include points on the boundary of the tetrahedron.

The use of equally spaced abscissas may be important for your application. That may how your data was collected, for instance. On the other hand, the use of equally spaced abscissas carries a few costs. In particular, for a given degree of polynomial accuracy, there will be rules that achieve this accuracy, but use fewer abscissas than Newton-Cotes. Moreover, the Newton-Cotes approach almost always results in negative weights for some abscissas. This is generally an undesirable feature, particularly when higher order quadrature rules are being used.

Note that the first rule included in the set is not, strictly speaking, a Newton-Cotes closed rule; it's just the rule that uses a single point at the centroid. However, by including this rule as the first in the set, we have a rule with each polynomial degree of exactness from 0 to 6.

### Languages:

NCC_TETRAHEDRON is available in a C++ version and a FORTRAN90 version and a MATLAB version

### Related Data and Programs:

CUBPACK, a FORTRAN90 library which estimates the integral of a function (or vector of functions) over a collection of M-dimensional hyperrectangles and simplices.

FELIPPA, a FORTRAN90 library which defines quadrature rules for lines, triangles, quadrilaterals, pyramids, wedges, tetrahedrons and hexahedrons.

GM_RULE, a FORTRAN90 library which defines a Grundmann-Moeller rule for quadrature over a triangle, tetrahedron, or general M-dimensional simplex.

KEAST, a FORTRAN90 library which defines a number of quadrature rules for a tetrahedron.

NCC_TRIANGLE, a FORTRAN90 library which defines Newton-Cotes closed quadrature rules on a triangle.

NCO_TETRAHEDRON, a FORTRAN90 library which defines Newton-Cotes open quadrature rules on a tetrahedron.

QUADRATURE_RULES_TET, a dataset directory which contains triples of files which defines various quadrature rules on tetrahedrons.

QUADRULE, a FORTRAN90 library which defines quadrature rules on a variety of intervals with different weight functions.

STROUD, a FORTRAN90 library which defines quadrature rules for a variety of unusual areas, surfaces and volumes in 2D, 3D and N-dimensions.

TET_MESH, a FORTRAN90 library which is useful for work with tetrahedral meshes in 3D;

TETRAHEDRON_EXACTNESS, a FORTRAN90 program which investigates the polynomial exactness of a quadrature rule for the tetrahedron.

TETRAHEDRON_MONTE_CARLO, a MATLAB program which uses the Monte Carlo method to estimate integrals over a tetrahedron.

### Reference:

1. Peter Silvester,
Mathematics of Computation,
Volume 24, Number 109, January 1970, pages 95-100.

### List of Routines:

• FILE_NAME_INC increments a partially numeric filename.
• GET_UNIT returns a free FORTRAN unit number.
• NCC_TETRAHEDRON_DEGREE returns the degree of an NCC rule.
• NCC_TETRAHEDRON_ORDER_NUM returns the order of an NCC rule.
• NCC_TETRAHEDRON_RULE returns the points and weights of an NCC rule.
• NCC_TETRAHEDRON_RULE_NUM returns the number of NCC rules available.
• NCC_TETRAHEDRON_SUBORDER returns the suborders for an NCC rule.
• NCC_TETRAHEDRON_SUBORDER_NUM returns the number of suborders for an NCC rule.
• NCC_TETRAHEDRON_SUBRULE returns a compressed NCC rule.
• R8MAT_DET_4D computes the determinant of a 4 by 4 matrix.
• REFERENCE_TO_PHYSICAL_T4 maps tetrahedron reference points to physical points.
• TETRAHEDRON_VOLUME computes the volume of a tetrahedron in 3D.
• TIMESTAMP prints the current YMDHMS date as a time stamp.

You can go up one level to the FORTRAN90 source codes.

Last revised on 21 December 2010.