A system to generate Fortran programs for calculating configuration traces of angular momentum coupled product operators

Three steps are usually involved in setting up a problem for numerical solution, 1) deriving algebraic expressions, 2) programming the equations, and 3) debugging the codes. We report here on a code, called 'compiler' in what follows, which accepts as input standardized output from the CONTRACTION-JT-RECOUPLING program and produces, using additional information on the permutation symmetry of the operators from the CONTRACTION-BASIC-DIAGRAM program, a FORTRAN IV code for evaluating configuration traces of a product of angular momentum coupled operator. As output from the CONTRACTION-BASIC-DIAGRAM program and the CONTRACTION-JT-RECOUPLING program provide input to the compiler, these two programs must be run first for each distinct operator product. This input to the compiler determines the number of basic diagrams and, for each basic diagram, the associated permutation structure, the number of summation variables, the appropriate phases and statistical weight factors, and the angular momentum recoupling information. The operators themselves are assumed to be of standard form, such as hamiltonian or electromagnetic excitation operators; all defining matrix elements are considered to be input variables. The program sets up the trace evaluation code by translating this information into Fortran IV programs. It does this by mimicking the detailed logic an individual would use if assigned the same task. Certain specific procedures that are common to many cases, such as inputing the defining, matrix elements, are written as library subprograms. The compiler logic is structured but not rigid; optimization is attended to so the output codes will execute efficiently. (orig./HSI)