FLOATING POINT COWELL (SECOND-SUM), RUNGE-KUTTA INTEGRATION OF SECOND-ORDER ORDINARY DIFFERENTIAL EQUATIONS (SUBROUTINE ASC DEQ4)
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ASC DEQ4 is a floating point subroutine, written in FORTRAN IV source language, which integrates numerically a set of N simultaneous second-order ordinary differential equations in which first derivatives may or may not appear. If the N equations can be separated into two groups IB and N-IB such that the first IB equations are not dependent on the final N-IB equations e.g., variational equations then DEQ-4 has the capability of integrating the final N- IB equations at a larger step size than the first IB equations, thus saving 2R- 1 N-IB derivatives per integration step. This subroutine obsoletes subroutine DEQ2 with the following improvements better accuracy controls, new starting procedure, improved halving and doubling procedure, reduction in computing time, and reduction in core storage requirements 10N less. The subroutine is restricted in that it contains 20 digit octal constants real constants for the CDC 6000 series machines.
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