Welcome to Adams/Solver Subroutines - Kxcad.net

Welcome to Adams/Solver Subroutines
FIESUB output must be strictly a function of the values in arrays disp and velo. Consequently, FIESUB
may not call the SYSARY or SYSFNC utility subroutine. FIESUB may call other utility subroutines,
such as AKISPL, and CUBSPL, that do not introduce a dependency on Solver states.
Caution: • The dfddis and dfdvel arrays must always be positive semidefinite. Adams/Solver
does not warn you if the dfddis array, the dfdvel array, or both, are not positive
semidefinite. An array A is positive semidefinite if xT A x > 0 for all x ¹ 0.
FORTRAN - Prototype
• Don't attempt to make any of the six field components dependent on system
variables other than those FIESUB passes through the arguments disp, velo, and
time. This rule prohibits calls to the utility subroutines SYSARY and SYSFNC.
Failure to comply with this rule does not produce error messages, but greatly
reduces the integration step sizes, increases the CPU time, and decreases the
probability of convergence to a solution.
• If FIESUB returns the six field components without their correct derivatives,
simulation times may correspondingly increase, and the probability of
convergence to a solution decreases.
• If AKISPL, CUBSPL, or any of the Adams/Solver utility subroutines are used,
don't forget to involve the derivatives returned by these subroutines when the
FIESUB derivatives are evaluated.
• Field components with continuous derivatives are desirable. Discontinuous
derivatives cause a reduction of integration step size at the discontinuity, and may
cause Adams/Solver to fail to converge to a solution.
• When the iflag argument is true, Adams/Solver sets the disp and velo arguments to
zeros. When you execute Adams/Solver, computations that divide by these values
result in fatal errors. You should check for nonzero values, or ensure the iflag
argument is false, before dividing by disp or velo values.
A sample structure for FIESUB is shown next. The comments explain how the subroutine works.
SUBROUTINE FIESUB (ID, TIME, PAR, NPAR, DISP,
& VELO, DFLAG, IFLAG, FIELD,
& DFDDIS, DFDVEL )
C
C === Type and dimension statements ===================
C
C - External variable definitions ---------
C
INTEGER ID
DOUBLE PRECISION TIME
DOUBLE PRECISION PAR( * )
INTEGER NPAR
DOUBLE PRECISION DISP( 6 )
DOUBLE PRECISION VELO( 6 )
LOGICAL DFLAG
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