Adams Basic Package > Adams Solver > Adams Solver C++ vs. FORTRAN > Side-to-side C++/FORTRAN comparison

Side-to-side C++/FORTRAN comparison

The following tables show a side-to-side comparison of statements, commands, functions and subroutine options available only in one code.

Statements comparison

STATEMENT	C++	FORTRAN
BEAM	Geometrically nonlinear formulation available	N/A
CONTACT	Flexible-flexible contact available	N/A
CLEARANCE	Distance between two or more geometries	N/A
ENVIRONMENT	Utility to set environment variables	N/A
EQUILIBRIUM	N/A	Dynamic option to find static equilibrium
FE_PART	Finite element beam elements natively supported	N/A
FIELD	Geometrically nonlinear formulation available	N/A
GSE	Implicit equations support	N/A
FLEX_BODY	Dynamic limit, stability, DB_FILE, representation, and BDF_FILE, number of threads, FEA_MEM_SETTINGS, BUFFER_SIZE and COMPUTE_RESOURCE for nonlinear finite element simulations.	N/A
GCON	Generalized user-defined constraint	N/A
INTEGRATOR	HHT, NEWMARK options.	N/A
	FIXIT, HRATIO and MAXERR options for fixed step integration.	N/A
	N/A	CONSTANT_BDF, ABAM, RKF45
LSOLVER	UMF package support	N/A
MARKER	Support for curve and surface MARKERs	N/A
	Support for specifying multiple or no NODE_ID.	N/A
MFORCE	Nonlinear definitions available	N/A
MOTION	Function depending on any state	N/A
PART	Support for 2D PARTs	N/A
PREFERENCES	Additional options	N/A
PSTATE	Support for defining user-defined linearization states	N/A
SURFACE	Surface definition	N/A
UCON	N/A	User-defined constraint

Commands comparison

COMMAND	C++	FORTRAN
ACTIVATE	More options available	N/A
DEACTIVATE	More options available	N/A
ENVIRONMENT	Utility to set environment variables	N/A
GCON	User-defined constraints	N/A
LINEAR	More options like RM, PSTATE, EXPORT	N/A
LSOLVER	Option to select UMF
PART	Option to set the products of inertia	N/A
RELOAD	Option to reload from a buffer in memory	N/A
SAVE	Option to save to a buffer in memory	N/A
SIMULATE	Settle simulation option	N/A
UCON	N/A	Option to redefine a user-defined constraint

Function comparison

FUNCTION	C++	FORTRAN
ACCXYZ	3D acceleration	N/A
AO	Isolates expression from reaction force in GCON	N/A
CLEAR	Set of measures for CLEARANCE statement	N/A
DELAY	Defines a delay differential equation	N/A
DXYZ	3D position	N/A
FXYZ	3D force	N/A
NJAC	Utility. Number of Jacobian evaluations	N/A
NRHS	Utility. Number of right-hand side evaluations	N/A
ORDER	Utility. Returns current integration order.	N/A
Q	Modal position	N/A
QDDOT	Modal acceleration	N/A
QDOT	Modal velocity	N/A
TXYZ	3D torque	N/A
UV	Unit vector	N/A
UVX	X component of unit vector	N/A
UVY	Y component of unit vector	N/A
UVZ	Z component of unit vector	N/A
VXYZ	3D velocity	N/A
WDTXYZ	3D angular acceleration	N/A
WXYZ	3D angular velocity	N/A

Utility subroutines comparison

UTILITY SUBROUTINE	C++	FORTRAN
ADAMS_DECLARE_THREAD_SAFE	Allows multiple threads to access user-written subroutines	N/A
ADAMS_SMP_GROUP	Allows multiple threads to access user-written subroutines	N/A
CBKSUB	Callback subroutine. Informs user about milestones.	N/A
GTCMAT	Allowed to be called from all simulation types	Limited to static/quasistatic simulations.
SYSPAR	Provides analytical partials from within user-written subroutines	Limited to GSE only.
UCOVAR	N/A	Used by UCOSUB
GSE_SET_IMPLICIT	Allows defining implicit GSE	N/A
UCOSUB	N/A	Used to define user-written subroutines.

Other differences

Other differences include:

1. The C++ solver computes the Jacobian and right-hand-entries of all matrices using symbolic computer algebra. The FORTRAN solver uses numerical differencing.

2. PART command in the C++ solver will generate a Jacobian refactorization.

3. FLEX_BODY's invar2 and invar3 are identically zero in the C++ solver. This means the formulation of the equations of motion for flexible bodies are different.

4. YPR and Euler measures in results may be different in both solvers but they define the same orientation.

5. The C++ solver does not generate an *.out file.

6. There are differences in the wording and structure of the *.msg file.

7. The LINEAR command behaves differently. History rules have been relaxed to provide a more analytical approach in the C++ solver.

8. Velocity reconciliation is done iteratively in the C++ solver. Given that GCONs can be used to create velocity constraints, the reconciliation solution is no longer a linear problem, hence the solution is iterative.

9. In the C++ solver, numerical differencing of user-written subroutines is done by perturbing the measures and using the chain rule. The FORTRAN solver perturbs the states when computing partial derivatives.

10. The C++ solver accepts a new signature in all use-written subroutines where the IFLAG parameter is of type INTEGER (FORTRAN) or int (C++) instead of BOOLEAN (F77).

11. The solution sequences implemented in the C++ solver are in general not identical to the ones implemented in the FORTRAN solver. One such difference is related to the number of equations in the assembly of the equations of motion for the dynamic simulations. In dynamic simulations, the FORTRAN solver defines additional equations labelled momenta equations in order to make the system sparser. The C++ solver does not create momenta equations by default. Users may set the environment variable MSC_ADAMS_USE_MOMENTA to mimic the FORTRAN solver's behavior.