[File: Boundary_condition_flag.txt]
Each node requires an input boundary condition flag. It consists
of one digit per degree of freedom, and is denoted by the integer
array IBC within the program.
IBC (J) = Parameters constraint indicators at node J. (Right justified)
Digit L equals constraint type of parameter L. (Default=0)
NOTE: The IBC boundary condition indicator is an integer consisting
of N_G_DOF digits that are constraint flags for the corresponding
degrees of freedom at that node. The first DOF is the leftmost
flag digit while the N_G_DOF-th DOF is the rightmost flag digit.
A zero denotes an unknown with no boundary conditions or constraint.
Each digit can be from 0 to 9 but only 0,1,2,3 are supported now.
Values other than 0 (free) or 1 (given value) rarely occur.
EXAMPLE, for N_G_DOF = 1
IBC Flag_1 Remarks
0 0 One free unknown
1 1 One type 1 constraint (assigned value)
2 2 DOF is part of a type 2 constraint pair
3 3 DOF is part of a type 3 constraint triplet
EXAMPLE, for N_G_DOF = 3
IBC Flag_1 Flag_2 Flag_3 Remarks
000 0 0 0 Three free unknowns
010 0 1 0 One type 1 constraint (assigned value)
110 1 1 0 Two type 1 constraints (assigned values)
002 0 0 2 DOF 3 has type 2 constraint
022 0 2 2 DOF's 2 & 3 have type 2 constraint
333 3 3 3 All coupled to type 3 constraint
The assigned value for each type 1 (essential) BC is given elsewhere
in the input. Likewise, the linear constraint equation (MPC) for
each type 2 or 3 constraint is given elsewhere.
[End: Boundary_condition_flag.txt]