COMSOL Multiphysics™

TABLE 2-4: ASSEMBLY AND EXTENDED MESH ERROR MESSAGES
ERROR NUMBER ERROR MESSAGE EXPLANATION
6170 Failed to evaluate variable An error occurred when evaluating the
variable. The domains in which COMSOL
Multiphysics tried to evaluate the variable
are indicated. Also, the error message
shows the expression that COMSOL
Multiphysics was unable to evaluate. Make
sure that you have defined the variables
correctly in the indicated domains.
6176 Attempt to evaluate real logarithm of
negative number
An expression contains log(a), where a
becomes negative or zero. To make the
logarithm well-defined, make sure that a>0.
Often, a becomes only slightly negative (due
to approximations in the solution process).
Then, a possible solution is to use
log(a+e), where e is a small constant.
Another remedy is to use log(abs(a)). If
you do want to have a complex logarithm,
go to the Advanced tab of Solver Parameters
and select the Use complex functions with
real input check box.
6177 Matrix has zero on diagonal When the equations have a structure such
that the stiffness matrix (Jacobian matrix)
has zeros on the diagonal, it is not possible
to use the following linear system solvers/
preconditioners/smoothers: all versions of
SOR and Diagonal scaling (Jacobi). Try the
Vanka preconditioner/smoother instead.
6194 Attempt to evaluate non-integral power of
negative number
An expression contains a^b, where a
becomes negative and b is non an integer. To
make the power well-defined, make sure
that a>0. Often, a becomes only slightly
negative (due to approximations in the
solution process). Then, a possible solution
is to use (a+e)^b, where e is a small
constant. Another remedy is to use
abs(a)^b. If you do want to have a
complex number a^b, go to the Advanced
tab of Solver Parameters and select Use
complex functions with real input.
414 | CHAPTER 2: DIAGNOSTICS