CFD Online Discussion Forums - What is this FOAM warning: Unknown matrix type combination means?

Hi, everyone

I got the following msg when I turned on DebugSwitches in rhoSimpleFoam.
Here is part of the log:
Code:
Starting time loop



forces forces1:

    Not including porosity effects

forceCoeffs forces1:

    Not including porosity effects

Time = 1



--> FOAM Warning : 

    From function void Foam::lduMatrix::operator-=(const Foam::lduMatrix&)

    in file matrices/lduMatrix/lduMatrix/lduMatrixOperations.C at line 286

    Unknown matrix type combination

    this : diagonal:0 symmetric:0 asymmetric:1

    A    : diagonal:0 symmetric:0 asymmetric:0

   Normalisation factor = 438.8332991218

DILUPBiCGStab:  Solving for Ux, Initial residual = 0.9999999196256, Final residual = 9.665819444403e-10, No Iterations 3

   Normalisation factor = 111.6043953712

DILUPBiCGStab:  Solving for Uy, Initial residual = 0.9999999122811, Final residual = 6.521155555565e-10, No Iterations 3

--> FOAM Warning : 

    From function void Foam::lduMatrix::operator-=(const Foam::lduMatrix&)

    in file matrices/lduMatrix/lduMatrix/lduMatrixOperations.C at line 286

    Unknown matrix type combination

    this : diagonal:0 symmetric:0 asymmetric:1

    A    : diagonal:0 symmetric:0 asymmetric:0

   Normalisation factor = 25947.66551949

DILUPBiCGStab:  Solving for e, Initial residual = 0.9999966481434, Final residual = 3.3088000014e-10, No Iterations 2

--> FOAM Warning : 

    From function void Foam::lduMatrix::operator-=(const Foam::lduMatrix&)

    in file matrices/lduMatrix/lduMatrix/lduMatrixOperations.C at line 286

    Unknown matrix type combination

    this : diagonal:0 symmetric:1 asymmetric:0

    A    : diagonal:0 symmetric:0 asymmetric:0

   Normalisation factor = 46.30762557178

DICPCG:  Solving for p, Initial residual = 0.9999999949062, Final residual = 9.456697817244e-11, No Iterations 103

--> FOAM Warning : 

    From function void Foam::lduMatrix::operator-=(const Foam::lduMatrix&)

    in file matrices/lduMatrix/lduMatrix/lduMatrixOperations.C at line 286

    Unknown matrix type combination

    this : diagonal:0 symmetric:1 asymmetric:0

    A    : diagonal:0 symmetric:0 asymmetric:0

   Normalisation factor = 69959.97350504

DICPCG:  Solving for p, Initial residual = 0.0007458501311764, Final residual = 8.84361415006e-11, No Iterations 69

time step continuity errors : sum local = 7.073776712562e-12, global = 1.62754446914e-13, cumulative = 1.62754446914e-13

rho max/min : 2.632186229715 1.93075973848

ExecutionTime = 0.08 s  ClockTime = 1 s



SIMPLE solution statistics:

    U: tolerance = 0.9999999196256 (1e-08)

SIMPLE solution statistics:

    p: tolerance = 0.9999999949062 (1e-08)

forceCoeffs forces1 write:

    Cm    = 1.668416584837

    Cd    = 2.102251277892

    Cl    = 6.004158371472

    Cl(f) = 4.670495770573

    Cl(r) = 1.333662600899



fieldMinMax fieldMinMax1 write:

    min(mag(U)) = 0 at location (0.9995180946345 -6.8329751524e-05 0.5)

    max(mag(U)) = 59.0424609648 at location (0.09116378316311 0.04698392201502 0.5)

    min(p) = 166205.3080159 at location (0.948828058586 0.007031629229023 0.5)

    max(p) = 226738.9321484 at location (0.001180689701005 -0.005843479396189 0.5)

    min(T) = 299.6079419896 at location (0.1926696369711 0.05614551067966 0.5)

    max(T) = 300.3763734475 at location (0.9966139497257 -0.0004883533836858 0.5)

    min(nuTilda) = 0 at location (0.9995180946345 -6.8329751524e-05 0.5)

    max(nuTilda) = 2.604143606306e-05 at location (398.1856161464 -4.245372262308e-06 0.5)



Time = 2
Any idea what is wrong? How could a matrix being either symmetric or asymmetric?