The support of log double

Matthew Knepley knepley at
Mon Dec 4 19:56:43 CST 2006

I strongly suspect that long double reals will not help
you at all. It is very unlikely that your nonlinear system
fails to converge due to loss of precision. If the Jacobian
does become near singular near the solution, it often
indicates a deficiency in the formulation. Could you
indicate why you think loss of precision is responsible
for non-convergence?


On 12/4/06, Gong Ding <gdiso at> wrote:
> Hi,
>   I found that PETSC supports long double type
> float point number, which may be useful in my
> semiconductor simulation code.
>   But as i know, no long double support exists in
> BLAS/LAPACK. So can any one tell me the truth
> about long double.
>   Another problem about SNES is my code diverged
> with gcc, but works well with Intel icc. Does any
> one meet the same problem? As a result, I 'd like
> to try long double, which seems more accurate to
> double.
> Thanks
> G.D.
> --
> USTC Alumni Email System

"Failure has a thousand explanations. Success doesn't need one" -- Sir
Alec Guiness

More information about the petsc-users mailing list