### LOBPCG single precision fails to converge for most problems

Posted:

**Fri Sep 20, 2019 10:24 am**Hello,

I have been testing the LOBPCG. On double precision, it works fine. On single precision, it seems quite sensitive.

I tried some examples from the matrix market :

https://math.nist.gov/MatrixMarket/data ... stm06.html

https://math.nist.gov/MatrixMarket/data ... stk01.html

https://math.nist.gov/MatrixMarket/data ... stk01.html

The command I tried was :

.\testing_ssolver.exe --solver LOBPCG --ev 1 --maxiter 10000 --rtol 1e-6 --verbose 1 --precond ILU /path/to/mtx

In doesn't converge. I tried a simple identity matrix with dimension five, and I played with the minimum value. The value lower than 1e-3 was already enough not to converge.

Is there any set of option that can improve this? I think I might be using it the wrong way.

Thanks in advance,

Eduardo.

I have been testing the LOBPCG. On double precision, it works fine. On single precision, it seems quite sensitive.

I tried some examples from the matrix market :

https://math.nist.gov/MatrixMarket/data ... stm06.html

https://math.nist.gov/MatrixMarket/data ... stk01.html

https://math.nist.gov/MatrixMarket/data ... stk01.html

The command I tried was :

.\testing_ssolver.exe --solver LOBPCG --ev 1 --maxiter 10000 --rtol 1e-6 --verbose 1 --precond ILU /path/to/mtx

In doesn't converge. I tried a simple identity matrix with dimension five, and I played with the minimum value. The value lower than 1e-3 was already enough not to converge.

Is there any set of option that can improve this? I think I might be using it the wrong way.

Thanks in advance,

Eduardo.