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## run pardiso twice on same matrix = not same result

Beginner
123 Views

I test case is attached to this message.I solve exactly the same matrix more than one time and I get different result.I can solve 10 times and get 8 times same result and 2 times another result. The next time, I get 6 times sames result and 4 times another result.Maybe you will need to run the case more than 1 time because sometime I get 10 time the same result.At each solve, it's a new surprise for me :)Here is a example result of X[2] whit 5 solve (fill matrix, facotrization and solve) :x[2] = 3.954994 +j 36.454584x[2] = 4.039025 +j 36.871752x[2] = 4.386890 +j 36.496321x[2] = 4.386890 +j 36.496321x[2] = 4.386890 +j 36.496321Marc

3 Replies
Moderator
123 Views
I just quickly checked the issue - I 've got the different numbers

x[2] = -0.220519 +j 26.730090
x[2] = -0.333848 +j 26.842847
x[2] = -0.220519 +j 26.730090
x[2] = -0.333848 +j 26.842847
x[2] = -0.220519 +j 26.730090
but the similar unrepeated results.
We will investigate the problem and back soon.
Did you check the condition number of this input?

Beginner
123 Views

Element magnitudes of your matrix vary in a huge range. I saw ones as large as 5000000 and as small as 1e-7. Typically this is not a good sign for numerical stability.

EDIT: Well, it is worse than that. The matrix is singular. The last row is all zeros. Changing the bottom right element to 1 produces a matrix with a 2-condition number of 1.8e27.

Employee
123 Views
Hi,

Indeed, if the matrix is singular (or highly ill-conditioned) than the solving process is highly unstable and, generally speaking, the result of computations is unpredictable.

Regards,
Konstantin