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

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 whit 5 solve (fill matrix, facotrization and solve) :x = 3.954994 +j 36.454584x = 4.039025 +j 36.871752x = 4.386890 +j 36.496321x = 4.386890 +j 36.496321x = 4.386890 +j 36.496321Marc

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

x = -0.220519 +j 26.730090
x = -0.333848 +j 26.842847
x = -0.220519 +j 26.730090
x = -0.333848 +j 26.842847
x = -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
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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
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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 