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<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">Hi all,
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<div>the natural norm for positive definite systems in Petsc uses the preconditioner B, and is defined by r' * B * r. Am I right assuming that this way we want to obtain an estimate for r' * K^-1 * r, which is impossible since we don't have K^-1? But we do
know B which is approximately K^-1.</div>
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<div>I'm sorry for this, I guess, basic question, but I just wanted to be sure.</div>
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<div>kind regards,</div>
<div>Vincent</div>
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