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<p style="margin-top:0;margin-bottom:0">Dear all,</p>
<p style="margin-top:0;margin-bottom:0">I'm debugging my application in which I'm trying to use the FIELDSPLIT preconditioner for solving a 2x2 block matrix.</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">Currently I'm testing the preconditioner on a decoupled system where I solve two identical and independent Poisson problems. Using the default fieldsplit type (multiplicative), I'm expecting the method to be equivalent
to a Block Jacobi solver. </p>
<p style="margin-top:0;margin-bottom:0">Setting </p>
<p style="margin-top:0;margin-bottom:0">-ksp_rtol 1e-6</p>
<p style="margin-top:0;margin-bottom:0">while u<span style="font-size: 12pt;">sing
</span><span style="font-size: 12pt;">gmres/h</span><span style="font-size: 12pt;">ypre on each subblock with</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 12pt;">-fieldsplit_0_ksp_rtol 1e-12</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 12pt;"><span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">-fieldsplit_1_ksp_rtol
1e-12</span><br>
</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 12pt;"><span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">I'm
expecting to converge in 1 iteration with a single solve for each block.</span></span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 12pt;"><span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;"><br>
</span></span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 12pt;"><span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">Asking
to output the iteration count for the subblocks with</span></span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 12pt;"><span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;"><span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;"></p>
<p style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">
<span style="font-size: 12pt;">-ksp_converged_reason<br>
</span></p>
<div>-fieldsplit_0_ksp_converged_reason<br>
</div>
</span></span></span>
<p></p>
<p style="margin-top:0;margin-bottom:0"></p>
<p style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">
<span style="font-size: 12pt;">-fieldsplit_1_ksp_converged_reason</span></p>
<p style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">
<span style="font-size: 12pt;">revealed that the outer solver converges in 1 iteration, but each block is solved for 3 times.</span></p>
<p style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">
<span style="font-size: 12pt;">This is the output I get:</span></p>
<p style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">
<span style="font-size: 12pt;"><br>
</span></p>
<p style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">
<span style="font-size: 12pt;"></p>
<div><span style="font-family: Consolas, Courier, monospace;"> Linear fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 7</span></div>
<div><span style="font-family: Consolas, Courier, monospace;"> Linear fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 7</span></div>
<div><span style="font-family: Consolas, Courier, monospace;"> 0 KSP preconditioned resid norm 9.334948012657e+01 true resid norm 1.280164130222e+02 ||r(i)||/||b|| 1.000000000000e+00</span></div>
<div><br>
</div>
<div><span style="font-family: Consolas, Courier, monospace;"> Linear fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 7</span></div>
<div><span style="font-family: Consolas, Courier, monospace;"> Linear fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 7</span></div>
<div><span style="font-family: Consolas, Courier, monospace;"> Linear fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 7</span></div>
<div><span style="font-family: Consolas, Courier, monospace;"> Linear fieldsplit_1_ solve converged due to CONVERGED_RTOL iterations 7</span></div>
<div><span style="font-family: Consolas, Courier, monospace;"> 1 KSP preconditioned resid norm 1.518151977611e-11 true resid norm 8.123270435936e-12 ||r(i)||/||b|| 6.345491366429e-14</span></div>
<div><br>
</div>
<div><span style="font-family: Consolas, Courier, monospace;">Linear solve converged due to CONVERGED_RTOL iterations 1</span></div>
</span>
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<span style="font-size: 12pt;"><br>
</span></p>
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</p>
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Are the subblocks actually solved for multiple times at every outer iteration? </p>
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Thanks for the help,</p>
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Simone </p>
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