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Hi Jed,<br>
<br>
This is my output when the error happens for gmres:<br>
<br>
2 KSP preconditioned resid norm 1.556688898463e+007 true resid
norm 2.58995443<br>
8801e+003 ||Ae||/||Ax|| 1.232088736212e+003<br>
2 KSP preconditioned resid norm 1.556688898463e+007 true resid
norm 2.58995443<br>
8801e+003 ||Ae||/||Ax|| 1.232088736212e+003<br>
3 KSP preconditioned resid norm 1.207952812560e+003 true resid
norm 9.05939430<br>
1179e+003 ||Ae||/||Ax|| 4.309719703237e+003<br>
3 KSP preconditioned resid norm 1.207952812560e+003 true resid
norm 9.05939430<br>
1179e+003 ||Ae||/||Ax|| 4.309719703237e+003<br>
3 KSP preconditioned resid norm 1.207952812560e+003 true resid
norm 9.05939430<br>
1179e+003 ||Ae||/||Ax|| 4.309719703237e+003<br>
3 KSP preconditioned resid norm 1.207952812560e+003 true resid
norm 9.05939430<br>
1179e+003 ||Ae||/||Ax|| 4.309719703237e+003<br>
3 KSP preconditioned resid norm 1.207952812560e+003 true resid
norm 9.05939430<br>
1179e+003 ||Ae||/||Ax|| 4.309719703237e+003<br>
4 KSP preconditioned resid norm 3.815055004710e+001 true resid
norm 1.96385966<br>
1729e+002 ||Ae||/||Ax|| 9.342439899591e+001<br>
4 KSP preconditioned resid norm 3.815055004710e+001 true resid
norm 1.96385966<br>
1729e+002 ||Ae||/||Ax|| 9.342439899591e+001<br>
4 KSP preconditioned resid norm 3.815055004710e+001 true resid
norm 1.96385966<br>
1729e+002 ||Ae||/||Ax|| 9.342439899591e+001<br>
4 KSP preconditioned resid norm 3.815055004710e+001 true resid
norm 1.96385966<br>
1729e+002 ||Ae||/||Ax|| 9.342439899591e+001<br>
4 KSP preconditioned resid norm 3.815055004710e+001 true resid
norm 1.96385966<br>
1729e+002 ||Ae||/||Ax|| 9.342439899591e+001<br>
<br>
for fgmres:<br>
<br>
34 KSP preconditioned resid norm 2.428114102327e-005 true resid
norm 3.35941610<br>
6265e-005 ||Ae||/||Ax|| 1.598129588716e-005<br>
34 KSP preconditioned resid norm 2.428114102327e-005 true resid
norm 3.35941610<br>
6265e-005 ||Ae||/||Ax|| 1.598129588716e-005<br>
35 KSP preconditioned resid norm 2.200715659545e-005 true resid
norm 3.88294769<br>
5703e-005 ||Ae||/||Ax|| 1.847182191086e-005<br>
35 KSP preconditioned resid norm 2.200715659545e-005 true resid
norm 3.88294769<br>
5703e-005 ||Ae||/||Ax|| 1.847182191086e-005<br>
35 KSP preconditioned resid norm 2.200715659545e-005 true resid
norm 3.88294769<br>
5703e-005 ||Ae||/||Ax|| 1.847182191086e-005<br>
35 KSP preconditioned resid norm 2.200715659545e-005 true resid
norm 3.88294769<br>
5703e-005 ||Ae||/||Ax|| 1.847182191086e-005<br>
35 KSP preconditioned resid norm 2.200715659545e-005 true resid
norm 3.88294769<br>
5703e-005 ||Ae||/||Ax|| 1.847182191086e-005<br>
36 KSP preconditioned resid norm 2.011575409369e-005 true resid
norm 3.89282805<br>
6204e-005 ||Ae||/||Ax|| 1.851882441357e-005<br>
36 KSP preconditioned resid norm 2.011575409369e-005 true resid
norm 3.89282805<br>
6204e-005 ||Ae||/||Ax|| 1.851882441357e-005<br>
36 KSP preconditioned resid norm 2.011575409369e-005 true resid
norm 3.89282805<br>
6204e-005 ||Ae||/||Ax|| 1.851882441357e-005<br>
36 KSP preconditioned resid norm 2.011575409369e-005 true resid
norm 3.89282805<br>
6204e-005 ||Ae||/||Ax|| 1.851882441357e-005<br>
36 KSP preconditioned resid norm 2.011575409369e-005 true resid
norm 3.89282805<br>
6204e-005 ||Ae||/||Ax|| 1.851882441357e-005<br>
<br>
Btw, I am solving the x and y momentum eqns so there 's 2 eqns to
solve. I am using windows so I can show only part of the output. If
req, I can transfer my code to linux and capture the output.<br>
<br>
Hope this explains something.<br>
<br>
Thanks!<br>
<br>
<br>
<pre class="moz-signature" cols="72">Yours sincerely,
TAY wee-beng</pre>
<br>
On 8/7/2011 3:34 PM, Jed Brown wrote:
<blockquote
cite="mid:CAM9tzSm_ZfOVB4zxGgJAjWb=FpL+XtxmMkoQkrL=MYwN9VoK8A@mail.gmail.com"
type="cite">
<div class="gmail_quote">On Fri, Jul 8, 2011 at 08:26, TAY
wee-beng <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:zonexo@gmail.com">zonexo@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">[0]PETSC ERROR:
KSPSolve_BCGS() line 75 in
src/ksp/ksp/impls/bcgs/C:\Codes\PETSC<br>
-~1.1-P\src\ksp\ksp\impls\bcgs\bcgs.c</div>
</blockquote>
</div>
<div><br>
</div>
<div>
<div> ierr = KSP_PCApplyBAorAB(ksp,P,V,T);CHKERRQ(ierr); /*
v <- K p */</div>
<div> ierr = VecDot(V,RP,&d1);CHKERRQ(ierr);</div>
<div> if (d1 == 0.0) SETERRQ(PETSC_ERR_PLIB,"Divide by
zero");</div>
</div>
<div><br>
</div>
<div>I suspect your preconditioner is singular. What options are
you running with? What happens if you use -ksp_type gmres
-ksp_gmres_restart 1000 -ksp_gmres_modifiedgramschmidt
-ksp_monitor_true_residual? Also do the same run with -ksp_type
fgmres.</div>
</blockquote>
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