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I added VecView() in the ex2f.F to check the three vectors (u,b, and x) in the code.<BR>
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-----The vectors of u and b are same. BUt, the value of vector x is different with different processes. For example,<BR>
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with only 1 process, the vector x is:<BR>
<BR>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">Process [0]<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">2.72322e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">3.81437e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">1.58922e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">3.81437e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">2.38878e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">-6.65645e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">1.58922e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">-6.65645e-07<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">-2.51219e-07</SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">with 2 processes, the vector is:</SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt"></SPAN> </P><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">Process [0]</SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">-1.11022e-16<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">0<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">2.22045e-16<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">2.22045e-16<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">0</SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt"><o:p></o:p></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">Process [1]<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">2.22045e-16<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">2.22045e-16<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">0<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left><SPAN lang=EN-US style="FONT-SIZE: 9pt; FONT-FAMILY: 'Courier New'; mso-font-kerning: 0pt">2.22045e-16<o:p></o:p></SPAN></P>
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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left>The example is supposed to get a vector x similar to u. Why the result is different with differnt number of processes used?</P>
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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left>----Also, if the runtime option -my_ksp_monitor is used, there is a error showing:</P>
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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left>[0]PETSC ERROR: ------------------------------------------------------------------------<BR>[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, probably memory access out of range</P>
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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left>It seems there is something wrong with calling 'call KSPBuildSolution(ksp,PETSC_NULL_OBJECT,x,ierr)' in user defined function MyKSPMonitor().</P>
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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-layout-grid-align: none" align=left>Any hints for this error? Thanks a lots.</P>
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