<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:SimSun;
panose-1:2 1 6 0 3 1 1 1 1 1;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"\@SimSun";
panose-1:2 1 6 0 3 1 1 1 1 1;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:3.0cm 2.0cm 3.0cm 2.0cm;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=DA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi everyone,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span lang=EN-US>Caveat: I have just started using petsc, so the answer to my question may very well be fairly trivial.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>I’m trying to run the following bits of code:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>DMDACreate2d(PETSC_COMM_WORLD, DMDA_BOUNDARY_GHOSTED, DMDA_BOUNDARY_GHOSTED, DMDA_STENCIL_BOX,10,10,PETSC_DECIDE,PETSC_DECIDE,1,1,PETSC_NULL,PETSC_NULL,&da);<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>[snip]<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>MatCreate(PETSC_COMM_WORLD,&((*FD).ddx));<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> MatSetSizes((*FD).ddx,PETSC_DECIDE,PETSC_DECIDE,100,100);<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> </span>MatSetFromOptions((*FD).ddx);<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> for (i=0;i<10;i++) {<o:p></o:p></p><p class=MsoNormal> <span lang=EN-US>col[0]=i*10;col[1]=i*10+1; row[0]=i*10;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> val[0]=1;val[1]=1;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> MatSetValues((*FD).ddx,1,row,2,col,val,INSERT_VALUES);<o:p></o:p></span></p><p class=MsoNormal> for (j=1;j<10-1;j++) {<o:p></o:p></p><p class=MsoNormal> col[0]=i*10+j-1;col[1]=i*10+j+1; row[0]=i*10+j;<o:p></o:p></p><p class=MsoNormal> <span lang=EN-US>val[0]=-1;val[1]=1;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> MatSetValues((*FD).ddx,1,row,2,col,val,INSERT_VALUES);<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> }<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> col[0]=i*10+10-2;col[1]=i*10+10-1; row[0]=i*10+10-1;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> val[0]=-1;val[1]=-1;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> MatSetValues((*FD).ddx,1,row,2,col,val,INSERT_VALUES);<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> }<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> MatAssemblyBegin((*FD).ddx,MAT_FINAL_ASSEMBLY);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US>MatAssemblyEnd((*FD).ddx,MAT_FINAL_ASSEMBLY);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'>MatScale((*FD).ddx,1/(2*(1/9)));<o:p></o:p></p><p class=MsoNormal style='text-indent:4.5pt'>[snip]<o:p></o:p></p><p class=MsoNormal style='text-indent:4.5pt'> DMCreateGlobalVector(da,&tmpvec2);<o:p></o:p></p><p class=MsoNormal style='text-indent:4.5pt'> <span lang=EN-US>VecSet(tmpvec2,1.0);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> VecAssemblyBegin(tmpvec2);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> VecAssemblyEnd(tmpvec2);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> </span>DMCreateGlobalVector(da,&tmpvec3);<o:p></o:p></p><p class=MsoNormal style='text-indent:4.5pt'> VecSet(tmpvec3,1.0);<o:p></o:p></p><p class=MsoNormal style='text-indent:4.5pt'> <span lang=EN-US>VecAssemblyBegin(tmpvec3);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> VecAssemblyEnd(tmpvec3);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> MatView((*FD).ddx,PETSC_VIEWER_STDOUT_WORLD);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> VecView(tmpvec2,PETSC_VIEWER_STDOUT_WORLD);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> MatMult((*FD).ddx,tmpvec2,tmpvec3);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> VecView(tmpvec3,PETSC_VIEWER_STDOUT_WORLD);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> int tid,first,last;<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> MPI_Comm_rank(PETSC_COMM_WORLD, &tid);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> sleep(1);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> MatGetOwnershipRange((*FD).ddx,&first,&last);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US> printf("rank: %d,first: %d,last: %d\n",tid,first,last);<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US>When running it on a single processor, everything works as expected, see attached file seqRes<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US>However when running with 4 processors (mpirun –np 4 ./progname) I get the output in mpiRes. Notice that there really is a difference, its not just a surprising division of points between the processes – I checked this with PETSC_VIEWER_DRAW_WORLD. How come? I notice that although in the end each process postulates that it has 25 rows, the result of matview is<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US>Matrix Object: 1 MPI processes<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US>type: mpiaij<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US>Is this OK? And if not, what am I doing wrong, presumably in the matrix allocation code?<o:p></o:p></span></p><p class=MsoNormal style='text-indent:4.5pt'><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal>---<o:p></o:p></p><p class=MsoNormal>yours sincerily<o:p></o:p></p><p class=MsoNormal>Frederik Treue<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>