<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">OK. I am now use MatGetSubMatrix.My code is as follows<br><br> PetscMalloc(n*sizeof(PetscInt),&indices); <br> for (j = 0; j < n; j++)<br> { <br> indices[j] = j; <br> } <br> ISCreateGeneral(PETSC_COMM_SELF,n,indices,&iy); // get all columns <br> .....<br><br> PetscMalloc(2*sizeof(PetscInt),&indices); <br> indices[0] = i;<br> indices[1] = j;<br> ISCreateGeneral(PETSC_COMM_SELF,2,indices,&ix); // only get i,j rows<br><br> Mat ui,uj; <br>// I am not sure how to set the third parameter : how many "local " columns. Since I want all columns, I set it to n<br> ierr = MatGetSubMatrix(U,ix,iy,n,
MAT_INITIAL_MATRIX,&ui);CHKERRQ(ierr);<br><br>What I really hope is to <br> <br> for (i = 0; i < n; i++)<br>{<br> PetscInt row = 0;<br> MatGetValues(ui,1,&row,1,&i,&u_ik);<br>}<br>It does not work. I tried to change the n to PETSC_DECIDE, it still does not work<br><br>So, I really doubt that whether I can get the entire row of the matrix.<br><br>BTW, the matrix is created as follows:<br> MatCreateMPIDense(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,m,n,PETSC_NULL,&U)<br><br>THank you<br>--- <b>09年12月2日，周三, Barry Smith <i><bsmith@mcs.anl.gov></i></b> 写道：<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>发件人: Barry Smith <bsmith@mcs.anl.gov><br>主题: Re: How
to copy global data to local ?<br>收件人: "PETSc users list" <petsc-users@mcs.anl.gov><br>日期: 2009年12月2日,周三,下午1:46<br><br><div class="plainMail"><br> Don't know what MatGetSubMatrixRaw() is, but based on the calling sequence you are asking for the ith row whatever that is, and n columns in the array indices<br><br> For MatGetSubMatrix() each process can ask for any rows it wants, but all the processors have to ask for the same columns that are wanted.<br><br> Barry<br><br>On Dec 1, 2009, at 9:59 PM, ming zhu wrote:<br><br>> Hi<br>> I tried MatGetSubMatrix() but I am a little confused by the column parameter. For example<br>> My matrix is U (m * n). I want to get i,j rows to local.<br>> my code is<br>> <br>> PetscInt* rowindex,colindex;<br>> PetscMalloc...<br>> for (k= 0; k < n; k++)<br>> colindex[k] = k;<br>> <br>> rowindex[0] =
i;<br>> rowindex[1] = j;<br>> <br>> MatGetSubMatrixRaw(U,1,&i,n,indices,n,MAT_INITIAL_MATRIX,&newmat);<br>> <br>> What I hope is newmat is 2 * n matrix. But I failed.<br>> <br>> Thank you<br>> <br>> <br>> --- 09年12月1日，周二, Barry Smith <<a ymailto="mailto:bsmith@mcs.anl.gov" href="/mc/compose?to=bsmith@mcs.anl.gov">bsmith@mcs.anl.gov</a>> 写道：<br>> <br>> 发件人: Barry Smith <<a ymailto="mailto:bsmith@mcs.anl.gov" href="/mc/compose?to=bsmith@mcs.anl.gov">bsmith@mcs.anl.gov</a>><br>> 主题: Re: How to copy global data to local ?<br>> 收件人: "PETSc users list" <<a ymailto="mailto:petsc-users@mcs.anl.gov" href="/mc/compose?to=petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>><br>> 日期: 2009年12月1日,周二,下午10:35<br>> <br>> <br>> You misunderstand the usage of MatGetSubMatrix(). Any process can request ANY row, including rows
that are not originally owned by that process.<br>> <br>> Barry<br>> <br>> On Dec 1, 2009, at 8:29 AM, ming zhu wrote:<br>> <br>> > It seems that MatGetSubMatrix() only get the local matrix for the processor If U is global(PETSC_COMM_WORLD), the local matrix may not store the column or row I wanted. For example, if U is 4*4, and there are 4 processors, processors one has local matrix 2*2, but i need the third row, Then,MatGetSubmatrix() may not work<br>> ><br>> > --- 09年12月1日，周二, Barry Smith <<a ymailto="mailto:bsmith@mcs.anl.gov" href="/mc/compose?to=bsmith@mcs.anl.gov">bsmith@mcs.anl.gov</a>> 写道：<br>> ><br>> > 发件人: Barry Smith <<a ymailto="mailto:bsmith@mcs.anl.gov" href="/mc/compose?to=bsmith@mcs.anl.gov">bsmith@mcs.anl.gov</a>><br>> > 主题: Re: How to copy global data to local ?<br>> > 收件人: "PETSc users list" <<a
ymailto="mailto:petsc-users@mcs.anl.gov" href="/mc/compose?to=petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>><br>> > 日期: 2009年12月1日,周二,下午10:23<br>> ><br>> ><br>> > On Nov 30, 2009, at 11:21 PM, ming zhu wrote:<br>> ><br>> > > Hi<br>> > > I have a huge matrix U for all processors (PETSC_COMM_WORLD). I only want to copy only two rows (i,j) for each local processor. i,j is different for each processor and not related to rank. I was trying to use a vector filter (like, 00000010000). However, if the vector is PETSC_COMM_WORLD, it will be changed by different processor. So, how to make it ?<br>> >
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^<br>> ><br>> > I do not understand what this means. To do the multiply you can and should use a vector of PETSC_COMM_WORLD.<br>> ><br>> > Also multiplying by a vector will not give you back "rows" of a matrix. Do you truly want the entire row of nonzeros of the matrix or something else. If you want the entire row or part of a row then you can use MatGetSubMatrix().<br>> ><br>> > Barry<br>> ><br>> > > Thank you<br>> > ><br>> > > My original code is<br>> > ><br>> > > Vec
filter<br>> > > VecCreate(PETSC_COMM_WORLD,&filter);<br>> > > VecSetsizes(filter,PETSC_DECIDE,m);<br>> > > VecSetFromOptions(filter);<br>> > ><br>> > > Vecset(filter,0);<br>> > > VecSetValue(filter,i,1,INSERT_VALUES);<br>> > ><br>> > > ...<br>> > > MatMult(U, filter,ui);<br>> > ><br>> > > If I create filter with PETSC_COMM_SELF, it is impossible for U and filter to multiply.<br>> > ><br>> > ><br>> > ><br>> > ><br>> > ><br>> > > 好玩贺卡等你发，邮箱贺卡全新上线！<br>> ><br>> ><br>> > 好玩贺卡等你发，邮箱贺卡全新上线！<br>> <br>> <br>> 好玩贺卡等你发，邮箱贺卡全新上线！<br><br></div></blockquote></td></tr></table><br>
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