Thanks very much. And I will have a try.
Jim
At 2012-06-09 06:10:50,"Barry Smith" <bsmith at mcs.anl.gov> wrote:
>
>http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateSeqAIJWithArrays.html
>http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateMPIAIJWithArrays.html
>
>
>
>On Jun 8, 2012, at 1:31 AM, w_ang_temp wrote:
>
>> Hello,
>> When solving a linear system Ax=b, the first step is assigning values to
>> matrix A. In my program, the subroutine PETSCSOLVE, which is used to slove
>> Ax=b
>> with PETSc, gets the CSR format matrix(values, columns, rowIndex) to set
>> values
>> to PETSc Mat A.
>> The variables 'values'?'columns'?'rowIndex' belong to the main function.
>> They are used to represent a matrix in CSR format. The following table
>> describes
>> the arrays in terms of the values, row, and column positions of the non-zero
>> elements in a sparse matrix.
>> values: A real or complex array that contains the non-zero elements of a
>> sparse matrix. The non-zero elements are mapped into the values
>> array using the row-major upper triangular storage mapping
>> described
>> above.
>> columns: Element i of the integer array columns is the number of the
>> column
>> that contains the i-th element in the values array.
>> rowIndex: Element j of the integer array rowIndex gives the index of the
>> element in the values array that is first non-zero element in
>> a row j.
>>
>> codes:
>> ---------Set Values to A From CSR
>> Format(values,rowIndex,columns)-------------------
>> !values:Non-Symmetric Matrix
>> ione = 1
>> do 10,II=Istart+1,Iend
>> !non-zero numbers of this row
>> rowNum=rowIndex(II+1)-rowIndex(II)
>> do 11,JJ=1,rowNum
>>
>> !elemnt index of the values/columns
>> kValNn=rowIndex(II)+JJ-1
>> !column index of this element
>> nCol=columns(kValNn)-1
>>
>> !Setdata:II-RowIndex,nCol-ColIndex
>> nRow=II-1
>> call
>> MatSetValues(A,ione,nRow,ione,nCol,values(kValNn),INSERT_VALUES,ierr)
>> 11 continue
>> 10 continue
>> --------------------------------------------------------------------------------------
>>
>> As we can see, it has to loop a number of times because it can only set
>> one data per
>> time. And this leads to low efficiency.
>> So is there a better way to do this?
>> Thank you.
>> Jim
>>
>>
>>
>
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