topic Thanks again for helping me in Intel® oneAPI Math Kernel Library

How can I remove a column from a sparse matrix (CSR) using MKL

rdees — Mon, 24 Feb 2014 20:54:18 GMT

I need to revove a column from a large sparse matrix that is stored in CSR format, using MKL. I cannot find an MKL routine that does this directly. Can anyone tell me how it can be done? I'm using Fortran. Thx. Bob

Here is an example where the

mecej4 — Tue, 25 Feb 2014 15:18:00 GMT

Here is an example where the input 8 X 8 matrix is symmetric and only the upper triangle is processed. The example shows the third column being deleted. The call to mkl_ddnscsr() is only for printing purposes, and is not needed for the column deletion.

[NOTE: The program listing is portrayed by the formatter as double spaced. That was not intended, and I request the Intel people to tell me how to avoid such unintended double spacing.]

[fortran] PROGRAM pardiso_sym
IMPLICIT NONE
C.. All other variables
INTEGER maxfct, mnum, mtype, phase, n, nrhs, error, msglvl
INTEGER iparm(64)
INTEGER ia(9),ian(9)
INTEGER ja(18)
REAL*8 a(18),ad(8,7)
REAL*8 b(8)
REAL*8 x(8)
INTEGER i, j,k,kn, idum,job(6), info, jdel
REAL*8 waltime1, waltime2, ddum
C.. Fill all arrays containing matrix data.
DATA n /8/, nrhs /1/, maxfct /1/, mnum /1/
DATA ia /1,5,8,10,12,15,17,18,19/
DATA ja
1 /1, 3, 6,7,
2 2,3, 5,
3 3, 8,
4 4, 7,
5 5,6,7,
6 6, 8,
7 7,
8 8/
DATA a
1 /7.d0, 1.d0, 2.d0,7.d0,
2 -4.d0,8.d0, 2.d0,
3 1.d0, 5.d0,
4 7.d0, 9.d0,
5 5.d0,1.d0,5.d0,
6 -1.d0, 5.d0,
7 11.d0,
8 5.d0/
c
c Drop column 3
c
data job/1,1,1,0,0,0/
c
jdel = 3 ! column to delete
kn = 0
ian(1)=1
do i=1,n
do k=ia(i),ia(i+1)-1 ! row i
if(ja(k).ne.jdel)then
kn=kn+1
if(ja(k).gt.jdel)then
ja(kn)=ja(k)-1
else
ja(kn)=ja(k)
endif
a(kn)=a(k)
endif
end do
ian(i+1)=kn+1
end do
c
do i=1,n
write(*,'(7(2x,I2,1x,F10.3))')(ja(j),a(j),j=ian(i),ian(i+1)-1)
end do
write(*,*)
call mkl_ddnscsr(job,n,n-1,ad,n,a,ja,ian,info)
write(*,*)'info = ',info
do i=1,n
write(*,'(7F10.3)')(ad(i,j),j=1,7)
end do
END[/fortran]

Here is an example that shows

mecej4 — Tue, 25 Feb 2014 15:26:00 GMT

Here is an example that shows how to perform the column deletion that you sought. I show how to delete a column in a symmetric matrix represented by only its upper triangular part. Please note that the call to mkl_ddnscsr() is not needed for the column deletion, but to facilitate printing the modified matrix.

[Note to Forum Moderators: My first response (#2) was held up for approval for several hours. Then, after it was approved, I noticed that the inline code was formatted with double spacing, and added a couple of sentences to #2 to disclaim that I had inserted the extra blank lines. When I did the edits and clicked "SUBMIT", the whole of #2 evaporated, and the forum TOC showed the number of replies as 0. In response to this event, I posted #3. Subsequently, #2 appeared again. There is much duplication between the two: readers please note this!]

mecej4, Thx so much. It

rdees — Tue, 25 Feb 2014 16:06:03 GMT

mecej4, Thx so much. It works great. Do you happen to have a version of this code that would work on an non-symmetric, sparse matrix. If you do, that would be very helpful too.

Here is similar code for an

mecej4 — Tue, 25 Feb 2014 18:33:00 GMT

Here is similar code for an unsymmetric, non-square matrix. The matrix is 7 X 8 and column-3 is deleted, giving a 7 X 7 matrix.

meje4 - Thx again - It works

rdees — Wed, 26 Feb 2014 14:09:48 GMT

meje4 - Thx again - It works great - I appreciate your help.

Thanks again for helping me

rdees — Mon, 05 May 2014 20:55:44 GMT

Thanks again for helping me with this. You have been very helpful.