Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
p?getrs
Solves a system of distributed linear equations with a general square matrix, using the LU factorization computed by p?getrf .
Syntax
call psgetrs ( trans , n , nrhs , a , ia , ja , desca , ipiv , b , ib , jb , descb , info )
call pdgetrs ( trans , n , nrhs , a , ia , ja , desca , ipiv , b , ib , jb , descb , info )
call pcgetrs ( trans , n , nrhs , a , ia , ja , desca , ipiv , b , ib , jb , descb , info )
call pzgetrs ( trans , n , nrhs , a , ia , ja , desca , ipiv , b , ib , jb , descb , info )
Include Files
mkl_scalapack.h
Description
psgetrs pdgetrs pcgetrs pzgetrs The p?getrs routine function solves a system of distributed linear equations with a general n -by- n distributed matrix sub( A ) = A ( ia : ia + n -1, ja : ja + n -1) using the LU factorization computed by p?getrf (Computes the LU factorization of a general m-by-n distributed matrix.) .
The system has one of the following forms specified by trans :
sub( A )* X = sub( B ) (no transpose),
sub( A ) :code:`T` * X = sub( B ) (transpose),
sub( A ) :code:`H` * X = sub( B ) (conjugate transpose),
where sub( B ) = B ( ib : ib + n -1, jb : jb + nrhs -1).
Before calling this routine function ,you must call p?getrf to compute the LU factorization of sub( A ).
Input Parameters
trans
(global) CHARACTER*1 . Must be ‘N’ or ‘T’ or ‘C’ .
Indicates the form of the equations: If trans = 'N' , then sub( A )* X = sub( B ) is solved for X . If trans = 'T' , then sub( A ) :code:`T` * X = sub( B ) is solved for X . If trans = 'C' , then sub( A ) :code:`H` * X = sub( B ) is solved for X .
n
(global) INTEGER . The number of linear equations; the order of the matrix sub( A ) ( n ≥ 0).
nrhs
(global) INTEGER . The number of right hand sides; the number of columns of the distributed matrix sub( B ) ( nrhs ≥ 0).
- a , b
-
(local) REAL for psgetrs DOUBLE PRECISION for pdgetrs COMPLEX for pcgetrs DOUBLE COMPLEX for pzgetrs .
Pointers into the local memory to arrays of local sizes (lld_a,LOCc(ja+n-1)) and (lld_b,LOCc(jb+nrhs-1)) , respectively.
On entry, the array a contains the local pieces of the factors L and U from the factorization sub( A ) = P*L*U ; the unit diagonal elements of L are not stored. On entry, the array b contains the right hand sides sub( B ).
ia , ja
(global) INTEGER . The row and column indices in the global matrix A indicating the first row and the first column of the matrix sub( A ), respectively.
desca
(global and local) INTEGER array of size dlen_ . The array descriptor for the distributed matrix A .
ipiv
(local) INTEGER Array of size of LOCr(m_a) + mb_a . Contains the pivoting information: local row i of the matrix was interchanged with the global row ipiv ( i ) .
This array is tied to the distributed matrix A .
ib , jb
(global) INTEGER . The row and column indices in the global matrix B indicating the first row and the first column of the matrix sub( B ), respectively.
descb
(global and local) INTEGER array of size dlen_ . The array descriptor for the distributed matrix B .
Output Parameters
- b
-
On exit, overwritten by the solution distributed matrix X .
info
INTEGER . If info=0 , the execution is successful. info < 0 :
If the i -th argument is an array and the j- th entry had an illegal value, then info = -( i *100+ j ); if the i- th argument is a scalar and had an illegal value, then info = -i .