12-14-2009
well, w/o seeing data access paths it's hard to say whether data access patterns are optimal or close to optimal and make any decisions regarding direct i/o. next, lets assume i decided to implement direct i/o - how do i tell whether my implementation is the optimal one. my case not about comparison or achieving certain kbps, it rather about getting best from disk.
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LEARN ABOUT REDHAT
sgetri
SGETRI(l) ) SGETRI(l)
NAME
SGETRI - compute the inverse of a matrix using the LU factorization computed by SGETRF
SYNOPSIS
SUBROUTINE SGETRI( N, A, LDA, IPIV, WORK, LWORK, INFO )
INTEGER INFO, LDA, LWORK, N
INTEGER IPIV( * )
REAL A( LDA, * ), WORK( * )
PURPOSE
SGETRI computes the inverse of a matrix using the LU factorization computed by SGETRF. This method inverts U and then computes inv(A) by
solving the system inv(A)*L = inv(U) for inv(A).
ARGUMENTS
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input/output) REAL array, dimension (LDA,N)
On entry, the factors L and U from the factorization A = P*L*U as computed by SGETRF. On exit, if INFO = 0, the inverse of the
original matrix A.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
IPIV (input) INTEGER array, dimension (N)
The pivot indices from SGETRF; for 1<=i<=N, row i of the matrix was interchanged with row IPIV(i).
WORK (workspace/output) REAL array, dimension (LWORK)
On exit, if INFO=0, then WORK(1) returns the optimal LWORK.
LWORK (input) INTEGER
The dimension of the array WORK. LWORK >= max(1,N). For optimal performance LWORK >= N*NB, where NB is the optimal blocksize
returned by ILAENV.
If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this
value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, U(i,i) is exactly zero; the matrix is singular and its inverse could not be computed.
LAPACK version 3.0 15 June 2000 SGETRI(l)