Estimates the reciprocal of the condition number of a general matrix in the 1norm or the infinitynorm.
Syntax

lapack_int LAPACKE_sgecon( int matrix_layout, char norm, lapack_int n, const float* a, lapack_int lda, float anorm, float* rcond );
lapack_int LAPACKE_dgecon( int matrix_layout, char norm, lapack_int n, const double* a, lapack_int lda, double anorm, double* rcond );
lapack_int LAPACKE_cgecon( int matrix_layout, char norm, lapack_int n, const lapack_complex_float* a, lapack_int lda, float anorm, float* rcond );
lapack_int LAPACKE_zgecon( int matrix_layout, char norm, lapack_int n, const lapack_complex_double* a, lapack_int lda, double anorm, double* rcond );
Include Files
 mkl.h
Description
The routine estimates the reciprocal of the condition number of a general matrix A in the 1norm or infinitynorm:
κ_{1}(A) =A_{1}A^{1}_{1} = κ_{∞}(A^{T}) = κ_{∞}(A^{H})
κ_{∞}(A) =A_{∞}A^{1}_{∞} = κ_{1}(A^{T}) = κ_{1}(A^{H}).
An estimate is obtained for A^{1}, and the reciprocal of the condition number is computed as rcond = 1 / (A A^{1}).
Before calling this routine:

compute anorm (either A_{1} = max_{j}Σ_{i} a_{ij} or A_{∞} = max_{i}Σ_{j} a_{ij})

call ?getrf to compute the LU factorization of A.
Input Parameters
matrix_layout 
Specifies whether matrix storage layout is row major (LAPACK_ROW_MAJOR) or column major (LAPACK_COL_MAJOR). 
norm 
Must be '1' or 'O' or 'I'. If norm = '1' or 'O', then the routine estimates the condition number of matrix A in 1norm. If norm = 'I', then the routine estimates the condition number of matrix A in infinitynorm. 
n 
The order of the matrix A; n≥ 0. 
a 
The array a contains the LUfactored matrix A, as returned by ?getrf. 
anorm 
The norm of the original matrix A (see Description). 
lda 
The leading dimension of a; lda≥ max(1, n). 
Output Parameters
rcond 
An estimate of the reciprocal of the condition number. The routine sets rcond = 0 if the estimate underflows; in this case the matrix is singular (to working precision). However, anytime rcond is small compared to 1.0, for the working precision, the matrix may be poorly conditioned or even singular. 
Return Values
This function returns a value info.
If info=0, the execution is successful.
If info = i, parameter i had an illegal value.
Application Notes
The computed rcond is never less than r (the reciprocal of the true condition number) and in practice is nearly always less than 10r. A call to this routine involves solving a number of systems of linear equations A*x = b or A^{H}*x = b; the number is usually 4 or 5 and never more than 11. Each solution requires approximately 2*n^{2} floatingpoint operations for real flavors and 8*n^{2} for complex flavors.