Extended Eigensolver Input Parameters

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 4/28/2026

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Extended Eigensolver Input Parameters

The input parameters for Extended Eigensolver routines are contained in an integer MKL_INT array named fpm . To call the Extended Eigensolver interfaces, this array should be initialized using the routine feastinit (Initialize Extended Eigensolver input parameters with default values.).

Parameter	Default	Description
`fpm(1)`	0	Specifies whether Extended Eigensolver routines print runtime status.
		`fpm(1)` =0
		Extended Eigensolver routines do not generate runtime messages at all.
		`fpm(1)` =1
		Extended Eigensolver routines print runtime status to the screen.
`fpm(2)`	8	The number of contour points `N`_e = 8 (see the description of FEAST algorithm). Must be one of {3,4,5,6,8,10,12,16,20,24,32,40,48}.
`fpm(3)`	12	Error trace double precision stopping criteria `ε` ( `ε` = 10 ^-fpm(3) ) .
`fpm(4)`	20	Maximum number of Extended Eigensolver refinement loops allowed. If no convergence is reached within `fpm(4)` refinement loops, Extended Eigensolver routines return `info` =2.
`fpm(5)`	0	User initial subspace. If `fpm(5)` =0 then Extended Eigensolver routines generate initial subspace, if `fpm(5)` =1 the user supplied initial subspace is used.
`fpm(6)`	0	Extended Eigensolver stopping test.
		`fpm(6)` =0
		Extended Eigensolvers are stopped if this residual stopping test is satisfied: generalized eigenvalue problem: standard eigenvalue problem:
		where `mode` is the total number of eigenvalues found in the search interval and `ε` = 10 ^-fpm(7) for real and complex or `ε` = 10 ^-fpm(3) for double precision and double complex.
		`fpm(6)` =1
		Extended Eigensolvers are stopped if this trace stopping test is satisfied: , where `\({trace}_{j}\)` denotes the sum of all eigenvalues found in the search interval [ `emin` , `emax` ] at the `j` -th Extended Eigensolver iteration:
`fpm(7)`	5	Error trace single precision stopping criteria (10 ^-fpm(7) ).
`fpm(14)`	0	`fpm(14)` =0
		Standard use for Extended Eigensolver routines.
		`fpm(14)` =0
		Non-standard use for Extended Eigensolver routines: return the computed eigenvectors subspace after one single contour integration.
`fpm(27)`	0	Specifies whether Extended Eigensolver routines check input matrices (applies to CSR format only).
		`fpm(27)` =0
		Extended Eigensolver routines do not check input matrices.
		`fpm(27)` =1
		Extended Eigensolver routines check input matrices.
`fpm(28)`	0	Check if matrix `B` is positive definite. Set `fpm(28)` =1 to check if `B` is positive definite.
`fpm(50)`	0	Specifies whether Extended Eigensolver routines compute the total number of eigenvalues located in the interval [ `emin` , `emax` ] (applies to CSR format only).
		`fpm(50)` =0
		Standard use for Extended Eigensolver routines.
		`fpm(50)` =1
		Non-standard use for Extended Eigensolver routines: return `m0` as the total number of eigenvalues. `fpm(50)` is set to 0 on exit.
`fpm(29)` to `fpm(49)`, `fpm(51)` to `fpm(63)`		Reserved for future use.
`fpm(64)`	0	Use the Intel® oneMKL PARDISO solver with the user-defined PARDISO `iparm` array settings.
		`fpm(64)` =0
		Extended Eigensolver routines use the Intel® oneMKL PARDISO default `iparm` settings defined by calling the `pardisoinit` subroutine.
		`fpm(64)` =1
		The values from `fpm(65)` to `fpm(128)` correspond to `iparm(1)` to `iparm(64)` respectively according to the formula `fpm(64 + i) = iparm(i)` for `i = 1, 2, ..., 64`.

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Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

Extended Eigensolver Input Parameters