# Examples of Using Multi-Threading for FFT Computation

The following sample program shows how to employ internal threading in Intel MKL for FFT computation.

To specify the number of threads inside Intel MKL, use the following settings:

set `MKL_NUM_THREADS = 1` for one-threaded mode;

set `MKL_NUM_THREADS = 4` for multi-threaded mode.

# Examples for Cluster FFT Functions

## 2D Out-of-place Cluster FFT Computation

The following C example computes a 2-dimensional out-of-place FFT using the cluster FFT interface:

# Auxiliary Data Transformations

This section presents code examples for conversion from the Cartesian to polar representation of complex data and vice versa.

# Appendix C: Specific Features of Fortran 95 Interfaces for LAPACK Routines

Intel® MKL implements Fortran 95 interface for LAPACK package, further referred to as MKL LAPACK95, to provide full capacity of MKL FORTRAN 77 LAPACK routines. This is the principal difference of Intel MKL from the Netlib Fortran 95 implementation for LAPACK.

# Interfaces Identical to Netlib

```GERFS(A,AF,IPIV,B,X[,TRANS][,FERR][,BERR][,INFO])
GETRI(A,IPIV[,INFO])
GEEQU(A,R,C[,ROWCND][,COLCND][,AMAX][,INFO])
GESV(A,B[,IPIV][,INFO])
GESVX(A,B,X[,AF][,IPIV][,FACT][,TRANS][,EQUED][,R][,C][,FERR][,BERR]
[,RCOND][,RPVGRW][,INFO])
GTSV(DL,D,DU,B[,INFO])
GTSVX(DL,D,DU,B,X[,DLF][,DF][,DUF][,DU2][,IPIV][,FACT][,TRANS][,FERR]
[,BERR][,RCOND][,INFO])
POSV(A,B[,UPLO][,INFO])```

# Interfaces with Replaced Argument Names

Argument names in the routines of this group are replaced as follows:

# Modified Netlib Interfaces

```SYEVX(A,W[,UPLO][,Z][,VL][,VU][,IL][,IU][,M][,IFAIL][,ABSTOL][,INFO])
!   Interface netlib95 exists, parameters:
!   netlib: (A,W,JOBZ,UPLO,VL,VU,IL,IU,M,IFAIL,ABSTOL,INFO)
!   Different order for parameter UPLO, netlib: 4, mkl: 3
!   Absent mkl parameter: JOBZ
!   Extra mkl parameter: Z
```

`HEEVX(A,W[,UPLO][,Z][,VL][,VU][,IL][,IU][,M][,IFAIL][,ABSTOL][,INFO])`