Developer Reference

  • 2020
  • 07/15/2020
  • Public Content
Contents

FFTFwd_RToPack
,
FFTFwd_RToPerm
,
FFTFwd_RToCCS

Computes the forward or inverse fast Fourier transform (FFT) of a real signal.

Syntax

Case 1: Not-in-place operation, result in
Pack
Format
IppStatus ippsFFTFwd_RToPack_32f(const Ipp32f*
pSrc
, Ipp32f*
pDst
, const IppsFFTSpec_R_32f*
pFFTSpec
, Ipp8u*
pBuffer
);
IppStatus ippsFFTFwd_RToPack_64f(const Ipp64f*
pSrc
, Ipp64f*
pDst
, const IppsFFTSpec_R_64f*
pFFTSpec
, Ipp8u*
pBuffer
);
Case 2: In-place operation, result in
Pack
Format.
IppStatus ippsFFTFwd_RToPack_32f_I(Ipp32f*
pSrcDst
, const IppsFFTSpec_R_32f*
pFFTSpec
, Ipp8u*
pBuffer
);
IppStatus ippsFFTFwd_RToPack_64f_I(Ipp64f*
pSrcDst
, const IppsFFTSpec_R_64f*
pFFTSpec
, Ipp8u*
pBuffer
);
Case 3: Not-in-place operation, result in
Perm
Format
IppStatus ippsFFTFwd_RToPerm_32f(const Ipp32f*
pSrc
, Ipp32f*
pDst
, const IppsFFTSpec_R_32f*
pFFTSpec
, Ipp8u*
pBuffer
);
IppStatus ippsFFTFwd_RToPerm_64f(const Ipp64f*
pSrc
, Ipp64f*
pDst
, const IppsFFTSpec_R_64f*
pFFTSpec
, Ipp8u*
pBuffer
);
Case 4: In-place operation, result in
Perm
Format.
IppStatus ippsFFTFwd_RToPerm_32f_I(Ipp32f*
pSrcDst
, const IppsFFTSpec_R_32f*
pFFTSpec
, Ipp8u*
pBuffer
);
IppStatus ippsFFTFwd_RToPerm_64f_I(Ipp64f*
pSrcDst
, const IppsFFTSpec_R_64f*
pFFTSpec
, Ipp8u*
pBuffer
);
Case 5: Not-in-place operation, result in
CCS
Format
IppStatus ippsFFTFwd_RToCCS_32f(const Ipp32f*
pSrc
, Ipp32f*
pDst
, const IppsFFTSpec_R_32f*
pFFTSpec
, Ipp8u*
pBuffer
);
IppStatus ippsFFTFwd_RToCCS_64f(const Ipp64f*
pSrc
, Ipp64f*
pDst
, const IppsFFTSpec_R_64f*
pFFTSpec
, Ipp8u*
pBuffer
);
Case 6: In-place operation, result in
CCS
Format.
IppStatus ippsFFTFwd_RToCCS_64f_I(Ipp64f*
pSrcDst
, const IppsFFTSpec_R_64f*
pFFTSpec
, Ipp8u*
pBuffer
);
IppStatus ippsFFTFwd_RToCCS_32f_I(Ipp32f*
pSrcDst
, const IppsFFTSpec_R_32f*
pFFTSpec
, Ipp8u*
pBuffer
);
Include Files
ipps.h
Domain Dependencies
Headers:
ippcore.h
,
ippvm.h
Libraries:
ippcore.lib
,
ippvm.lib
Parameters
pFFTSpec
Pointer to the FFT specification structure.
pSrc
Pointer to the input array.
pDst
Pointer to the output array containing packed complex values.
pSrcDst
Pointer to the input and output arrays for the in-place operation.
pBuffer
Pointer to the external work buffer.
Description
These functions compute the forward FFT of a real signal and store the result in Pack, Perm, or CCS packed formats respectively. The transform is performed in accordance with the
pFFTSpec
specification parameters: the transform
order
, the normalization
flag
, and the specific code
hint
. Before calling these functions the FFT specification structure must be initialized by the corresponding flavors of
ippsFFTInit_R
. The length of the FFT must be a power of 2.
The function may be used with the external work buffer
pBuffer
to avoid memory allocation within the functions. Once the work buffer is allocated, it can be used for all following calls to the functions computing FFT. As internal allocation of memory is too expensive operation and depends on operating system and/or runtime libraries used - the use of an external buffer improves performance significantly, especially for the small size transforms.
The size of the external buffer must be previously computed by the
ippsFFTGetSize_R
function.
If the external buffer is not specified (
pBuffer
is set to
NULL
), then the function itself allocates the memory needed for operation.
ippsFFTFwd_RToPack
. This function computes the forward FFT and stores the result in
Pack
format.
ippsFFTFwd_RToPerm
. This function computes the forward FFT and stores the result in
Perm
format.
ippsFFTFwd_RToCCS
. This function computes the forward FFT and stores the result in
CCS
format.
Return Values
ippStsNoErr
Indicates no error.
ippStsNullPtrErr
Indicates an error when one of the specified pointers with exception of
pBuffer
is
NULL
.
ippStsContextMatchErr
Indicates an error when the specification identifier
pFFTSpec
is incorrect.
ippStsMemAllocErr
Indicates an error when no memory is allocated.

Example

/******************************************************************************* * Copyright 2015-2020 Intel Corporation. * * This software and the related documents are Intel copyrighted materials, and * your use of them is governed by the express license under which they were * provided to you (License). Unless the License provides otherwise, you may not * use, modify, copy, publish, distribute, disclose or transmit this software or * the related documents without Intel's prior written permission. * * This software and the related documents are provided as is, with no express * or implied warranties, other than those that are expressly stated in the * License. *******************************************************************************/ // A simple example of performing the forward FFT for processing real data // for CCS packed formats and computing magnitude // implemented with Intel(R) Integrated Primitives (Intel(R) IPP) functions: // ippiFFTGetSize_R_32f // ippiFFTInit_R_32f // ippiFFTFwd_RToPack_32f_C1R // ippsMagnitude_32fc #include <stdio.h> #include <math.h> #include "ipp.h" /* Next two defines are created to simplify code reading and understanding */ #define EXIT_MAIN exitLine: /* Label for Exit */ #define check_sts(st) if((st) != ippStsNoErr) goto exitLine; /* Go to Exit if Intel(R) IPP function returned status different from ippStsNoErr */ /* Results of ippMalloc() are not validated because Intel(R) IPP functions perform bad arguments check and will return an appropriate status */ int main(void) { int i; IppStatus status = ippStsNoErr; Ipp32f pSrc[8], pDst[10]; /* Pointers to source/destination images */ Ipp32f pMagn[4]; /* Pointer to the computed magnitude values */ IppsFFTSpec_R_32f* pSpec = NULL; /* Pointer to FFT pSpec structure */ Ipp8u *pMemInit = NULL, *pBuffer = NULL, *pSpecMem = NULL; /* Pointer to the work buffers */ int sizeSpec = 0, sizeInit = 0, sizeBuf = 0; /* size of FFT pSpec structure, Init and work buffers */ check_sts( status = ippsFFTGetSize_R_32f(3, IPP_FFT_DIV_INV_BY_N, ippAlgHintNone, &sizeSpec, &sizeInit, &sizeBuf) ) /* memory allocation */ pSpecMem = (Ipp8u*) ippMalloc( sizeSpec ); pBuffer = (Ipp8u*) ippMalloc( sizeBuf ); pMemInit = (Ipp8u*) ippMalloc( sizeInit ); check_sts( status = ippsFFTInit_R_32f(&pSpec, 3, IPP_FFT_DIV_INV_BY_N, ippAlgHintNone, pSpecMem, pMemInit) ) for (i = 0; i< 8 ; ++i) { pSrc[i] = (float)cos(IPP_2PI * i * 16.0/64); } check_sts( status = ippsFFTFwd_RToCCS_32f( pSrc, pDst, pSpec, pBuffer ) ) check_sts( status = ippsMagnitude_32fc( (Ipp32fc*)pDst, pMagn, 4 ) ) printf("FFT Magnitude = %f %f %f %f\n", pMagn[0], pMagn[1], pMagn[2], pMagn[3]); EXIT_MAIN ippFree( pMemInit ); ippFree( pSpec ); ippFree( pBuffer ); printf("Exit status %d (%s)\n", (int)status, ippGetStatusString(status)); return (int)status; }

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804