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diff src/fftw-3.3.3/doc/html/New_002darray-Execute-Functions.html @ 10:37bf6b4a2645
Add FFTW3
| author | Chris Cannam |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.3/doc/html/New_002darray-Execute-Functions.html Wed Mar 20 15:35:50 2013 +0000 @@ -0,0 +1,152 @@ +<html lang="en"> +<head> +<title>New-array Execute Functions - FFTW 3.3.3</title> +<meta http-equiv="Content-Type" content="text/html"> +<meta name="description" content="FFTW 3.3.3"> +<meta name="generator" content="makeinfo 4.13"> +<link title="Top" rel="start" href="index.html#Top"> +<link rel="up" href="FFTW-Reference.html#FFTW-Reference" title="FFTW Reference"> +<link rel="prev" href="Guru-Interface.html#Guru-Interface" title="Guru Interface"> +<link rel="next" href="Wisdom.html#Wisdom" title="Wisdom"> +<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> +<!-- +This manual is for FFTW +(version 3.3.3, 25 November 2012). + +Copyright (C) 2003 Matteo Frigo. + +Copyright (C) 2003 Massachusetts Institute of Technology. + + Permission is granted to make and distribute verbatim copies of + this manual provided the copyright notice and this permission + notice are preserved on all copies. + + Permission is granted to copy and distribute modified versions of + this manual under the conditions for verbatim copying, provided + that the entire resulting derived work is distributed under the + terms of a permission notice identical to this one. + + Permission is granted to copy and distribute translations of this + manual into another language, under the above conditions for + modified versions, except that this permission notice may be + stated in a translation approved by the Free Software Foundation. + --> +<meta http-equiv="Content-Style-Type" content="text/css"> +<style type="text/css"><!-- + pre.display { font-family:inherit } + pre.format { font-family:inherit } + pre.smalldisplay { font-family:inherit; font-size:smaller } + pre.smallformat { font-family:inherit; font-size:smaller } + pre.smallexample { font-size:smaller } + pre.smalllisp { font-size:smaller } + span.sc { font-variant:small-caps } + span.roman { font-family:serif; font-weight:normal; } + span.sansserif { font-family:sans-serif; font-weight:normal; } +--></style> +</head> +<body> +<div class="node"> +<a name="New-array-Execute-Functions"></a> +<a name="New_002darray-Execute-Functions"></a> +<p> +Next: <a rel="next" accesskey="n" href="Wisdom.html#Wisdom">Wisdom</a>, +Previous: <a rel="previous" accesskey="p" href="Guru-Interface.html#Guru-Interface">Guru Interface</a>, +Up: <a rel="up" accesskey="u" href="FFTW-Reference.html#FFTW-Reference">FFTW Reference</a> +<hr> +</div> + +<h3 class="section">4.6 New-array Execute Functions</h3> + +<p><a name="index-execute-264"></a><a name="index-new_002darray-execution-265"></a> +Normally, one executes a plan for the arrays with which the plan was +created, by calling <code>fftw_execute(plan)</code> as described in <a href="Using-Plans.html#Using-Plans">Using Plans</a>. +<a name="index-fftw_005fexecute-266"></a>However, it is possible for sophisticated users to apply a given plan +to a <em>different</em> array using the “new-array execute” functions +detailed below, provided that the following conditions are met: + + <ul> +<li>The array size, strides, etcetera are the same (since those are set by +the plan). + + <li>The input and output arrays are the same (in-place) or different +(out-of-place) if the plan was originally created to be in-place or +out-of-place, respectively. + + <li>For split arrays, the separations between the real and imaginary +parts, <code>ii-ri</code> and <code>io-ro</code>, are the same as they were for +the input and output arrays when the plan was created. (This +condition is automatically satisfied for interleaved arrays.) + + <li>The <dfn>alignment</dfn> of the new input/output arrays is the same as that +of the input/output arrays when the plan was created, unless the plan +was created with the <code>FFTW_UNALIGNED</code> flag. +<a name="index-FFTW_005fUNALIGNED-267"></a>Here, the alignment is a platform-dependent quantity (for example, it is +the address modulo 16 if SSE SIMD instructions are used, but the address +modulo 4 for non-SIMD single-precision FFTW on the same machine). In +general, only arrays allocated with <code>fftw_malloc</code> are guaranteed to +be equally aligned (see <a href="SIMD-alignment-and-fftw_005fmalloc.html#SIMD-alignment-and-fftw_005fmalloc">SIMD alignment and fftw_malloc</a>). + + </ul> + + <p><a name="index-alignment-268"></a>The alignment issue is especially critical, because if you don't use +<code>fftw_malloc</code> then you may have little control over the alignment +of arrays in memory. For example, neither the C++ <code>new</code> function +nor the Fortran <code>allocate</code> statement provide strong enough +guarantees about data alignment. If you don't use <code>fftw_malloc</code>, +therefore, you probably have to use <code>FFTW_UNALIGNED</code> (which +disables most SIMD support). If possible, it is probably better for +you to simply create multiple plans (creating a new plan is quick once +one exists for a given size), or better yet re-use the same array for +your transforms. + + <p>If you are tempted to use the new-array execute interface because you +want to transform a known bunch of arrays of the same size, you should +probably go use the advanced interface instead (see <a href="Advanced-Interface.html#Advanced-Interface">Advanced Interface</a>)). + + <p>The new-array execute functions are: + +<pre class="example"> void fftw_execute_dft( + const fftw_plan p, + fftw_complex *in, fftw_complex *out); + + void fftw_execute_split_dft( + const fftw_plan p, + double *ri, double *ii, double *ro, double *io); + + void fftw_execute_dft_r2c( + const fftw_plan p, + double *in, fftw_complex *out); + + void fftw_execute_split_dft_r2c( + const fftw_plan p, + double *in, double *ro, double *io); + + void fftw_execute_dft_c2r( + const fftw_plan p, + fftw_complex *in, double *out); + + void fftw_execute_split_dft_c2r( + const fftw_plan p, + double *ri, double *ii, double *out); + + void fftw_execute_r2r( + const fftw_plan p, + double *in, double *out); +</pre> + <p><a name="index-fftw_005fexecute_005fdft-269"></a><a name="index-fftw_005fexecute_005fsplit_005fdft-270"></a><a name="index-fftw_005fexecute_005fdft_005fr2c-271"></a><a name="index-fftw_005fexecute_005fsplit_005fdft_005fr2c-272"></a><a name="index-fftw_005fexecute_005fdft_005fc2r-273"></a><a name="index-fftw_005fexecute_005fsplit_005fdft_005fc2r-274"></a><a name="index-fftw_005fexecute_005fr2r-275"></a> +These execute the <code>plan</code> to compute the corresponding transform on +the input/output arrays specified by the subsequent arguments. The +input/output array arguments have the same meanings as the ones passed +to the guru planner routines in the preceding sections. The <code>plan</code> +is not modified, and these routines can be called as many times as +desired, or intermixed with calls to the ordinary <code>fftw_execute</code>. + + <p>The <code>plan</code> <em>must</em> have been created for the transform type +corresponding to the execute function, e.g. it must be a complex-DFT +plan for <code>fftw_execute_dft</code>. Any of the planner routines for that +transform type, from the basic to the guru interface, could have been +used to create the plan, however. + +<!-- --> + </body></html> +