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diff src/fftw-3.3.5/doc/FAQ/fftw-faq.html/section2.html @ 42:2cd0e3b3e1fd
Current fftw source
| author | Chris Cannam |
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| date | Tue, 18 Oct 2016 13:40:26 +0100 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.5/doc/FAQ/fftw-faq.html/section2.html Tue Oct 18 13:40:26 2016 +0100 @@ -0,0 +1,285 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<html> +<head><title> +FFTW FAQ - Section 2 +</title> +<link rev="made" href="mailto:fftw@fftw.org"> +<link rel="Contents" href="index.html"> +<link rel="Start" href="index.html"> +<link rel="Next" href="section3.html"><link rel="Previous" href="section1.html"><link rel="Bookmark" title="FFTW FAQ" href="index.html"> +</head><body text="#000000" bgcolor="#FFFFFF"><h1> +FFTW FAQ - Section 2 <br> +Installing FFTW +</h1> + +<ul> +<li><a href="#systems" rel=subdocument>Q2.1. Which systems does FFTW run on?</a> +<li><a href="#runOnWindows" rel=subdocument>Q2.2. Does FFTW run on Windows?</a> +<li><a href="#compilerCrashes" rel=subdocument>Q2.3. My compiler has trouble with FFTW.</a> +<li><a href="#solarisSucks" rel=subdocument>Q2.4. FFTW does not compile on Solaris, complaining about +<code>const</code>.</a> +<li><a href="#3dnow" rel=subdocument>Q2.5. What's the difference between <code>--enable-3dnow</code> and <code>--enable-k7</code>?</a> +<li><a href="#fma" rel=subdocument>Q2.6. What's the difference between the fma and the non-fma +versions?</a> +<li><a href="#languages" rel=subdocument>Q2.7. Which language is FFTW written in?</a> +<li><a href="#fortran" rel=subdocument>Q2.8. Can I call FFTW from Fortran?</a> +<li><a href="#cplusplus" rel=subdocument>Q2.9. Can I call FFTW from C++?</a> +<li><a href="#whynotfortran" rel=subdocument>Q2.10. Why isn't FFTW written in Fortran/C++?</a> +<li><a href="#singleprec" rel=subdocument>Q2.11. How do I compile FFTW to run in single precision?</a> +<li><a href="#64bitk7" rel=subdocument>Q2.12. --enable-k7 does not work on x86-64</a> +</ul><hr> + +<h2><A name="systems"> +Question 2.1. Which systems does FFTW run +on? +</A></h2> + +FFTW is written in ANSI C, and should work on any system with a decent +C compiler. (See also <A href="#runOnWindows">Q2.2 `Does FFTW run on Windows?'</A>, <A href="#compilerCrashes">Q2.3 `My compiler has trouble with FFTW.'</A>.) FFTW can also take advantage of certain hardware-specific features, +such as cycle counters and SIMD instructions, but this is optional. + +<h2><A name="runOnWindows"> +Question 2.2. Does FFTW run on Windows? +</A></h2> + +Yes, many people have reported successfully using FFTW on Windows with +various compilers. FFTW was not developed on Windows, but the source +code is essentially straight ANSI C. See also the +<A href="http://www.fftw.org/install/windows.html">FFTW Windows installation notes</A>, <A href="#compilerCrashes">Q2.3 `My compiler has trouble with FFTW.'</A>, and <A href="section3.html#vbetalia">Q3.18 `How do I call FFTW from the Microsoft language du +jour?'</A>. +<h2><A name="compilerCrashes"> +Question 2.3. My compiler has trouble with +FFTW. +</A></h2> + +Complain fiercely to the vendor of the compiler. + +<p> +We have successfully used <code>gcc</code> 3.2.x on x86 and PPC, a recent Compaq C compiler for Alpha, version 6 of IBM's +<code>xlc</code> compiler for AIX, Intel's <code>icc</code> versions 5-7, and Sun WorkShop <code>cc</code> version 6. +<p> +FFTW is likely to push compilers to their limits, however, and several +compiler bugs have been exposed by FFTW. A partial list follows. + +<p> +<code>gcc</code> 2.95.x for Solaris/SPARC produces incorrect code for +the test program (workaround: recompile the +<code>libbench2</code> directory with <code>-O2</code>). +<p> +NetBSD/macppc 1.6 comes with a <code>gcc</code> version that also miscompiles the test program. (Please report a workaround if you know +one.) +<p> +<code>gcc</code> 3.2.3 for ARM reportedly crashes during compilation. +This bug is reportedly fixed in later versions of +<code>gcc</code>. +<p> +Versions 8.0 and 8.1 of Intel's <code>icc</code> falsely claim to be <code>gcc</code>, so you should specify <code>CC="icc -no-gcc"</code>; this is automatic in FFTW 3.1. <code>icc-8.0.066</code> reportely produces incorrect code for FFTW 2.1.5, but is fixed in version 8.1. +<code>icc-7.1</code> compiler build 20030402Z appears to produce +incorrect dependencies, causing the compilation to fail. +<code>icc-7.1</code> build 20030307Z appears to work fine. (Use +<code>icc -V</code> to check which build you have.) As of 2003/04/18, +build 20030402Z appears not to be available any longer on Intel's +website, whereas the older build 20030307Z is available. + +<p> +<code>ranlib</code> of GNU <code>binutils</code> 2.9.1 on Irix has been observed to corrupt the FFTW libraries, causing a link failure when +FFTW is compiled. Since <code>ranlib</code> is completely superfluous on Irix, we suggest deleting it from your system and replacing it with +a symbolic link to <code>/bin/echo</code>. +<p> +If support for SIMD instructions is enabled in FFTW, further compiler +problems may appear: +<p> +<code>gcc</code> 3.4.[0123] for x86 produces incorrect SSE2 code for +FFTW when <code>-O2</code> (the best choice for FFTW) is used, causing +FFTW to crash (<code>make check</code> crashes). This bug is fixed in <code>gcc</code> 3.4.4. On x86_64 (amd64/em64t), <code>gcc</code> 3.4.4 reportedly still has a similar problem, but this is fixed as of +<code>gcc</code> 3.4.6. +<p> +<code>gcc-3.2</code> for x86 produces incorrect SIMD code if +<code>-O3</code> is used. The same compiler produces incorrect SIMD +code if no optimization is used, too. When using +<code>gcc-3.2</code>, it is a good idea not to change the default +<code>CFLAGS</code> selected by the <code>configure</code> script. +<p> +Some 3.0.x and 3.1.x versions of <code>gcc</code> on <code>x86</code> may crash. <code>gcc</code> so-called 2.96 shipping with RedHat 7.3 crashes +when compiling SIMD code. In both cases, please upgrade to +<code>gcc-3.2</code> or later. +<p> +Intel's <code>icc</code> 6.0 misaligns SSE constants, but FFTW has a +workaround. <code>icc</code> 8.x fails to compile FFTW 3.0.x because it +falsely claims to be <code>gcc</code>; we believe this to be a bug in <code>icc</code>, but FFTW 3.1 has a workaround. +<p> +Visual C++ 2003 reportedly produces incorrect code for SSE/SSE2 when +compiling FFTW. This bug was reportedly fixed in VC++ 2005; +alternatively, you could switch to the Intel compiler. VC++ 6.0 also +reportedly produces incorrect code for the file +<code>reodft11e-r2hc-odd.c</code> unless optimizations are disabled for that file. +<p> +<code>gcc</code> 2.95 on MacOS X miscompiles AltiVec code (fixed in +later versions). <code>gcc</code> 3.2.x miscompiles AltiVec permutations, but FFTW has a workaround. +<code>gcc</code> 4.0.1 on MacOS for Intel crashes when compiling FFTW; a workaround is to +compile one file without optimization: <code>cd kernel; make CFLAGS=" " trig.lo</code>. +<p> +<code>gcc</code> 4.1.1 reportedly crashes when compiling FFTW for MIPS; +the workaround is to compile the file it crashes on +(<code>t2_64.c</code>) with a lower optimization level. +<p> +<code>gcc</code> versions 4.1.2 to 4.2.0 for x86 reportedly miscompile +FFTW 3.1's test program, causing <code>make check</code> to crash (<code>gcc</code> bug #26528). The bug was reportedly fixed in +<code>gcc</code> version 4.2.1 and later. A workaround is to compile +<code>libbench2/verify-lib.c</code> without optimization. +<h2><A name="solarisSucks"> +Question 2.4. FFTW does not compile on Solaris, complaining about +<code>const</code>. +</A></h2> + +We know that at least on Solaris 2.5.x with Sun's compilers 4.2 you +might get error messages from <code>make</code> such as +<p> +<code>"./fftw.h", line 88: warning: const is a keyword in ANSI +C</code> +<p> +This is the case when the <code>configure</code> script reports that <code>const</code> does not work: +<p> +<code>checking for working const... (cached) no</code> +<p> +You should be aware that Solaris comes with two compilers, namely, +<code>/opt/SUNWspro/SC4.2/bin/cc</code> and <code>/usr/ucb/cc</code>. The latter compiler is non-ANSI. Indeed, it is a perverse shell script +that calls the real compiler in non-ANSI mode. In order +to compile FFTW, change your path so that the right +<code>cc</code> is used. +<p> +To know whether your compiler is the right one, type +<code>cc -V</code>. If the compiler prints ``<code>ucbcc</code>'', as in +<p> +<code>ucbcc: WorkShop Compilers 4.2 30 Oct 1996 C +4.2</code> +<p> +then the compiler is wrong. The right message is something like + +<p> +<code>cc: WorkShop Compilers 4.2 30 Oct 1996 C +4.2</code> +<h2><A name="3dnow"> +Question 2.5. What's the difference between +<code>--enable-3dnow</code> and <code>--enable-k7</code>? +</A></h2> + +<code>--enable-k7</code> enables 3DNow! instructions on K7 processors +(AMD Athlon and its variants). K7 support is provided by assembly +routines generated by a special purpose compiler. +As of fftw-3.2, --enable-k7 is no longer supported. + +<p> +<code>--enable-3dnow</code> enables generic 3DNow! support using <code>gcc</code> builtin functions. This works on earlier AMD +processors, but it is not as fast as our special assembly routines. +As of fftw-3.1, --enable-3dnow is no longer supported. + +<h2><A name="fma"> +Question 2.6. What's the difference between the fma and the non-fma +versions? +</A></h2> + +The fma version tries to exploit the fused multiply-add instructions +implemented in many processors such as PowerPC, ia-64, and MIPS. The +two FFTW packages are otherwise identical. In FFTW 3.1, the fma and +non-fma versions were merged together into a single package, and the +<code>configure</code> script attempts to automatically guess which +version to use. +<p> +The FFTW 3.1 <code>configure</code> script enables fma by default on PowerPC, Itanium, and PA-RISC, and disables it otherwise. You can +force one or the other by using the <code>--enable-fma</code> or <code>--disable-fma</code> flag for <code>configure</code>. +<p> +Definitely use fma if you have a PowerPC-based system with +<code>gcc</code> (or IBM <code>xlc</code>). This includes all GNU/Linux systems for PowerPC and the older PowerPC-based MacOS systems. Also +use it on PA-RISC and Itanium with the HP/UX compiler. + +<p> +Definitely do not use the fma version if you have an ia-32 processor +(Intel, AMD, MacOS on Intel, etcetera). + +<p> +For other architectures/compilers, the situation is not so clear. For +example, ia-64 has the fma instruction, but +<code>gcc-3.2</code> appears not to exploit it correctly. Other compilers may do the right thing, +but we have not tried them. Please send us your feedback so that we +can update this FAQ entry. +<h2><A name="languages"> +Question 2.7. Which language is FFTW written +in? +</A></h2> + +FFTW is written in ANSI C. Most of the code, however, was +automatically generated by a program called +<code>genfft</code>, written in the Objective Caml dialect of ML. You do not need to know ML or to +have an Objective Caml compiler in order to use FFTW. + +<p> +<code>genfft</code> is provided with the FFTW sources, which means that +you can play with the code generator if you want. In this case, you +need a working Objective Caml system. Objective Caml is available +from <A href="http://caml.inria.fr">the Caml web page</A>. +<h2><A name="fortran"> +Question 2.8. Can I call FFTW from Fortran? +</A></h2> + +Yes, FFTW (versions 1.3 and higher) contains a Fortran-callable +interface, documented in the FFTW manual. + +<p> +By default, FFTW configures its Fortran interface to work with the +first compiler it finds, e.g. <code>g77</code>. To configure for a different, incompatible Fortran compiler +<code>foobar</code>, use <code>./configure F77=foobar</code> when installing FFTW. (In the case of <code>g77</code>, however, FFTW 3.x also includes an extra set of +Fortran-callable routines with one less underscore at the end of +identifiers, which should cover most other Fortran compilers on Linux +at least.) +<h2><A name="cplusplus"> +Question 2.9. Can I call FFTW from C++? +</A></h2> + +Most definitely. FFTW should compile and/or link under any C++ +compiler. Moreover, it is likely that the C++ +<code><complex></code> template class is bit-compatible with FFTW's complex-number format +(see the FFTW manual for more details). + +<h2><A name="whynotfortran"> +Question 2.10. Why isn't FFTW written in +Fortran/C++? +</A></h2> + +Because we don't like those languages, and neither approaches the +portability of C. +<h2><A name="singleprec"> +Question 2.11. How do I compile FFTW to run in single +precision? +</A></h2> + +On a Unix system: <code>configure --enable-float</code>. On a non-Unix system: edit <code>config.h</code> to <code>#define</code> the symbol <code>FFTW_SINGLE</code> (for FFTW 3.x). In both cases, you must then +recompile FFTW. In FFTW 3, all FFTW identifiers will then begin with +<code>fftwf_</code> instead of <code>fftw_</code>. +<h2><A name="64bitk7"> +Question 2.12. --enable-k7 does not work on +x86-64 +</A></h2> + +Support for --enable-k7 was discontinued in fftw-3.2. + +<p> +The fftw-3.1 release supports --enable-k7. This option only works on +32-bit x86 machines that implement 3DNow!, including the AMD Athlon +and the AMD Opteron in 32-bit mode. --enable-k7 does not work on AMD +Opteron in 64-bit mode. Use --enable-sse for x86-64 machines. + +<p> +FFTW supports 3DNow! by means of assembly code generated by a +special-purpose compiler. It is hard to produce assembly code that +works in both 32-bit and 64-bit mode. <hr> +Next: <a href="section3.html" rel=precedes>Using FFTW</a>.<br> +Back: <a href="section1.html" rev=precedes>Introduction and General Information</a>.<br> +<a href="index.html" rev=subdocument>Return to contents</a>.<p> +<address> +<A href="http://www.fftw.org">Matteo Frigo and Steven G. Johnson</A> / <A href="mailto:fftw@fftw.org">fftw@fftw.org</A> +- 30 July 2016 +</address><br> +Extracted from FFTW Frequently Asked Questions with Answers, +Copyright © 2016 Matteo Frigo and Massachusetts Institute of Technology. +</body></html>