mirror of
https://github.com/tildearrow/furnace.git
synced 2024-11-06 12:55:05 +00:00
285 lines
14 KiB
HTML
285 lines
14 KiB
HTML
<!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>
|
|
- 14 September 2021
|
|
</address><br>
|
|
Extracted from FFTW Frequently Asked Questions with Answers,
|
|
Copyright © 2021 Matteo Frigo and Massachusetts Institute of Technology.
|
|
</body></html>
|