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<HTML><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><!-- Created on November, 4 2004 by texi2html 1.64 --><!-- Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author) Karl Berry <karl@freefriends.org> Olaf Bachmann <obachman@mathematik.uni-kl.de> and many others.Maintained by: Olaf Bachmann <obachman@mathematik.uni-kl.de>Send bugs and suggestions to <texi2html@mathematik.uni-kl.de> --><HEAD><TITLE>Blitz++: FAQ</TITLE><META NAME="description" CONTENT="Blitz++: FAQ"><META NAME="keywords" CONTENT="Blitz++: FAQ"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META NAME="Generator" CONTENT="texi2html 1.64"></HEAD><BODY LANG="" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#800080" ALINK="#FF0000"><A NAME="SEC155"></A><TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0><TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_10.html#SEC154"> < </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC156"> > </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_2.html#SEC28"> << </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz.html#SEC_Top"> Up </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[ >> ]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz.html#SEC_Top">Top</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_toc.html#SEC_Contents">Contents</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_abt.html#SEC_About"> ? </A>]</TD></TR></TABLE><H1> 11. Frequently Asked Questions </H1><!--docid::SEC155::--><P><HR SIZE="6"><A NAME="SEC156"></A><TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0><TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC155"> < </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC157"> > </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC155"> << </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC155"> Up </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[ >> ]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz.html#SEC_Top">Top</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_toc.html#SEC_Contents">Contents</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_abt.html#SEC_About"> ? </A>]</TD></TR></TABLE><H2> 11.1 Questions about installation </H2><!--docid::SEC156::--><P><A NAME="IDX413"></A><A NAME="IDX414"></A></P><P><STRONG>* {I downloaded Blitz++, but when I try to gunzip it, I get</STRONG>"invalid compressed data--crc error"}</P><P>You forgot to set binary download mode in ftp. Do so withthe "binary" command.</P><P><A NAME="IDX415"></A></P><P><STRONG>* {The compiler complains that there is no Array class, even though I've</STRONG>included <CODE><blitz.h></CODE>.}</P><P>You need to have the line:</P><P><TABLE><tr><td> </td><td class=example><pre>using namespace blitz;</pre></td></tr></table></P><P>after including <CODE><blitz.h></CODE>.</P><P><A NAME="IDX416"></A><A NAME="IDX417"></A><A NAME="IDX418"></A><A NAME="IDX419"></A></P><P><STRONG>* I can't use gcc on my elderly PC because it requires 45--150Mbto compile with Blitz++</STRONG></P><P>Unfortunately this is true. If this problem is ever fixed, itwill be by the gcc developers, so my best suggestion is to posta bug report to the gcc-bugs list. </P><P><A NAME="IDX420"></A></P><P><STRONG>* {I am using gcc under Solaris, and I get errors about</STRONG>"relocation against external symbol"}</P><P>This problem can be fixed by installing the gnu linker andbinutils. Peter Nordlund found that by using <CODE>gnu-binutils-2.9.1</CODE>,this problem disappeared. You can read a detailed discussion at<A HREF="http://oonumerics.org/blitz/support/blitz-support/archive/0029.html">http://oonumerics.org/blitz/support/blitz-support/archive/0029.html</A>.</P><P><A NAME="IDX421"></A></P><P><STRONG>* {I am using gcc under Solaris, and the assembler gives</STRONG>me an error that a symbol is too long.}</P><P>This problem can also be fixed by installing the gnu linker andbinutils. See the above question.</P><P><A NAME="IDX422"></A></P><P><STRONG>* DECcxx reports problems about "templates with C linkage"</STRONG></P><P>This problem was caused by a problem in some versions of DECcxx's<TT>`math.h'</TT> header: XOPEN_SOURCE_EXTENDED was causing an<CODE>extern "C" { ... }</CODE> section to have no closing brace.There is a kludge which is included in recent versions ofBlitz++.</P><P><A NAME="IDX423"></A></P><P><STRONG>* {On some platforms (especially SGI) the testsuite program</STRONG><CODE>minsumpow</CODE> fails with the error: <CODE>Template instantiation resultedin an unexpected function type of...</CODE>}</P><P>This is a known bug in the older versions of the EDG front end,which many C++ compilers use. There is no known fix.Most of Blitz++ will work, but you won't be able to usesome array reductions.</P><P><HR SIZE="6"><A NAME="SEC157"></A><TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0><TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC156"> < </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_12.html#SEC158"> > </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC155"> << </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC155"> Up </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[ >> ]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz.html#SEC_Top">Top</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_toc.html#SEC_Contents">Contents</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_abt.html#SEC_About"> ? </A>]</TD></TR></TABLE><H2> 11.2 Questions about Blitz++ functionality </H2><!--docid::SEC157::--><P><A NAME="IDX424"></A><A NAME="IDX425"></A><A NAME="IDX426"></A><A NAME="IDX427"></A></P><P><STRONG>* For my problem, I need SVD, FFTs, QMRES, PLU, QR, ....</STRONG></P><P>Blitz++ does not currently provide any of these. However, there arenumerous C++ and C packages out there which do, and it is easy to move databack and forth between Blitz++ and other libraries. See these terms in theindex: creating an array from pre-existing data, <CODE>data()</CODE>,<CODE>stride()</CODE>, <CODE>extent()</CODE>, <CODE>fortranArray</CODE>. For a list of othernumerical C++ libraries, see the Object Oriented Numerics Page at<A HREF="http://oonumerics.org/oon/">http://oonumerics.org/oon/</A>.</P><P><A NAME="IDX428"></A></P><P><STRONG>* Can Blitz++ be interfaced with Python?</STRONG></P><P>Phil Austin has done so successfully. See a description of his setup in <A HREF="http://oonumerics.org/blitz/support/blitz-support/archive/0053.html">http://oonumerics.org/blitz/support/blitz-support/archive/0053.html</A>.</P><P><A NAME="IDX429"></A>Also see Harry Zuzan's Python/Blitz image processing example codeat <A HREF="http://www.stat.duke.edu/~hz/blitz_py/index.html">http://www.stat.duke.edu/~hz/blitz_py/index.html</A>.</P><P><A NAME="IDX430"></A><A NAME="IDX431"></A><A NAME="IDX432"></A><A NAME="IDX433"></A><A NAME="IDX434"></A></P><P><STRONG>* {If I try to allocate an array which is too big, my program just crashes</STRONG>or goes into an infinite loop. Is there some way I can handle this moreelegantly?}</P><P>Blitz++ uses <CODE>new</CODE> to allocate memory for arrays. In theory, yourcompiler should be throwing a <CODE>bad_alloc</CODE> exception when you run out ofmemory. If it does, you can use a <CODE>try/catch</CODE> block to handle the out ofmemory exception. If your compiler does not throw <CODE>bad_alloc</CODE>, you caninstall your own new handler to handle out of memory.</P><P>Here is an excerpt from the ISO/ANSI C++ standard which describes thebehaviour of <CODE>new</CODE>:</P><P><UL><LI>Executes a loop: Within the loop, the function first attempts toallocate the requested storage. Whether the attempt involves a call to theStandard C library function malloc is unspecified. <P><LI>Returns a pointer to the allocated storage if the attempt issuccessful. Otherwise, if the last argument to <CODE>set_new_handler()</CODE> wasa null pointer, throw <CODE>bad_alloc</CODE>. <P><LI>Otherwise, the function calls the current <CODE>new_handler</CODE>(lib.new.handler). If the called function returns, the loop repeats. <P><LI>The loop terminates when an attempt to allocate the requested storageis successful or when a called new_handler function does not return. <P></UL><P>You can use <CODE>set_new_handler</CODE> to create a new handler whichwill issue an error message or throw an exception. Forexample:</P><P><TABLE><tr><td> </td><td class=example><pre>void my_new_handler(){cerr << "Out of memory" << endl;cerr.flush();abort();}...// First line in main():set_new_handler(my_new_handler);</pre></td></tr></table></P><P><A NAME="IDX435"></A><A NAME="IDX436"></A></P><P><STRONG>* {When I pass arrays by value, the function which receives</STRONG>them can modify the array data. Why?}</P><P>It's a result of reference-counting. You have to think of array objects asbeing "handles" to underlying arrays. The function doesn't receive a copy ofthe array data, but rather a copy of the handle. The alternative would beto copy the array data when passing by value, which would be grosslyinefficient.</P><P><A NAME="IDX437"></A><A NAME="IDX438"></A><A NAME="IDX439"></A><A NAME="IDX440"></A><A NAME="IDX441"></A></P><P><STRONG>* Why can't I use e.g. <CODE>A >> 3</CODE> to do bitshifting on arrays?</STRONG></P><P>The operators <CODE><<</CODE> and <CODE>>></CODE> are used for input/ouput of arrays.It would cause problems with the expression templates implementation to alsouse them for bitshifting. However, it is easy enough to define your ownbitshifting function -- see <A HREF="blitz_3.html#SEC92">3.10 Declaring your own math functions on arrays</A>.</P><P><A NAME="IDX442"></A></P><P><STRONG>* When I write <CODE>TinyMatrix * TinyVector</CODE> I get an error.</STRONG></P><P>Try <CODE>product(d2,d1)</CODE>. This works for matrix-matrix and matrix-vectorproducts.</P><P><A NAME="Keyword Index"></A><HR SIZE="6"><TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0><TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_11.html#SEC155"> << </A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[ >> ]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT"> <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz.html#SEC_Top">Top</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_toc.html#SEC_Contents">Contents</A>]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="blitz_abt.html#SEC_About"> ? </A>]</TD></TR></TABLE><BR> <FONT SIZE="-1">This document was generatedby <I>Julian Cummings</I> on <I>November, 4 2004</I>using <A HREF="http://www.mathematik.uni-kl.de/~obachman/Texi2html"><I>texi2html</I></A></BODY></HTML>⌨️ 快捷键说明
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