@section Questions about installation@cindex FAQ@cindex CRC error in .tar.gz@cindex invalid compressed data@faq{I downloaded Blitz++, but when I try to gunzip it, I get``invalid compressed data--crc error''}You forgot to set binary download mode in ftp.  Do so withthe ``binary'' command.@cindex `Array' undeclared@faq{The compiler complains that there is no Array class, even though I'veincluded @code{<blitz.h>}.}You need to have the line:@exampleusing namespace blitz;@end exampleafter including @code{<blitz.h>}.@cindex gcc memory hog@cindex memory hog, gcc@cindex out of virtual memory, gcc@cindex virtual memory problems, gcc@faq{I can't use gcc on my elderly PC because it requires @w{45--150@dmn{Mb}}to compile with Blitz++}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.  @cindex external symbol relocation, Solaris@faq{I am using gcc under Solaris, and I get errors about ``relocation against external symbol''}This problem can be fixed by installing the gnu linker andbinutils.  Peter Nordlund found that by using  @code{gnu-binutils-2.9.1},this problem disappeared.  You can read a detailed discussion at@uref{http://oonumerics.org/blitz/support/blitz-support/archive/0029.html}.@cindex symbol too long, Solaris as@faq{I am using gcc under Solaris, and the assembler givesme an error that a symbol is too long.}This problem can also be fixed by installing the gnu linker andbinutils.  See the above question.@cindex templates with C linkage, DECcxx@faq{DECcxx reports problems about ``templates with C linkage''}This problem was caused by a problem in some versions of DECcxx's@file{math.h} header: XOPEN_SOURCE_EXTENDED was causing an@code{extern "C" @{ ... @}} section to have no closing brace.There is a kludge which is included in recent versions ofBlitz++.@cindex template instantiation resulted in an unexpected...@faq{On some platforms (especially SGI) the testsuite program@code{minsumpow} fails with the error: @code{Template instantiation resultedin an unexpected function type of...}}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.@section Questions about Blitz++ functionality@cindex eigenvector decomposition@cindex solving linear systems@cindex matrix inversion@cindex linear algebra@faq{For my problem, I need SVD, FFTs, QMRES, PLU, QR, ....}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{stride()}, @code{extent()}, @code{fortranArray}.  For a list of othernumerical C++ libraries, see the Object Oriented Numerics Page at@uref{http://oonumerics.org/oon/}.@cindex Python@faq{Can Blitz++ be interfaced with Python?}Phil Austin has done so successfully.  See a description of his setup in @uref{http://oonumerics.org/blitz/support/blitz-support/archive/0053.html}.@cindex image processingAlso see Harry Zuzan's Python/Blitz image processing example codeat @uref{http://www.stat.duke.edu/~hz/blitz_py/index.html}.@cindex out of memory@cindex handling out of memory@cindex new handler@findex set_new_handler()@findex bad_alloc@faq{If I try to allocate an array which is too big, my program just crashesor goes into an infinite loop.  Is there some way I can handle this moreelegantly?}Blitz++ uses @code{new} to allocate memory for arrays.  In theory, yourcompiler should be throwing a @code{bad_alloc} exception when you run out ofmemory.  If it does, you can use a @code{try/catch} block to handle the out ofmemory exception.  If your compiler does not throw @code{bad_alloc}, you caninstall your own new handler to handle out of memory.Here is an excerpt from the ISO/ANSI C++ standard which describes thebehaviour of @code{new}:@itemize @bullet@item  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. @item  Returns a pointer to the allocated storage if the attempt issuccessful. Otherwise, if the last argument to @code{set_new_handler()} wasa null pointer, throw @code{bad_alloc}. @item  Otherwise, the function calls the current @code{new_handler}(lib.new.handler). If the called function returns, the loop repeats. @item  The loop terminates when an attempt to allocate the requested storageis successful or when a called new_handler function does not return. @end itemizeYou can use @code{set_new_handler} to create a new handler whichwill issue an error message or throw an exception.  Forexample:@example void my_new_handler()@{cerr << "Out of memory" << endl;cerr.flush();abort();@}...// First line in main():set_new_handler(my_new_handler);@end example @cindex passing arrays by value@cindex constness problems@faq{When I pass arrays by value, the function which receivesthem can modify the array data.  Why?}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.@cindex @code{<<} operator, bitshift@cindex operator @code{<<}, bitshift@cindex operator @code{>>}, bitshift@cindex @code{>>} operator, bitshift@cindex bitshift operators@faq{Why can't I use e.g.@: @code{A >> 3} to do bitshifting on arrays?}The operators @code{<<} and @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 @ref{User et}.@cindex matrix multiply@faq{When I write @code{TinyMatrix * TinyVector} I get an error.}Try @code{product(d2,d1)}.  This works for matrix-matrix and matrix-vectorproducts.