Thanks Jesse for your answer to my previous question.
A lot of my work involves statistics of sparse vectors of positive
integers, so it seems ublas sparse vectors and matrices are going to be
very useful for me.
However, I find that sparse vectors of integers produce strange
floating point exceptions (they work great with floats and doubles).
When I use gdb to trace these exceptions I find unexplained calls to
sqrt(), even though my program doesn't involve sqrt() at all. I'd
appreciate any advice!
Here's a simple program that demonstrates the problem; I use feenableexcept() to trap
floating point exceptions.
#include
<boost/numeric/ublas/io.hpp>
#include <boost/numeric/ublas/vector.hpp>
#include
<boost/numeric/ublas/vector_expression.hpp>
#include
<boost/numeric/ublas/vector_proxy.hpp>
#include
<boost/numeric/ublas/vector_sparse.hpp>
#include <iostream>
// _GNU_SOURCE must be defined and fenv.h
included to
// trap floating-point exceptions (fpes).
//
#define _GNU_SOURCE 1
#include <fenv.h>
namespace ublas = boost::numeric::ublas;
int main(int argc, char** argv) {
// trap floating point exceptions
feenableexcept(FE_INVALID|FE_DIVBYZERO|FE_OVERFLOW);
ublas::mapped_vector<int> v =
ublas::unit_vector<int>(2, 1);
std::cout << "v = " << v <<
std::endl;
}
When I compile and run this program I get a floating point exception,
which is curious as there's no floating point math in the program at
all.
[mj@lugha tmp]$ g++ -g -O0 ublas-int.cc
-o ublas-int
[mj@lugha tmp]$ ./ublas-int
Floating point exception
Gdb shows that the exception is generated in a call to sqrt(-2147483648)
[mj@lugha tmp]$ gdb ublas-int
...(gdb) run
Starting program: /home/mj/tmp/ublas-int
Program received signal SIGFPE, Arithmetic exception.
0x0000000000405468 in std::sqrt<int> (__x=-2147483648) at
/usr/lib/gcc/x86_64-redhat-linux/4.4.0/../../../../include/c++/4.4.0/cmath:439
439 { return __builtin_sqrt(__x); }
Missing separate debuginfos, use: debuginfo-install
glibc-2.10.1-2.x86_64 libgcc-4.4.0-4.x86_64 libstdc++-4.4.0-4.x86_64
(gdb) bt
#0 0x0000000000405468 in std::sqrt<int> (__x=-2147483648) at
/usr/lib/gcc/x86_64-redhat-linux/4.4.0/../../../../include/c++/4.4.0/cmath:439
#1 0x0000000000401ac0 in (anonymous
namespace)::boost_numeric_ublas_sqrt<int> (t=@0x7fffffffdd98) at
/usr/include/boost/numeric/ublas/traits.hpp:32
#2 0x0000000000404759 in
boost::numeric::ublas::scalar_traits<int>::type_sqrt
(t=@0x7fffffffdd98) at /usr/include/boost/numeric/ublas/traits.hpp:107
#3 0x0000000000403fbe in
boost::numeric::ublas::detail::expression_type_check<boost::numeric::ublas::mapped_vector<int,
boost::numeric::ublas::map_std<unsigned long, int,
std::allocator<std::pair<unsigned long const, int> > >
>, boost::numeric::ublas::vector<int,
boost::numeric::ublas::unbounded_array<int,
std::allocator<int> > > > (e1=@0x7fffffffdee0,
e2=@0x7fffffffde00) at
/usr/include/boost/numeric/ublas/detail/vector_assign.hpp:42
#4 0x0000000000403466 in
boost::numeric::ublas::vector_assign<boost::numeric::ublas::scalar_assign,
boost::numeric::ublas::mapped_vector<int,
boost::numeric::ublas::map_std<unsigned long, int,
std::allocator<std::pair<unsigned long const, int> > >
>, boost::numeric::ublas::unit_vector<int,
std::allocator<int> > > (v=@0x7fffffffdee0,
e=@0x7fffffffdf20) at
/usr/include/boost/numeric/ublas/detail/vector_assign.hpp:369
#5 0x0000000000402e5c in
boost::numeric::ublas::vector_assign<boost::numeric::ublas::scalar_assign,
boost::numeric::ublas::mapped_vector<int,
boost::numeric::ublas::map_std<unsigned long, int,
std::allocator<std::pair<unsigned long const, int> > >
>, boost::numeric::ublas::unit_vector<int,
std::allocator<int> > > (v=@0x7fffffffdee0,
e=@0x7fffffffdf20) at
/usr/include/boost/numeric/ublas/detail/vector_assign.hpp:448
#6 0x0000000000402a19 in boost::numeric::ublas::mapped_vector<int,
boost::numeric::ublas::map_std<unsigned long, int,
std::allocator<std::pair<unsigned long const, int> > >
>::mapped_vector<boost::numeric::ublas::unit_vector<int,
std::allocator<int> > > (this=0x7fffffffdee0,
ae=@0x7fffffffdf20, non_zeros=0) at
/usr/include/boost/numeric/ublas/vector_sparse.hpp:312
#7 0x0000000000401a16 in main (argc=1, argv=0x7fffffffe028) at
ublas-int.cc:22
(gdb)
Any ideas as to what's happening? I must admit I don't
understand why the program is calling sqrt()!
Thanks in advance,
Mark