==19487== Memcheck, a memory error detector.
==19487== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.
==19487== Using LibVEX rev 1658, a library for dynamic binary translation.
==19487== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.
==19487== Using valgrind-3.2.1, a dynamic binary instrumentation framework.
==19487== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.
==19487== For more details, rerun with: -v
==19487== 

M =
[4,3]((1.1,0,0),(0,2.2,0),(0,0,0),(0,0,0))
==19487== Syscall param write(buf) points to uninitialised byte(s)
==19487==    at 0xC25933: __write_nocancel (in /lib/libc-2.5.so)
==19487==    by 0x2C8688: std::basic_filebuf<char, std::char_traits<char> >::_M_convert_to_external(char*, int) (in /usr/lib/libstdc++.so.6.0.8)
==19487==    by 0x2C9952: std::basic_filebuf<char, std::char_traits<char> >::overflow(int) (in /usr/lib/libstdc++.so.6.0.8)
==19487==    by 0x2C8176: std::basic_filebuf<char, std::char_traits<char> >::sync() (in /usr/lib/libstdc++.so.6.0.8)
==19487==    by 0x805C67B: boost::archive::basic_binary_oprimitive<boost::archive::binary_oarchive, char, std::char_traits<char> >::~basic_binary_oprimitive() (in /home/destefano/matlab/calcsw/C++/boost_tools/boost_extras/serialization/numeric/ublas/debug/compressed_mtx/compressed_mtx_ser)
==19487==    by 0x80554B6: boost::archive::binary_oarchive_impl<boost::archive::binary_oarchive, char, std::char_traits<char> >::~binary_oarchive_impl() (binary_oarchive_impl.hpp:31)
==19487==    by 0x8055554: boost::archive::binary_oarchive::~binary_oarchive() (binary_oarchive.hpp:33)
==19487==    by 0x804A8A2: main (compressed_mtx_ser.cpp:42)
==19487==  Address 0x402D773 is 75 bytes inside a block of size 8,192 alloc'd
==19487==    at 0x40057F5: operator new[](unsigned) (vg_replace_malloc.c:195)
==19487==    by 0x2C7DAB: std::basic_filebuf<char, std::char_traits<char> >::_M_allocate_internal_buffer() (in /usr/lib/libstdc++.so.6.0.8)
==19487==    by 0x2CBD41: std::basic_filebuf<char, std::char_traits<char> >::open(char const*, std::_Ios_Openmode) (in /usr/lib/libstdc++.so.6.0.8)
==19487==    by 0x2CCBB7: std::basic_ofstream<char, std::char_traits<char> >::basic_ofstream(char const*, std::_Ios_Openmode) (in /usr/lib/libstdc++.so.6.0.8)
==19487==    by 0x804A865: main (compressed_mtx_ser.cpp:38)

re-read matrix:
[4,3]((1.1,0,0),(0,2.2,0),(0,0,0),(0,0,0))

Done.

==19487== 
==19487== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 15 from 1)
==19487== malloc/free: in use at exit: 0 bytes in 0 blocks.
==19487== malloc/free: 49 allocs, 49 frees, 19,632 bytes allocated.
==19487== For counts of detected errors, rerun with: -v
==19487== All heap blocks were freed -- no leaks are possible.