I inferred that from the size of the text file required to store 100 trillion values like "0.335" (600 TB, assuming single-byte characters and single character separation), and the fact that he had earlier asked a question about sparse matrices. John ________________________________ From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Jonathan Franklin Sent: Tuesday, January 27, 2009 11:35 AM To: boost-users@lists.boost.org Subject: Re: [Boost-users] Maximum Size of Matrix in Boost On Tue, Jan 27, 2009 at 10:29 AM, John Wilkinson <jwilkinson@tsystem.com> wrote: So it seems likely that the matrix is sparse. I didn't get the impression from the OP that the matrix was sparse. All he said was that each element held a "double value like 0.333." Jon