[Pkg-octave-devel] Bug#706376: octave: sparse matrix n*2^16

[Miroslaw Kwasniak]

Package: octave
Version: 3.6.2-5
Severity: normal

Dear Maintainer,

it's something wrong whith sparse matrices A(n,n) when n is a multiple
of 65536=2^16.

Demonstration code ======================================

for i=1:3;
  for n=i*2^16+(-1:1);
    A=spdiags(ones(n,1),0,n,n);
    t=trace(A);
    printf("n=%8d trace=%8d %s\n",n,t,["ERR";"ok"]((t==n)+1,:));
  endfor;
endfor

Results ======================================

n=   65535 trace=   65535 ok
n=   65536 trace=       0 ERR
n=   65537 trace=   65537 ok
n=  131071 trace=  131071 ok
n=  131072 trace=       0 ERR
n=  131073 trace=  131073 ok
n=  196607 trace=  196607 ok
n=  196608 trace=       0 ERR
n=  196609 trace=  196609 ok

======================================

It isn't a bug in spdiags, but in the sparse matrices handling, the
same results are given when A=spdiags(ones(n,1),0,n,n); in above code
is replaced with (slower):

    B=sparse(n,n);for j=1:n;B(j,j)=1;endfor

Miroslaw Kwasniak

-- System Information:
Debian Release: 7.0
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'testing-updates'), (500, 'testing-proposed-updates'), (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.2.0-4-amd64 (SMP w/2 CPU cores)
Locale: LANG=pl_PL.UTF-8, LC_CTYPE=pl_PL.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages octave depends on:
ii  libamd2.2.0                      1:3.4.0-3
ii  libarpack2                       3.1.1-2.1
ii  libatlas3-base [liblapack.so.3]  3.8.4-9
ii  libblas3 [libblas.so.3]          1.2.20110419-5
ii  libc6                            2.13-38
ii  libcamd2.2.0                     1:3.4.0-3
ii  libccolamd2.7.1                  1:3.4.0-3
ii  libcholmod1.7.1                  1:3.4.0-3
ii  libcolamd2.7.1                   1:3.4.0-3
ii  libcurl3-gnutls                  7.26.0-1+wheezy2
ii  libcxsparse2.2.3                 1:3.4.0-3
ii  libfftw3-3                       3.3.2-3.1
ii  libfltk1.1                       1.1.10-14
ii  libfreetype6                     2.4.9-1.1
ii  libgcc1                          1:4.7.2-5
ii  libgl1-mesa-glx [libgl1]         8.0.5-4
ii  libglpk0                         4.45-1
ii  libgomp1                         4.7.2-5
ii  libgraphicsmagick++3             1.3.16-1.1
ii  libgraphicsmagick3               1.3.16-1.1
ii  liblapack3 [liblapack.so.3]      3.4.1+dfsg-1
ii  liboctave1                       3.6.2-5
ii  libpcre3                         1:8.30-5
ii  libqhull5                        2009.1-3
ii  libqrupdate1                     1.1.1-1
ii  libstdc++6                       4.7.2-5
ii  libumfpack5.4.0                  1:3.4.0-3
ii  octave-common                    3.6.2-5
ii  texinfo                          4.13a.dfsg.1-10
ii  zlib1g                           1:1.2.7.dfsg-13

Versions of packages octave recommends:
ii  gnuplot-x11     4.6.0-8
ii  libatlas3-base  3.8.4-9

Versions of packages octave suggests:
pn  octave-doc      <none>
pn  octave-htmldoc  <none>
ii  octave-info     3.6.2-5

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