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
-- no debconf information
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