Public bug reported:
Binary package hint: libatlas3gf-sse2
Complex matrix multiplication via zgemm gives a wrong result when using
/usr/lib/sse2/atlas/liblapack.so.3gf. When the same binary uses
/usr/lib/liblapack.so.3gf the result is ok.
sample code:
- atlas-test.cpp ---
/* compile:
g++ -Wall -o atlas-test atlas-test.cpp -lblitz -llapack
run:
LD_LIBRARY_PATH=/usr/lib LD_PRELOAD=/usr/lib/liblapack.so.3gf \
or
LD_LIBRARY_PATH=/usr/lib/sse2/atlas \
LD_PRELOAD=/usr/lib/sse2/atlas/liblapack.so.3gf \
with
./atlas-test
*/
#include
#include
typedef std::complex Complex;
typedef blitz::Array cMatrix;
#define F77NAME(x) x ## _
/* SUBROUTINE ZGEMM ( TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB,
BETA, C, LDC ) */
extern "C" void F77NAME(zgemm)
(const char*,const char*,const int&,const int&,const int&,const Complex&,
const Complex*,const int&,const Complex*,const int&,const Complex&,
const Complex*,const int&);
int main() {
blitz::firstIndex ii;
blitz::secondIndex jj;
const int M = 139, N = 128;
cMatrix prod( M, N );
prod = 0.1* ii + 0.4* jj;
cMatrix C( M, M );
char A_op = 'T', B_op = 'N';
int M1 = M, N1 = N;
F77NAME(zgemm)( &A_op, &B_op, M1, M1, N1, 1.0, prod.data(), N,
prod.data(), N, 0.0, C.data(), M );
std::cout << C( 0, 0 ) << " correct result = " <<
0.4*0.4*N1*(N1-1)*(2*N1-1)/6 << std::endl;
return 0;
}
- end of atlas-test.cpp -
For M1 = 72 the program gives a correct result, for M1 > 72 not. Tested
for other flavor of libatlas3gf (-base, -sse), similar behavior, but
different results.
Ubuntu 8.04.2, package versions:
libatlas3gf-sse2_3.6.0-21.1ubuntu3_i386.deb Source: atlas
libblitz0ldbl_0.9-7_i386.deb Source: blitz++
g++-4.2_4.2.4-1ubuntu3_i386.deb Source: gcc-4.2
HP 6510b, cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Core(TM)2 Duo CPU T9300 @ 2.50GHz
stepping: 6
cpu MHz : 800.000
cache size : 6144 KB
physical id : 0
siblings: 2
core id : 0
cpu cores : 2
fdiv_bug: no
hlt_bug : no
f00f_bug: no
coma_bug: no
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc
arch_perfmon pebs bts pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr sse4_1
lahf_lm ida
bogomips: 4992.42
clflush size: 64
processor : 1 - the same as processor 0
** Affects: atlas (Ubuntu)
Importance: Undecided
Status: New
--
matrix multiplication with libatlas gives wrong result for big matrices
https://bugs.launchpad.net/bugs/376739
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