incorrect maxModulus for Modular<double> in fflas-ffpack

[jack]

Hello,


is it possible for Modular<double> representation of Z/mZ the max
possible modulus is 2^25 and not 2^26
as returned by getMaxModulus() ?

I get wrong results for FFLAS::fgemm ( b*C + a * op(A)*op(B) )
( Matrix sizes about 300, a>=2 and b >=1 , char = 67108859.

The error is reproducible by generating dense matrices A, B and C with
'tests/dense_generator',
replacing ModularBalanced<double > in 'test-fgemm.C' with
Modular<double >, inlining
#define DEBUG 1
in 'test-fgemm.C' and running e.g.

./test-fgemm 67108859 A B 1 2 2 2 C 0 0


Best,


Jakob