Sanity check using absolute error. suggest using relative error

[philippdahm]

Hey all,
seems that the sanity check is using absolute error (difference in results) in checking definition of the vectorspace. When using a large-valued vector, this error is sometimes not achievable due to machine precision.

In my example, the inner products are of the order of 1e8 with a 1e-9 absolute error. This causes the check to fail with the default tolerance of 1e-12.

To me, it makes sense to turn this into a check on relative error (ratio of results) rather than absolute (difference of results) as to avoid machine precision issues.

modred/modred/vectorspace.py

Line 156 in bbe35c8

tol = 1e-12

modred/modred/vectorspace.py

Lines 202 to 207 in bbe35c8

	# Check that the inner product of a vector is correct after scalar
	# multiplication and vector addition.
	vec_add_mult = test_vec * scale_factor + test_vec
	if abs(
	self.inner_product(vec_add_mult, vec_add_mult) -
	vec_copy_mag_sq * (scale_factor + 1) ** 2) > tol: