Barry Smith <[email protected]> writes: > If we put all the options passed in into a hash table then won’t a > PetscOptions look up be pretty cheap, compute the hash, look in the > table, check that the strings match with a strncmp, done (usually) > and at worst do 2 or 3 string compares?
Yes, I have always thought that we should use a hash for the options table... > If we adopt the view that an options check is very cheap that we > don’t need to worry much about options being rechecked right? ... however, I don't think it changes the picture that we should move options testing out of the fast path for algorithms. The hash just pushes the pain point down somewhat, most importantly, in a way that is scalable in the total number of options in the options table. But with a big options table, it's still a lot of string hashing and a lot of likely cache misses probing into the options hash. I would like to make PETSc competitive for integrating 20-species chemical systems, and I don't see room for string operations in that world.
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