Add dummy segment to the left

[LindaGuiga]

This PR adds dummy segments to the left in generate_all_data_segments when necessary. Note that for this, we need to allow values that are not powers of two for max_cpu_len.

[Nashtare]

Not that for this, we need to allow values that are not powers of two for max_cpu_len.

Could you elaborate on this? As the max_cpu_len_log is purely a user argument, I don't get why it would need to be changed.

[LindaGuiga]

Not that for this, we need to allow values that are not powers of two for max_cpu_len.

Could you elaborate on this? As the max_cpu_len_log is purely a user argument, I don't get why it would need to be changed.

For dummy segments, we need to set the max number of CPU cycles to exactly the number of cycles in init, so that the dummy segments can be aggregated with the next segments without regenerating their GenerationSegmentData.

[Nashtare]

My point was that dummy segment generation is handled by the system, not the user, who only cares about actual segments lengths. So this notion should be handled arbitrarily of what the user sets as max cpu length (which should be a power of two).

[Nashtare]

overall 90% of the PR changes are just max_cpu_len_log -> max_cpu_len and corresponding changes, which I believe should not even happen in the first place out of safety. We should probably just handle the dummy segment specifically so that we can maintain the existing logic.

[LindaGuiga]

overall 90% of the PR changes are just max_cpu_len_log -> max_cpu_len and corresponding changes, which I believe should not even happen in the first place out of safety. We should probably just handle the dummy segment specifically so that we can maintain the existing logic.

I reverted those changes and instead added an is_dummy field in GenerationSegmentData so that at_end_segment can differentiate between dummy and real segments.

[Nashtare]

LGTM!