Skip to content

Avoid state vector normalization if it worsens the round offs #6556

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Apr 10, 2024
Merged

Avoid state vector normalization if it worsens the round offs #6556

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
43cb287
Avoid state vector normalization if it worsens the round offs
pavoljuhas Apr 9, 2024
754f40e
Merge branch 'main' into avoid-extra-round-offs-from-normalization
pavoljuhas Apr 10, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 5 additions & 1 deletion cirq-core/cirq/sim/state_vector_simulator.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -134,7 +134,11 @@ def final_state_vector(self) -> np.ndarray:
"skipping renormalization"
)
return ret
return ret / norm
# normalize only if doing so improves the round-off on total probability
ret_norm = ret / norm
round_off_change = abs(np.vdot(ret_norm, ret_norm) - 1) - abs(np.vdot(ret, ret) - 1)
result = ret_norm if round_off_change < 0 else ret
return result

def state_vector(self, copy: bool = False) -> np.ndarray:
"""Return the state vector at the end of the computation.
Expand Down