Add sliding-window decoding slide

src/final_presentation/gen_sliding_window_overlap_image.py

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+import warnings
+from typing import Sequence
+
+import numpy as np
+import matplotlib.pyplot as plt
+import matplotlib.patches as pt
+from scipy.sparse import csc_matrix
+
+from quits.decoder import spacetime
+from quits.decoder import detector_error_model_to_matrix
+
+from quits.qldpc_code import BbCode
+from quits import ErrorModel, CircuitBuildOptions
+
+
+def build_bb_circuit(N: int, num_rounds: int, p: float):
+    # fmt: off
+    if N == 72:
+        code = BbCode(l=6, m=6, A_x_pows=[3], A_y_pows=[1, 2], B_x_pows=[1, 2], B_y_pows=[3])
+    elif N == 90:
+        code = BbCode(l=15, m=3, A_x_pows=[9], A_y_pows=[1, 2], B_x_pows=[2, 7], B_y_pows=[0])
+    elif N == 108:
+        code = BbCode(l=9, m=6, A_x_pows=[3], A_y_pows=[1, 2], B_x_pows=[1, 2], B_y_pows=[3])
+    elif N == 144:
+        code = BbCode(l=12, m=6, A_x_pows=[3], A_y_pows=[1, 2], B_x_pows=[1, 2], B_y_pows=[3])
+    elif N == 288:
+        code = BbCode(l=12, m=12, A_x_pows=[3], A_y_pows=[2, 7], B_x_pows=[1, 2], B_y_pows=[3])
+    elif N == 360:
+        code = BbCode(l=30, m=6, A_x_pows=[9], A_y_pows=[1, 2], B_x_pows=[25, 26], B_y_pows=[3])
+    elif N == 756:
+        code = BbCode(l=21, m=18, A_x_pows=[3], A_y_pows=[10, 17], B_x_pows=[3, 19], B_y_pows=[5])
+    else:
+        assert False, "Unsupported code size"
+    # fmt: on
+
+    circuit = code.build_circuit(
+        error_model=ErrorModel(p, p, p, p),
+        num_rounds=num_rounds,
+        basis="Z",
+        circuit_build_options=CircuitBuildOptions(),
+        seed=1,
+    )
+
+    return code, circuit
+
+
+
+
+def compute_num_windows(num_rounds: int, W: int, F: int):
+    """
+    This was extracted from the function `sliding_window_circuit_mem()` of
+    `quits.decoder`.
+    """
+    if 2 + num_rounds - W >= 0:
+        # num_cor_rounds = num of windows before the last window
+        num_cor_rounds = (2 + num_rounds - W) // F
+
+        # we can slide one more window if the remaining rounds > W
+        if (2 + num_rounds - W) % F != 0:
+            num_cor_rounds += 1
+    else:
+        num_cor_rounds = 0
+        warnings.warn(
+            "Window size larger than the syndrome extraction rounds: Doing"
+            " whole history correction"
+        )
+
+    return num_cor_rounds + 1
+
+
+def get_overlap_info(
+    col_start_indices: Sequence, W: int, F: int, m: int, win_check_set: Sequence
+):
+    def i_B(k: int):
+        return col_start_indices[k]
+
+    def i_E(k: int):
+        return i_B(k) + win_check_set[k].shape[1]
+
+    def j_B(k: int):
+        return F * (k) * m
+
+    def j_E(k: int):
+        return (F * k + W) * m
+
+    num_windows = len(win_check_set)
+
+    overlap_begin_positions = []
+    for k in range(num_windows - 1):
+        overlap_begin_positions.append((j_B(k + 1) - j_B(k), i_B(k + 1) - i_B(k)))
+
+    overlap_end_positions = []
+    for k in range(1, num_windows):
+        overlap_end_positions.append((j_E(k - 1) - j_B(k), i_E(k - 1) - i_B(k)))
+
+    return overlap_begin_positions, overlap_end_positions
+
+
+def reconstruct_window_start_col_indices(win_observable_set: Sequence):
+    """
+    This function effectively just reconstructs the `col_min` values of each
+    window, from the `spacetime()` function of `quits.decoder`.
+    """
+    num_windows = len(win_observable_set)
+
+    col_mins = [0]
+
+    for k in range(num_windows - 1):
+        col_mins.append(col_mins[-1] + win_observable_set[k].shape[1])
+
+    return col_mins
+
+
+
+
+num_rounds = 12
+N = 72
+p = 0.005
+W = 5
+F = 3
+
+#
+# Get detector error matrix and split it into windows
+#
+
+code, circuit = build_bb_circuit(N, num_rounds, p)
+model = circuit.detector_error_model(decompose_errors=False)
+check_matrix, observable_matrix, priors = detector_error_model_to_matrix(model)
+
+num_windows = compute_num_windows(num_rounds, W, F)
+win_check_set, win_observable_set, win_priors_set, win_update = spacetime(
+    circuit, code.hz, W, F, num_windows - 1
+)
+
+col_start_indices = reconstruct_window_start_col_indices(win_observable_set)
+
+#
+# Paint rectangles
+#
+
+custom_colors = [
+    (162/255, 34/255, 35/255),
+    (223/255, 155/255, 27/255),
+    (70/255, 100/255, 170/255),
+    (163/255, 16/255, 124/255),
+]
+
+fig, ax = plt.subplots(1, 1, figsize=(10, 10))
+ax.spy(check_matrix.toarray())
+
+colors = [custom_colors[i % len(custom_colors)] for i in range(num_windows)]
+
+m = code.hz.shape[0]
+# for win_idx in range(num_windows):
+#     col_start_idx = col_start_indices[win_idx]
+#     row_start_idx = win_idx * F * m
+#
+#     ax.add_patch(
+#         pt.Rectangle(
+#             (col_start_idx, row_start_idx),
+#             win_check_set[win_idx].shape[1],
+#             win_check_set[win_idx].shape[0],
+#             fc="none",
+#             ec=colors[win_idx],
+#         )
+#     )
+
+# overlap_begin_positions, overlap_end_positions = get_overlap_info(
+#     col_start_indices, W, F, m, win_check_set
+# )
+
+# for k in range(len(win_check_set) - 1):
+#     ax.add_patch(
+#         pt.Rectangle(
+#             (
+#                 overlap_begin_positions[k][1] + col_start_indices[k],
+#                 overlap_begin_positions[k][0] + F * k * m,
+#             ),
+#             win_check_set[k].shape[1] - overlap_begin_positions[k][1],
+#             win_check_set[k].shape[0] - overlap_begin_positions[k][0],
+#             fc=colors[k],
+#             ec=colors[k],
+#             alpha=0.3,
+#         )
+#     )
+
+
+ax.set_xticks([])
+ax.set_yticks([])
+
+fig.savefig('72_bb_dem_no_windows.pdf', bbox_inches='tight')
+
+plt.show()
+
+