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linedance-app/venv/lib/python3.12/site-packages/sklearn/_isotonic.pyx

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+# Authors: The scikit-learn developers
+# SPDX-License-Identifier: BSD-3-Clause
+
+# Uses the pool adjacent violators algorithm (PAVA), with the
+# enhancement of searching for the longest decreasing subsequence to
+# pool at each step.
+
+import numpy as np
+from cython cimport floating
+
+
+def _inplace_contiguous_isotonic_regression(floating[::1] y, floating[::1] w):
+    cdef:
+        Py_ssize_t n = y.shape[0], i, k
+        floating prev_y, sum_wy, sum_w
+        Py_ssize_t[::1] target = np.arange(n, dtype=np.intp)
+
+    # target describes a list of blocks.  At any time, if [i..j] (inclusive) is
+    # an active block, then target[i] := j and target[j] := i.
+
+    # For "active" indices (block starts):
+    # w[i] := sum{w_orig[j], j=[i..target[i]]}
+    # y[i] := sum{y_orig[j]*w_orig[j], j=[i..target[i]]} / w[i]
+
+    with nogil:
+        i = 0
+        while i < n:
+            k = target[i] + 1
+            if k == n:
+                break
+            if y[i] < y[k]:
+                i = k
+                continue
+            sum_wy = w[i] * y[i]
+            sum_w = w[i]
+            while True:
+                # We are within a decreasing subsequence.
+                prev_y = y[k]
+                sum_wy += w[k] * y[k]
+                sum_w += w[k]
+                k = target[k] + 1
+                if k == n or prev_y < y[k]:
+                    # Non-singleton decreasing subsequence is finished,
+                    # update first entry.
+                    y[i] = sum_wy / sum_w
+                    w[i] = sum_w
+                    target[i] = k - 1
+                    target[k - 1] = i
+                    if i > 0:
+                        # Backtrack if we can.  This makes the algorithm
+                        # single-pass and ensures O(n) complexity.
+                        i = target[i - 1]
+                    # Otherwise, restart from the same point.
+                    break
+        # Reconstruct the solution.
+        i = 0
+        while i < n:
+            k = target[i] + 1
+            y[i + 1 : k] = y[i]
+            i = k
+
+
+def _make_unique(const floating[::1] X,
+                 const floating[::1] y,
+                 const floating[::1] sample_weights):
+    """Average targets for duplicate X, drop duplicates.
+
+    Aggregates duplicate X values into a single X value where
+    the target y is a (sample_weighted) average of the individual
+    targets.
+
+    Assumes that X is ordered, so that all duplicates follow each other.
+    """
+    unique_values = len(np.unique(X))
+
+    if floating is float:
+        dtype = np.float32
+    else:
+        dtype = np.float64
+
+    cdef floating[::1] y_out = np.empty(unique_values, dtype=dtype)
+    cdef floating[::1] x_out = np.empty_like(y_out)
+    cdef floating[::1] weights_out = np.empty_like(y_out)
+
+    cdef floating current_x = X[0]
+    cdef floating current_y = 0
+    cdef floating current_weight = 0
+    cdef int i = 0
+    cdef int j
+    cdef floating x
+    cdef int n_samples = len(X)
+    cdef floating eps = np.finfo(dtype).resolution
+
+    for j in range(n_samples):
+        x = X[j]
+        if x - current_x >= eps:
+            # next unique value
+            x_out[i] = current_x
+            weights_out[i] = current_weight
+            y_out[i] = current_y / current_weight
+            i += 1
+            current_x = x
+            current_weight = sample_weights[j]
+            current_y = y[j] * sample_weights[j]
+        else:
+            current_weight += sample_weights[j]
+            current_y += y[j] * sample_weights[j]
+
+    x_out[i] = current_x
+    weights_out[i] = current_weight
+    y_out[i] = current_y / current_weight
+    return(
+        np.asarray(x_out[:i+1]),
+        np.asarray(y_out[:i+1]),
+        np.asarray(weights_out[:i+1]),
+    )