fix: add butterfly_factor fn

extensions-builtin/Lora/lyco_helpers.py

@@ -66,3 +66,29 @@ def factorization(dimension: int, factor:int=-1) -> tuple[int, int]:
         n, m = m, n
     return m, n
 
+# from https://github.com/KohakuBlueleaf/LyCORIS/blob/dev/lycoris/modules/boft.py
+def butterfly_factor(dimension: int, factor: int = -1) -> tuple[int, int]:
+    """
+    m = 2k
+    n = 2**p
+    m*n = dim
+    """
+
+    # Find the first solution and check if it is even doable
+    m = n = 0
+    while m <= factor:
+        m += 2
+        while dimension % m != 0 and m < dimension:
+            m += 2
+        if m > factor:
+            break
+        if sum(int(i) for i in f"{dimension//m:b}") == 1:
+            n = dimension // m
+
+    if n == 0:
+        raise ValueError(
+            f"It is impossible to decompose {dimension} with factor {factor} under BOFT constrains."
+        )
+
+    #log_butterfly_factorize(dimension, factor, (dimension // n, n))
+    return dimension // n, n