From 77dd9cdfd685cc493a9d4d080d75ba10e8e0d640 Mon Sep 17 00:00:00 2001
From: "Davide Gessa (dakk)" <gessadavide@gmail.com>
Date: Tue, 16 Apr 2024 16:40:58 +0200
Subject: [PATCH] fix mul_even_const

---
 qlasskit/types/qint.py | 58 +++++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 26 deletions(-)

diff --git a/qlasskit/types/qint.py b/qlasskit/types/qint.py
index 1d19edef..9c45ecac 100644
--- a/qlasskit/types/qint.py
+++ b/qlasskit/types/qint.py
@@ -165,11 +165,10 @@ def add(cls, tleft: TExp, tright: TExp) -> TExp:
         return (cls if cls.BIT_SIZE > tleft_e[0].BIT_SIZE else tleft_e[0], sums)
 
     @staticmethod
-    def mul_even_const(t_num: TExp, t_const: TExp) -> TExp:
+    def mul_even_const(t_num: TExp, const: int, result_type: "QintImp") -> TExp:
         """Multiply by an even const using shift and add
         (x << 3) + (x << 1) # Here 10*x is computed as x*2^3 + x*2
         """
-        const = t_const[0].from_bool(t_const[1])
 
         # Multiply t_num by the nearest n | 2**n < t_const
         n = 1
@@ -178,22 +177,41 @@ def mul_even_const(t_num: TExp, t_const: TExp) -> TExp:
         if 2**n > const:
             n -= 1
 
-        t_num_r = t_num[0].crop(t_num[0].shift_left(t_num, n))
+        t_num_r = result_type.shift_left((result_type, t_num[1]), n)
 
         # Shift t_const by t_const - 2**n
         r = const - 2**n
         if r > 0:
             # Add the shift result to t_num
-            res = t_num_r[0].add(
-                t_num_r, t_num[0].crop(t_num[0].shift_left(t_num, int(r / 2)))
+            res = result_type.add(
+                (result_type, t_num_r[1]),
+                result_type.shift_left((result_type, t_num[1]), int(r / 2)),
             )
         else:
-            res = t_num_r
+            res = (result_type, t_num_r[1])
 
         return res
 
     @classmethod
     def mul(cls, tleft: TExp, tright: TExp) -> TExp:  # noqa: C901
+        def __mul_sizing(n, m):
+            if (n + m) <= 2:
+                return Qint2
+            elif (n + m) > 2 and (n + m) <= 4:
+                return Qint4
+            elif (n + m) > 4 and (n + m) <= 6:
+                return Qint6
+            elif (n + m) > 6 and (n + m) <= 8:
+                return Qint8
+            elif (n + m) > 8 and (n + m) <= 12:
+                return Qint12
+            elif (n + m) > 12 and (n + m) <= 16:
+                return Qint16
+            elif (n + m) > 16:
+                return Qint16
+            else:
+                raise Exception(f"Mul result size is too big ({n+m})")
+
         # Fill constants so explicit typecast is not needed
         if cls.is_const(tleft):
             tleft = tright[0].fill(tleft)
@@ -201,6 +219,9 @@ def mul(cls, tleft: TExp, tright: TExp) -> TExp:  # noqa: C901
         if cls.is_const(tright):
             tright = tleft[0].fill(tright)
 
+        n = len(tleft[1])
+        m = len(tright[1])
+
         # If one operand is an even constant, use mul_even_const
         if cls.is_const(tleft) or cls.is_const(tright):
             t_num = tleft if cls.is_const(tright) else tright
@@ -208,10 +229,9 @@ def mul(cls, tleft: TExp, tright: TExp) -> TExp:  # noqa: C901
             const = t_const[0].from_bool(t_const[1])
 
             if const % 2 == 0:
-                return cls.mul_even_const(t_num, t_const)
-
-        n = len(tleft[1])
-        m = len(tright[1])
+                t = __mul_sizing(n, m)
+                res = cls.mul_even_const(t_num, const, t)
+                return t.crop(t.fill(res))
 
         if n != m:
             raise Exception(f"Mul works only on same size Qint: {n} != {m}")
@@ -233,22 +253,8 @@ def mul(cls, tleft: TExp, tright: TExp) -> TExp:  # noqa: C901
             if i + m < n + m:
                 product[i + m] = carry
 
-        if (n + m) <= 2:
-            return Qint2, product
-        elif (n + m) > 2 and (n + m) <= 4:
-            return Qint4, product
-        elif (n + m) > 4 and (n + m) <= 6:
-            return Qint6, product
-        elif (n + m) > 6 and (n + m) <= 8:
-            return Qint8, product
-        elif (n + m) > 8 and (n + m) <= 12:
-            return Qint12, product
-        elif (n + m) > 12 and (n + m) <= 16:
-            return Qint16, product
-        elif (n + m) > 16:
-            return Qint16.crop((Qint16, product))
-
-        raise Exception(f"Mul result size is too big ({n+m})")
+        t = __mul_sizing(n, m)
+        return t.crop(t.fill((t, product)))
 
     @classmethod
     def sub(cls, tleft: TExp, tright: TExp) -> TExp: