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-rwxr-xr-xbooth_multiplier.py34
1 files changed, 18 insertions, 16 deletions
diff --git a/booth_multiplier.py b/booth_multiplier.py
index 517c613..58abe8b 100755
--- a/booth_multiplier.py
+++ b/booth_multiplier.py
@@ -9,15 +9,18 @@ def twos_comp(num, length):
return 0
return abs((num ^ ((1 << length) - 1)) + 1)
-def logical_shiftr(num, length, times):
- #print("SHIFT START___")
- #print(bin(num))
+def arithmatic_shiftr(num, length, times):
for t in range(times):
- num = (num >> 1) | ((1 << length) & num)
- #print(bin(num))
- #print("SHIFT END___")
+ num = (num >> 1) | ((1 << length - 1) & num)
return num
+def arithmatic_shiftl(num, length):
+ if num & (1 << length - 1):
+ return (num << 1) | (1 << length - 1)
+ else:
+ return (num << 1) & ~(1 << length - 1)
+
+
def convert_if_twoscomp(num, length):
if num & (1 << length - 1):
return (-1 * twos_comp(num, length))
@@ -49,29 +52,28 @@ def booth(multiplier, multiplicand, length):
if op == 0b10:
result += multiplicand_twos_comp << (length + 1)
result &= (1 << (length * 2) + 1) - 1 # get rid of any overflows
- result = logical_shiftr(result, length * 2, 1)
+ result = arithmatic_shiftr(result, (length * 2) + 1, 1)
result = result >> 1
return result
def booth_mod(multiplier, multiplicand, length):
- multiplicand_twos_comp = twos_comp(multiplicand, length)
+ multiplicand |= ((1 << length - 1) & multiplicand) << 1 # extend multiplicand sign to prevent overflow when mult/sub by 2
+ multiplicand_twos_comp = twos_comp(multiplicand, length + 1)
result = multiplier << 1 # extended bit
operations = 0
- for i in range(int(length / 2)):
+ for i in range(int((length) / 2)):
match result & 0b111:
case 0b010 | 0b001: # add
result += multiplicand << (length + 1)
case 0b011: # add * 2
- result += multiplicand << (length + 2) # extra shift is multiplying multiplicand by 2
+ result += arithmatic_shiftl(multiplicand, length + 1) << (length + 1) # extra shift is multiplying multiplicand by 2
case 0b100: # sub * 2
- result += multiplicand_twos_comp << (length + 2)
+ result += arithmatic_shiftl(multiplicand_twos_comp, length + 1) << (length + 1) # extra shift is multiplying multiplicand by 2
case 0b101 | 0b110: # sub
result += multiplicand_twos_comp << (length + 1)
- if result & (1 << length):
- print("{}: overflow".format(bin(multiplicand)))
- result &= (1 << ((length * 2) + 1)) - 1 # get rid of any overflows
- result = logical_shiftr(result, length * 2, 2)
- result = result >> 1
+ result &= (1 << ((length * 2) + 2)) - 1 # get rid of any overflows
+ result = arithmatic_shiftr(result, (length * 2) + 2, 2)
+ result = ((result | ((1 << ((length * 2) + 2)) >> 1)) & ((1 << ((length * 2) + 1)) - 1)) >> 1
return result