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math.big: optimize subtract_digit_array()

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Mike 2025-08-20 14:15:27 +03:00
parent b502d52280
commit 66dc835c49
1 changed files with 10 additions and 16 deletions
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26
vlib/math/big/array_ops.v
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@ -82,27 +82,21 @@ fn subtract_digit_array(operand_a []u64, operand_b []u64, mut storage []u64) {
for index in 0 .. operand_a.len {
storage[index] = operand_a[index]
}
return
}
mut carry := false
mut borrow := u64(0)
for index in 0 .. operand_b.len {
mut a_digit := operand_a[index]
b_digit := operand_b[index] + if carry { u64(1) } else { u64(0) }
carry = a_digit < b_digit
if carry {
a_digit = a_digit | (u64(1) << digit_bits)
a := operand_a[index]
b := operand_b[index] + borrow
diff := a - b
borrow = (diff >> digit_bits) & 1
storage[index] = diff + (borrow << digit_bits)
}
storage[index] = a_digit - b_digit
}
for index in operand_b.len .. operand_a.len {
mut a_digit := operand_a[index]
b_digit := if carry { u64(1) } else { u64(0) }
carry = a_digit < b_digit
if carry {
a_digit = a_digit | (u64(1) << digit_bits)
}
storage[index] = a_digit - b_digit
diff := operand_a[index] - borrow
borrow = (diff >> digit_bits) & 1
storage[index] = diff + (borrow << digit_bits)
}
shrink_tail_zeros(mut storage)