2.9 KiB
Use addition instead of multiplication by 2
Where fundamentals in mathematics might be useful for speed.
Summary
🍎 Multiplication is just another form of addition.
And when you're multiplying by 2, it's faster to use the addition counterpart.
This is always true if what you want to do is A=2*B and that you use variables and replace hardcoded constants with variables. If you don't, you might get mitigated results.
Demonstration:
10 A=123: B=2
20 C = A*B
30 END
Line 20 takes 3236 cycles.
Snippet #2:
10 A=123: B=2
20 C = A+A
30 END
Line 20 takes now 2321 cycles, a bonus of 915 cycles.
Of course it would be even more drastic if you didn't store (and use !) the constant 2 in variable B
10 A=123: B=2
20 C = A*2
30 END
Line 20 takes 3599 cycles, that's 1278 cycles more than using an addition !
Unfortunately, this tip does not work for anything else than multiplication by 2. Let's see what happens with multiplication by 3:
10 A=123: B=3
20 C = A*B
30 END
Line 20 takes 3236 cycles (again) While line 20 of snippet #2:
10 A=123: B=2
20 C = A+A+A
30 END
takes 3287 cycles, that is 51 cycles slower. Of course it gets worse with higher multiplication values.
🍎 Restrictions
It's also important to notice that this will work only if you already have a variable with the value you want to double.
Let's consider the following, you want to double the result of another calculation, like a division with code like D=2*A/B
Snippet #1
10 A=123: B=45: C=2: D=0: E=0
20 E=C*A/B
30 END
Line 20 takes 6795 cycles. Notice how line 10 declares five variables A-E. These variables will be used in the subsequent snippets. Declaring them, even though they're not used, allows us to ignore the extra cycles needed to create a new variable.
Now let's try with the addition:
10 A=123: B=45: C=2: D=0: E=0
20 D=A/B+A/B
30 END
Line 20 takes 9072 cycles, which is slower (2277 cycles slower).
Now you might think that storing the result of A/B would be faster. It's not. Except, maybe if you intend to use that result elsewhere in your code in which case it might be worth to spend those cycles storing a result in a variable.
First snippet demonstrates the speed if you don't care about the result of A/B
10 A=123: B=45: C=2: D=0: E=0
20 D=A/B: E=D+D
30 END
Line 20 takes 7090 cycles, it's 295 cycles slower than using directly E=C*A/B.
This second snippet illustrates the speed if the result of A/B is of any interest and is meant to be reused several other times: it's thus calculated on line 10 and excluded from cycles count.
10 A=123: B=45: C=2: D=A/B: E=0
20 E=D+D
30 END
line 20 takes only 2409 cycles. Using 20 E=C*D would take 2283 cycles more.