nested if? or logical operators?

[Xander Lopez]

Which is faster and more efficient? I have tons of the following code, so I thought I would make up my mind

case1

        if(press ==  nametag1) llSay(0,"I found " + (string)press);
        else if(press ==  nametag2) llSay(0,"I found " + (string)press);
        else if(press ==  nametag3) llSay(0,"I found " + (string)press);
 

vs...

case2

if (press == nametag1 || press == nametag2 || press == nametag3) llSay(0,"I found " + (string)press);

[Wulfie Reanimator]

Theoretically speaking, both could be faster. It depends on how the compiler translates it.

Case 2 could be slower because we know for a fact that conditions are fully evaluated in LSL. if "press == nametag1" is true, the other two are still checked.

The if-else chain could create a "jump table" or even optimize the order of the conditions so that the "most common case" is assumed before any checks, but I don't think we know how the LSL compiler handles these. I don't think we even have any way to access the compiler either, since scripts are compiled server-side.

I'm of the opinion that things like this is not something you should focus on, because the decision to use case 1 or case 2 is not going to be noticeable at all, compared to the readability and what the code implies. If you have 3 different cases that all lead to the same result, you shouldn't separate them like in case 1. That's one way to set yourself up for bugs and duplicated code. (And since we're on the topic of micro-optimizations, that duplicate code in case 1 is going to cost you some memory.)

But it would be interesting to know from a technical standpoint.

Edited December 1, 2020 by Wulfie Reanimator

[Rachel1206]

One way to handle logical large conditions would be compare to a  list and avoid the long if else statements (or case switch using #define USE_SWITCHES in FS) and avoid the duplicated code, like this sample:

string press= "Nerd";

list listNameTags= ["Sweet", "Beauty", "Nerd", "Fun"];

integer bPositive= FALSE;
integer i= 0;        
while(!bPositive && i<llGetListLength( listNameTags))
{
    if ( press==llList2String( listNameTags, i))
        bPositive= TRUE;
    i++;
}

if (bPositive)
    llSay( 0, "I found "+ press);
else
    llSay( 0, "I found nothing");

 

In case of more complex lists, usage of strided list and optional JSON can be clever solutions using the above. In this case though, your attention should be on the memory usage.

Edited December 1, 2020 by Rachel1206

[Nova Convair]

This works too:

searchfor = ["nametag1","nametag2","nametag3"];

if (~llListFindList(searchfor,[press])) llSay(0,"found "+press); else llSay(0,"not found");

I stumble about the question about speed. How many times per second you want to do this? 😁
However, enclose the solutions in a loop from 1 to 100000, get time b4 loop and after loop and show the difference. Then you get the answer about speed.

[Lucia Nightfire]

In terms of speed, llListFindList() is on avg. 6x - 7x faster than llJsonGetValue() with the same sized/dimension list and array.

Hardcoded lists use a slightly higher memory footprint on query than the unwrapping/expanding caused by llJsonGetValue() reading a hardcoded json string.

Pick your poison.

Edited December 2, 2020 by Lucia Nightfire