Why is TI-Basic so slow?

Question

I decided to implement a program that can find the GCD of any two numbers (including non-integers) in TI-Basic. I've used this just fine in Java, so I know it works. It works just fine in TI-Basic, but when compared with the built-in gcd( function, it's very sluggish; the gcd( function seems to get a result in milliseconds, where mine can take several seconds. Why is TI-Basic so much slower than the predefined calculator functions?

The code

---

Here is the program's code in TI-Basic, for your inspection:

PROGRAM:GCD

:ClrHome
:Disp "Greatest Common","    Divisor","      ---"
:Input "First number? ",X
:Input "Second number? ",Y
:
:X→I
:Y→J
:
:If (I≠int(I) or J≠int(J))
:Then
:ClrHome
:Disp "Non-integer","inputs may be","innacurate!",""
:End
:If (I=1 or J=1)
:Then
:1→I
:1→J
:Goto Z
:End
:For(C,0,2^8)
:If I=J
:Goto Z
:
:If I>J
:I-J→I
:
:If J>I
:J-I→J
:
:End
:
:Disp "This is a hard","one! Thinking","harder..."
:
:For(C,0,2^15)
:If (I=J)
:Goto Z
:While (I>J)
:I-J→I
:C+1→C
:End
:While (J>I)
:J-I→J
:C+1→C
:End
:End
:
:Disp "TIMED OUT!","Either:",J,"or"
:Pause
:
:Lbl Z
:ClrHome
:Disp "GCD of",X,"and",Y,"is",I

Disclaimer: This is the result of me looking at my TI-84 and typing it here. Some typos might be in it, though I tried my best to keep it the same

For those of you who might not know what this means, pseudocode is provided below:

program gcd()
{
Console.clear();
Console.writeln("Greatest Common");
Console.writeln("    Divisor");
Console.writeln("      ---");

float X = Console.readFloat("First Number? ");
float Y = Console.readFloat("Second number? ");

float I = X;
float J = Y;

if (I != (int)I || J != (int)J)
{
  Console.clear();
  Console.writeln("Non-integer");
  Console.writeln("inputs may be");
  Console.writeln("inaccurate!");
  Console.writeln("");
}
if (I == 1 or J == 1)
{
  I = 1;
  J = 1;
  goto Z;
}

for(int C = 0, limit = Math.pow(2,8); C < limit; C++)
{
  if (I == J)
    goto Z;

  if (I > J)
    I = I - J;

  if (J > I)
    J = J - I;
}

Console.writeln("This is a hard");
Console.writeln("one! Thinking");
Console.writeln("harder...");

for(int C = 0, limit = Math.pow(2,15); C < limit; C++)
{
  if (I == J)
    goto z;
  while (I > J)
  {
    I = I - J;
    C++;
  }
  while (J>I)
  {
    J = J-I;
    C++;
  }
}

Console.writeln("TIMED OUT!");
Console.writeln("Either:");
Console.writeln(J);
Console.writeln("or");
Console.pause();

Z:
Console.clear();
Console.writeln("GCD of");
Console.writeln(X);
Console.writeln("and");
Console.writeln(Y);
Console.writeln("is");
Console.writeln(I);
}

Gillard

limit=Math.pow(2,8) is happening tens, hundreds, maybe thousands of times because it is re interpreted every iteration of the loop. It's slow because your code is not as efficient as the gcd source. – Agoraphobia

@EricLeschinski That's where you're wrong. Note that it's only called when limit is declared, and its return is immediately stored in limit. After that, the value is only read from limit each loop. Good eye, though! – Gillard

Oh, god, TI-Basic. This takes me back. – Orchardist

Answer 1

It's slow because it's an interpreted language - Disadvantages of interpreted languages.

Basically this affects grabbing user input, as well as displaying graphics on-screen.

Carolyn

But would it really be THAT much slower? I mean, we're talking minutes versus milliseconds, here. – Gillard

Yep. See tibasicdev.wikidot.com/whytibasic for a TI specific explanation, and tibasicdev.wikidot.com/optimize-loops for information on optimizing your program (without rewriting it in assembly). – Invigilate

Thanks for those links! I already knew this, but didn't think it mattered this much. I'll keep it all in mind from now on ;D – Gillard

Answer 2

You could fix a lot of the code, like not using Goto, leaving parentheses off the ends of lines, not using ClrHome, etc. More info: https://en.wikibooks.org/wiki/TI-Basic_Z80_Programming/Tips,_Tricks_and_Optimizations

Stomatal

Thank you; seven years of software engineering experience has taught me things like that, and I'm glad you made note of it on this question in case future readers don't know 🙂 – Gillard

Answer 3

Another reason for it being slow, is because of the clrHome, I have realized while using them, clr-home takes a moment to complete, maybe half a second, at least on the Ti-83 plus, normally disp and input don't take much, also instead of the two inputs, you could also use prompt fist number','second number'

Airlie