LoginFor Educators

Question

What is an off by one error?

StudyStudyStudyStudy

Solution

PrepMate

An off by one error is a common programming mistake that occurs when an algorithm iterates one time too many or one time too few. This type of error is often encountered in loops and can lead to incorrect results or runtime errors. Understanding and avoiding off by one errors is crucial for software developers, as they can cause significant issues in both simple and complex programs.
An off by one error is a common programming mistake that occurs when an algorithm iterates one time too many or one time too few. This type of error is often encountered in loops and can lead to incorrect results or runtime errors. Understanding and avoiding off by one errors is crucial for software developers, as they can cause significant issues in both simple and complex programs.

Here is a step-by-step explanation of what an off by one error is and how it can occur:

1. Understanding Iteration in Programming:
In programming, iteration refers to the process of repeating a set of instructions a certain number of times. This is typically done using loops, such as `for` loops, `while` loops, or `do-while` loops.

2. Identifying the Bounds of Iteration:
When setting up a loop, you must define the starting point and the ending point of the iteration. This is known as defining the bounds of the loop.

3. Setting the Correct Bounds:
The bounds must be set correctly to ensure that the loop iterates the intended number of times. For example, if you want to iterate over an array with `n` elements, you would typically start at index `0` and end at index `n-1`, because array indexing is zero-based in many programming languages.

4. Common Off by One Error Scenarios:
- Forgetting Zero-based Indexing: If you mistakenly set the loop to end at index `n` instead of `n-1`, the loop will attempt to access an element beyond the end of the array, leading to an off by one error.
- Incorrect Inequality Operator: Using `<=` (less than or equal to) instead of `<` (less than) in the loop condition can cause the loop to execute one additional iteration than intended.
- Improper Initialization or Update: Starting the loop index at `1` instead of `0`, or incorrectly updating the loop counter, can also result in an off by one error.

5. Consequences of Off by One Errors:
The impact of an off by one error can range from minor (such as producing an incorrect output) to severe (such as causing a program crash or buffer overflow).

6. Debugging Off by One Errors:
To debug an off by one error, carefully review the loop's bounds and the conditions set for iteration. Ensure that the loop starts and ends at the correct points, and that the loop counter is being updated correctly after each iteration.

7. Preventing Off by One Errors:
Preventing off by one errors involves careful planning and testing. Always consider the starting and ending conditions of your loops, and test your loops with boundary values to ensure they behave as expected.

By understanding the concept of iteration and being meticulous with loop bounds and conditions, programmers can minimize the occurrence of off by one errors in their code. It is also helpful to include comments and documentation that clarify the intended bounds of iteration, which can aid in both writing and reviewing code.

Exercise 1 part b-Compute sin3⁰ with an error of less than 0.001.

Solved: Unlock Proprep's Full Access

Gain Full Access to Proprep for In-Depth Answers and Video Explanations

Signup to watch the full video 03:36 minutes

In this exercise, we have to estimate the sine of 3 degrees,
and I'll just write that in radians,
that sine of Pi over 60,
because Pi is 180,
180 over 60 is 3,
and within an error of less than 0.001,
which I can write as 1 over 1,000 so I want the error to be less than.
Now, this is in the section on Taylor and Maclaurin series,
so the obvious thing to do is to start off with the Maclaurin series for sine.
Here it is, this was taken from the appendix in the Maclaurin table.
We'll use the expanded form,
not the Sigma form.
We can get the sine of Pi over 60,
which is what I get when I just put x equals Pi over 60 is going to equal x,
which is Pi over 60 minus this term is
Pi over 60 cubed over 3 factorial is 6.
1 more, Pi over 60 to the 5th over 5 factorial,
which is 120, and so on.
Notice that what we have here is an alternating series: plus,
minus, plus, minus, and each successive term gets smaller and smaller.
In other words, it's a Leibnitz series,
sometimes called Leibnitz alternating series.
Because of this, we can use the theorem,
if we take a partial sum,
the error is less than the next term in absolute value.
Let's see, we'll keep going along until we get to a term that's less than 1,000th.
This is Pi over 60.
This is about 3 over 60,
120th, not good enough, minus,
the next term is Pi cubed over,
let's see, 60 cubed.
6 cubed is 216,
but it's 60 so it's 216,000 times 6.
Clearly, this is going to be less than 1,000th.
You can do it on the calculator,
but Pi cubed is about 3 times 3 times 3,
and this is 100s of thousands.
This is already less than 1,000th.
Well, anyway, do it on the calculator,
you'll see it's much smaller.
We can actually stop here, the partial sum,
and say that the sine of Pi over
60 is actually approximately equal to Pi over 60,
with an error that's less than way much smaller than 1,000th,
but certainly within 0.01.
This is what I'll leave as the answer.
I won't do it on the calculator.
You can do it if you want.
But just to fully answer the question,
I can say that sine of 3 degrees is approximately Pi over
60 with error less than this expression from here,
which is way less than 0.01.
We are done.
This video explains how to estimate the sine of 3 degrees (or Pi over 60 in radians) within an error of less than 0.001. The speaker uses the Maclaurin series for sine and the Leibnitz alternating series theorem to calculate the approximate value of the sine. The speaker concludes that the sine of 3 degrees is approximately equal to Pi over 60, with an error that is less than 0.01: • The speaker uses the Maclaurin series for sine to calculate the approximate value of the sine of 3 degrees (or Pi over 60 in radians). • The speaker uses the Leibnitz alternating series theorem to calculate the error of the approximation. • The speaker concludes that the sine of 3 degrees is approximately equal to Pi over 60, with an error that is less than 0.01.

Ask a tutor

If you have any additional questions, you can ask one of our experts.

Recently Asked Questions