science

Stride of an array

Stride of an array is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Stride of an array rather than just read about it. In short: In computer programming, the stride of an array (also referred to as increment, pitch or step size) is the number of locations in memory between beginnings of successive array elements, measured in bytes or in units of the size of the array's elements. The stride cannot be smaller than the element size but can be larger, indicating extra space between elements.

Key takeaways

Stride of an array belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Stride of an array to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Stride of an array from memory before moving on to harder problems.

Reference excerpt

In computer programming, the stride of an array (also referred to as increment, pitch or step size) is the number of locations in memory between beginnings of successive array elements, measured in bytes or in units of the size of the array's elements. The stride cannot be smaller than the element size but can be larger, indicating extra space between elements. An array with stride of exactly the same size as the size of each of its elements is contiguous in memory. Such arrays are sometimes said to have unit stride. Unit stride arrays are sometimes more efficient than non-unit stride arrays, but non-unit stride arrays can be more efficient for 2D or multi-dimensional arrays, depending on the effects of caching and the access patterns used. This can be attributed to the principle of locality, specifically spatial locality.

Reasons for non-unit stride Arrays may have a stride larger than their elements' width in bytes in at least two cases:

Overlapping parallel arrays Some languages allow arrays of structures to be treated as overlapping parallel arrays with non-unit stride:

This idiom is a form of type punning.

Array cross-section Some languages like PL/I or Fortran allow what is known as an array cross-section, which selects certain columns or rows from a larger array. For example, if a two-dimensional array is declared as

an array of one dimension consisting only of the second column may be referenced as

Example of multidimensional array with non-unit stride Non-unit stride is particularly useful for images. It allows for creating subimages without copying the pixel data. Java example:

References

Worked examples

Example 1 — a first encounter with Stride of an array

Start with the simplest possible case. Write down what Stride of an array claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Stride of an array before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Stride of an array ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Stride of an array

In research: Stride of an array appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Stride of an array in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Stride of an array is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arrays, so understanding it makes those chapters shorter.
In everyday life: Look for Stride of an array outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Stride of an array in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Stride of an array means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Stride of an array out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Stride of an array in simple terms?

Why does Stride of an array matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Stride of an array?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Stride of an array.