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Fix grammar in beginners-guide.md #458

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Expand Up @@ -25,7 +25,7 @@ SIMD has a few special vocabulary terms you should know:

* **Scalar:** "Scalar" in mathematical contexts refers to values that can be represented as a single element, mostly numbers like 6, 3.14, or -2. It can also be used to describe "scalar operations" that use strictly scalar values, like addition. This term is mostly used to differentiate between vectorized operations that use SIMD instructions and scalar operations that don't.

* **Lane:** A single element position within a vector is called a lane. If you have `N` lanes available then they're numbered from `0` to `N-1` when referring to them, again like an array. The biggest difference between an array element and a vector lane is that in general is *relatively costly* to access an individual lane value. On most architectures, the vector has to be pushed out of the SIMD register onto the stack, then an individual lane is accessed while it's on the stack (and possibly the stack value is read back into a register). For this reason, when working with SIMD you should avoid reading or writing the value of an individual lane during hot loops.
* **Lane:** A single element position within a vector is called a lane. If you have `N` lanes available then they're numbered from `0` to `N-1` when referring to them, again like an array. The biggest difference between an array element and a vector lane is that in general it is *relatively costly* to access an individual lane value. On most architectures, the vector has to be pushed out of the SIMD register onto the stack, then an individual lane is accessed while it's on the stack (and possibly the stack value is read back into a register). For this reason, when working with SIMD you should avoid reading or writing the value of an individual lane during hot loops.

* **Bit Widths:** When talking about SIMD, the bit widths used are the bit size of the vectors involved, *not* the individual elements. So "128-bit SIMD" has 128-bit vectors, and that might be `f32x4`, `i32x4`, `i16x8`, or other variations. While 128-bit SIMD is the most common, there's also 64-bit, 256-bit, and even 512-bit on the newest CPUs.

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