feat: amdahls law (dwmkerr#47)

* feat: added Amdhal's Law

Closes dwmkerr#46.

.gitignore

@@ -0,0 +1 @@
+.DS_Store

README.md

@@ -6,6 +6,7 @@ Laws, Theories, Principles and Patterns that developers will find useful.
 
 * [Introduction](#introduction)
 * [Laws](#laws)
+    * [Amdahl's Law](#amdahls-law)
     * [Brooks's Law](#brookss-law)
     * [Conway's Law](#conways-law)
     * [The Hype Cycle & Amara's Law](#the-hype-cycle--amaras-law)
@@ -38,6 +39,29 @@ There are lots of laws which people discuss when talking about development. This
 
 And here we go!
 
+### Amdahl's Law
+
+[Amdahl's Law on Wikipedia](https://en.wikipedia.org/wiki/Amdahl%27s_law)
+
+> Amdahl's Law is a formula which shows the _potential speedup_ of a computational task which can be achieved by increasing the resources of a system. Normally used in parallel computing, it can predict the actual benefit of increasing the number of processors, which is limited by the parallelisability of the program.
+
+Best illustrated with an example. If a program is made up of two parts, part A, which must be executed by a single processor, and part B, which can be parallelised, then we see that adding multiple processors to the system executing the program can only have a limited benefit. It can potentially greatly improve the speed of part B - but the speed of part A will remain unchanged.
+
+The diagram below shows some examples of potential improvements in speed:
+
+![Diagram: Amdahl's Law](./images/amdahls_law.png)
+
+*(Image Reference: By Daniels220 at English Wikipedia, Creative Commons Attribution-Share Alike 3.0 Unported, https://en.wikipedia.org/wiki/File:AmdahlsLaw.svg)*
+
+As can be seen, even a program which is 50% parallelisable will benefit very little beyond 10 processing units, where as a program which is 95% parallelisable can still achieve significant speed improvements with over a thousand processing units.
+
+As [Moore's Law](#TODO) slows, and the acceleration of individual processor speed slows, parallelisation is key to improving performance. Graphics programming is an excellent example - with modern Shader based computing, individual pixels or fragments can be rendered in parallel - this is why modern graphics cards often have many thousands of processing cores (GPUs or Shader Units).
+
+See also:
+
+- [Brooks's Law](#brookss-law)
+- [Moore's Law](#TODO)
+
 ### Brooks's Law
 
 [Brooks's Law on Wikipedia](https://en.m.wikipedia.org/wiki/Brooks%27s_law)