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performance-aware-programming/notes.org

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+#+TITLE: Performance-Aware Programming
+#+AUTHOR: Casey Muratori
+
+
+* Definition
+  Just knowing what you're doing can affect performance
+  Not doing actual low level performance optimization for specific hardware
+
+  "If you understand CSS you should understand this"
+
+* Thinking about the CPU
+
+If you think of a processor as a box which takes instructions as inputs
+and then they do some work before producing the output, you have two
+levers to pull for performance.
+
+1. Reduce the # of instructions
+   Simplify the program or generally reduce the work that the CPU needs
+2. Speed of the Instruction
+   Change the set of instructions you're passing through the CPU based
+   on how much time it might take to process.
+
+* Prologue
+
+In a simple python program below: We achieve ~0.006 adds/cycle
+
+#+begin_src python
+  def add(a, b):
+      a + b
+
+  c = 1234 + 5678
+#+end_src
+
+
+In the naive C version we're looking at ~0.8 adds/cycle
+
+If we get smarter and do some optimization with SIMD we can achive up to 16 adds/cycle.