added instructions for exercise

README.md

@@ -2,20 +2,51 @@
 **Important**: these are instructor notes, remove this file before showing the materials to the students. The notes can be added after the lecture, of course.
 
 ## Introduction
-  - [Puzzle](puzzle.ipynb) (how swapping two nested for-loops makes out for a >27× slowdown
+  - [Puzzle](/puzzle.ipynb) ➔ [read-only rendered notebook](https://nbviewer.org/urls/git.aspp.school/ASPP/2024-heraklion-comp-arch/raw/branch/main/puzzle.ipynb)
+  - Question: how come that swapping dimensions in a for-loop makes out for a huge slowdown?
   - Let students play around with the notebook and try to find the "bug"
-  - A more thorough benchmark using the same code is [here](benchmark_python/)
+  - A more thorough [benchmark](benchmark_python/)
+
 
 ## A digression in CPU architecture and the memory hierarchy
 
-  - Go to [A Primer in CPU architecture](architecture)
-  - The need for a hierarchical access to data for the CPU should be clear now ➔ the "starving" CPU problem
-  - Have a look at the historical evolution of [speeds](speed/) of different components in a computer:
-    - the CPU clock rate
-    - the memory (RAM) bandwidth, latency clock rate
-    - the storage media access rates
+  - Go to [A Primer in CPU architecture](architecture/)
+  - Measure size and timings for the memory hierarchy on my machine with a low level [C benchmark](benchmark_low_level/)
+
+## Analog programming
+Two exercises to activate the body and the mind
+
+Common goal of both exercises is to sort a deck of tarot cards by value
+### First experiment: human sorting
+Setup:
+- 1 volunteer to keep the time spent sorting
+- each person picks up a tarot card from the randomly shuffled deck on the table
+- moving around and speaking is allowed until the tarot cards are displayed sorted on the table
+
+### Second experiment: machine sorting
+Setup:
+- 2 volunteers to keep the time:
+  - one volunteer keeps the time spent *programming*
+  - one volunteer keeps the time spent *executing* the program
+- 2 volunteers to be the *programmers*:
+  - can use the whiteboard
+  - can and should speak and think loudly and ask for help
+- 2 volunteers to be two CPUs:
+  - only understand the instructions:
+    - **fetch** a value from a memory address into register `N` ➔ returns `0` if succeded else `1` 
+    - **push** the value from register `N` to a memory address ➔ returns `0` if succeded else `1` 
+    - **compare** var0 and var1 ➔ returns `0` if `var0 ≥ var1` else `1`
+- 4 volunteers to be CPU registers:
+  - each register has a tag: `R1`, `R2`, `R3`, `R4`
+  - a value fetched from memory is kept in short-term memory by the registers
+  - the result value of an operation is stored in one register
+- everyone else sits on their seats and represent RAM:
+  - they own a *value*, i.e. they hold on a tarot card
+  - they have an address based on their seating order: 0th seat, 1st seat, 2nd seat, 3rd seat, 4th seat, etc…
+  - when *fetched*, walk to the corresponding register and hand in their *value* (card)
+  - when *pushed*, walk to the corresponding register and fetch their new *value* (card)
+- each RAM address comes and picks up a random tarot card as initialization step
 
-  - Measure size and timings for the memory hierarchy on my machine with a low level [C benchmark](benchmark_low_level)
 
 ## Back to the Python benchmark (second try)
 
@@ -25,19 +56,28 @@
 
 ## Anatomy of a numpy array
 
-  - [memory layout of numpy arrays](numpy)
+  - [memory layout of numpy arrays](numpy/)
 
 ## Back to the Python benchmark (third try)
   - can we explain what is happening now? Yes, more or less ;-)
-  - quick fix for the [puzzle](puzzle.ipynb): try and add `order='F'` in the "bad" snippet and see that is "fixes" the bug ➔ why?
+  - quick fix for the [puzzle](/puzzle.ipynb): try and add `order='F'` in the "bad" snippet and see that is "fixes" the bug ➔ why?
 
 Notes on the [Python benchmark](benchmark_python/):
   - while running it attached to the P-core (`cpu0`), the P-core was running under a constant load of 100% (almost completely user-time) and at a fixed frequency of 3.8 GHz, where the theoretical max would be 5.2 GHz
-  - while running it attached to the E-core (`cpu10`), the E-core was running under a constant load of 100% (almost completely user-time) and at a fixed requency of 2.5 GHz, where the theoretical max would be 3.9 GHz
-  - ... ➔ the CPU does not "starve" because it scales its speed down to match the memory throughput? Or I am misinterpreting this? This problem which at first sight should be perfectly memory-bound, becomes CPU-bound, or actually, exactly balanced? ;-)
-
-## Excerpts of parallel Python
-  - [The dangers and joys of automatic parallelization](parallel) (like in numpy linear algebra routines) and the use of clusters/schedulers (but also on your laptop)
+    
+    ➔ the CPU does not "starve" because it scales its speed down to match the memory throughput? Or I am misinterpreting this? This problem which at first sight should be perfectly memory-bound, becomes CPU-bound, or actually, exactly balanced? From the [Intel documentation](https://lenovopress.lenovo.com/lp1836-tuning-uefi-settings-4th-gen-intel-xeon-scalable-processor):
+    > **Energy Efficient Turbo**
+    >
+    > When `Energy Efficient Turbo` is enabled, the CPU’s optimal turbo
+    > frequency will be tuned dynamically based on CPU utilization. The actual
+    > turbo frequency the CPU is set to is proportionally adjusted based on the
+    > duration of the turbo request. Memory usage of the OS is also monitored.
+    > If the OS is using memory heavily and the CPU core performance is limited
+    > by the available memory resources, the turbo frequency will be reduced
+    > until more memory load dissipates, and more memory resources become
+    > available. The power/performance bias setting also influences energy
+    > efficient turbo. `Energy Efficient Turbo` is best used when attempting to
+    > maximize power consumption over performance.
 
 ## Concluding remarks
   - how is all of this relevant for the users of a computing cluster?