From af2d7f19c7182013844188a068936d3f0c72e2df Mon Sep 17 00:00:00 2001
From: Marco Realacci <marco@marcorealacci.me>
Date: Wed, 2 Apr 2025 23:20:03 +0200
Subject: [PATCH] vault backup: 2025-04-02 23:20:03

---
 .obsidian/workspace.json            | 36 ++++++++++++++---------------
 Concurrent Systems/test/Untitled.md | 25 +++++++++++++++++++-
 2 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/.obsidian/workspace.json b/.obsidian/workspace.json
index 20f023b..c5dd9da 100644
--- a/.obsidian/workspace.json
+++ b/.obsidian/workspace.json
@@ -13,30 +13,29 @@
             "state": {
               "type": "markdown",
               "state": {
-                "file": "Concurrent Systems/notes/1 - CS Basics.md",
+                "file": "Concurrent Systems/test/Untitled.md",
                 "mode": "source",
                 "source": false
               },
               "icon": "lucide-file",
-              "title": "1 - CS Basics"
+              "title": "Untitled"
             }
           },
           {
-            "id": "ae1e669229aa09dc",
+            "id": "e453bba00fdc57d6",
             "type": "leaf",
             "state": {
               "type": "markdown",
               "state": {
-                "file": "Concurrent Systems/notes/1 - CS Basics.md",
+                "file": "Concurrent Systems/notes/4 - Semaphores.md",
                 "mode": "source",
                 "source": false
               },
               "icon": "lucide-file",
-              "title": "1 - CS Basics"
+              "title": "4 - Semaphores"
             }
           }
-        ],
-        "currentTab": 1
+        ]
       }
     ],
     "direction": "vertical"
@@ -205,31 +204,31 @@
       "companion:Toggle completion": false
     }
   },
-  "active": "2b2245f56092006e",
+  "active": "7c5b0ca6f7687800",
   "lastOpenFiles": [
-    "Concurrent Systems/notes/4b - Monitors.md",
-    "Concurrent Systems/notes/1 - CS Basics.md",
-    "Concurrent Systems/test/Untitled.md",
     "Concurrent Systems/notes/4 - Semaphores.md",
+    "Concurrent Systems/test/Untitled.md",
+    "Concurrent Systems/notes/4b - Monitors.md",
+    "Concurrent Systems/notes/4c - Dining Philosophers.md",
+    "Concurrent Systems/notes/5 - Software Transactional Memory.md",
+    "Concurrent Systems/notes/6 - Atomicity.md",
+    "Concurrent Systems/notes/7- MUTEX-free concurrency.md",
+    "Concurrent Systems/notes/9 - Consensus.md",
+    "Concurrent Systems/slides/class 9.pdf",
+    "Concurrent Systems/slides/class 10.pdf",
+    "Concurrent Systems/notes/1 - CS Basics.md",
     "Concurrent Systems/test",
     "Concurrent Systems/notes/3a - Hardware primitives & Lamport Bakery algorithm.md",
-    "Concurrent Systems/notes/9 - Consensus.md",
-    "Concurrent Systems/notes/6 - Atomicity.md",
-    "Concurrent Systems/notes/5 - Software Transactional Memory.md",
     "Concurrent Systems/notes/10 - Implementing Consensus.md",
     "HCIW/slides/Tangible User Interfaces.pdf",
     "Concurrent Systems/notes/images/Pasted image 20250401083747.png",
     "Concurrent Systems/notes/images/Pasted image 20250401092557.png",
     "Concurrent Systems/notes/3b - Aravind's algorithm and improvements.md",
-    "Concurrent Systems/notes/4c - Dining Philosophers.md",
     "Concurrent Systems/notes/1b - Peterson algorithm.md",
     "Concurrent Systems/notes/2 - Fast mutex by Lamport.md",
-    "Concurrent Systems/notes/7- MUTEX-free concurrency.md",
-    "Concurrent Systems/slides/class 10.pdf",
     "Concurrent Systems/notes/2b - Round Robin algorithm.md",
     "Concurrent Systems/notes/6a - Alternatives to Atomicity.md",
     "Concurrent Systems/notes/8 - Enhancing Liveness Properties.md",
-    "Concurrent Systems/slides/class 9.pdf",
     "Concurrent Systems/slides/class 6.pdf",
     "Concurrent Systems/slides/class 5.pdf",
     "Concurrent Systems/notes/images/Pasted image 20250325090735.png",
@@ -252,7 +251,6 @@
     "HCIW/exercises/Exercise.md",
     "Foundation of data science/notes/1 CV Basics.md",
     "Foundation of data science/notes/7 Autoencoders.md",
-    "Foundation of data science/notes/6 PCA.md",
     "Senza nome.canvas"
   ]
 }
\ No newline at end of file
diff --git a/Concurrent Systems/test/Untitled.md b/Concurrent Systems/test/Untitled.md
index 8a0bf5c..d28100e 100644
--- a/Concurrent Systems/test/Untitled.md	
+++ b/Concurrent Systems/test/Untitled.md	
@@ -1,3 +1,26 @@
 ```
-barrier() :=
+GLOB_MUTEX and R_MUTEX semaphores init. at 1
+R a shared register init. at 0
+
+begin_read() :=
+	R_MUTEX.down()
+	R++ # currently active readers
+	if R = 1 then GLOB_MUTEX.down()
+	R_MUTEX.up()
+	return
+
+end_read() :=
+	R_MUTEX.down()
+	R--
+	if R = 0 then GLOB_MUTEX.up()
+	R_MUTEX.up()
+	return
+
+begin_write() :=
+	GLOB_MUTEX.down()
+	return
+
+end_write() :=
+	GLOB_MUTEX.up()
+	return
 ```
\ No newline at end of file