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docs/diary/2023-11-30-parallel-inet.md

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+---
+title: Parallel iNet
+date: 2023-11-30
+---
+
+# Problem
+
+To implement parallel interaction nets,
+we need to let many threads share the same memory.
+
+To allocate memory of cells of the same size,
+we can use an array, and a stack of unused indexes
+(let's call this free-stack).
+
+But the stack will still be the part where multi-thread is not safe
+right? If any part of the implementation is not lock-free, the fine
+grain parallel advantage of inet might be lost.
+
+# Solution A
+
+Maybe i can just use 8 "free-stacks" for 8 threads.
+
+When a used index is to be freed, i can see which thread is having the
+least free indexes, and give the new freed index to it.
+
+And a "free-stack" can be viewed as a ring, i give back to the front
+instead of the end, thus lock-free.
+
+The query about "the least free indexes" is just heuristic, thus also
+lock-free.
+
+# Datatypes
+
+I need to allocate the following kinds of datatypes:
+
+```
+Node {
+  definition: NodeDefinition
+  ports: List<Port>
+}
+
+Port {
+  node: Node
+  halfEdge?: HalfEdge
+}
+
+HalfEdge {
+  otherHalfEdge: HalfEdge
+  port?: Port
+}
+```