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+# MULTI-core/processor/computer
+
+SMC/SMP/cluster/Grid/Cloud...
+
+multi: shared memory, multi-CPU
+
+UMA-NUMA
+
+multiple spinlock, bus
+
+- Avoid cache thrashing!
+- Time sharing, the  art of scheduling
+
+"Gang scheduling" : A gang of related threads are scheduled as a unit, a "gang"
+
+"Computational Graph": ->"A platform for ML"
+
+"Distributed Shared Memory":  Like page table, with indices
+
+## Graph computing
+
+relations between Nodes, allocation of resources,...
+
+GraphChi
+
+Speed up executing, space less, locality is good.
+
+And we have algorithms.
+
+Object-based middleware "**CORBA**"
+
+Based on CORBA. Distributed systems.
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+# Process & Thread
+
+## Sync
+
+### Lock, Mutex and Semaphore
+
+Race condition
+
+Semaphore by Dijkstra
+
+- need a counter
+- a waiting queue (either kernel or user)
+- maybe two locks (mutex and a flag/slot)
+- order (as a stack)
+
+Mutex
+```c
+pthread_mutex_lock(&mutex);
+pthread_cond_wait(&cond, &mutex);
+```
+
+The second line is to avoid sleep with a mutex locked and to make it possible for the consumer to wake it.
+
+### Monitor
+
+To design a sync function in language level.
+
+Avoid the problem caused by a breaking change in architecture
+
+### Memory Barrier
+
+To make sure the consistency
+
+- Before this statement, no matter what the order is (for multi-thread), nothing happened.
+- After this statement, ...
+- But the statements after this statement cannot be executed before the memory barrier. And vice versa.
+
+### Thread Scheduling
+
+For a scheduler, it should determine who is next.
+
+Algorithm:
+- RR
+- O(1): In O(1) time complexity
+- Staircase Down
+- RSDL
+- CFS
+- Brain Fuck
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+# Dead Lock
+
+## Conditions
+
+1. Mutual exclusion
+1. Hold and wait
+1. No preemption
+1. Circular wait condition
+
+## Solution
+
+- Don't care!
+- Detection and recovery. Let deadlocks occur, detect them, and then take action.
+- Dynamic avoidance by careful resource allocation.
+- Prevention, by structurally negating one of the four required conditions.
+
+### Detection
+
+Banker's algorithm
+
+### Avoiding
+
+- Resource Trajectories
+- In numeric order