W3D2,W7D2 and W11D2:Bao Chenhao

W11D2/W11D2_BaoChenhao_note.md

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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.

W3D2/W3D2_BaoChenhao_note.md

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+### Process & Thread
+
+#### synchronize
+
+- lock, mutex, semaphore
+  - mutex means: mutual exclusion.
+  - method 1: lock variable. if lock=0, lock=1 and run; if lock =1,wait til lock=0and then run.
+  - method 2: **Peterson.** Always try to let others run. Run when all else quit the competition.
+
+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 solve the problem at language level. There will be only one procedure running at a time.
+
+### process scheduling
+
+#### Memory consistency
+
+**memory barriers:** to protect the code sequences, which might be edit by compiler, tomasulo,  etc..
+
+#### scheduling
+
+- Q: who's next?!
+  - according to priority.
+- Avoiding locks
+  - Read-copy-update

W7D2/W7D2_BaoChenhao_note.md

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+# Dead Lock
+
+## Conditions
+
+- 1. Mutual exclusion
+- 2. Hold and wait
+- 3. No preemption
+- 4. 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