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[NFC] fix typo applications/ and colossalai/ (#3735)
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@@ -16,8 +16,8 @@ A *symbolic profiler* for collecting computing and memory overhead related to st
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### Solver
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**Solver** is designed to find the optimal execution plan for a given computation graph and cluster in two stages:
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1) *Intra-op parallelism stage* is to find the plan with the minimum total execution time of all nodes with respect to the constraint of the memory budget. The optimaztion goal of intra-op parallelism solver is modified from <a href="https://arxiv.org/abs/2201.12023"> Alpa </a>'s intra-op parallelsim ILP solver.
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2) *Activation checkpoint stage* is to search for the fastest execution plan that meets the memory budget on the computation graph after inserting the communication nodes by the intra-op parallelism stage. The algorithm to find optimial activation checkpoint is modified from <a href="https://hal.inria.fr/hal-02352969"> Rotor </a>. The reason we use two-stage optimization is that if the two tasks are formulated together, the solving time will be significantly increased, which will greatly affect the user experience of the system. On the contrary, solving in two hierarchical levels has many advantages. Firstly, compared with the computation graph with activation checkpointing, the original graph has fewer nodes, which can reduce the solving cost of intra-op parallelism solver. In addition, a more optimal solution can be found by adding the communication overhead into the activation checkpoint modeling.
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1) *Intra-op parallelism stage* is to find the plan with the minimum total execution time of all nodes with respect to the constraint of the memory budget. The optimization goal of intra-op parallelism solver is modified from <a href="https://arxiv.org/abs/2201.12023"> Alpa </a>'s intra-op parallelism ILP solver.
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2) *Activation checkpoint stage* is to search for the fastest execution plan that meets the memory budget on the computation graph after inserting the communication nodes by the intra-op parallelism stage. The algorithm to find optimal activation checkpoint is modified from <a href="https://hal.inria.fr/hal-02352969"> Rotor </a>. The reason we use two-stage optimization is that if the two tasks are formulated together, the solving time will be significantly increased, which will greatly affect the user experience of the system. On the contrary, solving in two hierarchical levels has many advantages. Firstly, compared with the computation graph with activation checkpointing, the original graph has fewer nodes, which can reduce the solving cost of intra-op parallelism solver. In addition, a more optimal solution can be found by adding the communication overhead into the activation checkpoint modeling.
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### Generator
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**Generator** applies the searched execution plan to the computation graph and recompiles the computation graph to optimized PyTorch code. It has *a series compile pass* to insert a communication node or do the kernel substitution as the intra-op parallelism solver required. Additionally, we implement a *code generation* feature to recognize the annotation from the activation checkpoint solver and inject the activation checkpoint block following annotation instructions.
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