From f8a209c2dee0ce16dbf12857ae88556c9917e458 Mon Sep 17 00:00:00 2001 From: Yu Yang Date: Thu, 22 Jun 2017 17:48:19 +0800 Subject: [PATCH] Rearrange description. --- doc/design/scope.md | 31 ++++++++++++++----------------- 1 file changed, 14 insertions(+), 17 deletions(-) diff --git a/doc/design/scope.md b/doc/design/scope.md index 23893308b2a..1740019f3d5 100644 --- a/doc/design/scope.md +++ b/doc/design/scope.md @@ -10,33 +10,30 @@ Scope is an important concept in programming languages, which defines a program A detailed explanation of these two attributes goes as following. -## Scope is a Container of Variables. +## Scope is an association of a name to variable. -Scope is used to provide a running environment for Net. +Scope is an association of a name to variable. All variables belong to `Scope`. You need to specify a scope to run a Net, i.e., `net.Run(&scope)`. One net can run in different scopes and update different variable in the scope. -1. Scope mainly has Variables as it's data member. - Scope is a running environment for Net. Net should get all it need to do computation from a scope, such as data buffer, state(momentum) etc. - All these data/state can be abstracted and create as variable in Paddle, so the only thing Scope need to care about is Variable. -1. Variable can only be created by Scope. -1. Variable can only be got from Scope. -1. Scope contains methods that are used to manage Variables, such as Create/Get. +1. Scope only contains a map of a name to variable. - Because we only need to care about Variable, we only need method to manage the lifecycle of Variable. + All parameters, data, states in a Net should be variables and stored inside a scope. Each op should get inputs and outputs to do computation from a scope, such as data buffer, state(momentum) etc. + +1. Variable can only be created by Scope and a variable can only be got from Scope. User cannot create or get a variable outside a scope. This is a constraints of our framework, and will keep our framework simple and clear. + +1. Scope only contains methods that are used to Create and Get Variables. Scope do not contain Operators and have no information to run them. + + `Net` is designed to drive the computation and Scope only contains a map of variables. There is no computation logic inside a `Scope`. Scope just handles the lifetime management of variables. - `Create` is used to create a Variable by its name and add the mapping relation. - `Get` is used to find a Variable by name. 1. Every variable only belongs to one certain Scope. - Variable can not be shared between scopes, if we want to use variables from different scope we can use `Parent scope`. - -1. Scope should destruct all Variables within it when itself is destructed. - - Because Variable can only be got from Scope, when destroying Scope, we also need to destroy all the Vars in it. + Variable can not belong to many scopes. If you want to use variables from parent scope, you can use `parent scope`. -1. Scope do not contain Operators and have no information to run them. +1. Scope should destruct all Variables inside it when itself is destructed. User can never store `Variable` pointer somewhere else. - Net is designed to drive the computation, Scope is only used to provide a running environment. + Because Variable can only be got from Scope. When destroying Scope, we also need to destroy all the Variables in it. If user store `Variable` pointer to private data member or some global variable, the pointer will be a invalid pointer when associated `Scope` is destroyed. ```cpp class Scope { @@ -45,7 +42,7 @@ class Scope { const Variable* GetVariable(const std::string& name) const; private: - std::unordered_map> vars_; + std::unordered_map> vars_; }; ``` -- GitLab