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Fix links and formatting in langref (apache#2440)
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slyubomirsky authored and tqchen committed Jan 16, 2019
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2 changes: 2 additions & 0 deletions docs/dev/relay_add_op.rst
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.. _relay-add-op:

Adding an Operator to Relay
===========================

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2 changes: 2 additions & 0 deletions docs/dev/relay_intro.rst
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.. _relay-dev-intro:

Introduction to Relay IR
========================
This article introduces Relay IR -- the second generation of NNVM.
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42 changes: 17 additions & 25 deletions docs/langref/relay_expr.rst
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Expand Up @@ -16,6 +16,7 @@ be viewed as a traditional comptuation graph when writing and expressing transfo
The dataflow fragment covers the set of Relay expressions that do not involve
control flow. That is, any portion of a program containing only the following
constructs corresponds to a pure computation graph:

- `Variables`_
- Tuple `Construction`_ and `Projection`_
- `Let Bindings`_
Expand All @@ -25,6 +26,7 @@ constructs corresponds to a pure computation graph:
Control flow expressions allow the graph topology to change
based on the value of previously executed expressions. The control
fragment in Relay includes the following constructs:

- `If-Then-Else`_ Expressions
- Recursive Calls in Functions

Expand All @@ -50,11 +52,9 @@ Global Variable

Global identifiers are prefixed by the :code:`@` sigil, such as ":code:`@global`".
A global identifier always references a globally visible definition contained in the
globally visible environment, known as the `module`__.
globally visible environment, known as the `module <Module and Global Functions_>`__.
Global identifiers must be unique.

__ `Module and Global Functions`_

See :py:class:`~tvm.relay.expr.GlobalVar` for its implementation
and documentation.

Expand Down Expand Up @@ -187,7 +187,7 @@ a tensor of zero values because the closure for :code:`%f` stores the value of
Polymorphism and Type Relations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. *Note: type parameter syntax is not yet supported in the text format.*
*Note: type parameter syntax is not yet supported in the text format.*

A function may also be given a set of type parameters, which can be
substituted for specific types at call sites. Functions with
Expand All @@ -199,9 +199,7 @@ Type parameters are classified by *kind* and can
only appear in parts of the type signature where their kind is appropriate
(e.g., type parameters of kind :code:`Shape` can only appear where a shape
would be expected in a tensor type); for a full discussion,
see `the documentation on type parameters`__.

__ `Type Parameter`_
see :ref:`the documentation on type parameters <type-parameter>`.

For example, one can define a polymorphic identity function for
any Relay type as follows:
Expand All @@ -221,7 +219,7 @@ arguments to tensor types:
Notice that the return type is omitted and will be inferred.

.. *Note: :code:`where` syntax is not yet supported in the text format.*
*Note: :code:`where` syntax is not yet supported in the text format.*

A function may also be subject to one or more type relations, such as in
the following:
Expand All @@ -241,7 +239,7 @@ constraints on types (especially tensor shapes).
All function relations must hold at all call sites;
type checking is thus treated as a constraint-solving problem.
For more detail on type relations and their implementations,
please see the documentation on `Relay's Type System`_.
please see :ref:`their section in the documentation on Relay's type system <type-relation>`.

Operators
=========
Expand All @@ -260,14 +258,12 @@ by optimization passes) may be registered as a new column.
From the perspective of Relay's type system, an operator is a function,
so operators may be called like any other function and have function
types. In particular, operator types are registered using a single
type relation (see `the documentation on type relations`__), typically a relation
type relation (see :ref:`the documentation on type relations <type-relation>`), typically a relation
specialized to that operator. For example, the :code:`add` operator
is registered with the :code:`Broadcast` relation, indicating that the
arguments of :code:`add` must be tensors and that the return type
is a tensor whose shape depends on those of its arguments.

__ `Type Relation`_

Operators are rendered without a sigil (e.g :code:`conv2d`, :code:`flatten`)
when pretty-printing Relay programs.
Operators are explicitly contained in the program and are uniquely
Expand All @@ -281,11 +277,9 @@ See :py:class:`~tvm.relay.op.Op` for the definition and documentation
of operator nodes, demonstrating the infrastructure for registering
operator metadata. The other files in :py:class:`~tvm.relay.op` give
handles for generating a call to various pre-registered operators.
The `tutorial on adding operators to Relay`__ shows how to add further
The :ref:`tutorial on adding operators to Relay <relay-add-op>` shows how to add further
operators into the language.

__ `Adding an Operator to Relay`_

Call
====

Expand All @@ -312,7 +306,7 @@ Thus, in the above example, the call evaluates to 22.
In the case of operators, the implementation is opaque to Relay,
so the result is left up to the registered TVM implementation.

.. *Note: type parameters are not yet supported in the text format.*
*Note: type parameters are not yet supported in the text format.*

A type-polymorphic function can also include type arguments at a call
site. The type arguments are substituted for type parameters when
Expand Down Expand Up @@ -489,12 +483,10 @@ These bindings allow for a style of programming that corresponds to that already
employed by NNVM and other dataflow graph-based input formats. The fact that the variables
are not scoped offers some flexibility in evaluation order compared to :code:`let`
bindings, though this can also introduce some ambiguity in programs (the
`developer introduction to the Relay IR`__ includes more detailed discussion
:ref:`developer introduction to the Relay IR<relay-dev-intro>` includes more detailed discussion
of this nuance).

__ `Introduction to Relay IR`_

.. *Note: Graph bindings are not currently parsed by the text format.*
*Note: Graph bindings are not currently parsed by the text format.*

In Relay's text format, a graph binding can be written as below (note the lack of a
:code:`let` keyword and a semicolon):
Expand All @@ -521,7 +513,7 @@ For development purposes and to enable certain optimizations, Relay includes pas
convert between dataflow graphs defined using graph bindings and programs with :code:`let`
bindings in A-normal form, employed by many compiler optimizations from the functional
programming community (see `"A-Normalization: Why and How" by
Matt Might<http://matt.might.net/articles/a-normalization/>`__ for an introduction
Matt Might <http://matt.might.net/articles/a-normalization/>`__ for an introduction
to A-normal form).

If-Then-Else
Expand Down Expand Up @@ -555,11 +547,11 @@ Program transformations (passes) in Relay may require inserting temporary
state into the program AST to guide further transformations. The
:code:`TempExpr` node is provided as a utility to developers for this purpose;
nodes inheriting from :code:`TempExpr` cannot appear directly in user-provided
code but may be inserted in a pass. Any :code:`TempExpr`s created in a pass
should ideally be eliminated before the pass is complete, as
:code:`TempExpr`s only store internal state and have no semantics of their own.
code but may be inserted in a pass. Any :code:`TempExpr` created in a pass
should ideally be eliminated before the pass is complete, as a
:code:`TempExpr` only stores internal state and has no semantics of its own.

For an example of :code:`TempExpr`s being used in a pass,
For an example of :code:`TempExpr` being used in a pass,
see :code:`src/relay/pass/alter_op_layout.cc`, which uses :code:`TempExpr` nodes
to store information about operator layouts as the pass tries to rearrange operator
calls.
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17 changes: 10 additions & 7 deletions docs/langref/relay_type.rst
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Expand Up @@ -81,8 +81,8 @@ Because a tuple type is of statically known size, the type of a tuple projection
is simply the corresponding index into the tuple type.

For example, in the below code, :code:`%t` is of type
`(Tensor[(), bool], Tensor[(10, 10), float32])`
and :code:`%c` is of type `Tensor[(10, 10), float32]`.
:code:`(Tensor[(), bool], Tensor[(10, 10), float32])`
and :code:`%c` is of type :code:`Tensor[(10, 10), float32]`.

.. code-block:: python
let %t = (False, Constant(1, (10, 10), float32));
Expand All @@ -91,6 +91,8 @@ and :code:`%c` is of type `Tensor[(10, 10), float32]`.
See :py:class:`~tvm.relay.ty.TupleType` for its definition and documentation.

.. _type-parameter:

Type Parameter
~~~~~~~~~~~~~~

Expand Down Expand Up @@ -153,6 +155,8 @@ type as arguments, but may take a subset instead.

See :py:class:`~tvm.relay.ty.FuncType` for its definition and documentation.

.. _type-relation:

Type Relation
~~~~~~~~~~~~~

Expand Down Expand Up @@ -193,8 +197,8 @@ to type operators like :code:`add`:
where Broadcast
The inclusion of :code:`Broadcast` above indicates that the argument
types and the return type must be tensors where the shape of `t3` is
the broadcast of the shapes of `t1` and `t2`. The type system will
types and the return type must be tensors where the shape of :code:`t3` is
the broadcast of the shapes of :code:`t1` and :code:`t2`. The type system will
accept any argument types and return type so long as they fulfill
:code:`Broadcast`.

Expand All @@ -213,11 +217,10 @@ until one of the following conditions holds:

1. All relations hold and no incomplete types remain (typechecking succeeds).
2. A relation fails to hold (a type error).
3. A fixpoint is reached where shape variables or incomplete types
remain (either a type error or more type annotations may be needed).
3. A fixpoint is reached where shape variables or incomplete types remain (either a type error or more type annotations may be needed).

Presently all of the relations used in Relay are implemented in C++.
See the files in `src/relay/op` for examples of relations implemented
See the files in :code:`src/relay/op` for examples of relations implemented
in C++.

See :py:class:`~tvm.relay.ty.TypeRelation` for its definition and documentation.
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