auxten / parser

A simple parser that turns a formulae written in unicode into an ExprGraph

About

The goal of this project is to parse a mathematical formulae written in unicode and to transpile is into an ExprGraph of the Gorgonia project.

Principle

This parser is generated from a yacc file from the subdirectory src. If you want to contribute or add some new functionalities, you may need the goyacc tool and then run go generate from the src dubdirectory. For a more complete explanation, you can refer to this blog post

Available operations

As of today, the parser understands the following opreations on node objects (tensor based):

Operation	Gorgonia Operation	Symbol	Unicode character
Multiplication	Mul	·	U+00B7
Hadamard Product	HadamardProd	*
Addition	Add	+
Substraction	Sub	-
Pointwise Negation	Neg	-
Sigmoid	Sigmoid	σ	U+03C3
Tanh	Tanh	tanh
Softmax	Softmax	softmax

Example

import (
	G "gorgonia.org/gorgonia"
	"github.com/gorgonia/parser"
	"gorgonia.org/tensor"
)

func main(){
	g := G.NewGraph()
	wfT := tensor.New(tensor.WithShape(2, 2), tensor.WithBacking([]float32{1, 1, 1, 1}))
	wf := G.NewMatrix(g, tensor.Float32, G.WithName("wf"), G.WithShape(2, 2), G.WithValue(wfT))
	htprevT := tensor.New(tensor.WithBacking([]float32{1, 1}), tensor.WithShape(2))
	htprev := G.NewVector(g, tensor.Float32, G.WithName("ht-1"), G.WithShape(2), G.WithValue(htprevT))
	xtT := tensor.New(tensor.WithBacking([]float32{1, 1}), tensor.WithShape(2))
	xt := G.NewVector(g, tensor.Float32, G.WithName("xt"), G.WithShape(2), G.WithValue(xtT))
	bfT := tensor.New(tensor.WithBacking([]float32{1, 1}), tensor.WithShape(2))
	bf := G.NewVector(g, tensor.Float32, G.WithName("bf"), G.WithShape(2), G.WithValue(bfT))

	p := parser.NewParser(g)
	p.Set(`Wf`, wf)
	p.Set(`h`, htprev)
	p.Set(`x`, xt)
	p.Set(`bf`, bf)
        result, _ := p.Parse(`σ(1*Wf·h+ Wf·x+ bf)`)
        machine := G.NewLispMachine(g, G.ExecuteFwdOnly())
        if err := machine.RunAll(); err != nil {
              t.Fatal(err)
        }
        res := result.Value().Data().([]float32)
}

Caution

• The parser is internally using a map and is not concurrent safe.
• The errors are not handle correctly