layered.go

package neural

import (
	"fmt"
	"github.com/antongulenko/golearn/base"
	"github.com/antongulenko/golearn/filters"
	"gonum.org/v1/gonum/mat"
	"math"
	"math/rand"
)

// MultiLayerNet creates a new Network which is conceptually
// organised into layers, zero or more of which are hidden.
//
// Within each layer, no neurons are connected.
//
// No neurons in a given layer are connected with any neurons
// in a previous layer.
//
// Neurons can only be connected to neurons in the layer above.
type MultiLayerNet struct {
	network         *Network
	attrs           map[base.Attribute]int
	layers          []int
	classAttrOffset int
	classAttrCount  int
	Convergence     float64
	MaxIterations   int
	LearningRate    float64
}

// NewMultiLayerNet returns an underlying
// Network conceptuallyorganised into layers
//
// Layers variable = slice of integers representing
// node count at each layer.
func NewMultiLayerNet(layers []int) *MultiLayerNet {
	return &MultiLayerNet{
		nil,
		make(map[base.Attribute]int),
		layers,
		0,
		0,
		0.001,
		500,
		0.90,
	}
}

// String returns a human-readable summary of this network.
func (m *MultiLayerNet) String() string {
	return fmt.Sprintf("MultiLayerNet(%v, %v, %f, %f, %d", m.layers, m.network, m.Convergence, m.LearningRate, m.MaxIterations)
}

func (m *MultiLayerNet) convertToFloatInsts(X base.FixedDataGrid) base.FixedDataGrid {

	// Make sure everything's a FloatAttribute
	fFilt := filters.NewFloatConvertFilter()
	for _, a := range X.AllAttributes() {
		fFilt.AddAttribute(a)
	}
	fFilt.Train()
	insts := base.NewLazilyFilteredInstances(X, fFilt)
	return insts
}

// Predict uses the underlying network to produce predictions for the
// class variables of X.
//
// Can only predict one CategoricalAttribute at a time, or up to n
// FloatAttributes. Set or unset ClassAttributes to work around this
// limitation.
func (m *MultiLayerNet) Predict(X base.FixedDataGrid) base.FixedDataGrid {

	// Create the return vector
	ret := base.GeneratePredictionVector(X)

	// Make sure everything's a FloatAttribute
	insts := m.convertToFloatInsts(X)

	// Get the input/output Attributes
	inputAttrs := base.NonClassAttributes(insts)
	outputAttrs := ret.AllClassAttributes()

	// Compute layers
	layers := 2 + len(m.layers)

	// Check that we're operating in a singular mode
	floatMode := 0
	categoricalMode := 0
	for _, a := range outputAttrs {
		if _, ok := a.(*base.CategoricalAttribute); ok {
			categoricalMode++
		} else if _, ok := a.(*base.FloatAttribute); ok {
			floatMode++
		} else {
			panic("Unsupported output Attribute type!")
		}
	}

	if floatMode > 0 && categoricalMode > 0 {
		panic("Can't predict a mix of float and categorical Attributes")
	} else if categoricalMode > 1 {
		panic("Can't predict more than one categorical class Attribute")
	}

	// Create the activation vector
	a := mat.NewDense(m.network.size, 1, make([]float64, m.network.size))

	// Resolve the input AttributeSpecs
	inputAs := base.ResolveAttributes(insts, inputAttrs)

	// Resolve the output Attributespecs
	outputAs := base.ResolveAttributes(ret, outputAttrs)

	// Map over each input row
	insts.MapOverRows(inputAs, func(row [][]byte, rc int) (bool, error) {
		// Clear the activation vector
		for i := 0; i < m.network.size; i++ {
			a.Set(i, 0, 0.0)
		}
		// Build the activation vector
		for i, vb := range row {
			if cIndex, ok := m.attrs[inputAs[i].GetAttribute()]; !ok {
				panic("Can't resolve the Attribute!")
			} else {
				a.Set(cIndex, 0, base.UnpackBytesToFloat(vb))
			}
		}
		// Robots, activate!
		m.network.Activate(a, layers)

		// Decide which class to set
		if floatMode > 0 {
			for _, as := range outputAs {
				cIndex := m.attrs[as.GetAttribute()]
				ret.Set(as, rc, base.PackFloatToBytes(a.At(cIndex, 0)))
			}
		} else {
			maxIndex := 0
			maxVal := 0.0
			for i := m.classAttrOffset; i < m.classAttrOffset+m.classAttrCount; i++ {
				val := a.At(i, 0)
				if val > maxVal {
					maxIndex = i
					maxVal = val
				}
			}
			maxIndex -= m.classAttrOffset
			ret.Set(outputAs[0], rc, base.PackU64ToBytes(uint64(maxIndex)))
		}
		return true, nil
	})

	return ret

}

// Fit trains the neural network on the given fixed datagrid.
//
// Training stops when the mean-squared error acheived is less
// than the Convergence value, or when back-propagation has occured
// more times than the value set by MaxIterations.
func (m *MultiLayerNet) Fit(X base.FixedDataGrid) {

	// Make sure everything's a FloatAttribute
	insts := m.convertToFloatInsts(X)

	// The size of the first layer is the number of things
	// in the revised instances which aren't class Attributes
	inputAttrsVec := base.NonClassAttributes(insts)

	// The size of the output layer is the number of things
	// in the revised instances which are class Attributes
	classAttrsVec := insts.AllClassAttributes()

	// The total number of layers is input layer + output layer
	// plus number of layers specified
	totalLayers := 2 + len(m.layers)

	// The size is then augmented by the number of nodes
	// in the centre
	size := len(inputAttrsVec)
	size += len(classAttrsVec)
	hiddenSize := 0
	for _, a := range m.layers {
		size += a
		hiddenSize += a
	}

	// Enumerate the Attributes
	trainingAttrs := make(map[base.Attribute]int)
	classAttrs := make(map[base.Attribute]int)
	attrCounter := 0
	for i, a := range inputAttrsVec {
		attrCounter = i
		m.attrs[a] = attrCounter
		trainingAttrs[a] = attrCounter
	}
	m.classAttrOffset = attrCounter + 1
	for _, a := range classAttrsVec {
		attrCounter++
		m.attrs[a] = attrCounter + hiddenSize
		classAttrs[a] = attrCounter + hiddenSize
		m.classAttrCount++
	}

	// Create the underlying Network
	m.network = NewNetwork(size, len(inputAttrsVec), Sigmoid)

	// Initialise inter-hidden layer weights and biases to small random values
	layerOffset := len(inputAttrsVec)
	for i := 0; i < len(m.layers)-1; i++ {
		// Get the size of this layer
		thisLayerSize := m.layers[i]
		// Next layer size
		nextLayerSize := m.layers[i+1]
		// For every node in this layer
		for j := 1; j <= thisLayerSize; j++ {
			// Compute the offset
			nodeOffset1 := layerOffset + j
			// For every node in the next layer
			for k := 1; k <= nextLayerSize; k++ {
				// Compute offset
				nodeOffset2 := layerOffset + thisLayerSize + k
				// Set weight randomly
				m.network.SetWeight(nodeOffset1, nodeOffset2, rand.NormFloat64()*0.1)
			}
		}
		layerOffset += thisLayerSize
	}

	// Initialise biases with each hidden layer
	layerOffset = len(inputAttrsVec)
	for _, l := range m.layers {
		for j := 1; j <= l; j++ {
			nodeOffset := layerOffset + j
			m.network.SetBias(nodeOffset, rand.NormFloat64()*0.1)
		}
		layerOffset += l
	}

	// Initialise biases for output layer
	for i := 0; i < len(classAttrsVec); i++ {
		nodeOffset := layerOffset + i
		m.network.SetBias(nodeOffset, rand.NormFloat64()*0.1)
	}

	// Connect final hidden layer with the output layer
	layerOffset = len(inputAttrsVec)
	for i, l := range m.layers {
		if i == len(m.layers)-1 {
			for j := 1; j <= l; j++ {
				nodeOffset1 := layerOffset + j
				for k := 1; k <= len(classAttrsVec); k++ {
					nodeOffset2 := layerOffset + l + k
					m.network.SetWeight(nodeOffset1, nodeOffset2, rand.NormFloat64()*0.1)
				}
			}
		}
		layerOffset += l
	}

	// Connect input layer with first hidden layer (or output layer
	for i := 1; i <= len(inputAttrsVec); i++ {
		nextLayerLen := 0
		if len(m.layers) > 0 {
			nextLayerLen = m.layers[0]
		} else {
			nextLayerLen = len(classAttrsVec)
		}
		for j := 1; j <= nextLayerLen; j++ {
			nodeOffset := len(inputAttrsVec) + j
			v := rand.NormFloat64() * 0.1
			m.network.SetWeight(i, nodeOffset, v)
		}
	}

	// Create the training activation vector
	trainVec := mat.NewDense(size, 1, make([]float64, size))
	// Create the error vector
	errVec := mat.NewDense(size, 1, make([]float64, size))

	// Resolve training AttributeSpecs
	trainAs := base.ResolveAllAttributes(insts)

	// Feed-forward, compute error and update for each training example
	// until convergence (what's that)
	for iteration := 0; iteration < m.MaxIterations; iteration++ {
		totalError := 0.0
		maxRow := 0
		insts.MapOverRows(trainAs, func(row [][]byte, i int) (bool, error) {

			maxRow = i
			// Clear vectors
			for i := 0; i < size; i++ {
				trainVec.Set(i, 0, 0.0)
				errVec.Set(i, 0, 0.0)
			}

			// Build vectors
			for i, vb := range row {
				v := base.UnpackBytesToFloat(vb)
				if attrIndex, ok := trainingAttrs[trainAs[i].GetAttribute()]; ok {
					// Add to Activation vector
					trainVec.Set(attrIndex, 0, v)
				} else if attrIndex, ok := classAttrs[trainAs[i].GetAttribute()]; ok {
					// Set to error vector
					errVec.Set(attrIndex, 0, v)
				} else {
					panic("Should be able to find this Attribute!")
				}
			}

			// Activate the network
			m.network.Activate(trainVec, totalLayers-1)

			// Compute the error
			for a := range classAttrs {
				cIndex := classAttrs[a]
				errVec.Set(cIndex, 0, errVec.At(cIndex, 0)-trainVec.At(cIndex, 0))
			}

			// Update total error
			totalError += math.Abs(mat.Sum(errVec))

			// Back-propagate the error
			b := m.network.Error(trainVec, errVec, totalLayers)

			// Update the weights
			m.network.UpdateWeights(trainVec, b, m.LearningRate)

			// Update the biases
			m.network.UpdateBias(b, m.LearningRate)

			return true, nil
		})

		totalError /= float64(maxRow)
		// If we've converged, no need to carry on
		if totalError < m.Convergence {
			break
		}
	}
}