// Package nn provides neural network layer operations
package nn

import (
	"math"

	"makarna/pkg/backend/cpu"
)

// RMSNorm normalizes input in-place using RMS normalization
// x: [batch, dim], w: [dim]
func RMSNorm(x, w *cpu.Tensor, eps float32) error {
	xData := x.DataFloat32()
	wData := w.DataFloat32()

	dim := w.Shape().NumElements()
	numRows := x.Shape().NumElements() / dim

	for i := 0; i < numRows; i++ {
		row := xData[i*dim : (i+1)*dim]

		// Sum of squares (uses SIMD dot when available)
		ss := cpu.DotFloat32(row, row) / float32(dim)

		// Normalize and scale
		invRMS := 1.0 / float32(math.Sqrt(float64(ss+eps)))
		for j := 0; j < dim; j++ {
			row[j] = row[j] * invRMS * wData[j]
		}
	}
	return nil
}