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 // Copyright ©2019 The Gonum Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package f32 import "gonum.org/v1/gonum/internal/math32" // L2NormUnitary is the level 2 norm of x. func L2NormUnitary(x []float32) (sum float32) { var scale float32 var sumSquares float32 = 1 for _, v := range x { if v == 0 { continue } absxi := math32.Abs(v) if math32.IsNaN(absxi) { return math32.NaN() } if scale < absxi { s := scale / absxi sumSquares = 1 + sumSquares*s*s scale = absxi } else { s := absxi / scale sumSquares += s * s } } if math32.IsInf(scale, 1) { return math32.Inf(1) } return scale * math32.Sqrt(sumSquares) } // L2NormInc is the level 2 norm of x. func L2NormInc(x []float32, n, incX uintptr) (sum float32) { var scale float32 var sumSquares float32 = 1 for ix := uintptr(0); ix < n*incX; ix += incX { val := x[ix] if val == 0 { continue } absxi := math32.Abs(val) if math32.IsNaN(absxi) { return math32.NaN() } if scale < absxi { s := scale / absxi sumSquares = 1 + sumSquares*s*s scale = absxi } else { s := absxi / scale sumSquares += s * s } } if math32.IsInf(scale, 1) { return math32.Inf(1) } return scale * math32.Sqrt(sumSquares) } // L2DistanceUnitary is the L2 norm of x-y. func L2DistanceUnitary(x, y []float32) (sum float32) { var scale float32 var sumSquares float32 = 1 for i, v := range x { v -= y[i] if v == 0 { continue } absxi := math32.Abs(v) if math32.IsNaN(absxi) { return math32.NaN() } if scale < absxi { s := scale / absxi sumSquares = 1 + sumSquares*s*s scale = absxi } else { s := absxi / scale sumSquares += s * s } } if math32.IsInf(scale, 1) { return math32.Inf(1) } return scale * math32.Sqrt(sumSquares) }