error while trying to fit the Gaussian Process Regressor

[AlishSem]

Hello!
I am really new to this topic and golang in general, so sorry if this is too obvious

But i ran into the problem

I am trying to run the simple GP with the help of YouTube and ChatGPT, but my below code fails

package main

import (
	"fmt"
	"github.com/pa-m/sklearn/gaussian_process"
	"github.com/pa-m/sklearn/gaussian_process/kernels"
	"gonum.org/v1/gonum/mat"
	"log"
	"math/rand"
)

func main() {
	// Generate some sample data
	X := mat.NewDense(10, 1, nil)
	y := make([]float64, 10)
	for i := 0; i < 10; i++ {
		X.Set(i, 0, float64(i))
		y[i] = float64(i*i) + rand.NormFloat64() // Adding some noise
	}

	yMat := mat.NewDense(len(y), 1, y)

	// Print the training data for debugging
	fmt.Println("Training data X:")
	matPrint(X)
	fmt.Println("Training data y:")
	fmt.Println(yMat)

	// Define the kernel: ConstantKernel * RBF
	constantKernel := &kernels.ConstantKernel{ConstantValue: 1.0, ConstantValueBounds: [2]float64{1e-5, 1e5}}
	rbfKernel := &kernels.RBF{LengthScale: []float64{1.5}, LengthScaleBounds: [][2]float64{{1e-5, 1e5}}}
	productKernel := &kernels.Product{
		KernelOperator: kernels.KernelOperator{
			K1: constantKernel,
			K2: rbfKernel,
		},
	}
	// Create the Gaussian Process Regressor
	gp := gaussianprocess.NewRegressor(productKernel)

	// Print Alpha for debugging
	fmt.Println("Alpha:", gp.Alpha)

	// Fit the model with X and yVec
	err := gp.Fit(X, yMat)
	if err != nil {
		log.Fatalf("Error fitting model: %v", err)
	}

	// Print fitted model info
	fmt.Println("Model fitted successfully.")
	fmt.Println("Xtrain:", gp.Xtrain)
	fmt.Println("Ytrain:", gp.Ytrain)

	// Predict new values
	X_test := mat.NewDense(5, 1, []float64{0, 2, 4, 6, 8})
	y_pred := gp.Predict(X_test, nil)

	// Print the test data and prediction results for debugging
	fmt.Println("Test data X_test:")
	matPrint(X_test)
	fmt.Println("Predicted values:")
	matPrint(y_pred)
}

// Helper function to print matrix
func matPrint(X mat.Matrix) {
	fr, fc := X.Dims()
	for r := 0; r < fr; r++ {
		for c := 0; c < fc; c++ {
			fmt.Printf("%f ", X.At(r, c))
		}
		fmt.Println()
	}
}

the output i am getting is below

Training data X:
0.000000 
1.000000 
2.000000 
3.000000 
4.000000 
5.000000 
6.000000 
7.000000 
8.000000 
9.000000 
Training data y:
&{{10 1 [0.5188212784827827 1.6037047407115053 3.7898678224401436 9.925588854546554 14.542592015266568 24.547637573998195 35.40832007088673 47.42076179321582 64.03240815464373 82.19464262249846] 1} 10 1}
1
Alpha: [1e-10]
2024/07/11 18:52:45 Error fitting model: 1**2 * RBF([1.5])

I cannot understand what that error about fitting model means

I analyzed the fit method's code and cannot see where it can go wrong, or I am just blind

Would really appreciate the help!
Thanks for the hard work