Loading data to DataGridView is taking lot of time.

using System;
using System.Windows.Forms;


namespace MatrixToDataGridView
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
   
            for (int k = 0; k < 100; k++)
            {
                dataGridView1.TopLeftHeaderCell.Value = "Theta / Phi";
                dataGridView1.Columns.Add("", k.ToString() );// dynamic cloumn adding
                dataGridView1.Rows.Add();//dynamic row adding
            }              
        }       
        public void function()
        {
            double [,] num = new double[100, 100];

            //Populates the array
            for (int i = 0; i < 100; i++)
            {
                for (int j = 0; j < 100; j++)
                {
                    num[i, j] = i+j;                     
                }
            }
            //Populates the dataGridView1
            for (int i = 0; i < 100; i++)
            {
                for (int j = 0; j < 100; j++)
                {
                    dataGridView1.Rows[i].Cells[j].Value = num[i, j].ToString();                    
                }
            }       
        }

        //Button for calling the function() to populate the array num and dataGridView1
        private void button1_Click(object sender, EventArgs e)
        {
            function(); 
        }
    }
}