using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Azimuth.UnitTests
{
    public class KahanAccumulatorTests : UnitTestSharp.TestFixture
    {
        RobustAccumulator accumulator;

        public override void TestSetup()
        {
            accumulator = new RobustAccumulator();
        }

        public void Basic()
        {
            accumulator.Add(1);
            accumulator.Add(2);
            accumulator.Add(3);
            accumulator.Add(4);

            Check(Scalar.FuzzyEquality(10, accumulator.ComputedSum, 1e-30));
        }

        public void CancellationError_Scalars()
        {
            Scalar sum = 0;

            sum += 1e-20;
            sum += 1;
            sum += -1;

            CheckEqual(0, sum.Value);
        }

        public void CancellationError()
        {
            accumulator.Add(1e-20);
            accumulator.Add(1);
            accumulator.Add(-1);

            Check(Scalar.FuzzyEquality(1e-20, accumulator.ComputedSum, 1e-40));   
        }

        public void List()
        {
            var list = new Scalar[] { 1e-20, 1, -1 };

            accumulator.AddList(list);

            Check(Scalar.FuzzyEquality(1e-20, accumulator.ComputedSum, 1e-40));   
        }
    }
}