refactor: clean up Ema and EmaVector tests for consistency, update TValue equality check

lib/averages/ema/Ema.Tests.cs

@@ -195,6 +195,8 @@ public class EmaTests
             series.Add(bar.Time, bar.Close);
         }
 
+        Assert.True(series.Count > 0);
+
         // Calculate iteratively
         var iterativeResults = new TSeries();
         foreach (var item in series)
@@ -234,7 +236,6 @@ public class EmaTests
         // Feed some valid values
         ema.Update(new TValue(DateTime.UtcNow, 100));
         ema.Update(new TValue(DateTime.UtcNow, 110));
-        double valueBeforeNaN = ema.Value;
 
         // Feed NaN - should use last valid value (110)
         var resultAfterNaN = ema.Update(new TValue(DateTime.UtcNow, double.NaN));

lib/averages/ema/Ema.Validation.Tests.cs

@@ -15,7 +15,6 @@ public class EmaValidationTests
     private readonly TBarSeries _bars;
     private readonly TSeries _data;
     private readonly List<Quote> _skenderQuotes;
-    private readonly Random _rnd = new(42);
     private readonly ITestOutputHelper _output;
 
     public EmaValidationTests(ITestOutputHelper output)
@@ -35,7 +34,7 @@ public class EmaValidationTests
         {
             _skenderQuotes.Add(new Quote
             {
-                Date = new DateTime(_bars.Open.Times[i]),
+                Date = new DateTime(_bars.Open.Times[i], DateTimeKind.Utc),
                 Open = (decimal)_bars.Open[i].Value,
                 High = (decimal)_bars.High[i].Value,
                 Low = (decimal)_bars.Low[i].Value,
@@ -60,7 +59,7 @@ public class EmaValidationTests
             var sResult = _skenderQuotes.GetEma(period).ToList();
 
             // Compare last 100 records
-            VerifyData(qResult, sResult, period);
+            VerifyData(qResult, sResult);
         }
         _output.WriteLine("EMA validated successfully against Skender");
     }
@@ -90,7 +89,7 @@ public class EmaValidationTests
             int lookback = TALib.Functions.EmaLookback(period);
 
             // Compare last 100 records
-            VerifyData_Talib(qResult, output, outRange, lookback, period);
+            VerifyData_Talib(qResult, output, outRange, lookback);
         }
         _output.WriteLine("EMA validated successfully against TA-Lib");
     }
@@ -119,12 +118,12 @@ public class EmaValidationTests
             var tResult = outputs[0];
 
             // Compare last 100 records
-            VerifyData(qResult, tResult.ToList(), period);
+            VerifyData(qResult, tResult.ToList());
         }
         _output.WriteLine("EMA validated successfully against Tulip");
     }
 
-    private void VerifyData(TSeries qSeries, List<double> tSeries, int period)
+    private static void VerifyData(TSeries qSeries, List<double> tSeries)
     {
         // Ensure we have enough data
         Assert.Equal(qSeries.Count, tSeries.Count);
@@ -136,13 +135,13 @@ public class EmaValidationTests
         {
             double qValue = qSeries[i].Value;
             double tValue = tSeries[i];
-            if (tValue == 0) continue;
+            if (Math.Abs(tValue) < 1e-10) continue;
 
             Assert.Equal(tValue, qValue, 1e-6);
         }
     }
 
-    private void VerifyData(TSeries qSeries, List<EmaResult> sSeries, int period)
+    private static void VerifyData(TSeries qSeries, List<EmaResult> sSeries)
     {
         // Ensure we have enough data
         Assert.Equal(qSeries.Count, sSeries.Count);
@@ -163,7 +162,7 @@ public class EmaValidationTests
         }
     }
 
-    private void VerifyData_Talib(TSeries qSeries, double[] tOutput, Range outRange, int lookback, int period)
+    private static void VerifyData_Talib(TSeries qSeries, double[] tOutput, Range outRange, int lookback)
     {
         int count = qSeries.Count;
         int skip = count - 100; // Last 100 records

lib/averages/ema/Ema.cs

@@ -3,28 +3,39 @@ using System.Runtime.InteropServices;
 
 namespace QuanTAlib;
 
-internal struct EmaState
-{
-    public double Ema { get; set; }
-    public double E { get; set; }
-    public bool IsHot { get; set; }
-
-    public static EmaState New() => new() { Ema = 0, E = 1.0, IsHot = false };
-}
-
 /// <summary>
-/// Exponential Moving Average (EMA) - IIR filter with exponential warmup compensator.
+/// EMA: Exponential Moving Average
-/// Provides valid output from first bar with O(1) complexity.
 /// </summary>
 /// <remarks>
-/// Algorithm uses exponential smoothing with compensator for immediate valid results.
+/// EMA needs very short history buffer and calculates the EMA value using just the
-/// Reference: https://github.com/mihakralj/pinescript/blob/main/indicators/trends_IIR/ema.md
+/// previous EMA value. The weight of the new datapoint (alpha) is alpha = 2 / (period + 1)
+///
+/// Key characteristics:
+/// - Uses no buffer, relying only on the previous EMA value.
+/// - The weight of new data points is calculated as alpha = 2 / (period + 1).
+/// - Provides a balance between responsiveness and smoothing. No overshooting. Significant lag
+///
+/// Calculation method:
+/// This implementation can use SMA for the first Period bars as a seeding value for EMA when useSma is true.
+///
+/// Sources:
+/// - https://stockcharts.com/school/doku.php?id=chart_school:technical_indicators:moving_averages
+/// - https://www.investopedia.com/ask/answers/122314/what-exponential-moving-average-ema-formula-and-how-ema-calculated.asp
+/// - https://blog.fugue88.ws/archives/2017-01/The-correct-way-to-start-an-Exponential-Moving-Average-EMA
 /// </remarks>
 public class Ema
 {
+    private struct State
+    {
+        public double Ema;
+        public double E;
+        public bool IsHot;
+        public static State New() => new() { Ema = 0, E = 1.0, IsHot = false };
+    }
+
     private readonly double _alpha;
-    private EmaState _state = EmaState.New();
+    private State _state = State.New();
-    private EmaState _p_state = EmaState.New();
+    private State _p_state = State.New();
     private double _lastValidValue;
 
     /// <summary>
@@ -81,7 +92,7 @@ public class Ema
     /// Assumes input has already been validated via GetValidValue().
     /// </summary>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    internal static double Compute(double input, double alpha, ref EmaState state)
+    private static double Compute(double input, double alpha, ref State state)
     {
         state.Ema += alpha * (input - state.Ema);
 
@@ -144,7 +155,7 @@ public class Ema
         var sourceTimes = source.Times;
 
         // Local state for batch processing
-        EmaState state = _state;
+        State state = _state;
 
         for (int i = 0; i < len; i++)
         {
@@ -180,7 +191,7 @@ public class Ema
     /// </summary>
     public void Reset()
     {
-        _state = EmaState.New();
+        _state = State.New();
         _p_state = _state;
         _lastValidValue = 0;
         Value = default;

lib/averages/ema/EmaVector.Tests.cs

@@ -168,7 +168,7 @@ public class EmaVectorTests
 
         for (int i = 0; i < len; i++)
         {
-            var tVal = new TValue(new DateTime(t[i]), v[i]);
+            var tVal = new TValue(new DateTime(t[i], DateTimeKind.Utc), v[i]);
             var streamRes = emaVectorStream.Update(tVal);
 
             for (int j = 0; j < periods.Length; j++)

lib/averages/ema/EmaVector.cs

@@ -23,7 +23,9 @@ public class EmaVector
     /// <summary>
     /// Current EMA values for all periods.
     /// </summary>
-    public TValue[] Values { get; private set; }
+    public ReadOnlySpan<TValue> Values => _values;
+
+    private readonly TValue[] _values;
 
     /// <summary>
     /// Initializes EmaVector with specified periods.
@@ -37,7 +39,7 @@ public class EmaVector
         _Es = new double[_count];
         _p_emas = new double[_count];
         _p_Es = new double[_count];
-        Values = new TValue[_count];
+        _values = new TValue[_count];
 
         for (int i = 0; i < _count; i++)
         {
@@ -59,7 +61,7 @@ public class EmaVector
         _Es = new double[_count];
         _p_emas = new double[_count];
         _p_Es = new double[_count];
-        Values = new TValue[_count];
+        _values = new TValue[_count];
 
         for (int i = 0; i < _count; i++)
         {
@@ -100,7 +102,7 @@ public class EmaVector
             ResetAt(i);
         }
         _lastValidValue = 0;
-        Array.Clear(Values);
+        Array.Clear(_values);
     }
 
     /// <summary>
@@ -177,7 +179,7 @@ public class EmaVector
                 // Store result
                 for (int j = 0; j < vecCount; j++)
                 {
-                    Values[i + j] = new TValue(input.Time, vecResult[j]);
+                    _values[i + j] = new TValue(input.Time, vecResult[j]);
                 }
             }
         }
@@ -198,10 +200,10 @@ public class EmaVector
                 }
             }
 
-            Values[i] = new TValue(input.Time, result);
+            _values[i] = new TValue(input.Time, result);
         }
 
-        return Values;
+        return _values;
     }
 
     /// <summary>
@@ -305,7 +307,7 @@ public class EmaVector
             resultSeries[i] = new TSeries(tLists[i], vLists[i]);
             var lastT = CollectionsMarshal.AsSpan(tLists[i])[len - 1];
             var lastV = CollectionsMarshal.AsSpan(vLists[i])[len - 1];
-            Values[i] = new TValue(lastT, lastV);
+            _values[i] = new TValue(lastT, lastV);
         }
 
         return resultSeries;

lib/core/tvalue/tvalue.cs

@@ -48,7 +48,7 @@ public readonly struct TValue : IEquatable<TValue>
     public override string ToString() => $"[{AsDateTime:yyyy-MM-dd HH:mm:ss}, {Value:F2}]";
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public bool Equals(TValue other) => Time == other.Time && Value == other.Value;
+    public bool Equals(TValue other) => Time == other.Time && Math.Abs(Value - other.Value) < 1e-9;
 
     public override bool Equals(object? obj) => obj is TValue other && Equals(other);
     public override int GetHashCode() => HashCode.Combine(Time, Value);