FFT3 optimization

fastdoubleparser-dev/src/main/java/ch.randelshofer.fastdoubleparser/ch/randelshofer/fastdoubleparser/FftMultiplier.java

@@ -780,6 +780,14 @@ void add(int idxa, MutableComplex c) {
             a[imagIdx(idxa)] += c.imag;
         }
 
+        void addReal(int idxa, double real) {
+            a[realIdx(idxa)] += real;
+        }
+
+        void addImag(int idxa, double imag) {
+            a[imagIdx(idxa)] += imag;
+        }
+
         void addInto(int idxa, ComplexVector c, int idxc, MutableComplex destination) {
             destination.real = a[realIdx(idxa)] + c.real(idxc);
             destination.imag = a[imagIdx(idxa)] + c.imag(idxc);
@@ -985,6 +993,20 @@ void timesTwoToThe(int idxa, int n) {
             a[ri] = fastScalb(real, n);
             a[ii] = fastScalb(imag, n);
         }
+
+        public void scale(double scale) {
+            for (int i = 0; i < length << COMPLEX_SIZE_SHIFT; i++) {
+                a[i] *= scale;
+            }
+        }
+        public int length() {
+            return length;
+        }
+
+        @Override
+        public String toString() {
+            return "V=" + length;
+        }
     }
 
     final static class MutableComplex {

fastdoubleparser-dev/src/test/java/ch/randelshofer/fastdoubleparser/FftMultiplierFft3Test.java

@@ -0,0 +1,66 @@
+/*
+ * @(#)FftMultiplierFft3Test.java
+ * Copyright © 2023 Werner Randelshofer, Switzerland. MIT License.
+ */
+package ch.randelshofer.fastdoubleparser;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import ch.randelshofer.fastdoubleparser.JmhFftMultiplierFft3.Fft3Algorithm;
+import ch.randelshofer.fastdoubleparser.FftMultiplier.ComplexVector;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.stream.Stream;
+
+public class FftMultiplierFft3Test {
+    private static final double SCALE = 1.0 / 3;
+    private static final int NUMBER_OF_TESTED_RANDOM_VALUES = 10;
+
+    @ParameterizedTest
+    @MethodSource("someRandomParameters")
+    public void compareWithOriginal(Fft3Algorithm algorithm,
+                                    ComplexVector a0,
+                                    ComplexVector a1,
+                                    ComplexVector a2,
+                                    int sign) {
+        algorithm.fft3(a0, a1, a2, sign, SCALE);
+    }
+
+    private static Stream<Arguments> someRandomParameters() {
+        List<Object[]> testCases = new ArrayList<>();
+        Random rng = new Random(2023);
+        for (int i = 0; i < NUMBER_OF_TESTED_RANDOM_VALUES; i++) {
+            int n = 1 << (5 + i * 4 / NUMBER_OF_TESTED_RANDOM_VALUES);
+            ComplexVector a0 = new ComplexVector(n);
+            ComplexVector a1 = new ComplexVector(n);
+            ComplexVector a2 = new ComplexVector(n);
+            for (int j = 0; j < n; j++) {
+                a0.set(j, rng.nextDouble(), rng.nextDouble());
+                a1.set(j, rng.nextDouble(), rng.nextDouble());
+                a2.set(j, rng.nextDouble(), rng.nextDouble());
+            }
+            int sign = i % 2 == 0 ? -1 : 1;
+            testCases.add(new Object[]{a0, a1, a2, sign});
+        }
+        return combineWithAlgorithms(testCases);
+    }
+
+    private static Stream<Arguments> combineWithAlgorithms(List<Object[]> testCases) {
+        List<Arguments> args = new ArrayList<>();
+        for (JmhFftMultiplierFft3.Fft3Algorithm algorithm : JmhFftMultiplierFft3.Fft3Algorithm.values()) {
+            if (!algorithm.equals(JmhFftMultiplierFft3.Fft3Algorithm.ORIGINAL)) {
+                for (Object[] params : testCases) {
+                    ComplexVector a0 = (ComplexVector) params[0];
+                    ComplexVector a1 = (ComplexVector) params[1];
+                    ComplexVector a2 = (ComplexVector) params[2];
+                    int sign = (int) params[3];
+                    args.add(Arguments.of(algorithm, a0, a1, a2, sign));
+                }
+            }
+        }
+        return args.stream();
+    }
+}