optimizing the code: up to +19% performance on core i7 2700k with -O2 option

Source/Noise.cpp

@@ -49,49 +49,40 @@ static inline float lerp (float a0, float a1, float w)
     return (1.0f - w) * a0 + w * a1;
 }
 
-float Noise::gen1 (float z, float torsion)
+inline float gen1 (float *gradients, float z, float torsion)
 {
-    float g1, g2, d2;
-    float result = 0;
+    const int z1 = static_cast<int>(z);
+    const float dz1 = z - z1;
+    const float dz2 = dz1 - 1.0f;
 
-    int z1 = (int) z;
-    int z2 = (z1 + 1);
+    float g1 = gradients[z1] + torsion;
+    float g2 = gradients[z1 + 1] + torsion;
 
-    float dz1 = z - z1; 
-    float dz2 = dz1 - 1.0f;
+    float d1 = 1.0f - (dz1 * dz1);
+    d1 = d1 * d1 * d1 * d1;
 
-    g1 = gradients[z1];
-    g2 = gradients[z2];
+    float d2 = 1.0f - (dz2 * dz2);
+    d2 = d2 * d2 * d2 * d2;
 
-    g1 = g1 + torsion;
     if (g1 > 1.0f) { g1 = 2.0f - g1; }
-    if (g1 < -1.0f) { g1 = -2.0f - g1; }
+    else if (g1 < -1.0f) { g1 = -2.0f - g1; }
 
-    g2 = g2 + torsion;
     if (g2 > 1.0f) { g2 = 2.0f - g2; }
-    if (g2 < -1.0f) { g2 = -2.0f - g2; }
-
-    d2 = 1.0 - (dz1 * dz1);
-    d2 = d2 * d2 * d2 * d2;
-    result += d2 * (g1 * dz1);
-
-    d2 = 1.0 - (dz2 * dz2);
-    d2 = d2 * d2 * d2 * d2;
-    result += d2 * (g2 * dz2);
+    else if (g2 < -1.0f) { g2 = -2.0f - g2; }
 
-    return result * 3.33; // temp normalization value
+    return (d1 * (g1 * dz1) + d2 * (g2 * dz2)) * 3.33f; // temp normalization value
 }
 
 float Noise::gen (float z, int octaves, float persistence, float torsion, float warping)
 {
     float result = 0;
     float multiplier = 1.0f;
-    float offset = gen1 (z, torsion) * warping;
+    float offset = gen1 (gradients, z, torsion) * warping;
 
     for (int octave = 0; octave < octaves; ++octave)
     {
-        float t = fmod(torsion, 4);
-        float value = gen1 (z * (1 << octave) + offset, t) * multiplier;
+        float t = fmodf(torsion, 4);
+        float value = gen1 (gradients, z * (1 << octave) + offset, t) * multiplier;
         offset = value * warping;
         result += value;
         multiplier *= persistence;

Source/Noise.h

@@ -35,6 +35,4 @@ class Noise
     float gradients[65536];
     std::mt19937 random;
     uint32_t seed_;
-
-    float gen1 (float z, float torsion);
 };