Program: 60006
Project: 60006
Buggy source:
@Override public boolean generate(World world,Random rand,int x,int y,int z){
  int blocks=genClusterSize;
  if (blocks < 4) {
    return generateTiny(world,rand,x,y,z);
  }
  float f=rand.nextFloat() * (float)Math.PI;
  float xMin=x + 8 + (MathHelper.sin(f) * blocks) / 8F;
  float xMax=x + 8 - (MathHelper.sin(f) * blocks) / 8F;
  float zMin=z + 8 + (MathHelper.cos(f) * blocks) / 8F;
  float zMax=z + 8 - (MathHelper.cos(f) * blocks) / 8F;
  float yMin=(y + rand.nextInt(3)) - 2;
  float yMax=(y + rand.nextInt(3)) - 2;
  xMax-=xMin;
  yMax-=yMin;
  zMax-=zMin;
  boolean r=false;
  for (int i=0; i <= blocks; i++) {
    float xCenter=xMin + (xMax * i) / blocks;
    float yCenter=yMin + (yMax * i) / blocks;
    float zCenter=zMin + (zMax * i) / blocks;
    float size=((float)rand.nextDouble() * blocks) / 16f;
    float hMod=((MathHelper.sin((i * (float)Math.PI) / blocks) + 1f) * size + 1f) * .5f;
    float vMod=((MathHelper.sin((i * (float)Math.PI) / blocks) + 1f) * size + 1f) * .5f;
    int xStart=MathHelper.floor_float(xCenter - hMod);
    int yStart=MathHelper.floor_float(yCenter - vMod);
    int zStart=MathHelper.floor_float(zCenter - hMod);
    int xStop=MathHelper.floor_float(xCenter + hMod);
    int yStop=MathHelper.floor_float(yCenter + vMod);
    int zStop=MathHelper.floor_float(zCenter + hMod);
    for (int blockX=xStart; blockX <= xStop; blockX++) {
      float xDistSq=((blockX + .5f) - xCenter) / hMod;
      xDistSq*=xDistSq;
      if (xDistSq >= 1f) {
        continue;
      }
      for (int blockY=yStart; blockY <= yStop; blockY++) {
        float yDistSq=((blockY + .5f) - yCenter) / vMod;
        yDistSq*=yDistSq;
        float xyDistSq=yDistSq + xDistSq;
        if (xyDistSq >= 1f) {
          continue;
        }
        for (int blockZ=zStart; blockZ <= zStop; blockZ++) {
          float zDistSq=((blockZ + .5f) - zCenter) / hMod;
          xDistSq*=zDistSq;
          if (zDistSq + xyDistSq >= 1f) {
            continue;
          }
          r|=generateBlock(world,blockX,blockY,blockZ,genBlock,cluster);
        }
      }
    }
  }
  return r;
}

Fixed version (ground truth):
@Override public boolean generate(World world,Random rand,int x,int y,int z){
  int blocks=genClusterSize;
  if (blocks < 4) {
    return generateTiny(world,rand,x,y,z);
  }
  float f=rand.nextFloat() * (float)Math.PI;
  float xMin=x + 8 + (MathHelper.sin(f) * blocks) / 8F;
  float xMax=x + 8 - (MathHelper.sin(f) * blocks) / 8F;
  float zMin=z + 8 + (MathHelper.cos(f) * blocks) / 8F;
  float zMax=z + 8 - (MathHelper.cos(f) * blocks) / 8F;
  float yMin=(y + rand.nextInt(3)) - 2;
  float yMax=(y + rand.nextInt(3)) - 2;
  xMax-=xMin;
  yMax-=yMin;
  zMax-=zMin;
  boolean r=false;
  for (int i=0; i <= blocks; i++) {
    float xCenter=xMin + (xMax * i) / blocks;
    float yCenter=yMin + (yMax * i) / blocks;
    float zCenter=zMin + (zMax * i) / blocks;
    float size=((float)rand.nextDouble() * blocks) / 16f;
    float hMod=((MathHelper.sin((i * (float)Math.PI) / blocks) + 1f) * size + 1f) * .5f;
    float vMod=((MathHelper.sin((i * (float)Math.PI) / blocks) + 1f) * size + 1f) * .5f;
    int xStart=MathHelper.floor_float(xCenter - hMod);
    int yStart=MathHelper.floor_float(yCenter - vMod);
    int zStart=MathHelper.floor_float(zCenter - hMod);
    int xStop=MathHelper.floor_float(xCenter + hMod);
    int yStop=MathHelper.floor_float(yCenter + vMod);
    int zStop=MathHelper.floor_float(zCenter + hMod);
    for (int blockX=xStart; blockX <= xStop; blockX++) {
      float xDistSq=((blockX + .5f) - xCenter) / hMod;
      xDistSq*=xDistSq;
      if (xDistSq >= 1f) {
        continue;
      }
      for (int blockY=yStart; blockY <= yStop; blockY++) {
        float yDistSq=((blockY + .5f) - yCenter) / vMod;
        yDistSq*=yDistSq;
        float xyDistSq=yDistSq + xDistSq;
        if (xyDistSq >= 1f) {
          continue;
        }
        for (int blockZ=zStart; blockZ <= zStop; blockZ++) {
          float zDistSq=((blockZ + .5f) - zCenter) / hMod;
          zDistSq*=zDistSq;
          if (zDistSq + xyDistSq >= 1f) {
            continue;
          }
          r|=generateBlock(world,blockX,blockY,blockZ,genBlock,cluster);
        }
      }
    }
  }
  return r;
}