Program: 34109
Project: 34109
Buggy source:
public byte[][] generateBlockSections(World world,Random random,int chunkX,int chunkZ,BiomeGrid biomeGrid){
  rand.setSeed(world.getSeed());
  gen=new PerlinOctaveGenerator((long)(random.nextLong() * random.nextGaussian()),8);
  byte[][] result=new byte[world.getMaxHeight() / 16][];
  if (!world.getEnvironment().equals(Environment.NETHER)) {
    return result;
  }
  for (int x=0; x < 16; x++) {
    for (int z=0; z < 16; z++) {
      setBlock(result,x,(world.getMaxHeight() - 1),z,(byte)Material.BEDROCK.getId());
      for (int y=2; y < 5; y++) {
        double r=gen.noise(x,(world.getMaxHeight() - y),z,0.5,0.5);
        if (r > 0D) {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.BEDROCK.getId());
        }
 else {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.NETHERRACK.getId());
        }
      }
      for (int y=5; y < 8; y++) {
        double r=gen.noise(x,world.getMaxHeight() - y,z,0.5,0.5);
        if (r > 0D) {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.NETHERRACK.getId());
        }
 else {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.AIR.getId());
        }
      }
      double r=gen.noise(x,world.getMaxHeight() - 8,z,random.nextFloat(),random.nextFloat());
      if (r > 0.5D) {
        setBlock(result,x,(world.getMaxHeight() - 8),z,(byte)Material.GLOWSTONE.getId());
      }
 else {
        setBlock(result,x,(world.getMaxHeight() - 8),z,(byte)Material.AIR.getId());
      }
    }
  }
  int actualX=chunkX * 16;
  int actualZ=chunkZ * 16;
  int chunkDist=Math.round((float)Settings.islandDistance / 16F);
  if (chunkX % chunkDist == 0 && chunkZ % chunkDist == 0) {
    for (int x=0; x < 16; x++) {
      for (int z=0; z < 16; z++) {
        int island_height=Settings.island_level;
        for (int y=island_height - 13; y < island_height; y++) {
          double r=gen.noise(x,y,z,0.5,0.5);
          if (y == (island_height - 1)) {
            if (x == 0 || z == 0 || x == 15 || z == 15) {
              setBlock(result,x,y,z,(byte)Material.NETHER_FENCE.getId());
            }
          }
 else           if (y == (island_height - 2)) {
            if (x == 0 || z == 0 || x == 15 || z == 15) {
              setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
            }
 else {
              if (r > 0.5D) {
                setBlock(result,x,y,z,(byte)Material.FIRE.getId());
              }
            }
          }
 else {
            if (x == 0 || z == 0 || x == 15 || z == 15) {
              if (r > -0.5D) {
                setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
              }
            }
 else {
              if (r > 0D) {
                setBlock(result,x,y,z,(byte)Material.QUARTZ_ORE.getId());
              }
 else               if (r > -0.4D) {
                setBlock(result,x,y,z,(byte)Material.NETHERRACK.getId());
              }
 else               if (y < island_height - 10) {
                setBlock(result,x,y,z,(byte)Material.LAVA.getId());
              }
            }
          }
        }
      }
    }
  }
 else   if (Math.abs(chunkX % chunkDist) == 2 && Math.abs(chunkZ % chunkDist) == 2) {
    for (int x=5; x < 11; x++) {
      for (int z=5; z < 11; z++) {
        int island_height=Settings.island_level + 25;
        for (int y=Settings.island_level - 20; y < island_height; y++) {
          double r=gen.noise(x,y,z,0.5,0.5);
          if (y == (island_height - 1)) {
            if (x == 5 || z == 5 || x == 10 || z == 10) {
              setBlock(result,x,y,z,(byte)Material.NETHER_FENCE.getId());
            }
 else {
              if (r > 0.1D) {
                setBlock(result,x,y,z,(byte)Material.MOB_SPAWNER.getId());
              }
            }
          }
 else           if (y == (island_height - 2)) {
            setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
          }
 else {
            if (x == 5 || z == 5 || x == 10 || z == 10) {
              if (r > -0.5D) {
                setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
              }
 else {
                setBlock(result,x,y,z,(byte)Material.LAVA.getId());
              }
            }
 else {
              if (r > 0.8D) {
                setBlock(result,x,y,z,(byte)Material.LAVA.getId());
              }
 else               if (r > 0.45D) {
                setBlock(result,x,y,z,(byte)Material.QUARTZ_ORE.getId());
              }
 else               if (r > 0.20D) {
                setBlock(result,x,y,z,(byte)Material.SOUL_SAND.getId());
              }
 else               if (r > -0.5D) {
                setBlock(result,x,y,z,(byte)Material.NETHERRACK.getId());
              }
            }
          }
        }
      }
    }
  }
 else {
  }
  return result;
}

Fixed version (ground truth):
public byte[][] generateBlockSections(World world,Random random,int chunkX,int chunkZ,BiomeGrid biomeGrid){
  rand.setSeed(world.getSeed());
  gen=new PerlinOctaveGenerator((long)(random.nextLong() * random.nextGaussian()),8);
  byte[][] result=new byte[world.getMaxHeight() / 16][];
  if (!world.getEnvironment().equals(Environment.NETHER)) {
    return result;
  }
  for (int x=0; x < 16; x++) {
    for (int z=0; z < 16; z++) {
      setBlock(result,x,(world.getMaxHeight() - 1),z,(byte)Material.BEDROCK.getId());
      for (int y=2; y < 5; y++) {
        double r=gen.noise(x,(world.getMaxHeight() - y),z,0.5,0.5);
        if (r > 0D) {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.BEDROCK.getId());
        }
 else {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.NETHERRACK.getId());
        }
      }
      for (int y=5; y < 8; y++) {
        double r=gen.noise(x,world.getMaxHeight() - y,z,0.5,0.5);
        if (r > 0D) {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.NETHERRACK.getId());
        }
 else {
          setBlock(result,x,(world.getMaxHeight() - y),z,(byte)Material.AIR.getId());
        }
      }
      double r=gen.noise(x,world.getMaxHeight() - 8,z,random.nextFloat(),random.nextFloat());
      if (r > 0.5D) {
        setBlock(result,x,(world.getMaxHeight() - 8),z,(byte)Material.GLOWSTONE.getId());
      }
 else {
        setBlock(result,x,(world.getMaxHeight() - 8),z,(byte)Material.AIR.getId());
      }
    }
  }
  int actualX=chunkX * 16;
  int actualZ=chunkZ * 16;
  int chunkDist=Math.round((float)Settings.islandDistance / 16F);
  if (chunkX % chunkDist == 0 && chunkZ % chunkDist == 0) {
    for (int x=0; x < 16; x++) {
      for (int z=0; z < 16; z++) {
        int island_height=Settings.island_level;
        for (int y=island_height - 13; y < island_height; y++) {
          double r=gen.noise(x,y,z,0.5,0.5);
          if (y == (island_height - 1)) {
            if (x == 0 || z == 0 || x == 15 || z == 15) {
              setBlock(result,x,y,z,(byte)Material.NETHER_FENCE.getId());
            }
          }
 else           if (y == (island_height - 2)) {
            if (x == 0 || z == 0 || x == 15 || z == 15) {
              setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
            }
 else {
              if (r > 0.5D) {
                setBlock(result,x,y,z,(byte)Material.FIRE.getId());
              }
            }
          }
 else {
            if (x == 0 || z == 0 || x == 15 || z == 15) {
              if (r > -0.5D) {
                setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
              }
            }
 else {
              if (r > 0.25D) {
                setBlock(result,x,y,z,(byte)Material.AIR.getId());
              }
 else               if (r > 0D) {
                setBlock(result,x,y,z,(byte)Material.STONE.getId());
              }
 else               if (r > -0.4D) {
                setBlock(result,x,y,z,(byte)Material.NETHERRACK.getId());
              }
 else               if (y < island_height - 10) {
                setBlock(result,x,y,z,(byte)Material.LAVA.getId());
              }
            }
          }
        }
      }
    }
  }
 else   if (Math.abs(chunkX % chunkDist) == 2 && Math.abs(chunkZ % chunkDist) == 2) {
    for (int x=0; x < 11; x++) {
      for (int z=0; z < 11; z++) {
        int island_height=Settings.island_level + 25;
        for (int y=Settings.island_level - 20; y < island_height; y++) {
          double r=gen.noise(x,y,z,0.5,0.5);
          if (y == (island_height - 1)) {
            if (x == 0 || z == 0 || x == 10 || z == 10) {
              setBlock(result,x,y,z,(byte)Material.NETHER_FENCE.getId());
            }
 else {
              if (random.nextInt(10) > 8) {
                setBlock(result,x,y,z,(byte)Material.OBSIDIAN.getId());
              }
 else               if (random.nextInt(10) > 8) {
                setBlock(result,x,y,z,(byte)Material.MOB_SPAWNER.getId());
              }
            }
          }
 else           if (y == (island_height - 2)) {
            setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
          }
 else {
            if (x == 0 || z == 0 || x == 10 || z == 10) {
              if (r > -0.5D) {
                setBlock(result,x,y,z,(byte)Material.NETHER_BRICK.getId());
              }
 else {
                if (random.nextInt(2) == 1) {
                  setBlock(result,x,y,z,(byte)Material.LAVA.getId());
                }
 else {
                  setBlock(result,x,y,z,(byte)Material.AIR.getId());
                }
              }
            }
 else {
              if (r > 0.8D) {
                setBlock(result,x,y,z,(byte)Material.LAVA.getId());
              }
 else               if (r > 0.5D) {
                setBlock(result,x,y,z,(byte)Material.AIR.getId());
              }
 else               if (r > 0.4D) {
                setBlock(result,x,y,z,(byte)Material.STONE.getId());
              }
 else               if (r > 0.2D) {
                setBlock(result,x,y,z,(byte)Material.SOUL_SAND.getId());
              }
 else               if (r > -0.5D) {
                setBlock(result,x,y,z,(byte)Material.NETHERRACK.getId());
              }
            }
            if (y < Settings.island_level - 15) {
              if (r > 0D) {
                setBlock(result,x,y,z,(byte)Material.AIR.getId());
              }
            }
          }
        }
      }
    }
  }
 else {
  }
  return result;
}