Program: 81810
Project: 81810
Buggy source:
public void tickSnowFall(){
  if (!ConfigSnow.Snow_PerformSnowfall)   return;
  if (!isPrecipitating())   return;
  World world=manager.getWorld();
  final long startTime=System.nanoTime();
  int xx=0;
  int zz=0;
  for (xx=(int)(pos.xCoord - size / 2); xx < pos.xCoord + size / 2; xx+=16) {
    for (zz=(int)(pos.zCoord - size / 2); zz < pos.zCoord + size / 2; zz+=16) {
      int chunkX=xx / 16;
      int chunkZ=zz / 16;
      int x=chunkX * 16;
      int z=chunkZ * 16;
      if (!world.isBlockLoaded(new BlockPos(x,128,z))) {
        continue;
      }
      Chunk chunk=world.getChunkFromChunkCoords(chunkX,chunkZ);
      int i1;
      int xxx;
      int zzz;
      int setBlockHeight;
      int i2;
      if (world.provider.canDoRainSnowIce(chunk) && (ConfigSnow.Snow_RarityOfBuildup == 0 || world.rand.nextInt(ConfigSnow.Snow_RarityOfBuildup) == 0)) {
        updateLCG=updateLCG * 3 + 1013904223;
        i1=updateLCG >> 2;
        xxx=i1 & 15;
        zzz=i1 >> 8 & 15;
        double d0=pos.xCoord - (xx + xxx);
        double d2=pos.zCoord - (zz + zzz);
        if ((double)MathHelper.sqrt(d0 * d0 + d2 * d2) > size)         continue;
        int snowMetaMax=7;
        setBlockHeight=world.getPrecipitationHeight(new BlockPos(xxx + x,0,zzz + z)).getY();
        if (canSnowAtBody(xxx + x,setBlockHeight,zzz + z) && Blocks.SNOW.canPlaceBlockAt(world,new BlockPos(xxx + x,setBlockHeight,zzz + z))) {
          boolean betterBuildup=true;
          if (betterBuildup) {
            WindManager windMan=manager.getWindManager();
            float angle=windMan.getWindAngleForClouds();
            Vec3 vecPos=new Vec3(xxx + x,setBlockHeight,zzz + z);
            if (!world.isBlockLoaded(vecPos.toBlockPos()))             continue;
            WeatherUtilBlock.fillAgainstWallSmoothly(world,vecPos,angle,15,2,Blocks.SNOW_LAYER);
          }
 else {
          }
        }
      }
    }
  }
}

Fixed version (ground truth):
public void tickSnowFall(){
  if (!ConfigSnow.Snow_PerformSnowfall)   return;
  if (!isPrecipitating())   return;
  World world=manager.getWorld();
  final long startTime=System.nanoTime();
  int xx=0;
  int zz=0;
  for (xx=(int)(pos.xCoord - size / 2); xx < pos.xCoord + size / 2; xx+=16) {
    for (zz=(int)(pos.zCoord - size / 2); zz < pos.zCoord + size / 2; zz+=16) {
      int chunkX=xx / 16;
      int chunkZ=zz / 16;
      int x=chunkX * 16;
      int z=chunkZ * 16;
      if (!world.isBlockLoaded(new BlockPos(x,128,z))) {
        continue;
      }
      Chunk chunk=world.getChunkFromChunkCoords(chunkX,chunkZ);
      int i1;
      int xxx;
      int zzz;
      int setBlockHeight;
      int i2;
      if (world.provider.canDoRainSnowIce(chunk) && (ConfigSnow.Snow_RarityOfBuildup == 0 || world.rand.nextInt(ConfigSnow.Snow_RarityOfBuildup) == 0)) {
        updateLCG=updateLCG * 3 + 1013904223;
        i1=updateLCG >> 2;
        xxx=i1 & 15;
        zzz=i1 >> 8 & 15;
        double d0=pos.xCoord - (xx + xxx);
        double d2=pos.zCoord - (zz + zzz);
        if ((double)MathHelper.sqrt(d0 * d0 + d2 * d2) > size)         continue;
        int snowMetaMax=7;
        setBlockHeight=world.getPrecipitationHeight(new BlockPos(xxx + x,0,zzz + z)).getY();
        if (canSnowAtBody(xxx + x,setBlockHeight,zzz + z) && Blocks.SNOW.canPlaceBlockAt(world,new BlockPos(xxx + x,setBlockHeight,zzz + z))) {
          boolean betterBuildup=true;
          if (betterBuildup) {
            WindManager windMan=manager.getWindManager();
            float angle=windMan.getWindAngleForClouds();
            Vec3 vecPos=new Vec3(xxx + x,setBlockHeight,zzz + z);
            if (!world.isBlockLoaded(vecPos.toBlockPos()))             continue;
            if (!ConfigMisc.overcastMode) {
              if (world.isAirBlock(vecPos.toBlockPos())) {
                world.setBlockState(vecPos.toBlockPos(),Blocks.SNOW_LAYER.getDefaultState());
              }
            }
            WeatherUtilBlock.fillAgainstWallSmoothly(world,vecPos,angle,15,2,Blocks.SNOW_LAYER);
          }
 else {
          }
        }
      }
    }
  }
}