How to use

numberOfLeadingZeros

method

in

java.lang.Integer

/**
 * Find the next larger positive power of two value up from the given value. If value is a power of two then
 * this value will be returned.
 *
 * @param value from which next positive power of two will be found.
 * @return the next positive power of 2 or this value if it is a power of 2.
 */
public static int roundToPowerOfTwo(final int value) {
  return 1 << (32 - Integer.numberOfLeadingZeros(value - 1));
}

private static int log2(int val) {
  // compute the (0-based, with lsb = 0) position of highest set bit i.e, log2
  return INTEGER_SIZE_MINUS_ONE - Integer.numberOfLeadingZeros(val);
}

/**
 * Fast method of finding the next power of 2 greater than or equal to the supplied value.
 *
 * <p>If the value is {@code <= 0} then 1 will be returned.
 * This method is not suitable for {@link Integer#MIN_VALUE} or numbers greater than 2^30.
 *
 * @param value from which to search for next power of 2
 * @return The next power of 2 or the value itself if it is a power of 2
 */
public static int findNextPositivePowerOfTwo(final int value) {
  assert value > Integer.MIN_VALUE && value < 0x40000000;
  return 1 << (32 - Integer.numberOfLeadingZeros(value - 1));
}

/**
 * Calculate the next power of 2, greater than or equal to x.<p>
 * From Hacker's Delight, Chapter 3, Harry S. Warren Jr.
 *
 * @param x Value to round up
 * @return The next power of 2 from x inclusive
 */
public static int ceilingNextPowerOfTwo(final int x)
{
  return 1 << (32 - Integer.numberOfLeadingZeros(x - 1));
}

private static int encodedLengthSize(int length)
{
  if (length < 128) {
    return 1;
  }
  int numberOfBits = 32 - Integer.numberOfLeadingZeros(length);
  int numberOfBytes = (numberOfBits + 7) / 8;
  return numberOfBytes + 1;
}

/**
 * Find the next larger positive power of two value up from the given value. If value is a power of two then
 * this value will be returned.
 *
 * @param value from which next positive power of two will be found.
 * @return the next positive power of 2 or this value if it is a power of 2.
 */
public static int roundToPowerOfTwo(final int value) {
  return 1 << (32 - Integer.numberOfLeadingZeros(value - 1));
}

public static int getBitSize(long value) {
  if (value > Integer.MAX_VALUE) {
    return 64 - Integer.numberOfLeadingZeros((int) (value >> 32));
  } else {
    return 32 - Integer.numberOfLeadingZeros((int) value);
  }
}

/**
 * Fast method of finding the next power of 2 greater than or equal to the supplied value.
 *
 * <p>If the value is {@code <= 0} then 1 will be returned.
 * This method is not suitable for {@link Integer#MIN_VALUE} or numbers greater than 2^30.
 *
 * @param value from which to search for next power of 2
 * @return The next power of 2 or the value itself if it is a power of 2
 */
public static int findNextPositivePowerOfTwo(final int value) {
  assert value > Integer.MIN_VALUE && value < 0x40000000;
  return 1 << (32 - Integer.numberOfLeadingZeros(value - 1));
}

int computeListIndex( int len ) {
  int powIndex = 32-Integer.numberOfLeadingZeros(len-1);
  return powIndex;
}

private static int log2(int val) {
  // compute the (0-based, with lsb = 0) position of highest set bit i.e, log2
  return INTEGER_SIZE_MINUS_ONE - Integer.numberOfLeadingZeros(val);
}

int computeLen( int len ) {
  int powIndex = 32-Integer.numberOfLeadingZeros(len-1);
  return 1<<powIndex;
}

private static int validateAndCalculatePageShifts(int pageSize) {
  if (pageSize < MIN_PAGE_SIZE) {
    throw new IllegalArgumentException("pageSize: " + pageSize + " (expected: " + MIN_PAGE_SIZE + ")");
  }
  if ((pageSize & pageSize - 1) != 0) {
    throw new IllegalArgumentException("pageSize: " + pageSize + " (expected: power of 2)");
  }
  // Logarithm base 2. At this point we know that pageSize is a power of two.
  return Integer.SIZE - 1 - Integer.numberOfLeadingZeros(pageSize);
}

/**
 * Calculates compression level on the basis of block size.
 */
private static int compressionLevel(int blockSize) {
  if (blockSize < MIN_BLOCK_SIZE || blockSize > MAX_BLOCK_SIZE) {
    throw new IllegalArgumentException(String.format(
        "blockSize: %d (expected: %d-%d)", blockSize, MIN_BLOCK_SIZE, MAX_BLOCK_SIZE));
  }
  int compressionLevel = 32 - Integer.numberOfLeadingZeros(blockSize - 1); // ceil of log2
  compressionLevel = Math.max(0, compressionLevel - COMPRESSION_LEVEL_BASE);
  return compressionLevel;
}

private static int validateAndCalculatePageShifts(int pageSize) {
  if (pageSize < MIN_PAGE_SIZE) {
    throw new IllegalArgumentException("pageSize: " + pageSize + " (expected: " + MIN_PAGE_SIZE + ")");
  }
  if ((pageSize & pageSize - 1) != 0) {
    throw new IllegalArgumentException("pageSize: " + pageSize + " (expected: power of 2)");
  }
  // Logarithm base 2. At this point we know that pageSize is a power of two.
  return Integer.SIZE - 1 - Integer.numberOfLeadingZeros(pageSize);
}

/**
 * Calculates compression level on the basis of block size.
 */
private static int compressionLevel(int blockSize) {
  if (blockSize < MIN_BLOCK_SIZE || blockSize > MAX_BLOCK_SIZE) {
    throw new IllegalArgumentException(String.format(
        "blockSize: %d (expected: %d-%d)", blockSize, MIN_BLOCK_SIZE, MAX_BLOCK_SIZE));
  }
  int compressionLevel = 32 - Integer.numberOfLeadingZeros(blockSize - 1); // ceil of log2
  compressionLevel = Math.max(0, compressionLevel - COMPRESSION_LEVEL_BASE);
  return compressionLevel;
}

private static int log10Floor(int x) {
 /*
  * Based on Hacker's Delight Fig. 11-5, the two-table-lookup, branch-free implementation.
  *
  * The key idea is that based on the number of leading zeros (equivalently, floor(log2(x))), we
  * can narrow the possible floor(log10(x)) values to two. For example, if floor(log2(x)) is 6,
  * then 64 <= x < 128, so floor(log10(x)) is either 1 or 2.
  */
 int y = maxLog10ForLeadingZeros[Integer.numberOfLeadingZeros(x)];
 /*
  * y is the higher of the two possible values of floor(log10(x)). If x < 10^y, then we want the
  * lower of the two possible values, or y - 1, otherwise, we want y.
  */
 return y - lessThanBranchFree(x, powersOf10[y]);
}

/**
 * Returns the smallest power of two greater than or equal to {@code x}. This is equivalent to
 * {@code checkedPow(2, log2(x, CEILING))}.
 *
 * @throws IllegalArgumentException if {@code x <= 0}
 * @throws ArithmeticException of the next-higher power of two is not representable as an {@code
 *     int}, i.e. when {@code x > 2^30}
 * @since 20.0
 */
@Beta
public static int ceilingPowerOfTwo(int x) {
 checkPositive("x", x);
 if (x > MAX_SIGNED_POWER_OF_TWO) {
  throw new ArithmeticException("ceilingPowerOfTwo(" + x + ") not representable as an int");
 }
 return 1 << -Integer.numberOfLeadingZeros(x - 1);
}

public NodeLabelsCache( NumberArrayFactory cacheFactory, int highLabelId, int chunkSize )
{
  this.cache = cacheFactory.newDynamicLongArray( chunkSize, 0 );
  this.spillOver = cacheFactory.newDynamicLongArray( chunkSize / 5, 0 ); // expect way less of these
  this.bitsPerLabel = max( Integer.SIZE - numberOfLeadingZeros( highLabelId ), 1 );
  this.worstCaseLongsNeeded = ((bitsPerLabel * (highLabelId + 1 /*length slot*/)) - 1) / Long.SIZE + 1;
  this.putClient = new Client( worstCaseLongsNeeded );
}

@Override
public Mesh obtain (VertexAttributes vertexAttributes, int vertexCount, int indexCount) {
  for (int i = 0, n = freeMeshes.size; i < n; ++i) {
    final Mesh mesh = freeMeshes.get(i);
    if (mesh.getVertexAttributes().equals(vertexAttributes) && mesh.getMaxVertices() >= vertexCount
      && mesh.getMaxIndices() >= indexCount) {
      freeMeshes.removeIndex(i);
      usedMeshes.add(mesh);
      return mesh;
    }
  }
  vertexCount = 1 + (int)Short.MAX_VALUE;
  indexCount = Math.max(1 + (int)Short.MAX_VALUE, 1 << (32 - Integer.numberOfLeadingZeros(indexCount - 1)));
  Mesh result = new Mesh(false, vertexCount, indexCount, vertexAttributes);
  usedMeshes.add(result);
  return result;
}

@Override
public Mesh obtain (VertexAttributes vertexAttributes, int vertexCount, int indexCount) {
  for (int i = 0, n = freeMeshes.size; i < n; ++i) {
    final Mesh mesh = freeMeshes.get(i);
    if (mesh.getVertexAttributes().equals(vertexAttributes) && mesh.getMaxVertices() >= vertexCount
      && mesh.getMaxIndices() >= indexCount) {
      freeMeshes.removeIndex(i);
      usedMeshes.add(mesh);
      return mesh;
    }
  }
  vertexCount = 1 + (int)Short.MAX_VALUE;
  indexCount = Math.max(1 + (int)Short.MAX_VALUE, 1 << (32 - Integer.numberOfLeadingZeros(indexCount - 1)));
  Mesh result = new Mesh(false, vertexCount, indexCount, vertexAttributes);
  usedMeshes.add(result);
  return result;
}