public void Value_HashCheck()
{
byte partitionBits = 1;
int id = 1253432;
// Get Value, Hash, and Partition Index
Value idValue = Value.Create(id);
int hash = idValue.GetHashCode();
int partition = PartitionMask.IndexOfHash(hash, partitionBits);
// Verify Matches reports consistently with IndexOfHash
PartitionMask mask = PartitionMask.BuildSet(partitionBits)[partition];
string maskName = mask.ToString();
Assert.IsTrue(mask.Matches(hash));
// Verify Value.Assign hash is consistent
Value n = Value.Create(null);
n.Assign(id);
int hashViaAssign = n.GetHashCode();
Assert.AreEqual(hash, hashViaAssign);
// Get Hash of unwrapped value [debuggability]
int wrongHash = id.GetHashCode();
int wrongPartition = PartitionMask.IndexOfHash(wrongHash, partitionBits);
}
/// <summary>
/// Creates a new table large enough to hold the number of items specified
/// </summary>
/// <param name="tableName">name of the table</param>
/// <param name="requiredItemCount">number of items the table is required to hold (it may be capable of holding more); this will dictate the partition count</param>
public Table(string tableName, long requiredItemCount) : this()
{
this.Name = tableName;
// Translate the item limit to a number of partition bits (64k items per partition)
_partitionBits = (byte)Math.Max(Math.Ceiling(Math.Log(requiredItemCount, 2)) - 16, 0);
// Create the partitions
PartitionMask[] maskSet = PartitionMask.BuildSet(_partitionBits);
_partitions.Clear();
for (int i = 0; i < maskSet.Length; ++i)
{
Partition p = new Partition(maskSet[i]);
_partitions.Add(p);
}
}
/// <summary>
/// Creates a new table large enough to hold the number of items specified
/// </summary>
/// <param name="tableName">name of the table</param>
/// <param name="requiredItemCount">number of items the table is required to hold (it may be capable of holding more); this will dictate the partition count</param>
public Table(string tableName, long requiredItemCount) : this()
{
this.Name = tableName;
// Pad the min row count by 5% to account for imperfect distribution of items
// based on the hashing algorithm.
long paddedMinItemCount = (long)(requiredItemCount * 1.05);
// Translate the item limit to a number of partition bits (64k items per partition)
_partitionBits = (byte)Math.Max(Math.Ceiling(Math.Log(requiredItemCount, 2)) - 16, 0);
// Create the partitions
PartitionMask[] maskSet = PartitionMask.BuildSet(_partitionBits);
_partitions.Clear();
for (int i = 0; i < maskSet.Length; ++i)
{
Partition p = new Partition(maskSet[i]);
_partitions.Add(p);
}
}
public void PartitionMask_GetHashIndex()
{
const byte bitsPerByte = 8;
byte bitCount = 2;
Assert.AreEqual("00, 01, 10, 11", String.Join(", ", (IEnumerable <PartitionMask>)PartitionMask.BuildSet(bitCount)));
for (byte b = 0; b < byte.MaxValue; ++b)
{
int value = b << (32 - bitsPerByte); // shift so the test value is in the highest bits
int expectedIndex = b >> (8 - bitCount);
Assert.AreEqual(expectedIndex, PartitionMask.IndexOfHash(value, bitCount));
}
}
public void PartitionMask_BuildSet()
{
Assert.AreEqual("", String.Join(", ", (IEnumerable <PartitionMask>)PartitionMask.BuildSet(0)));
Assert.AreEqual("0, 1", String.Join(", ", (IEnumerable <PartitionMask>)PartitionMask.BuildSet(1)));
Assert.AreEqual("00, 01, 10, 11", String.Join(", ", (IEnumerable <PartitionMask>)PartitionMask.BuildSet(2)));
}
