Example #1
0
        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);
        }
Example #2
0
        /// <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);
            }
        }
Example #3
0
        /// <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)));
 }