package org.apache.lucene.util; /** * Copyright 2005 The Apache Software Foundation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.util.Random; /** * @version $Id$ */ public class TestSmallFloat extends LuceneTestCase { // original lucene byteToFloat static float orig_byteToFloat(byte b) { if (b == 0) // zero is a special case return 0.0f; int mantissa = b & 7; int exponent = (b >> 3) & 31; int bits = ((exponent+(63-15)) << 24) | (mantissa << 21); return Float.intBitsToFloat(bits); } // original lucene floatToByte static byte orig_floatToByte(float f) { if (f < 0.0f) // round negatives up to zero f = 0.0f; if (f == 0.0f) // zero is a special case return 0; int bits = Float.floatToIntBits(f); // parse float into parts int mantissa = (bits & 0xffffff) >> 21; int exponent = (((bits >> 24) & 0x7f) - 63) + 15; if (exponent > 31) { // overflow: use max value exponent = 31; mantissa = 7; } if (exponent < 0) { // underflow: use min value exponent = 0; mantissa = 1; } return (byte)((exponent << 3) | mantissa); // pack into a byte } public void testByteToFloat() { for (int i=0; i<256; i++) { float f1 = orig_byteToFloat((byte)i); float f2 = SmallFloat.byteToFloat((byte)i, 3,15); float f3 = SmallFloat.byte315ToFloat((byte)i); assertEquals(f1,f2,0.0); assertEquals(f2,f3,0.0); float f4 = SmallFloat.byteToFloat((byte)i,5,2); float f5 = SmallFloat.byte52ToFloat((byte)i); assertEquals(f4,f5,0.0); } } public void testFloatToByte() { Random rand = newRandom(); // up iterations for more exhaustive test after changing something for (int i=0; i<100000; i++) { float f = Float.intBitsToFloat(rand.nextInt()); if (f!=f) continue; // skip NaN byte b1 = orig_floatToByte(f); byte b2 = SmallFloat.floatToByte(f,3,15); byte b3 = SmallFloat.floatToByte315(f); assertEquals(b1,b2); assertEquals(b2,b3); byte b4 = SmallFloat.floatToByte(f,5,2); byte b5 = SmallFloat.floatToByte52(f); assertEquals(b4,b5); } } /*** // Do an exhaustive test of all possible floating point values // for the 315 float against the original norm encoding in Similarity. // Takes 75 seconds on my Pentium4 3GHz, with Java5 -server public void testAllFloats() { for(int i = Integer.MIN_VALUE;;i++) { float f = Float.intBitsToFloat(i); if (f==f) { // skip non-numbers byte b1 = orig_floatToByte(f); byte b2 = SmallFloat.floatToByte315(f); if (b1!=b2) { TestCase.fail("Failed floatToByte315 for float " + f); } } if (i==Integer.MAX_VALUE) break; } } ***/ }