cpc/include/kxp_byte_lookup.hpp

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

#ifndef KXP_BYTE_LOOKUP_HPP_
#define KXP_BYTE_LOOKUP_HPP_

namespace datasketches {

// the table was created by the following procedure:

//void fill_kxp_byte_table() {
//  for (int byte = 0; byte < 256; byte++) {
//    double sum = 0.0;
//    for (int col = 0; col < 8; col++) {
//      const uint8_t bit = (byte >> col) & 1;
//      if (bit == 0) { // note the inverted logic
//        sum += INVERSE_POWERS_OF_2[col + 1]; // note the "+1"
//      }
//    }
//    kxp_byte_table[byte] = sum;
//
//    printf("%.17g", kxp_byte_table[byte]);
//    if (byte != 255) printf(", ");
//    if ((byte + 1) % 8 == 0) printf("\n");
//  }
//}

static const double KXP_BYTE_TABLE[256] = {
    0.99609375, 0.49609375, 0.74609375, 0.24609375, 0.87109375, 0.37109375, 0.62109375, 0.12109375,
    0.93359375, 0.43359375, 0.68359375, 0.18359375, 0.80859375, 0.30859375, 0.55859375, 0.05859375,
    0.96484375, 0.46484375, 0.71484375, 0.21484375, 0.83984375, 0.33984375, 0.58984375, 0.08984375,
    0.90234375, 0.40234375, 0.65234375, 0.15234375, 0.77734375, 0.27734375, 0.52734375, 0.02734375,
    0.98046875, 0.48046875, 0.73046875, 0.23046875, 0.85546875, 0.35546875, 0.60546875, 0.10546875,
    0.91796875, 0.41796875, 0.66796875, 0.16796875, 0.79296875, 0.29296875, 0.54296875, 0.04296875,
    0.94921875, 0.44921875, 0.69921875, 0.19921875, 0.82421875, 0.32421875, 0.57421875, 0.07421875,
    0.88671875, 0.38671875, 0.63671875, 0.13671875, 0.76171875, 0.26171875, 0.51171875, 0.01171875,
    0.98828125, 0.48828125, 0.73828125, 0.23828125, 0.86328125, 0.36328125, 0.61328125, 0.11328125,
    0.92578125, 0.42578125, 0.67578125, 0.17578125, 0.80078125, 0.30078125, 0.55078125, 0.05078125,
    0.95703125, 0.45703125, 0.70703125, 0.20703125, 0.83203125, 0.33203125, 0.58203125, 0.08203125,
    0.89453125, 0.39453125, 0.64453125, 0.14453125, 0.76953125, 0.26953125, 0.51953125, 0.01953125,
    0.97265625, 0.47265625, 0.72265625, 0.22265625, 0.84765625, 0.34765625, 0.59765625, 0.09765625,
    0.91015625, 0.41015625, 0.66015625, 0.16015625, 0.78515625, 0.28515625, 0.53515625, 0.03515625,
    0.94140625, 0.44140625, 0.69140625, 0.19140625, 0.81640625, 0.31640625, 0.56640625, 0.06640625,
    0.87890625, 0.37890625, 0.62890625, 0.12890625, 0.75390625, 0.25390625, 0.50390625, 0.00390625,
    0.9921875, 0.4921875, 0.7421875, 0.2421875, 0.8671875, 0.3671875, 0.6171875, 0.1171875,
    0.9296875, 0.4296875, 0.6796875, 0.1796875, 0.8046875, 0.3046875, 0.5546875, 0.0546875,
    0.9609375, 0.4609375, 0.7109375, 0.2109375, 0.8359375, 0.3359375, 0.5859375, 0.0859375,
    0.8984375, 0.3984375, 0.6484375, 0.1484375, 0.7734375, 0.2734375, 0.5234375, 0.0234375,
    0.9765625, 0.4765625, 0.7265625, 0.2265625, 0.8515625, 0.3515625, 0.6015625, 0.1015625,
    0.9140625, 0.4140625, 0.6640625, 0.1640625, 0.7890625, 0.2890625, 0.5390625, 0.0390625,
    0.9453125, 0.4453125, 0.6953125, 0.1953125, 0.8203125, 0.3203125, 0.5703125, 0.0703125,
    0.8828125, 0.3828125, 0.6328125, 0.1328125, 0.7578125, 0.2578125, 0.5078125, 0.0078125,
    0.984375, 0.484375, 0.734375, 0.234375, 0.859375, 0.359375, 0.609375, 0.109375,
    0.921875, 0.421875, 0.671875, 0.171875, 0.796875, 0.296875, 0.546875, 0.046875,
    0.953125, 0.453125, 0.703125, 0.203125, 0.828125, 0.328125, 0.578125, 0.078125,
    0.890625, 0.390625, 0.640625, 0.140625, 0.765625, 0.265625, 0.515625, 0.015625,
    0.96875, 0.46875, 0.71875, 0.21875, 0.84375, 0.34375, 0.59375, 0.09375,
    0.90625, 0.40625, 0.65625, 0.15625, 0.78125, 0.28125, 0.53125, 0.03125,
    0.9375, 0.4375, 0.6875, 0.1875, 0.8125, 0.3125, 0.5625, 0.0625,
    0.875, 0.375, 0.625, 0.125, 0.75, 0.25, 0.5, 0
};

} /* namespace datasketches */

#endif