datasketches 0.3.0

A software library of stochastic streaming algorithms (a.k.a. sketches)
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// 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.

pub(super) static KXP_BYTE_TABLE: [f64; 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, 0.0,
];

#[cfg(test)]
mod tests {
    use super::*;
    use crate::common::inv_pow2_table::INVERSE_POWERS_OF_2;

    #[test]
    fn assert_kxp_byte_table() {
        for byte in 0u8..=255 {
            // expected value
            let expected = KXP_BYTE_TABLE[byte as usize];

            // computed value
            let mut computed = 0.0;
            for col in 0..8 {
                let bit = (byte >> col) & 1;
                if bit == 0 {
                    // note the inverted logic
                    computed += INVERSE_POWERS_OF_2[col + 1]; //note the "+1"
                }
            }

            assert_eq!(expected, computed);
        }
    }
}