Ed Warnicke | cb9cada | 2015-12-08 15:45:58 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2015 Cisco and/or its affiliates. |
| 3 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | * you may not use this file except in compliance with the License. |
| 5 | * You may obtain a copy of the License at: |
| 6 | * |
| 7 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | * |
| 9 | * Unless required by applicable law or agreed to in writing, software |
| 10 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | * See the License for the specific language governing permissions and |
| 13 | * limitations under the License. |
| 14 | */ |
| 15 | /* |
| 16 | Copyright (c) 2001, 2002, 2003 Eliot Dresselhaus |
| 17 | |
| 18 | Permission is hereby granted, free of charge, to any person obtaining |
| 19 | a copy of this software and associated documentation files (the |
| 20 | "Software"), to deal in the Software without restriction, including |
| 21 | without limitation the rights to use, copy, modify, merge, publish, |
| 22 | distribute, sublicense, and/or sell copies of the Software, and to |
| 23 | permit persons to whom the Software is furnished to do so, subject to |
| 24 | the following conditions: |
| 25 | |
| 26 | The above copyright notice and this permission notice shall be |
| 27 | included in all copies or substantial portions of the Software. |
| 28 | |
| 29 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
| 30 | EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
| 31 | MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
| 32 | NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE |
| 33 | LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION |
| 34 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
| 35 | WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
| 36 | */ |
| 37 | |
| 38 | #include <vppinfra/random.h> |
| 39 | |
Dave Barach | 0c332a3 | 2017-12-12 10:22:27 -0500 | [diff] [blame^] | 40 | /** \file Random number support |
| 41 | */ |
| 42 | |
| 43 | /** \brief Default random seed for standalone version of library. |
Ed Warnicke | cb9cada | 2015-12-08 15:45:58 -0700 | [diff] [blame] | 44 | Value can be overridden by platform code from e.g. |
| 45 | machine's clock count register. */ |
| 46 | u32 standalone_random_default_seed = 1; |
Dave Barach | c379999 | 2016-08-15 11:12:27 -0400 | [diff] [blame] | 47 | |
Dave Barach | 0c332a3 | 2017-12-12 10:22:27 -0500 | [diff] [blame^] | 48 | /** |
| 49 | * \brief Compute the X2 test statistic for a vector of counts. |
| 50 | * Each value element corresponds to a histogram bucket. |
| 51 | * |
| 52 | * Typical use-case: test the hypothesis that a set of octets |
| 53 | * are uniformly distributed (aka random). |
| 54 | * |
| 55 | * In a 1-dimensional use-case, the result should be compared |
| 56 | * with the critical value from chi square tables with |
| 57 | * vec_len(values) - 1 degrees of freedom. |
| 58 | * |
| 59 | * @param[in] values vector of histogram bucket values |
| 60 | * @return d - Pearson's X2 test statistic |
| 61 | */ |
| 62 | |
| 63 | f64 |
| 64 | clib_chisquare (u64 * values) |
| 65 | { |
| 66 | int i; |
| 67 | f64 d, delta_d, actual_frequency, expected_frequency; |
| 68 | u64 n_observations = 0; |
| 69 | |
| 70 | ASSERT (vec_len (values)); |
| 71 | |
| 72 | for (i = 0; i < vec_len (values); i++) |
| 73 | n_observations += values[i]; |
| 74 | |
| 75 | expected_frequency = (1.0 / (f64) vec_len (values)) * (f64) n_observations; |
| 76 | |
| 77 | d = 0.0; |
| 78 | |
| 79 | for (i = 0; i < vec_len (values); i++) |
| 80 | { |
| 81 | actual_frequency = ((f64) values[i]); |
| 82 | delta_d = ((actual_frequency - expected_frequency) |
| 83 | * (actual_frequency - expected_frequency)) |
| 84 | / expected_frequency; |
| 85 | d += delta_d; |
| 86 | } |
| 87 | return d; |
| 88 | } |
| 89 | |
Dave Barach | c379999 | 2016-08-15 11:12:27 -0400 | [diff] [blame] | 90 | /* |
| 91 | * fd.io coding-style-patch-verification: ON |
| 92 | * |
| 93 | * Local Variables: |
| 94 | * eval: (c-set-style "gnu") |
| 95 | * End: |
| 96 | */ |