1 /* 2 * Copyright 2023 Google LLC 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef FCP_SECAGG_SERVER_DISTRIBUTION_UTILITIES_H_ 18 #define FCP_SECAGG_SERVER_DISTRIBUTION_UTILITIES_H_ 19 20 #include <memory> 21 22 #include "fcp/base/monitoring.h" 23 24 namespace fcp { 25 namespace secagg { 26 27 // Represents a Hypergeometric distribution with parameters fixed at creation of 28 // the object. Allows to query certain distribution functions. 29 class HypergeometricDistribution { 30 public: 31 static StatusOr<std::unique_ptr<HypergeometricDistribution>> Create( 32 int total, int marked, int sampled); 33 34 // Evaluates the probability mass funciton of the random variable at x. 35 double PMF(double x); 36 37 // Evaluates the cumulative distribution function of the random variable at x. 38 double CDF(double x); 39 40 // Finds the value whose cdf is quantile rounded outwards to an integer. 41 // Setting complement to true is equivalent to setting quantile = 1 - quantile 42 // but can avoid numerical error in the extreme upper tail. 43 double FindQuantile(double quantile, bool complement = false); 44 45 private: 46 const int total_; 47 const int marked_; 48 const int sampled_; 49 HypergeometricDistribution(int total,int marked,int sampled)50 HypergeometricDistribution(int total, int marked, int sampled) 51 : total_(total), marked_(marked), sampled_(sampled) {} 52 53 double PMFImpl(double x, int counted); 54 55 double CDFImpl(double x, int counted); 56 57 double FindQuantileImpl(double quantile, int counted); 58 }; 59 60 } // namespace secagg 61 } // namespace fcp 62 #endif // FCP_SECAGG_SERVER_DISTRIBUTION_UTILITIES_H_ 63