55 lines · cpp
1// RUN: %clangxx_nsan -O0 -g -DSOFTMAX=softmax %s -o %t2// RUN: env NSAN_OPTIONS=check_nan=true,halt_on_error=0,log2_max_relative_error=19 %run %t 2>&1 | FileCheck %s3 4// RUN: %clangxx_nsan -O3 -g -DSOFTMAX=softmax %s -o %t5// RUN: env NSAN_OPTIONS=check_nan=true,halt_on_error=0,log2_max_relative_error=19 %run %t 2>&1 | FileCheck %s6 7// RUN: %clangxx_nsan -O0 -g -DSOFTMAX=stable_softmax %s -o %t8// RUN: env NSAN_OPTIONS=check_nan=true,halt_on_error=1,log2_max_relative_error=19 %run %t 9 10// RUN: %clangxx_nsan -O3 -g -DSOFTMAX=stable_softmax %s -o %t11// RUN: env NSAN_OPTIONS=check_nan=true,halt_on_error=1,log2_max_relative_error=19 %run %t12 13#include<iostream>14#include<vector>15#include<algorithm>16#include<cmath>17 18// unstable softmax19template <typename T>20__attribute__((noinline)) void softmax(std::vector<T> &values) {21 T sum_exp = 0.0;22 for (auto &i: values) {23 i = std::exp(i);24 sum_exp += i;25 }26 for (auto &i: values) {27 i /= sum_exp;28 }29}30 31// use max value to avoid overflow32// \sigma_i exp(x_i) / \sum_j exp(x_j) = \sigma_i exp(x_i - max(x)) / \sum_j exp(x_j - max(x))33template <typename T>34__attribute__((noinline)) void stable_softmax(std::vector<T> &values) {35 T sum_exp = 0.0;36 T max_values = *std::max_element(values.begin(), values.end());37 for (auto &i: values) {38 i = std::exp(i - max_values);39 sum_exp += i;40 }41 for (auto &i:values) {42 i /= sum_exp;43 }44}45 46int main() {47 std::vector<double> data = {1000, 1001, 1002};48 SOFTMAX(data);49 for (auto i: data) {50 printf("%f", i);51 // CHECK: WARNING: NumericalStabilitySanitizer: NaN detected52 }53 return 0;54}55