无处不在,我为这个功能得到了很大的成果……它应该很简单,但我现在看不到它.
double prob_calculator_t::pimpl_t::B_full_term() const
{
double result = 0.0;
for (uint32_t j=0,j_end=U; j<j_end; j++)
{
uint32_t inhabited_columns = doc->row_sums[j];
// DEBUG
cout << "inhabited_columns: " << inhabited_columns << endl;
cout << "log_of_sum[j]: " << log_of_sum[j] << endl;
cout << "sum_of_log[j]: " << sum_of_log[j] << endl;
// end DEBUG
result += ( -inhabited_columns * log( log_of_sum[j] ) + sum_of_log[ j ] );
cout << "result: " << result << endl;
}
return result;
}
跟踪在哪里：
inhabited_columns: 1 log_of_sum[j]: 110.56 sum_of_log[j]: -2.81341 result: 2.02102e+10 inhabited_columns: 42 log_of_sum[j]: 110.56 sum_of_log[j]: -143.064 result: 4.04204e+10
谢谢您的帮助！
解决方法
inhabited_columns是无符号的,我看到一个一元 – 就在它之前：-inhabited_columns.
(注意,一元 – 具有非常高的运算符优先级;高于*等).
这就是你的问题所在！引用Mike Seymour的回答：
When you negate it,the result is still unsigned; the value is reduced
modulo 232 to give a large positive value.
一个修复就是写
-(inhabited_columns * log(log_of_sum[j]))
因为那时否定将以浮点进行
