#include <valarray>
#include<iostream>
typedef std::valarray<int> valarray_t;
typedef std::valarray<bool> maskarray_t;
int main(void) {
valarray_t::value_type ibuf[10] = {0,1,2,3,4,5,6,7,8,9};
valarray_t vi1(ibuf, 10);
valarray_t vi2(ibuf, 10);
// Create a valarray of bools for a mask.
maskarray_t::value_type mbuf[10] = {0,1,0,1,1,0,1,0,1,1};
maskarray_t mask(mbuf,10);
maskarray_t::value_type mbuf2[10] = {0,1,1,1,1,1,1,0,0,0};
maskarray_t mask2(mbuf2,10);
// test 1:
vi1[mask] = static_cast<valarray_t> (vi1[mask2]);
std::cout << "vi1[mask] = vi1[mask2]\n\n" << vi1[0] <<'\t'<<vi1[1]<<'\t' <<vi1[2]<<'\t'<<vi1[3]<<'\t'<<vi1[4]<<'\t'<<vi1[5]<<'\t'<<vi1[6]<<'\t'<<vi1[7]<<'\t'<<vi1[8]<<'\t'<<vi1[9]<<'\t'<< std::endl;
//test2:
std::cout<<"**********************test result=result2"<<std::endl;
std::mask_array<int> result1= vi2[mask];
std::mask_array<int> result2 = vi2[mask2];
std::valarray<int> temp1(result1);
std::cout<<"temp1[0]="<<temp1[0]<<" temp1[1]="<<temp1[1]<<" temp1[2]="<<temp1[2]<<" temp1[3]="<<temp1[3]<<std::endl;
result1=result2;
std::valarray<int> temp2(result1);
std::cout<<"temp2[0]="<<temp2[0]<<" temp2[1]="<<temp2[1]<<" temp2[2]="<<temp2[2]<<" temp2[3]="<<temp2[3]<<std::endl;
result1=result2;
std::cout << "result1= result2\n" << vi2[0] <<'\t'<<vi2[1]<<'\t' <<vi2[2]<<'\t'<<vi2[3]<<'\t'<<vi2[4]<<'\t'<<vi2[5]<<'\t'<<vi2[6]<<'\t'<<vi2[7]<<'\t'<<vi2[8]<<'\t'<<vi2[9]<<'\t'<< std::endl;
return 0;
}
Testing the code above, I got
vi1[mask] = vi1[mask2]
0 1 2 2 3 5 4 7 5 6
**********************test result=result2
temp1[0]=1 temp1[1]=3 temp1[2]=4 temp1[3]=6
temp2[0]=1 temp2[1]=3 temp2[2]=4 temp2[3]=6
result1= result2
0 1 2 3 4 5 6 7 8 9
For my understanding, both of the results are wrong.
orig: 0 1 2 3 4 5 6 7 8 9
mask: ^ ^ ^ ^ ^ ^
mask2: ^ ^ ^ ^ ^ ^
vi1[mask]=vi1[mask2] or result1=result2
0 1 2 2 2 5 2 7 5 2
orig[3]=orig[2] //orig[2] is 2, so orig[3] is 2
orig[4]=orig[3] //orig[3] is set to 2 from last step, so orig[4] is set to 2.
...
So my questions are:
- why do I get different outputs from test1 and test2? Should test1 and test2 give the same result?
- Are both outputs wrong? if not, why?
- For test2, the original array doesn't seem to be updated. Why? Is it a bug?
I used a pretty old compiler and llvm c++ library, try to figure out if it is a bug or I understand/use mask_array wrong.
Please kindly share your thoughts. Thanks for any comments.
