sysrap/tests/signbitTest.cc

0001 // name=signbitTest ; gcc $name.cc -std=c++11 -lstdc++ -o /tmp/$name && /tmp/$name
0002
0003 #include <vector>
0004 #include <cmath>
0005 #include <cstdio>
0006 #include <cassert>
0007
0008
0009
0010 void check_nan()
0011 {
0012     unsigned n = 8 ;
0013     float* pairs = new float[n*2]
0014     {
0015         1.f,  1.f,
0016        -1.f,  1.f,
0017         1.f,  0.f,
0018        -1.f,  0.f,
0019         0.f,  0.f,
0020        -0.f,  0.f,
0021         0.f, -0.f,
0022        -0.f, -0.f
0023     };
0024
0025     for(unsigned i=0 ; i < n ; i++ )
0026     {
0027         float num = pairs[2*i+0] ;
0028         float den = pairs[2*i+1] ;
0029         float rat = num/den ;
0030         bool  neg = signbit(rat);
0031
0032         float nrat = -rat ;
0033         float rat0 = rat + 0.f ;
0034         float rat2 = rat*2.f ;
0035         // all expressions with nan yield nan
0036
0037         bool gt_0 = rat > 0.f ;
0038         bool ge_0 = rat >= 0.f ;
0039         bool lt_0 = rat < 0.f ;
0040         bool le_0 = rat <= 0.f ;
0041         bool eq_0 = rat == 0.f ;
0042         bool or_expr_0 = num < 100.f || rat > 0.f ;   // the nan always false does NOT spread to short circuit OR result
0043         bool or_expr_1 = rat > 0.f || num < 100.f ;
0044         bool or_expr_2 = rat > 0.f || num > 100.f ;
0045
0046
0047         printf("//signbitTest  i %d num %10.4f den %10.4f rat %10.4f signbit %d  -rat %10.4f  rat+0.f %10.4f rat*2.f %10.4f ", i, num, den, rat, neg, nrat, rat0, rat2 );
0048         printf(" gt_0 %d ge_0 %d lt_0 %d le_0 %d eq_0 %d or_expr_0 %d or_expr_1 %d or_expr_2 %d  \n", gt_0, ge_0, lt_0, le_0, eq_0, or_expr_0, or_expr_1, or_expr_2 );
0049
0050         if(std::isnan(rat))
0051         {
0052             //printf("//isnan : all comparisons with nan return false \n");
0053             assert( gt_0 == false );
0054             assert( ge_0 == false );
0055             assert( lt_0 == false );
0056             assert( le_0 == false );
0057             assert( eq_0 == false );
0058         }
0059
0060     }
0061 }
0062
0063
0064 void check_inf()
0065 {
0066     float inf = 1.f/0.f ;
0067     float ninf = -inf;
0068
0069     float inf_times_zero = inf*0.f ;
0070     float inf_plus_zero = inf+0.f ;
0071     float inf_times_one = inf*1.f ;
0072     float inf_plus_one = inf+1.f ;
0073
0074     float ninf_times_zero = ninf*0.f ;
0075     float ninf_plus_zero = ninf+0.f ;
0076     float ninf_times_one = ninf*1.f ;
0077     float ninf_plus_one = ninf+1.f ;
0078
0079     float ninf_times_minus_one = ninf*-1.f ;
0080
0081
0082     printf("// inf      %10.4f \n", inf );
0083     printf("// ninf     %10.4f \n", ninf );
0084
0085     printf("// inf_times_zero %10.4f \n", inf_times_zero );
0086     printf("// inf_plus_zero %10.4f \n",  inf_plus_zero );
0087     printf("// inf_times_one %10.4f \n", inf_times_one );
0088     printf("// inf_plus_one %10.4f \n",  inf_plus_one );
0089
0090     assert( std::isnan(inf_times_zero) );
0091     assert( std::isinf(inf_plus_zero) );
0092     assert( std::isinf(inf_times_one) );
0093     assert( std::isinf(inf_plus_one) );
0094
0095     printf("// ninf_times_zero %10.4f \n", ninf_times_zero );
0096     printf("// ninf_times_minus_one %10.4f \n", ninf_times_minus_one );
0097     printf("// ninf_plus_zero %10.4f \n",  ninf_plus_zero );
0098     printf("// ninf_times_one %10.4f \n", ninf_times_one );
0099     printf("// ninf_plus_one %10.4f \n",  ninf_plus_one );
0100
0101     assert( std::isnan(ninf_times_zero) );
0102     assert( std::isinf(ninf_plus_zero) );
0103     assert( std::isinf(ninf_times_one) );
0104     assert( std::isinf(ninf_plus_one) );
0105 }
0106
0107
0108
0109
0110 int main(int argc, char** argv)
0111 {
0112     // check_nan();
0113     check_inf();
0114     return 0 ;
0115 }