Improve an example and also cover lines

example/exercise_threading_log_agm.cpp

@@ -30,7 +30,7 @@
 //
 // cpp_dec_float:
 // result_is_ok_concurrent: true, calculation_time_concurrent: 2.1s
-// result_is_ok_sequential: true, calculation_time_sequential: 15.2s
+// result_is_ok_sequential: true, calculation_time_sequential: 14.7s
 //
 // cpp_bin_float:
 // result_is_ok_concurrent: true, calculation_time_concurrent: 0.28s
@@ -52,6 +52,7 @@
 #include <iomanip>
 #include <iostream>
 #include <limits>
+#include <sstream>
 #include <thread>
 #include <vector>
 
@@ -70,7 +71,7 @@
 //#define BOOST_MP_EXERCISE_THREADING_BACKEND_TYPE BOOST_MP_EXERCISE_THREADING_BACKEND_MPFR_FLOAT
 #endif
 
-constexpr unsigned local_mp_digits { 301U };
+constexpr unsigned local_mp_digits { 101U };
 
 #if  (BOOST_MP_EXERCISE_THREADING_BACKEND_TYPE == BOOST_MP_EXERCISE_THREADING_BACKEND_CPP_DEC_FLOAT)
 #include <boost/multiprecision/cpp_dec_float.hpp>
@@ -379,7 +380,10 @@ bool log_agm_concurrent(float& calculation_time)
     result_is_ok &= (close_fraction < tol);
   }
 
-  std::cout << std::boolalpha << result_is_ok << std::endl;
+  std::stringstream strm { };
+  strm << std::boolalpha << result_is_ok;
+
+  std::cout << strm.str() << std::endl;
 
   return result_is_ok;
 }
@@ -440,7 +444,10 @@ bool log_agm_sequential(float& calculation_time)
     result_is_ok &= (close_fraction < tol);
   }
 
-  std::cout << std::boolalpha << result_is_ok << std::endl;
+  std::stringstream strm { };
+  strm << std::boolalpha << result_is_ok;
+
+  std::cout << strm.str() << std::endl;
 
   return result_is_ok;
 }

include/boost/multiprecision/cpp_dec_float.hpp

@@ -472,11 +472,14 @@ class cpp_dec_float // LCOV_EXCL_LINE This causes a false negative on lcov cover
 
    exponent_type order() const
    {
-      const bool bo_order_is_zero = ((!(isfinite)()) || (data[0] == static_cast<std::uint32_t>(0u)));
+      const bool
+         bo_order_is_zero
+         {
+            ((!(isfinite)()) || (data[0] == static_cast<std::uint32_t>(0u)))
+         };
 
-      exponent_type prefix = limb_order(data[static_cast<std::size_t>(UINT8_C(0))]);
-
-      return (bo_order_is_zero ? static_cast<exponent_type>(0) : static_cast<exponent_type>(exp + prefix));
+      return (bo_order_is_zero ? static_cast<exponent_type>(0)
+                               : static_cast<exponent_type>(exp + limb_order(data[static_cast<std::size_t>(UINT8_C(0))])));
    }
 
    #ifndef BOOST_MP_STANDALONE

test/test_various_edges_more.cpp

@@ -622,6 +622,50 @@ namespace local
       }
     }
 
+    BOOST_IF_CONSTEXPR((std::numeric_limits<float>::digits >= 24) && std::numeric_limits<float_type>::is_specialized)
+    {
+      for(auto index = static_cast<unsigned>(UINT8_C(0)); index < static_cast<unsigned>(UINT8_C(16)); ++index)
+      {
+        // This test is specifically designed to pick up hard-to-reach lines
+        // in cpp_dec_float. Notice how the printed string is expected to have
+        // (or not have) rounding at the 8th fixed-point digit.
+
+        // N[1 + 1/2^4 + 1/2^5 + 1/2^7  + 1/2^9, 20]
+        const float flt_builtin { 1.1035156250000000000F };
+
+        const float_type delta = std::numeric_limits<float_type>::epsilon() * dis(gen) * static_cast<float>(index + 1U);
+
+        const float_type flt_val_base  { flt_builtin };
+
+        const float_type flt_val_close_upper { flt_builtin + delta };
+        const float_type flt_val_close_lower { flt_builtin - delta };
+
+        {
+          std::stringstream strm { };
+
+          strm << std::fixed << std::setprecision(std::streamsize { INT8_C(8) }) << flt_val_base;
+
+          BOOST_TEST(strm.str() == "1.10351562");
+        }
+
+        {
+          std::stringstream strm { };
+
+          strm << std::fixed << std::setprecision(std::streamsize { INT8_C(8) }) << flt_val_close_upper;
+
+          BOOST_TEST(strm.str() > "1.10351562");
+        }
+
+        {
+          std::stringstream strm { };
+
+          strm << std::fixed << std::setprecision(std::streamsize { INT8_C(8) }) << flt_val_close_lower;
+
+          BOOST_TEST(strm.str() == "1.10351562");
+        }
+      }
+    }
+
     return result_is_ok;
   }