Simplify pow2 via ctor from init-list add test

2026-01-19 04:22:11 +00:00 · 2021-03-31 15:30:37 +02:00
parent 5349c05523
commit e1fbbfaebf
3 changed files with 106 additions and 279 deletions
--- a/include/boost/multiprecision/cpp_dec_float.hpp
+++ b/include/boost/multiprecision/cpp_dec_float.hpp
@@ -17,10 +17,13 @@
 #define BOOST_MP_CPP_DEC_FLOAT_BACKEND_HPP

 #include <boost/config.hpp>
-#include <cstdint>
-#include <limits>
+
+#include <algorithm>
 #include <array>
 #include <cstdint>
+#include <initializer_list>
+#include <limits>
+
 #include <boost/multiprecision/detail/hash.hpp>
 #include <boost/multiprecision/number.hpp>
 #include <boost/multiprecision/detail/big_lanczos.hpp>
@@ -549,6 +552,23 @@ class cpp_dec_float
   }

 private:
+   cpp_dec_float(std::initializer_list<std::uint32_t> lst,
+                 const exponent_type e = 0,
+                 const bool n = false) : data(),
+                                         exp(e),
+                                         neg(n),
+                                         fpclass(cpp_dec_float_finite),
+                                         prec_elem(cpp_dec_float_elem_number)
+   {
+      std::copy(lst.begin(),
+                lst.begin() + (std::min)(std::int32_t(lst.size()), cpp_dec_float_elem_number),
+                data.begin());
+
+      std::fill(data.begin() + (std::min)(std::int32_t(lst.size()), cpp_dec_float_elem_number),
+                data.end(),
+                std::uint32_t(0u));
+   }
+
   static bool data_elem_is_non_zero_predicate(const std::uint32_t& d) { return (d != static_cast<std::uint32_t>(0u)); }
   static bool data_elem_is_non_nine_predicate(const std::uint32_t& d) { return (d != static_cast<std::uint32_t>(cpp_dec_float::cpp_dec_float_elem_mask - 1)); }
   static bool char_is_nonzero_predicate(const char& c) { return (c != static_cast<char>('0')); }
@@ -2350,284 +2370,34 @@ std::uint32_t cpp_dec_float<Digits10, ExponentType, Allocator>::div_loop_n(std::
 template <unsigned Digits10, class ExponentType, class Allocator>
 cpp_dec_float<Digits10, ExponentType, Allocator> cpp_dec_float<Digits10, ExponentType, Allocator>::pow2(const boost::long_long_type p)
 {
-   // Create a static const table of p^2 for -128 < p < +128.
-   // Note: The size of this table must be odd-numbered and
-   // symmetric about 0.
-   static const std::array<cpp_dec_float<Digits10, ExponentType, Allocator>, 255u> p2_data =
-       {{cpp_dec_float("5.877471754111437539843682686111228389093327783860437607543758531392086297273635864257812500000000000e-39"),
-         cpp_dec_float("1.175494350822287507968736537222245677818665556772087521508751706278417259454727172851562500000000000e-38"),
-         cpp_dec_float("2.350988701644575015937473074444491355637331113544175043017503412556834518909454345703125000000000000e-38"),
-         cpp_dec_float("4.701977403289150031874946148888982711274662227088350086035006825113669037818908691406250000000000000e-38"),
-         cpp_dec_float("9.403954806578300063749892297777965422549324454176700172070013650227338075637817382812500000000000000e-38"),
-         cpp_dec_float("1.880790961315660012749978459555593084509864890835340034414002730045467615127563476562500000000000000e-37"),
-         cpp_dec_float("3.761581922631320025499956919111186169019729781670680068828005460090935230255126953125000000000000000e-37"),
-         cpp_dec_float("7.523163845262640050999913838222372338039459563341360137656010920181870460510253906250000000000000000e-37"),
-         cpp_dec_float("1.504632769052528010199982767644474467607891912668272027531202184036374092102050781250000000000000000e-36"),
-         cpp_dec_float("3.009265538105056020399965535288948935215783825336544055062404368072748184204101562500000000000000000e-36"),
-         cpp_dec_float("6.018531076210112040799931070577897870431567650673088110124808736145496368408203125000000000000000000e-36"),
-         cpp_dec_float("1.203706215242022408159986214115579574086313530134617622024961747229099273681640625000000000000000000e-35"),
-         cpp_dec_float("2.407412430484044816319972428231159148172627060269235244049923494458198547363281250000000000000000000e-35"),
-         cpp_dec_float("4.814824860968089632639944856462318296345254120538470488099846988916397094726562500000000000000000000e-35"),
-         cpp_dec_float("9.629649721936179265279889712924636592690508241076940976199693977832794189453125000000000000000000000e-35"),
-         cpp_dec_float("1.925929944387235853055977942584927318538101648215388195239938795566558837890625000000000000000000000e-34"),
-         cpp_dec_float("3.851859888774471706111955885169854637076203296430776390479877591133117675781250000000000000000000000e-34"),
-         cpp_dec_float("7.703719777548943412223911770339709274152406592861552780959755182266235351562500000000000000000000000e-34"),
-         cpp_dec_float("1.540743955509788682444782354067941854830481318572310556191951036453247070312500000000000000000000000e-33"),
-         cpp_dec_float("3.081487911019577364889564708135883709660962637144621112383902072906494140625000000000000000000000000e-33"),
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-         cpp_dec_float("1.972152263052529513529321413206965574183016087772557511925697326660156250000000000000000000000000000e-31"),
-         cpp_dec_float("3.944304526105059027058642826413931148366032175545115023851394653320312500000000000000000000000000000e-31"),
-         cpp_dec_float("7.888609052210118054117285652827862296732064351090230047702789306640625000000000000000000000000000000e-31"),
-         cpp_dec_float("1.577721810442023610823457130565572459346412870218046009540557861328125000000000000000000000000000000e-30"),
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-         cpp_dec_float("0.125"),
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-         cpp_dec_float("0.5"),
-         one(),
-         two(),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(4)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(8)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(16)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(32)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(64)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(128)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(256)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(512)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(1024)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(2048)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(4096)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(8192)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(16384)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(32768)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(65536)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(131072)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(262144)),
-         cpp_dec_float(static_cast<boost::ulong_long_type>(524288)),
-         cpp_dec_float(static_cast<std::uint64_t>(1uL << 20u)),
-         cpp_dec_float(static_cast<std::uint64_t>(1uL << 21u)),
-         cpp_dec_float(static_cast<std::uint64_t>(1uL << 22u)),
-         cpp_dec_float(static_cast<std::uint64_t>(1uL << 23u)),
-         cpp_dec_float(static_cast<std::uint64_t>(1uL << 24u)),
-         cpp_dec_float(static_cast<std::uint64_t>(1uL << 25u)),
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-         cpp_dec_float(static_cast<std::uint64_t>(1uL << 27u)),
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-         cpp_dec_float("6.189700196426901374495621120000000000000000000000000000000000000000000000000000000000000000000000000e26"),
-         cpp_dec_float("1.237940039285380274899124224000000000000000000000000000000000000000000000000000000000000000000000000e27"),
-         cpp_dec_float("2.475880078570760549798248448000000000000000000000000000000000000000000000000000000000000000000000000e27"),
-         cpp_dec_float("4.951760157141521099596496896000000000000000000000000000000000000000000000000000000000000000000000000e27"),
-         cpp_dec_float("9.903520314283042199192993792000000000000000000000000000000000000000000000000000000000000000000000000e27"),
-         cpp_dec_float("1.980704062856608439838598758400000000000000000000000000000000000000000000000000000000000000000000000e28"),
-         cpp_dec_float("3.961408125713216879677197516800000000000000000000000000000000000000000000000000000000000000000000000e28"),
-         cpp_dec_float("7.922816251426433759354395033600000000000000000000000000000000000000000000000000000000000000000000000e28"),
-         cpp_dec_float("1.584563250285286751870879006720000000000000000000000000000000000000000000000000000000000000000000000e29"),
-         cpp_dec_float("3.169126500570573503741758013440000000000000000000000000000000000000000000000000000000000000000000000e29"),
-         cpp_dec_float("6.338253001141147007483516026880000000000000000000000000000000000000000000000000000000000000000000000e29"),
-         cpp_dec_float("1.267650600228229401496703205376000000000000000000000000000000000000000000000000000000000000000000000e30"),
-         cpp_dec_float("2.535301200456458802993406410752000000000000000000000000000000000000000000000000000000000000000000000e30"),
-         cpp_dec_float("5.070602400912917605986812821504000000000000000000000000000000000000000000000000000000000000000000000e30"),
-         cpp_dec_float("1.014120480182583521197362564300800000000000000000000000000000000000000000000000000000000000000000000e31"),
-         cpp_dec_float("2.028240960365167042394725128601600000000000000000000000000000000000000000000000000000000000000000000e31"),
-         cpp_dec_float("4.056481920730334084789450257203200000000000000000000000000000000000000000000000000000000000000000000e31"),
-         cpp_dec_float("8.112963841460668169578900514406400000000000000000000000000000000000000000000000000000000000000000000e31"),
-         cpp_dec_float("1.622592768292133633915780102881280000000000000000000000000000000000000000000000000000000000000000000e32"),
-         cpp_dec_float("3.245185536584267267831560205762560000000000000000000000000000000000000000000000000000000000000000000e32"),
-         cpp_dec_float("6.490371073168534535663120411525120000000000000000000000000000000000000000000000000000000000000000000e32"),
-         cpp_dec_float("1.298074214633706907132624082305024000000000000000000000000000000000000000000000000000000000000000000e33"),
-         cpp_dec_float("2.596148429267413814265248164610048000000000000000000000000000000000000000000000000000000000000000000e33"),
-         cpp_dec_float("5.192296858534827628530496329220096000000000000000000000000000000000000000000000000000000000000000000e33"),
-         cpp_dec_float("1.038459371706965525706099265844019200000000000000000000000000000000000000000000000000000000000000000e34"),
-         cpp_dec_float("2.076918743413931051412198531688038400000000000000000000000000000000000000000000000000000000000000000e34"),
-         cpp_dec_float("4.153837486827862102824397063376076800000000000000000000000000000000000000000000000000000000000000000e34"),
-         cpp_dec_float("8.307674973655724205648794126752153600000000000000000000000000000000000000000000000000000000000000000e34"),
-         cpp_dec_float("1.661534994731144841129758825350430720000000000000000000000000000000000000000000000000000000000000000e35"),
-         cpp_dec_float("3.323069989462289682259517650700861440000000000000000000000000000000000000000000000000000000000000000e35"),
-         cpp_dec_float("6.646139978924579364519035301401722880000000000000000000000000000000000000000000000000000000000000000e35"),
-         cpp_dec_float("1.329227995784915872903807060280344576000000000000000000000000000000000000000000000000000000000000000e36"),
-         cpp_dec_float("2.658455991569831745807614120560689152000000000000000000000000000000000000000000000000000000000000000e36"),
-         cpp_dec_float("5.316911983139663491615228241121378304000000000000000000000000000000000000000000000000000000000000000e36"),
-         cpp_dec_float("1.063382396627932698323045648224275660800000000000000000000000000000000000000000000000000000000000000e37"),
-         cpp_dec_float("2.126764793255865396646091296448551321600000000000000000000000000000000000000000000000000000000000000e37"),
-         cpp_dec_float("4.253529586511730793292182592897102643200000000000000000000000000000000000000000000000000000000000000e37"),
-         cpp_dec_float("8.507059173023461586584365185794205286400000000000000000000000000000000000000000000000000000000000000e37"),
-         cpp_dec_float("1.701411834604692317316873037158841057280000000000000000000000000000000000000000000000000000000000000e38")}};
+   static const std::array<cpp_dec_float<Digits10, ExponentType, Allocator>, 9u> local_pow2_data =
+   {{
+      cpp_dec_float<Digits10, ExponentType, Allocator>({  6250000u }, -8),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 12500000u }, -8),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 25000000u }, -8),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 50000000u }, -8),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 1u }),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 2u }),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 4u }),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 8u }),
+      cpp_dec_float<Digits10, ExponentType, Allocator>({ 16u })
+   }};

-   if ((p > static_cast<boost::long_long_type>(-128)) && (p < static_cast<boost::long_long_type>(+128)))
-   {
-      return p2_data[static_cast<std::size_t>(p + ((p2_data.size() - 1u) / 2u))];
-   }
-   else
-   {
-      // Compute and return 2^p.
-      if (p < static_cast<boost::long_long_type>(0))
-      {
-         return pow2(static_cast<boost::long_long_type>(-p)).calculate_inv();
-      }
-      else
-      {
-         cpp_dec_float<Digits10, ExponentType, Allocator> t;
-         default_ops::detail::pow_imp(t, two(), p, std::integral_constant<bool, true>());
-         return t;
-      }
-   }
+   cpp_dec_float<Digits10, ExponentType, Allocator> t;
+
+   if      (p <  -4) { default_ops::detail::pow_imp(t, local_pow2_data[3u], boost::ulong_long_type(-p), std::integral_constant<bool, false>()); }
+   else if (p == -4) { t = local_pow2_data[0u]; }
+   else if (p == -3) { t = local_pow2_data[1u]; }
+   else if (p == -2) { t = local_pow2_data[2u]; }
+   else if (p == -1) { t = local_pow2_data[3u]; }
+   else if (p ==  0) { t = local_pow2_data[4u]; }
+   else if (p ==  1) { t = local_pow2_data[5u]; }
+   else if (p ==  2) { t = local_pow2_data[6u]; }
+   else if (p ==  3) { t = local_pow2_data[7u]; }
+   else if (p ==  4) { t = local_pow2_data[8u]; }
+   else              { default_ops::detail::pow_imp(t, local_pow2_data[5u], boost::ulong_long_type(p), std::integral_constant<bool, false>()); }
+
+   return t;
 }

 template <unsigned Digits10, class ExponentType, class Allocator>
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -1034,6 +1034,7 @@ test-suite misc :
      [ run git_issue_248.cpp ]
      [ run git_issue_265.cpp : : : [ check-target-builds ../config//has_mpfr : <source>gmp <source>mpfr : <build>no ] ]
      [ run git_issue_277.cpp ]
+      [ run git_issue_313.cpp ]
      [ compile git_issue_98.cpp : 
         [ check-target-builds ../config//has_float128 : <define>TEST_FLOAT128 <source>quadmath : ]
         [ check-target-builds ../config//has_gmp : <define>TEST_GMP <source>gmp : ]
--- a/test/git_issue_313.cpp
+++ b/test/git_issue_313.cpp
@@ -0,0 +1,56 @@
+///////////////////////////////////////////////////////////////////////////////
+//  Copyright 2021 Christopher Kormanyos. Distributed under the Boost
+//  Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <iomanip>
+#include <sstream>
+
+#include <boost/multiprecision/cpp_dec_float.hpp>
+
+#include "test.hpp"
+
+void test()
+{
+   using local_decfloat_type = boost::multiprecision::cpp_dec_float_100;
+
+   bool result0_is_ok = false;
+   bool result1_is_ok = false;
+
+   {
+      const local_decfloat_type test = pow(local_decfloat_type{2}, 30) * pow(local_decfloat_type{10}, -3);
+
+      std::stringstream strm;
+
+      strm << std::setprecision(std::numeric_limits<local_decfloat_type>::digits10)
+           << std::fixed
+           << test;
+
+      result0_is_ok =
+         (strm.str() == "1073741.8240000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
+   }
+
+   {
+      const local_decfloat_type test(0.625F);
+
+      std::stringstream strm;
+
+      strm << std::setprecision(std::numeric_limits<local_decfloat_type>::digits10)
+           << std::fixed
+           << test;
+
+      result1_is_ok =
+         (strm.str() == "0.6250000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000");
+   }
+
+   const bool result_is_ok = (result0_is_ok && result1_is_ok);
+
+   BOOST_CHECK_EQUAL(result_is_ok, true);
+}
+
+int main()
+{
+   test();
+
+   return boost::report_errors();
+}