calculate 1000000 numbers

.gitignore

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+# IDE
+.vscode/
+uncrustify.cfg
+
+# Xmake cache
+.xmake/
+build/
+
+# MacOS Cache
+.DS_Store
+
+

src/main.cpp

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+#include <iostream>
+#include "mpfr.h"
+
+using namespace std;
+
+int main(int argc, char **argv) {
+  mpfr_t a_0, b_0, s_0, a_k, b_k, s_k, approx_pi, tmp_1, tmp_2;
+  mpfr_inits2(3600000, a_0, b_0, s_0, a_k, b_k, s_k, approx_pi, tmp_1, tmp_2, NULL);
+  mpfr_set_d(a_0, 1.0, MPFR_RNDF);
+  mpfr_sqrt_ui(b_0, 2, MPFR_RNDF);
+  mpfr_div_ui(b_0, b_0, 2, MPFR_RNDF);
+  mpfr_set_d(s_0, 0.5, MPFR_RNDF);
+  for (int k = 1; k <= 20; k++) {
+    mpfr_add(a_k, a_0, b_0, MPFR_RNDF);
+    mpfr_div_ui(a_k, a_k, 2, MPFR_RNDF);
+
+    mpfr_mul(b_k, a_0, b_0, MPFR_RNDF);
+    mpfr_sqrt(b_k, b_k, MPFR_RNDF);
+
+    mpfr_add(tmp_1, a_k, b_k, MPFR_RNDF);
+    mpfr_sub(tmp_2, a_k, b_k, MPFR_RNDF);
+    mpfr_mul(tmp_1, tmp_1, tmp_2, MPFR_RNDF);
+    mpfr_ui_pow_ui(tmp_2,2, k, MPFR_RNDF);
+    mpfr_mul(tmp_1, tmp_1, tmp_2, MPFR_RNDF);
+    mpfr_sub(s_k, s_0, tmp_1, MPFR_RNDF);
+
+    mpfr_set(a_0, a_k, MPFR_RNDF);
+    mpfr_set(b_0, b_k, MPFR_RNDF);
+    mpfr_set(s_0, s_k, MPFR_RNDF);
+  }
+  mpfr_mul(approx_pi, a_0, a_0, MPFR_RNDF);
+  mpfr_mul_ui(approx_pi, approx_pi, 2, MPFR_RNDF);
+  mpfr_div(approx_pi, approx_pi, s_0, MPFR_RNDF);
+  mpfr_printf("%.1000000Rf\n", approx_pi);
+  return 0;
+}

xmake.lua

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+add_rules("mode.debug", "mode.release")
+
+add_requires("mpfr")
+
+target("PiCalculatorCpp")
+    set_kind("binary")
+    set_languages("c99", "c++11")
+    set_optimize("fastest")
+    add_packages("mpfr")
+    add_files("src/*.cpp")
+
+--
+-- If you want to known more usage about xmake, please see https://xmake.io
+--
+-- ## FAQ
+--
+-- You can enter the project directory firstly before building project.
+--
+--   $ cd projectdir
+--
+-- 1. How to build project?
+--
+--   $ xmake
+--
+-- 2. How to configure project?
+--
+--   $ xmake f -p [macosx|linux|iphoneos ..] -a [x86_64|i386|arm64 ..] -m [debug|release]
+--
+-- 3. Where is the build output directory?
+--
+--   The default output directory is `./build` and you can configure the output directory.
+--
+--   $ xmake f -o outputdir
+--   $ xmake
+--
+-- 4. How to run and debug target after building project?
+--
+--   $ xmake run [targetname]
+--   $ xmake run -d [targetname]
+--
+-- 5. How to install target to the system directory or other output directory?
+--
+--   $ xmake install
+--   $ xmake install -o installdir
+--
+-- 6. Add some frequently-used compilation flags in xmake.lua
+--
+-- @code
+--    -- add debug and release modes
+--    add_rules("mode.debug", "mode.release")
+--
+--    -- add macro definition
+--    add_defines("NDEBUG", "_GNU_SOURCE=1")
+--
+--    -- set warning all as error
+--    set_warnings("all", "error")
+--
+--    -- set language: c99, c++11
+--    set_languages("c99", "c++11")
+--
+--    -- set optimization: none, faster, fastest, smallest
+--    set_optimize("fastest")
+--
+--    -- add include search directories
+--    add_includedirs("/usr/include", "/usr/local/include")
+--
+--    -- add link libraries and search directories
+--    add_links("tbox")
+--    add_linkdirs("/usr/local/lib", "/usr/lib")
+--
+--    -- add system link libraries
+--    add_syslinks("z", "pthread")
+--
+--    -- add compilation and link flags
+--    add_cxflags("-stdnolib", "-fno-strict-aliasing")
+--    add_ldflags("-L/usr/local/lib", "-lpthread", {force = true})
+--
+-- @endcode
+--
+