diff options
Diffstat (limited to 'Help/guide/tutorial/Step9/MathFunctions')
6 files changed, 127 insertions, 0 deletions
diff --git a/Help/guide/tutorial/Step9/MathFunctions/CMakeLists.txt b/Help/guide/tutorial/Step9/MathFunctions/CMakeLists.txt new file mode 100644 index 0000000..c8cd1dd --- /dev/null +++ b/Help/guide/tutorial/Step9/MathFunctions/CMakeLists.txt @@ -0,0 +1,36 @@ +# first we add the executable that generates the table +add_executable(MakeTable MakeTable.cxx) + +# add the command to generate the source code +add_custom_command( + OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/Table.h + COMMAND MakeTable ${CMAKE_CURRENT_BINARY_DIR}/Table.h + DEPENDS MakeTable + ) + +# add the main library +add_library(MathFunctions + mysqrt.cxx + ${CMAKE_CURRENT_BINARY_DIR}/Table.h + ) + +# state that anybody linking to us needs to include the current source dir +# to find MathFunctions.h, while we don't. +# state that we depend on our binary dir to find Table.h +target_include_directories(MathFunctions + INTERFACE ${CMAKE_CURRENT_SOURCE_DIR} + PRIVATE ${CMAKE_CURRENT_BINARY_DIR} + ) + +# use compile definitions to state if we have enabled USE_MYMATH +# and that anything that links to use will get this define +target_compile_definitions(MathFunctions INTERFACE "USE_MYMATH") + +if(HAVE_LOG AND HAVE_EXP) + target_compile_definitions(MathFunctions + PRIVATE "HAVE_LOG" "HAVE_EXP") +endif() + +# install rules +install(TARGETS MathFunctions DESTINATION lib) +install(FILES MathFunctions.h DESTINATION include) diff --git a/Help/guide/tutorial/Step9/MathFunctions/MakeTable.cxx b/Help/guide/tutorial/Step9/MathFunctions/MakeTable.cxx new file mode 100644 index 0000000..ee58556 --- /dev/null +++ b/Help/guide/tutorial/Step9/MathFunctions/MakeTable.cxx @@ -0,0 +1,25 @@ +// A simple program that builds a sqrt table +#include <cmath> +#include <fstream> +#include <iostream> + +int main(int argc, char* argv[]) +{ + // make sure we have enough arguments + if (argc < 2) { + return 1; + } + + std::ofstream fout(argv[1], std::ios_base::out); + const bool fileOpen = fout.is_open(); + if (fileOpen) { + fout << "double sqrtTable[] = {" << std::endl; + for (int i = 0; i < 10; ++i) { + fout << sqrt(static_cast<double>(i)) << "," << std::endl; + } + // close the table with a zero + fout << "0};" << std::endl; + fout.close(); + } + return fileOpen ? 0 : 1; // return 0 if wrote the file +} diff --git a/Help/guide/tutorial/Step9/MathFunctions/MathFunctions.cxx b/Help/guide/tutorial/Step9/MathFunctions/MathFunctions.cxx new file mode 100644 index 0000000..5351184 --- /dev/null +++ b/Help/guide/tutorial/Step9/MathFunctions/MathFunctions.cxx @@ -0,0 +1,18 @@ + +#include "MathFunctions.h" +#include <cmath> + +#ifdef USE_MYMATH +# include "mysqrt.h" +#endif + +namespace mathfunctions { +double sqrt(double x) +{ +#ifdef USE_MYMATH + return detail::mysqrt(x); +#else + return std::sqrt(x); +#endif +} +} diff --git a/Help/guide/tutorial/Step9/MathFunctions/MathFunctions.h b/Help/guide/tutorial/Step9/MathFunctions/MathFunctions.h new file mode 100644 index 0000000..cd36bcc --- /dev/null +++ b/Help/guide/tutorial/Step9/MathFunctions/MathFunctions.h @@ -0,0 +1 @@ +double mysqrt(double x); diff --git a/Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx b/Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx new file mode 100644 index 0000000..8b82141 --- /dev/null +++ b/Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx @@ -0,0 +1,41 @@ +#include "MathFunctions.h" +#include <iostream> + +// include the generated table +#include "Table.h" + +#include <cmath> + +// a hack square root calculation using simple operations +double mysqrt(double x) +{ + if (x <= 0) { + return 0; + } + + // if we have both log and exp then use them +#if defined(HAVE_LOG) && defined(HAVE_EXP) + double result = exp(log(x) * 0.5); + std::cout << "Computing sqrt of " << x << " to be " << result << " using log" + << std::endl; +#else + // use the table to help find an initial value + double result = x; + if (x >= 1 && x < 10) { + result = sqrtTable[static_cast<int>(x)]; + } + + // if we have both log and exp then use them + + // do ten iterations + for (int i = 0; i < 10; ++i) { + if (result <= 0) { + result = 0.1; + } + double delta = x - (result * result); + result = result + 0.5 * delta / result; + std::cout << "Computing sqrt of " << x << " to be " << result << std::endl; + } +#endif + return result; +} diff --git a/Help/guide/tutorial/Step9/MathFunctions/mysqrt.h b/Help/guide/tutorial/Step9/MathFunctions/mysqrt.h new file mode 100644 index 0000000..e1c42ef --- /dev/null +++ b/Help/guide/tutorial/Step9/MathFunctions/mysqrt.h @@ -0,0 +1,6 @@ + +namespace mathfunctions { +namespace detail { +double mysqrt(double x); +} +} |