Started a cmake tutorial
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44
Step9/MathFunctions/CMakeLists.txt
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44
Step9/MathFunctions/CMakeLists.txt
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add_library(MathFunctions MathFunctions.cxx)
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# state that anybody linking to us needs to include the current source dir
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# to find MathFunctions.h, while we don't.
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target_include_directories(MathFunctions
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INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}
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)
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# should we use our own math functions
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option(USE_MYMATH "Use tutorial provided math implementation" ON)
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if (USE_MYMATH)
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target_compile_definitions(MathFunctions PRIVATE "USE_MYMATH")
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# generate Table.h
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include(MakeTable.cmake)
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# library that just does sqrt
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add_library(SqrtLibrary STATIC
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mysqrt.cxx
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${CMAKE_CURRENT_BINARY_DIR}/Table.h
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)
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# state that we depend on our binary dir to find Table.h
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target_include_directories(SqrtLibrary PRIVATE
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${CMAKE_CURRENT_BINARY_DIR}
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)
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# link SqrtLibrary to tutorial_compiler_flags
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target_link_libraries(SqrtLibrary PUBLIC tutorial_compiler_flags)
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target_link_libraries(MathFunctions PRIVATE SqrtLibrary)
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endif()
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# link MathFunctions to tutorial_compiler_flags
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target_link_libraries(MathFunctions PUBLIC tutorial_compiler_flags)
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# install libs
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set(installable_libs MathFunctions tutorial_compiler_flags)
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if(TARGET SqrtLibrary)
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list(APPEND installable_libs SqrtLibrary)
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endif()
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install(TARGETS ${installable_libs} DESTINATION lib)
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# install include headers
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install(FILES MathFunctions.h DESTINATION include)
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10
Step9/MathFunctions/MakeTable.cmake
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10
Step9/MathFunctions/MakeTable.cmake
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# first we add the executable that generates the table
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add_executable(MakeTable MakeTable.cxx)
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target_link_libraries(MakeTable PRIVATE tutorial_compiler_flags)
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# add the command to generate the source code
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add_custom_command(
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OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/Table.h
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COMMAND MakeTable ${CMAKE_CURRENT_BINARY_DIR}/Table.h
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DEPENDS MakeTable
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)
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25
Step9/MathFunctions/MakeTable.cxx
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25
Step9/MathFunctions/MakeTable.cxx
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// A simple program that builds a sqrt table
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#include <cmath>
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#include <fstream>
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#include <iostream>
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int main(int argc, char* argv[])
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{
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// make sure we have enough arguments
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if (argc < 2) {
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return 1;
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}
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std::ofstream fout(argv[1], std::ios_base::out);
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const bool fileOpen = fout.is_open();
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if (fileOpen) {
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fout << "double sqrtTable[] = {" << std::endl;
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for (int i = 0; i < 10; ++i) {
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fout << sqrt(static_cast<double>(i)) << "," << std::endl;
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}
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// close the table with a zero
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fout << "0};" << std::endl;
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fout.close();
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}
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return fileOpen ? 0 : 1; // return 0 if wrote the file
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}
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19
Step9/MathFunctions/MathFunctions.cxx
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19
Step9/MathFunctions/MathFunctions.cxx
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#include "MathFunctions.h"
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#include <cmath>
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#ifdef USE_MYMATH
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# include "mysqrt.h"
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#endif
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namespace mathfunctions {
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double sqrt(double x)
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{
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// which square root function should we use?
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#ifdef USE_MYMATH
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return detail::mysqrt(x);
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#else
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return std::sqrt(x);
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#endif
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}
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}
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5
Step9/MathFunctions/MathFunctions.h
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5
Step9/MathFunctions/MathFunctions.h
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#pragma once
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namespace mathfunctions {
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double sqrt(double x);
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}
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37
Step9/MathFunctions/mysqrt.cxx
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37
Step9/MathFunctions/mysqrt.cxx
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#include "mysqrt.h"
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#include <iostream>
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// include the generated table
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#include "Table.h"
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namespace mathfunctions {
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namespace detail {
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// a hack square root calculation using simple operations
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double mysqrt(double x)
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{
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if (x <= 0) {
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return 0;
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}
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// use the table to help find an initial value
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double result = x;
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if (x >= 1 && x < 10) {
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std::cout << "Use the table to help find an initial value " << std::endl;
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result = sqrtTable[static_cast<int>(x)];
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}
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// do ten iterations
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for (int i = 0; i < 10; ++i) {
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if (result <= 0) {
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result = 0.1;
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}
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double delta = x - (result * result);
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result = result + 0.5 * delta / result;
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std::cout << "Computing sqrt of " << x << " to be " << result << std::endl;
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}
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return result;
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}
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}
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}
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7
Step9/MathFunctions/mysqrt.h
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7
Step9/MathFunctions/mysqrt.h
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#pragma once
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namespace mathfunctions {
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namespace detail {
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double mysqrt(double x);
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}
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}
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