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Tutorial: Improve Step 6

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* Print message when using the table
* Remove duplicated comment
* Remove HAVE_LOG and HAVE_EXP checks, use generated table instead
This commit is contained in:
Betsy McPhail
2019-07-26 12:46:08 -04:00
committed by Brad King
parent df9cdf629c
commit a36731c634
15 changed files with 35 additions and 145 deletions
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11
Help/guide/tutorial/Step9/MathFunctions/CMakeLists.txt
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@@ -26,17 +26,6 @@ target_include_directories(MathFunctions
# and that anything that links to use will get this define
target_compile_definitions(MathFunctions INTERFACE "USE_MYMATH")
# does this system provide the log and exp functions?
include(CheckSymbolExists)
set(CMAKE_REQUIRED_LIBRARIES "m")
check_symbol_exists(log "math.h" HAVE_LOG)
check_symbol_exists(exp "math.h" HAVE_EXP)
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)

13
Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx
View File

@@ -4,8 +4,6 @@
// include the generated table
#include "Table.h"
#include <cmath>
// a hack square root calculation using simple operations
double mysqrt(double x)
{
@@ -13,20 +11,13 @@ double mysqrt(double x)
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 and exp" << std::endl;
#else
// use the table to help find an initial value
double result = x;
if (x >= 1 && x < 10) {
std::cout << "Use the table to help find an initial value " << std::endl;
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) {
@@ -36,6 +27,6 @@ double mysqrt(double x)
result = result + 0.5 * delta / result;
std::cout << "Computing sqrt of " << x << " to be " << result << std::endl;
}
#endif
return result;
}