Return type is T which can be an integral type, float or double. By
dividing by 2 we avoid float operation on the first case and do the
right thing on the second and third.
Return type is float, so operate on float types everywhere.
Fixes this warning while building for PX4:
../../libraries/AP_Math/AP_Math.cpp: In instantiation of 'float safe_asin(T) [with T = double]':
../../libraries/AP_Math/AP_Math.cpp:56:48: required from here
../../libraries/AP_Math/AP_Math.cpp:44:11: warning: implicit conversion from 'float' to 'double' to match other operand of binary expression [-Wdouble-promotion]
if (v >= 1.0f) {
^
../../libraries/AP_Math/AP_Math.cpp:47:11: warning: implicit conversion from 'float' to 'double' to match other operand of binary expression [-Wdouble-promotion]
if (v <= -1.0f) {
^
We are calling fabsf(), which returns a float. We should use the epsilon
from float type, not from the argument type passed to fabsf().
On the other hand when the double version is instantiated we do want to
use the std::numeric_limits<double>::epsilon() value.
This adds a branch to the function, but it's removed when the function
is intantiated by the compiler since the type is known at compile-time.
Fixes this warning when building for PX4:
../../libraries/AP_Math/AP_Math.cpp: In instantiation of 'typename std::enable_if<std::is_floating_point<typename std::common_type<_Tp, _Up>::type>::value, bool>::type is_equal(Arithmetic1, Arithmetic2) [with Arithmetic1 = double; Arithmetic2 = double; typename std::enable_if<std::is_floating_point<typename std::common_type<_Tp, _Up>::type>::value, bool>::type = bool]':
../../libraries/AP_Math/AP_Math.cpp:23:66: required from here
../../libraries/AP_Math/AP_Math.cpp:17:29: warning: implicit conversion from 'float' to 'double' to match other operand of binary expression [-Wdouble-promotion]
return fabsf(v_1 - v_2) < std::numeric_limits<decltype(v_1 - v_2)>::epsilon();
^
When using wrap_180_cd() we are adding a small float (180 * 100) to a
possibly big number. This may lose float precision as illustrated by the
unit test failing:
OUT: ../../libraries/AP_Math/tests/test_math.cpp:195: Failure
OUT: Value of: wrap_180_cd(-3600000000.f)
OUT: Actual: -80
OUT: Expected: 0.f
OUT: Which is: 0
compile time optimization
Functions like sq() are better moved to the header file as inline.
Compiler can then optimize these out when used in code, this saves cpu
cycles with stack push, pop during function calls.
per Randy's suggestion, fast_atan2() is no longer necessary over atan2() because only copter uses it and copter is no longer supported on future builds of APM
ccd578664f (commitcomment-11025083)
- Allows use of hardware floating point on the Cortex-M4.
- Added "f" suffix to floating point literals.
- Call floating point versions of stdlib math functions.
Andrew Tridgell
Peter Barker
Mark Whitehorn
Tom Pittenger
Miguel Arroyo
Francisco Ferreira
Lucas De Marchi
murata
Pierre Kancir
Ricardo de Almeida Gonzaga
dgrat
Valmantas Palikša
Randy Mackay
Tom Pittenger
Jonathan Challinger
David Dewey
Andrew Tridgell
James Bielman