Subject: [Boost-commit] svn:boost r85333 - trunk/boost/multiprecision/detail/functions
From: john_at_[hidden]
Date: 2013-08-13 13:05:54
Author: johnmaddock
Date: 2013-08-13 13:05:54 EDT (Tue, 13 Aug 2013)
New Revision: 85333
URL: http://svn.boost.org/trac/boost/changeset/85333
Log:
Modify cosine default evaluation code to call the sin code: less code and better precision.
Text files modified:
trunk/boost/multiprecision/detail/functions/trig.hpp | 44 +++------------------------------------
1 files changed, 4 insertions(+), 40 deletions(-)
Modified: trunk/boost/multiprecision/detail/functions/trig.hpp
==============================================================================
--- trunk/boost/multiprecision/detail/functions/trig.hpp Tue Aug 13 09:40:57 2013 (r85332)
+++ trunk/boost/multiprecision/detail/functions/trig.hpp 2013-08-13 13:05:54 EDT (Tue, 13 Aug 2013) (r85333)
@@ -292,10 +292,8 @@
const bool b_zero = eval_get_sign(xx) == 0;
const bool b_pi_half = com == 0;
- // Check if the reduced argument is very close to 0 or pi/2.
- const bool b_near_zero = xx.compare(fp_type(1e-4)) < 0;
- eval_subtract(t, xx);
- const bool b_near_pi_half = t.compare(fp_type(1e-4)) < 0;
+ // Check if the reduced argument is very close to 0.
+ const bool b_near_zero = xx.compare(fp_type(1e-1)) < 0;
if(b_zero)
{
@@ -313,44 +311,10 @@
hyp0F1(result, n_pi, t);
BOOST_MATH_INSTRUMENT_CODE(result.str(0, std::ios_base::scientific));
}
- else if(b_near_pi_half)
- {
- T t2(t);
- eval_multiply(t, t);
- eval_divide(t, si_type(-4));
- n_pi = fp_type(1.5f);
- hyp0F1(result, n_pi, t);
- eval_multiply(result, t2);
- BOOST_MATH_INSTRUMENT_CODE(result.str(0, std::ios_base::scientific));
- }
else
{
- // Scale to a small argument for an efficient Taylor series,
- // implemented as a hypergeometric function. Use a standard
- // divide by three identity a certain number of times.
- // Here we use division by 3^9 --> (19683 = 3^9).
-
- static const ui_type n_scale = 9;
- static const ui_type n_three_pow_scale = 19683;
- eval_divide(xx, n_three_pow_scale);
-
- eval_multiply(t, xx, xx);
- eval_divide(t, si_type(-4));
- n_pi = fp_type(0.5f);
-
- // Now with small arguments, we are ready for a series expansion.
- hyp0F1(result, n_pi, t);
- BOOST_MATH_INSTRUMENT_CODE(result.str(0, std::ios_base::scientific));
-
- // Convert back using multiple angle identity.
- for(ui_type k = 0; k < n_scale; k++)
- {
- eval_multiply(t, result, result);
- eval_multiply(t, result);
- eval_multiply(t, ui_type(4));
- eval_multiply(result, si_type(-3));
- eval_add(result, t);
- }
+ eval_subtract(t, xx);
+ eval_sin(result, t);
}
if(b_negate_cos)
result.negate();