Subject: [Boost-commit] svn:boost r85419 - in sandbox/multiprecision.cpp_bin_float: boost/multiprecision libs/multiprecision/test
From: john_at_[hidden]
Date: 2013-08-22 08:35:25
Author: johnmaddock
Date: 2013-08-22 08:35:25 EDT (Thu, 22 Aug 2013)
New Revision: 85419
URL: http://svn.boost.org/trac/boost/changeset/85419
Log:
Change powers on 10 to powers of 5 to reduce memory usage.
Text files modified:
sandbox/multiprecision.cpp_bin_float/boost/multiprecision/cpp_bin_float.hpp | 25 ++++++++++++++++---------
sandbox/multiprecision.cpp_bin_float/libs/multiprecision/test/test_cpp_bin_float_io.cpp | 4 ++++
2 files changed, 20 insertions(+), 9 deletions(-)
Modified: sandbox/multiprecision.cpp_bin_float/boost/multiprecision/cpp_bin_float.hpp
==============================================================================
--- sandbox/multiprecision.cpp_bin_float/boost/multiprecision/cpp_bin_float.hpp Wed Aug 21 19:24:54 2013 (r85418)
+++ sandbox/multiprecision.cpp_bin_float/boost/multiprecision/cpp_bin_float.hpp 2013-08-22 08:35:25 EDT (Thu, 22 Aug 2013) (r85419)
@@ -316,8 +316,9 @@
else if(decimal_exp >= 0)
{
// Nice and simple, the result is an integer...
- n *= pow(cpp_int(10), decimal_exp);
+ n *= pow(cpp_int(5), decimal_exp);
exponent() = (int)Bits - 1;
+ exponent() += decimal_exp;
copy_and_round(*this, n.backend());
if(ss != sign())
negate();
@@ -327,9 +328,9 @@
// Result is the ratio of two integers: we need to organise the
// division so as to produce at least an N-bit result which we can
// round according to the remainder.
- cpp_int d = pow(cpp_int(10), -decimal_exp);
+ cpp_int d = pow(cpp_int(5), -decimal_exp);
int shift = (int)Bits - msb(n) + msb(d);
- exponent() = Bits - 1;
+ exponent() = Bits - 1 + decimal_exp;
if(shift > 0)
{
n <<= shift;
@@ -432,24 +433,29 @@
// to convert our denormalised number to an integer with the right number of digits:
//
int power10 = digits_wanted - base10_exp - 1;
+ //
+ // If we calculate 5^power10 rather than 10^power10 we need to move
+ // 2^power10 into /shift/
+ //
+ shift -= power10;
cpp_int i;
std::string s;
int roundup = 0; // 0=no rounding, 1=tie, 2=up
do
{
//
- // Our integer is: bits() * 2^-shift * 10^power10
+ // Our integer is: bits() * 2^-shift * 5^power10
//
i = bits();
if(shift < 0)
{
i <<= -shift;
if(power10 > 0)
- i *= pow(cpp_int(10), power10);
+ i *= pow(cpp_int(5), power10);
else if(power10 < 0)
{
cpp_int r;
- cpp_int d = pow(cpp_int(10), -power10);
+ cpp_int d = pow(cpp_int(5), -power10);
divide_qr(i, d, i, r);
r <<= 1;
int c = r.compare(d);
@@ -464,7 +470,7 @@
if(power10 >= 0)
{
if(power10)
- i *= pow(cpp_int(10), power10);
+ i *= pow(cpp_int(5), power10);
if(shift && bit_test(i, shift - 1))
{
if((int)lsb(i) == shift - 1)
@@ -477,7 +483,7 @@
else
{
cpp_int r;
- cpp_int d = pow(cpp_int(10), -power10);
+ cpp_int d = pow(cpp_int(5), -power10);
d <<= shift;
divide_qr(i, d, i, r);
r <<= 1;
@@ -496,8 +502,9 @@
{
base10_exp += digits_got - digits_wanted;
if(fixed)
- digits_wanted = digits_got;
+ digits_wanted = digits_got; // strange but true.
power10 = digits_wanted - base10_exp - 1;
+ shift = (int)Bits - exponent() - 1 - power10;
if(fixed)
break;
roundup = 0;
Modified: sandbox/multiprecision.cpp_bin_float/libs/multiprecision/test/test_cpp_bin_float_io.cpp
==============================================================================
--- sandbox/multiprecision.cpp_bin_float/libs/multiprecision/test/test_cpp_bin_float_io.cpp Wed Aug 21 19:24:54 2013 (r85418)
+++ sandbox/multiprecision.cpp_bin_float/libs/multiprecision/test/test_cpp_bin_float_io.cpp 2013-08-22 08:35:25 EDT (Thu, 22 Aug 2013) (r85419)
@@ -204,6 +204,10 @@
using namespace boost::multiprecision;
test<number<cpp_bin_float<113> > >();
test_round_trip<number<cpp_bin_float<113> > >();
+
+ test<number<cpp_bin_float<53> > >();
+ test_round_trip<number<cpp_bin_float<53> > >();
+
return boost::report_errors();
}