Overflow in multDiv code about decimal_for_cpp HOT 8 CLOSED

You are correct, but I decided this part needs some rewrite, so it is corrected in a different way.
Overflow issue is corrected, please test with your case.

from decimal_for_cpp.

Thanks, will send tomorrow.
I inherited from your class and had to change the /= operator to use
(inefficient but effective) subtraction because 364.92 / 304.1001 was
coming out with 1.2 and I needed it to be 1.199999.
On Jul 12, 2015 4:40 AM, "vpiotr" [email protected] wrote:

Please provide test values for this issue. I don't see when it can be a
problem.

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#13 (comment)
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from decimal_for_cpp.

using dec::decimal6 as my type

1341.93115 / 10000.000000 was executed and caused me to find the issue

void test_abs(void)
{
dec::int64 resAbs, resllabs;
dec::int64 val = 1341931150L;

resAbs = abs(val);
resllabs = llabs(val);

std::cout << std::endl << "  test_abs starting" << std::endl;

std::cout << "val : " << val << ", abs(): " << resAbs << ", llabs(): "

<< resllabs << std::endl;

val = 10000000000;
resAbs = abs(val);
resllabs = llabs(val);

std::cout << "val : " << val << ", abs(): " << resAbs << ", llabs(): "

<< resllabs << std::endl;

std::cout << std::endl << "  test_abs finished" << std::endl;
std::cout << std::endl;

return;

}

test_abs starting
val : 1341931150, abs(): 1341931150, llabs(): 1341931150
val : 10000000000, abs(): 1410065408, llabs(): 10000000000

test_abs finished

exiting....

$ g++ -v
Using built-in specs.
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla
--enable-bootstrap --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada
--enable-java-awt=gtk --disable-dssi
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre
--enable-libgcj-multifile --enable-java-maintainer-mode
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libjava-multilib
--with-ppl --with-cloog --with-tune=generic --with-arch_32=i686
--build=x86_64-redhat-linux
Thread model: posix
gcc version 4.4.7 20120313 (Red Hat 4.4.7-11) (GCC)

On Sun, Jul 12, 2015 at 12:50 PM, Bob Weidman [email protected] wrote:

Thanks, will send tomorrow.
I inherited from your class and had to change the /= operator to use
(inefficient but effective) subtraction because 364.92 / 304.1001 was
coming out with 1.2 and I needed it to be 1.199999.
On Jul 12, 2015 4:40 AM, "vpiotr" [email protected] wrote:

Please provide test values for this issue. I don't see when it can be a
problem.

—
Reply to this email directly or view it on GitHub
#13 (comment)
.

from decimal_for_cpp.

Please test with most recent version. For the first pair of values, correct result is in fact 1.2 (with rounding to 6 decimal places).

Without rounding result is equal to:
364.92 / 304.1001 = 1,1999996053930926033894760310832

from decimal_for_cpp.

yes the answer is coming out 1.2.
I'm reading code now to see where the rounding is taking place. I need to
emulate the division without the rounding taking place.
The program does rounding or truncation of digits to right of the decimal
place at various locations - meaning at specific times. (Wants to retain
the values as is until rounding or truncation of digits is desired.)

On Mon, Jul 13, 2015 at 5:26 AM, vpiotr [email protected] wrote:

Please test with most recent version. For the first pair of values,
correct result is in fact 1.2 (with rounding to 6 decimal places).

Without rounding result is equal to:
364.92 / 304.1001 = 1,1999996053930926033894760310832

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#13 (comment)
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from decimal_for_cpp.

Currently you can switch off rounding for all class instances by the following steps:

• define DEC_EXTERNAL_ROUND
• define own round() function which simply performs cast
• modify multDiv() function in no-overflow section

I suppose it can be useful if I define rounding as a policy for this class, you can expect easier solution in the near future.

from decimal_for_cpp.

See BOOST_AUTO_TEST_CASE(decimalNoRoundPolicy) for no-rounding mode.

from decimal_for_cpp.

Sorry for delay...
Trying to download this and will test.
Thanks for incorporating my change requests.
On Jul 15, 2015 9:55 AM, "vpiotr" [email protected] wrote:

See BOOST_AUTO_TEST_CASE(decimalNoRoundPolicy) for no-rounding mode.

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#13 (comment)
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