19 Nov
2013
19 Nov
'13
1:01 p.m.
You could try the follow command
cc -o precision_test -lm precision_test.c
uname -p
AMD Phenom(tm) II X6 1090T Processor
# Usage: precision_test step
./precision_test 0.01 | column -t
A 1.000000000000
B 100.000000000000
A/B 0.010000000000
precision 2
If your output is different, there is a round off problem, I presume
with `rint'.
/* precision_test.c */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <ctype.h>
int main(int argc, char **argv)
{
double A, B, s;
int i, c = 0;
char temp[32];
if (argc < 2) return 1;
s = atof(argv[1]);
/* Used in `Fl_Valuator::step' */
A = rint(s);
B = 1;
while (fabs(s-A/B) > 4.66e-10 && B<=(0x7fffffff/10)) {
B *= 10;
A = rint(s*B);
}
/* Used in `Fl_Valuator::format' to calculate the precision for snprintf */
snprintf(temp, sizeof(temp), "%.12f", A/B);
for (i=(int) strlen(temp)-1; i>0; i--)
if (temp[i]!='0') break;
for (; i>0; i--, c++)
if (!isdigit(temp[i])) break;
printf("A %.12f\nB %.12f\nA/B %.12f\nprecision %d\n", A, B, A/B, c);
return 0;
}
On Mon, Nov 18, 2013 at 09:14:44PM +0000, Will Godfrey wrote:
I've been slowing working my way though Yoshimi,
looking for bugs and trying
to understand the code, with some success. However, I've come across something
that has me completely stumped.
On a modern machine if you look in the AdSynth edit window 'Detune' shows a
variable number of trailing digits, where it should only show 2 after the
decimal point. This is also true of all cases where a recalculated slider value
is indirectly shown in an associated uneditable box. It happens nowhere else.
I've seen this on 64bit dual core AMDs and on 32bit Atoms. However, on an
AthlonXP the problem doesn't occur.
At first I thought it might be due to different version of FLTK but having tried
various releases of debian, from 'lenny' up to the current 'testing',
the
*only* differentiating feature I can discover is that the AthlonXP doesn't
recognise the sse flag.
Finally, to add to the confusion, compiling on any of the other machines,
without the sse flag set, still produces the fault - I'm wondering if even
without this, some math feature is still being used that causes the fault.
Any help or suggestions would be gratefully welcomed!
--
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.
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