Re: [PATCH] iio:temperature:mlx90632: Reduce number of equal calulcations
Hi Andy, Thanks for the comments. This is indeed a cut-out section of what I wanted to submit next. On Mon, 3 Aug 2020 at 18:35, Andy Shevchenko wrote: > > On Mon, Aug 3, 2020 at 6:17 PM Crt Mori wrote: > > > > TAdut4 was calculated each iteration although it did not change. In light > > of near future additions of the Extended range DSP calculations, this > > function refactoring will help reduce unrelated changes in that series as > > well as reduce the number of new functions needed. > > Okay! > > > Also converted shifts in this function of signed integers to divisions as > > that is less implementation-defined behavior. > > This is what I'm wondering about. Why? > > ... The reason for this is that whenever something is wrong with the calculation I am looking into the shifts which are implementation-defined and might not keep the signed bit. Division however would. > > > - Ha_customer = ((s64)Ha * 100LL) >> 14ULL; > > - Hb_customer = ((s64)Hb * 100) >> 10ULL; > > + Ha_customer = div64_s64((s64)Ha * 100LL, 16384); > > + Hb_customer = div64_s64((s64)Hb * 100, 1024); > > Have you checked the code on 32-bit machines? > As far as I can see the div64_*64() do not have power of two divisor > optimizations. I bet it will generate a bulk of unneeded code. > > ... > > > - calcedKsTO = ((s64)((s64)Ga * (prev_object_temp - 25 * 1000LL) > > -* 1000LL)) >> 36LL; > > - calcedKsTA = ((s64)(Fb * (TAdut - 25 * 100LL))) >> 36LL; > > - Alpha_corr = div64_s64s64)(Fa * 100LL) >> 46LL) > > - * Ha_customer), 1000LL); > > > + calcedKsTO = div64_s64((s64)((s64)Ga * (prev_object_temp - 25 * > > 1000LL) > > +* 1000LL), 68719476736); > > + calcedKsTA = div64_s64((s64)(Fb * (TAdut - 25 * 100LL)), > > 68719476736); > > + Alpha_corr = div64_s64(div64_s64((s64)(Fa * 100LL), > > 70368744177664) > > + * Ha_customer, 1000LL); > > This is less readable and full of magic numbers in comparison to the > above (however, also full of magics, but at least gives better hint). > > ... These are coefficients so there is not much to unmagic. I can keep the shifts, if you think that is more readable or add comments after lines with 2^46 or something? > > > + TAdut4 = (div64_s64(TAdut, 1LL) + 27315) * > > + (div64_s64(TAdut, 1LL) + 27315) * > > + (div64_s64(TAdut, 1LL) + 27315) * > > + (div64_s64(TAdut, 1LL) + 27315); > > Shouldn't you switch to definitions from units.h? (perhaps as a separate > change) > > -- > With Best Regards, > Andy Shevchenko
Re: [PATCH] iio:temperature:mlx90632: Reduce number of equal calulcations
Hi Crt,
I love your patch! Yet something to improve:
[auto build test ERROR on iio/togreg]
[also build test ERROR on v5.8 next-20200803]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url:
https://github.com/0day-ci/linux/commits/Crt-Mori/iio-temperature-mlx90632-Reduce-number-of-equal-calulcations/20200803-231936
base: https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
config: x86_64-randconfig-a001-20200803 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project
4ffa6a27aca17fe88fa6bdd605b198df6632a570)
reproduce (this is a W=1 build):
wget
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
~/bin/make.cross
chmod +x ~/bin/make.cross
# install x86_64 cross compiling tool for clang build
# apt-get install binutils-x86-64-linux-gnu
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot
All errors (new ones prefixed by >>):
>> drivers/iio/temperature/mlx90632.c:381:40: error: redefinition of 'TAdut4'
s64 calcedKsTO, calcedKsTA, ir_Alpha, TAdut4, Alpha_corr;
^
drivers/iio/temperature/mlx90632.c:377:28: note: previous definition is here
s64 TAdut, s64 TAdut4, s32
Fa, s32 Fb,
^
>> drivers/iio/temperature/mlx90632.c:412:2: error: use of undeclared
>> identifier 'TAdut4'; did you mean 'TAdut'?
TAdut4 = (div64_s64(TAdut, 1LL) + 27315) *
^~
TAdut
drivers/iio/temperature/mlx90632.c:405:17: note: 'TAdut' declared here
s64 kTA, kTA0, TAdut;
^
drivers/iio/temperature/mlx90632.c:419:67: error: use of undeclared
identifier 'TAdut4'; did you mean 'TAdut'?
temp = mlx90632_calc_temp_object_iteration(temp, object,
TAdut, TAdut4,
^~
TAdut
drivers/iio/temperature/mlx90632.c:405:17: note: 'TAdut' declared here
s64 kTA, kTA0, TAdut;
^
3 errors generated.
vim +/TAdut4 +381 drivers/iio/temperature/mlx90632.c
c87742abfc80b3 Crt Mori 2018-01-11 375
c87742abfc80b3 Crt Mori 2018-01-11 376 static s32
mlx90632_calc_temp_object_iteration(s32 prev_object_temp, s64 object,
dd5b04efd05f22 Crt Mori 2020-08-03 377
s64 TAdut, s64 TAdut4, s32 Fa, s32 Fb,
c87742abfc80b3 Crt Mori 2018-01-11 378
s32 Ga, s16 Ha, s16 Hb,
c87742abfc80b3 Crt Mori 2018-01-11 379
u16 emissivity)
c87742abfc80b3 Crt Mori 2018-01-11 380 {
c87742abfc80b3 Crt Mori 2018-01-11 @381 s64 calcedKsTO, calcedKsTA,
ir_Alpha, TAdut4, Alpha_corr;
c87742abfc80b3 Crt Mori 2018-01-11 382 s64 Ha_customer, Hb_customer;
c87742abfc80b3 Crt Mori 2018-01-11 383
dd5b04efd05f22 Crt Mori 2020-08-03 384 Ha_customer = div64_s64((s64)Ha
* 100LL, 16384);
dd5b04efd05f22 Crt Mori 2020-08-03 385 Hb_customer = div64_s64((s64)Hb
* 100, 1024);
c87742abfc80b3 Crt Mori 2018-01-11 386
dd5b04efd05f22 Crt Mori 2020-08-03 387 calcedKsTO =
div64_s64((s64)((s64)Ga * (prev_object_temp - 25 * 1000LL)
dd5b04efd05f22 Crt Mori 2020-08-03 388 *
1000LL), 68719476736);
dd5b04efd05f22 Crt Mori 2020-08-03 389 calcedKsTA = div64_s64((s64)(Fb
* (TAdut - 25 * 100LL)), 68719476736);
dd5b04efd05f22 Crt Mori 2020-08-03 390 Alpha_corr =
div64_s64(div64_s64((s64)(Fa * 100LL), 70368744177664)
dd5b04efd05f22 Crt Mori 2020-08-03 391*
Ha_customer, 1000LL);
c87742abfc80b3 Crt Mori 2018-01-11 392 Alpha_corr *= ((s64)(1 *
100LL + calcedKsTO + calcedKsTA));
c87742abfc80b3 Crt Mori 2018-01-11 393 Alpha_corr = emissivity *
div64_s64(Alpha_corr, 10LL);
c87742abfc80b3 Crt Mori 2018-01-11 394 Alpha_corr =
div64_s64(Alpha_corr, 1000LL);
c87742abfc80b3 Crt Mori 2018-01-11 395 ir_Alpha =
div64_s64((s64)object * 1000LL, Alpha_corr);
c87742abfc80b3 Crt Mori 2018-01-11 396
c87742abfc80b3 Crt Mori 2018-01-11 397 return
(int_sqrt64(int_sqrt64(ir_Alpha * 1LL + TAdut4))
c87742abfc80b3 Crt Mori 2018-01-11 398 - 27315 - Hb_customer)
* 10;
c87742abfc80b3 Crt Mori 2018-01-11 399 }
c87742abfc80b3 Crt Mori 2018-01-11 400
Re: [PATCH] iio:temperature:mlx90632: Reduce number of equal calulcations
On Mon, Aug 3, 2020 at 6:17 PM Crt Mori wrote: > > TAdut4 was calculated each iteration although it did not change. In light > of near future additions of the Extended range DSP calculations, this > function refactoring will help reduce unrelated changes in that series as > well as reduce the number of new functions needed. Okay! > Also converted shifts in this function of signed integers to divisions as > that is less implementation-defined behavior. This is what I'm wondering about. Why? ... > - Ha_customer = ((s64)Ha * 100LL) >> 14ULL; > - Hb_customer = ((s64)Hb * 100) >> 10ULL; > + Ha_customer = div64_s64((s64)Ha * 100LL, 16384); > + Hb_customer = div64_s64((s64)Hb * 100, 1024); Have you checked the code on 32-bit machines? As far as I can see the div64_*64() do not have power of two divisor optimizations. I bet it will generate a bulk of unneeded code. ... > - calcedKsTO = ((s64)((s64)Ga * (prev_object_temp - 25 * 1000LL) > -* 1000LL)) >> 36LL; > - calcedKsTA = ((s64)(Fb * (TAdut - 25 * 100LL))) >> 36LL; > - Alpha_corr = div64_s64s64)(Fa * 100LL) >> 46LL) > - * Ha_customer), 1000LL); > + calcedKsTO = div64_s64((s64)((s64)Ga * (prev_object_temp - 25 * > 1000LL) > +* 1000LL), 68719476736); > + calcedKsTA = div64_s64((s64)(Fb * (TAdut - 25 * 100LL)), > 68719476736); > + Alpha_corr = div64_s64(div64_s64((s64)(Fa * 100LL), > 70368744177664) > + * Ha_customer, 1000LL); This is less readable and full of magic numbers in comparison to the above (however, also full of magics, but at least gives better hint). ... > + TAdut4 = (div64_s64(TAdut, 1LL) + 27315) * > + (div64_s64(TAdut, 1LL) + 27315) * > + (div64_s64(TAdut, 1LL) + 27315) * > + (div64_s64(TAdut, 1LL) + 27315); Shouldn't you switch to definitions from units.h? (perhaps as a separate change) -- With Best Regards, Andy Shevchenko
