[petsc-dev] quad precision

Thu Mar 17 07:23:37 CDT 2011

Cool!

On Thu, Mar 17, 2011 at 1:00 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>
> On Feb 8, 2011, at 6:31 AM, Jed Brown wrote:
>
>> > GCC now ships with the LGPL-licensed libquadmath library, which provides for targets with a __float128 datatype quad-precision mathematical functions. __float128 is available for targets on 32-bit x86, x86-64 and Itanium architectures. The libquadmath library is automatically built on such targets when building the Fortran compiler.
>>
>> http://gcc.gnu.org/gcc-4.6/changes.html#libquadmath
>> http://gcc.gnu.org/onlinedocs/libquadmath/
>>
>> Looks like this is something that actually works. GCC-4.6 is probably about two months away from a release, but this should be functional now. Perhaps it should be supported by petsc-3.2?
>
>  Done (use ./configure --with-precision=__float128 --download-qblaslapack
>
> barry-smiths-macbook-pro:tutorials barrysmith$ petscmpiexec -n 2 ./ex19 -snes_monitor -ksp_monitor -ksp_rtol 1.e-30 -snes_rtol 1.e-28
> lid velocity = Qe, prandtl # = Qe, grashof # = Qe
>  0 SNES Function norm 1.461936698223e-01
>    0 KSP Residual norm 1.461936698223e-01
>    1 KSP Residual norm 1.831093524630e-02
>    2 KSP Residual norm 3.842156479462e-03
>    3 KSP Residual norm 1.288406516834e-04
>    4 KSP Residual norm 6.151749539864e-06
>    5 KSP Residual norm 5.304145544729e-07
>    6 KSP Residual norm 1.885113023052e-08
>    7 KSP Residual norm 7.029816194041e-10
>    8 KSP Residual norm 5.197815114974e-11
>    9 KSP Residual norm 1.551090319297e-12
>   10 KSP Residual norm 6.563825928589e-14
>   11 KSP Residual norm 4.237666605992e-15
>   12 KSP Residual norm 1.991927370291e-16
>   13 KSP Residual norm 2.039546156320e-17
>   14 KSP Residual norm 1.399229447695e-17
>   15 KSP Residual norm 1.137432635542e-17
>   16 KSP Residual norm 9.814665753619e-18
>   17 KSP Residual norm 8.761318174145e-18
>   18 KSP Residual norm 7.987316427844e-18
>   19 KSP Residual norm 7.387832309954e-18
>   20 KSP Residual norm 6.905793284234e-18
>   21 KSP Residual norm 6.507264709320e-18
>   22 KSP Residual norm 6.170620606220e-18
>   23 KSP Residual norm 5.881342212029e-18
>   24 KSP Residual norm 5.629271709982e-18
>   25 KSP Residual norm 5.407060816706e-18
>   26 KSP Residual norm 5.209244641147e-18
>   27 KSP Residual norm 5.031663281118e-18
>   28 KSP Residual norm 4.871086689542e-18
>   29 KSP Residual norm 4.724963445290e-18
>   30 KSP Residual norm 1.945800083119e-17
>   31 KSP Residual norm 3.878029318777e-18
>   32 KSP Residual norm 8.021501106718e-19
>   33 KSP Residual norm 3.209251006205e-20
>   34 KSP Residual norm 9.713771954068e-22
>   35 KSP Residual norm 7.628163240222e-23
>   36 KSP Residual norm 4.108476441305e-24
>   37 KSP Residual norm 1.743186899274e-25
>   38 KSP Residual norm 1.115126800943e-26
>   39 KSP Residual norm 6.198813188878e-28
>   40 KSP Residual norm 2.869837519115e-29
>   41 KSP Residual norm 1.515585472682e-30
>   42 KSP Residual norm 5.770691059470e-32
>  1 SNES Function norm 2.507018921541e-05
>    0 KSP Residual norm 2.507018921541e-05
>    1 KSP Residual norm 7.131114735363e-07
>    2 KSP Residual norm 6.965532093127e-08
>    3 KSP Residual norm 8.087355337901e-09
>    4 KSP Residual norm 2.749048294679e-10
>    5 KSP Residual norm 1.113870556134e-11
>    6 KSP Residual norm 4.684216963041e-13
>    7 KSP Residual norm 4.911624900830e-14
>    8 KSP Residual norm 2.475960732046e-15
>    9 KSP Residual norm 1.012965264508e-16
>   10 KSP Residual norm 5.199268899437e-18
>   11 KSP Residual norm 2.361382990671e-19
>   12 KSP Residual norm 1.624218498133e-20
>   13 KSP Residual norm 1.626389274652e-21
>   14 KSP Residual norm 1.086627523198e-21
>   15 KSP Residual norm 8.796270682258e-22
>   16 KSP Residual norm 7.562576022670e-22
>   17 KSP Residual norm 6.738068994025e-22
>   18 KSP Residual norm 6.134859714231e-22
>   19 KSP Residual norm 5.669225669612e-22
>   20 KSP Residual norm 5.295704884674e-22
>   21 KSP Residual norm 4.987454291392e-22
>   22 KSP Residual norm 4.727440148233e-22
>   23 KSP Residual norm 4.504266287687e-22
>   24 KSP Residual norm 4.309981502786e-22
>   25 KSP Residual norm 4.138846776251e-22
>   26 KSP Residual norm 3.986602059865e-22
>   27 KSP Residual norm 3.850009759823e-22
>   28 KSP Residual norm 3.726559420703e-22
>   29 KSP Residual norm 3.614270387400e-22
>   30 KSP Residual norm 1.485730798507e-21
>   31 KSP Residual norm 5.734533095762e-23
>   32 KSP Residual norm 2.917983740862e-24
>   33 KSP Residual norm 2.415955278478e-25
>   34 KSP Residual norm 2.754121553256e-26
>   35 KSP Residual norm 1.530546077890e-27
>   36 KSP Residual norm 1.236527954824e-28
>   37 KSP Residual norm 5.968984750158e-30
>   38 KSP Residual norm 2.679693674423e-31
>   39 KSP Residual norm 2.728339059485e-32
>   40 KSP Residual norm 8.956127952264e-34
>   41 KSP Residual norm 2.732653737468e-35
>   42 KSP Residual norm 1.278928596713e-36
>  2 SNES Function norm 5.123354965471e-13
>    0 KSP Residual norm 5.123354965471e-13
>    1 KSP Residual norm 1.922138659280e-14
>    2 KSP Residual norm 1.916027080380e-15
>    3 KSP Residual norm 1.173166951366e-16
>    4 KSP Residual norm 6.562671109080e-18
>    5 KSP Residual norm 1.982740889768e-19
>    6 KSP Residual norm 1.593609248118e-20
>    7 KSP Residual norm 5.849655936465e-22
>    8 KSP Residual norm 2.871644899437e-23
>    9 KSP Residual norm 8.762292108710e-25
>   10 KSP Residual norm 2.883597656362e-26
>   11 KSP Residual norm 1.508069830626e-27
>   12 KSP Residual norm 9.552654188779e-29
>   13 KSP Residual norm 5.964437523019e-29
>   14 KSP Residual norm 4.773742821457e-29
>   15 KSP Residual norm 4.073114192114e-29
>   16 KSP Residual norm 3.613955807224e-29
>   17 KSP Residual norm 3.281398363062e-29
>   18 KSP Residual norm 3.026482504508e-29
>   19 KSP Residual norm 2.823023108355e-29
>   20 KSP Residual norm 2.655755272176e-29
>   21 KSP Residual norm 2.515082243565e-29
>   22 KSP Residual norm 2.394629606506e-29
>   23 KSP Residual norm 2.289975422292e-29
>   24 KSP Residual norm 2.197943014798e-29
>   25 KSP Residual norm 2.116183578028e-29
>   26 KSP Residual norm 2.042917954989e-29
>   27 KSP Residual norm 1.976770491487e-29
>   28 KSP Residual norm 1.916658520825e-29
>   29 KSP Residual norm 1.861716726173e-29
>   30 KSP Residual norm 7.847792961992e-29
>   31 KSP Residual norm 3.265251638392e-30
>   32 KSP Residual norm 2.554035610120e-31
>   33 KSP Residual norm 1.708749092417e-32
>   34 KSP Residual norm 1.088457747082e-33
>   35 KSP Residual norm 4.004032418947e-35
>   36 KSP Residual norm 3.626864425969e-36
>   37 KSP Residual norm 1.998928979977e-37
>   38 KSP Residual norm 5.929794876014e-39
>   39 KSP Residual norm 3.867971851833e-40
>   40 KSP Residual norm 2.306219660368e-41
>   41 KSP Residual norm 1.109502994834e-42
>   42 KSP Residual norm 7.010253552905e-44
>  3 SNES Function norm 1.676590295787e-28
>
>