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f41b0a43e4
Optimized log using carefully generated lookup table with 1/c and log(c) values for small intervalls around 1. The log(c) is very near a double precision value, it has about 62 bits precision. The algorithm is log(2^k x) = k log(2) + log(c) + log(x/c), where the last term is approximated by a polynomial of x/c - 1. Near 1 a single polynomial of x - 1 is used. There is separate code path when fma instruction is not available for computing x/c - 1 precisely, in which case the table size is doubled. The code uses __builtin_fma under __FP_FAST_FMA to ensure it is inlined as an instruction. With the default configuration settings the worst case error is 0.519 ULP (and 0.520 without fma), the rodata size is 2192 bytes (4240 without fma). The non-nearest rounding error is less than 1 ULP. Improvements on Cortex-A72 compared to current glibc master: log thruput: 3.28x in [0.01 11.1] log latency: 2.23x in [0.01 11.1] log thruput: 1.56x in [0.999 1.001] log latency: 1.57x in [0.999 1.001] Tested on aarch64-linux-gnu (defined __FP_FAST_FMA) arm-linux-gnueabihf (!defined __FP_FAST_FMA) x86_64-linux-gnu (!defined __FP_FAST_FMA) powerpc64le-linux-gnu (defined __FP_FAST_FMA) targets. * NEWS: Mention log improvement. * math/Makefile (type-double-routines): Add e_log_data. * sysdeps/i386/fpu/e_log_data.c: New file. * sysdeps/ia64/fpu/e_log_data.c: New file. * sysdeps/ieee754/dbl-64/e_log.c: Rewrite. * sysdeps/ieee754/dbl-64/e_log_data.c: New file. * sysdeps/ieee754/dbl-64/math_config.h (__log_data): Add. * sysdeps/ieee754/dbl-64/ulog.h: Remove. * sysdeps/ieee754/dbl-64/ulog.tbl: Remove. * sysdeps/m68k/m680x0/fpu/e_log_data.c: New file. |
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| assert | ||
| benchtests | ||
| bits | ||
| catgets | ||
| ChangeLog.old | ||
| conform | ||
| crypt | ||
| csu | ||
| ctype | ||
| debug | ||
| dirent | ||
| dlfcn | ||
| elf | ||
| gmon | ||
| gnulib | ||
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| hesiod | ||
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| iconv | ||
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| include | ||
| inet | ||
| intl | ||
| io | ||
| libio | ||
| locale | ||
| localedata | ||
| login | ||
| mach | ||
| malloc | ||
| manual | ||
| math | ||
| mathvec | ||
| misc | ||
| nis | ||
| nptl | ||
| nptl_db | ||
| nscd | ||
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| posix | ||
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| rt | ||
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| setjmp | ||
| shadow | ||
| signal | ||
| socket | ||
| soft-fp | ||
| stdio-common | ||
| stdlib | ||
| streams | ||
| string | ||
| sunrpc | ||
| support | ||
| sysdeps | ||
| sysvipc | ||
| termios | ||
| time | ||
| timezone | ||
| wcsmbs | ||
| wctype | ||
| .gitattributes | ||
| .gitignore | ||
| abi-tags | ||
| aclocal.m4 | ||
| ChangeLog | ||
| config.h.in | ||
| config.make.in | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING.LIB | ||
| extra-lib.mk | ||
| gen-locales.mk | ||
| INSTALL | ||
| libc-abis | ||
| libof-iterator.mk | ||
| LICENSES | ||
| MAINTAINERS | ||
| Makeconfig | ||
| Makefile | ||
| Makefile.in | ||
| Makerules | ||
| NEWS | ||
| o-iterator.mk | ||
| README | ||
| Rules | ||
| shlib-versions | ||
| test-skeleton.c | ||
| version.h | ||
This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arm-*-linux-gnueabi hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see http://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at http://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see http://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.