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author | Ulrich Drepper <drepper@redhat.com> | 1998-02-13 17:54:15 +0000 |
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committer | Ulrich Drepper <drepper@redhat.com> | 1998-02-13 17:54:15 +0000 |
commit | dc30f461575342ffeb6c0f2d5931493c1c3a91c0 (patch) | |
tree | 99243511beca706f0743fe2316854c5a30709f17 /sysdeps/libm-ieee754/s_exp2f.c | |
parent | e15867921d8f3b75deb0d91628cf9a323709ea9f (diff) | |
download | glibc-dc30f461575342ffeb6c0f2d5931493c1c3a91c0.tar.gz glibc-dc30f461575342ffeb6c0f2d5931493c1c3a91c0.tar.xz glibc-dc30f461575342ffeb6c0f2d5931493c1c3a91c0.zip |
Update.
1998-02-13 17:39 Ulrich Drepper <drepper@cygnus.com> * elf/Makefile: Don't use --version-script parameter to link ld.so unconditionally. 1998-01-02 04:19 Geoff Keating <geoffk@ozemail.com.au> * math/Makefile: Add t_exp. * math/libm-test.c: Tighten accuracy bounds for exp(), correct constants. * math/test-reduce.c: Remove temporarily, it seems to be broken. * sysdeps/libm-ieee754/e_exp.c: Use accurate table method. * sysdeps/libm-ieee754/e_expf.c: Use table & double precision for better accuracy. * sysdeps/libm-ieee754/s_exp2.c: Use better polynomial; correct algorithm for very large/very small arguments. * sysdeps/libm-ieee754/s_exp2f.c: Use slightly better polynomial; correct algorithm for very large/very small arguments; adjust for new table. * sysdeps/libm-ieee754/t_exp.c: New file. * sysdeps/libm-ieee754/t_exp2f.h: Use table with smaller deltas. * sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c: Put 'strange test' back, with comment that explains what breaks when you remove it :-(. * localedata/xfrm-test.c: Avoid integer overflow. * stdlib/strfmon.c: char is unsigned, sometimes. *sysdeps/powerpc * sysdeps/powerpc/Makefile: Remove quad float support. * sysdeps/powerpc/q_*.c: Remove, they will become an add-on. * sysdeps/powerpc/quad_float.h: Likewise. * sysdeps/powerpc/test-arith.c: Likewise. * sysdeps/powerpc/test-arithf.c: Likewise. * sysdeps/generic/s_exp2.c: Remove, we have this implemented now. * sysdeps/generic/s_exp2f.c: Likewise. * sysdeps/powerpc/bits/mathinline.h: Use underscores around __asm__, don't try anything if _SOFT_FLOAT. 1997-12-31 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * locale/C-ctype.c (_nl_C_LC_CTYPE_class32): Undo last change. * locale/programs/ld-ctype.c (CHAR_CLASS32_TRANS): Likewise. * wctype/wctype.c: Likewise. * wctype/wctype.h (_ISwxxx): Renamed from _ISxxx, all uses changed. They are incompatible with the _ISxxx values from <ctype.h> on little endian machines. (_ISwbit) [__BYTE_ORDER == __LITTLE_ENDIAN]: Correctly transform bit number. This fixes the real bug and restores the integrity of the ctype locale file. * wctype/wcfuncs.c: Change all _ISxxx to _ISwxxx. * wctype/wcfuncs_l.c: Likewise. * wctype/wcextra.c: Likewise. * wctype/wctype_l.c [__BYTE_ORDER == __LITTLE_ENDIAN]: Use correct byte swapping. 1998-02-09 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * sysdeps/unix/sysv/linux/sparc/sparc32/sysdep.S (errno): Put it into .bss segment instead of .common, so that aliases on it work. * sysdeps/unix/sysv/linux/i386/sysdep.S (errno): Add .type and .size directives, put into .bss segment instead of initializing it to 4. 1998-02-12 08:00 H.J. Lu <hjl@gnu.org> * libc.map (gnu_get_libc_release, gnu_get_libc_version): Added. * version.c (__gnu_get_libc_release, __gnu_get_libc_version): New functions. Make names without __ weak aliases. (__libc_release, __libc_version): Make them static. * include/gnu/libc-version.h: New file. * Makefile (headers): Add gnu/libc-version.h. 1998-02-13 Ulrich Drepper <drepper@cygnus.com> * stdlib/stdlib.h (struct drand48_data): Leave X to user macros and use x for member name. Reported by Daniel Lyddy <daniell@cs.berkeley.edu>. * stdlib/drand48.c: Change according to member name change. * stdlib/drand48_r.c: Likewise. * stdlib/lcong48_r.c: Likewise. * stdlib/lrand48.c: Likewise. * stdlib/lrand48_r.c: Likewise. * stdlib/mrand48.c: Likewise. * stdlib/mrand48_r.c: Likewise. * stdlib/seed48.c: Likewise. * stdlib/seed48_r.c: Likewise. * stdlib/srand48_r.c: Likewise. 1998-02-11 Andreas Jaeger <aj@arthur.rhein-neckar.de> * nss/test-netdb.c: Add some more test cases. 1998-02-13 11:39 Ulrich Drepper <drepper@cygnus.com> * libio/iovsscanf.c: Undo last change modifying errno. 1998-02-12 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * stdio-common/vfscanf.c: Never try to read another character after EOF. Don't decrement read_in after EOF, it wasn't incremented in the first place. (NEXT_WIDE_CHAR): Set First, not first. 1998-02-06 07:48 H.J. Lu <hjl@gnu.org> * db/Makefile ($(inst_libdir)/libndbm.a, $(inst_libdir)/libndbm.so): New targets. * db2/Makefile: Likewise. 1998-02-12 08:20 H.J. Lu <hjl@gnu.org> * sysdeps/gnu/errlist.awk (sys_errlist, sys_nerr): Create weak aliases if HAVE_ELF or PIC or DO_VERSIONING is not defined. 1998-02-12 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * sysdeps/generic/_G_config.h: Define _G_wchar_t, for C++ <streambuf.h>. * sysdeps/unix/sysv/linux/_G_config.h: Likewise. 1998-02-11 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * sysdeps/unix/make-syscalls.sh: Fix sed pattern when dealing with versioned symbols. 1998-02-13 08:14 H.J. Lu <hjl@gnu.org> * libc.map (_dl_global_scope, _dl_lookup_symbol_skip, _dl_lookup_versioned_symbol, _dl_lookup_versioned_symbol_skip): Added for libdl.so. * elf/rtld.map: New file. Needed to define the GLIBC_2.* * manual/socket.texi (Host Address Functions): Clarify description * sysdeps/unix/sysv/linux/alpha/bits/time.h (struct timeval):
Diffstat (limited to 'sysdeps/libm-ieee754/s_exp2f.c')
-rw-r--r-- | sysdeps/libm-ieee754/s_exp2f.c | 77 |
1 files changed, 41 insertions, 36 deletions
diff --git a/sysdeps/libm-ieee754/s_exp2f.c b/sysdeps/libm-ieee754/s_exp2f.c index 05e79c9f5a..11c5d55e2e 100644 --- a/sysdeps/libm-ieee754/s_exp2f.c +++ b/sysdeps/libm-ieee754/s_exp2f.c @@ -38,20 +38,22 @@ #include "t_exp2f.h" static const volatile float TWOM100 = 7.88860905e-31; -static const volatile float huge = 1e+30; +static const volatile float TWO127 = 1.7014118346e+38; float __ieee754_exp2f (float x) { - static const uint32_t a_inf = 0x7f800000; + static const uint32_t a_minf = 0xff800000; + static const float himark = (float) FLT_MAX_EXP; + static const float lomark = (float) (FLT_MIN_EXP - FLT_MANT_DIG - 1) - 1.0; + /* Check for usual case. */ - if (isless (x, (float) FLT_MAX_EXP) - && isgreater (x, (float) (FLT_MIN_EXP - 1))) + if (isless (x, himark) && isgreater (x, lomark)) { - static const float TWO16 = 65536.0; - int tval; - float rx, x22; - union ieee754_float ex2_u; + static const float TWO15 = 32768.0; + int tval, unsafe; + float rx, x22, result; + union ieee754_float ex2_u, scale_u; fenv_t oldenv; feholdexcept (&oldenv); @@ -68,13 +70,13 @@ __ieee754_exp2f (float x) First, calculate rx = ex + t/256. */ if (x >= 0) { - rx = x + TWO16; - rx -= TWO16; + rx = x + TWO15; + rx -= TWO15; } else { - rx = x - TWO16; - rx += TWO16; + rx = x - TWO15; ++ rx += TWO15; } x -= rx; /* Compute x=x1. */ /* Compute tval = (ex*256 + t)+128. @@ -92,40 +94,43 @@ __ieee754_exp2f (float x) /* 'tval & 255' is the same as 'tval%256' except that it's always positive. Compute x = x2. */ - x -= exp2_deltatable[tval & 255]; + x -= __exp2_deltatable[tval & 255]; /* 3. Compute ex2 = 2^(t/255+e+ex). */ - ex2_u.f = exp2_accuratetable[tval & 255]; - ex2_u.ieee.exponent += tval >> 8; + ex2_u.f = __exp2f_atable[tval & 255]; + tval >>= 8; + unsafe = abs(tval) >= -FLT_MIN_EXP - 1; + ex2_u.ieee.exponent += tval >> unsafe; + scale_u.f = 1.0; + scale_u.ieee.exponent += tval - (tval >> unsafe); /* 4. Approximate 2^x2 - 1, using a second-degree polynomial, - 2^x2 ~= sum(k=0..2 | (x2 * ln(2))^k / k! ) + - so - 2^x2 - 1 ~= sum(k=1..4 | (x2 * ln(2))^k / k! ) - with error less than 2^(1/512+7e-4) * (x2 * ln(2))^3 / 3! < 1.2e-18. */ + with maximum error in [-2^-9 - 2^-14, 2^-9 + 2^-14] + less than 1.3e-10. */ - x22 = (.240226507f * x + .6931471806f) * ex2_u.f; + x22 = (.24022656679f * x + .69314736128f) * ex2_u.f; /* 5. Return (2^x2-1) * 2^(t/512+e+ex) + 2^(t/512+e+ex). */ fesetenv (&oldenv); - /* Need to check: does this set FE_INEXACT correctly? */ - return x22 * x + ex2_u.f; + result = x22 * x + ex2_u.f; + + if (!unsafe) + return result; + else + return result * scale_u.f; } - /* 2^inf == inf, with no error. */ - else if (x == *(const float *)&a_inf) + /* Exceptional cases: */ + else if (isless (x, himark)) { - return x; + if (x == *(const float *) &a_minf) + /* e^-inf == 0, with no error. */ + return 0; + else + /* Underflow */ + return TWOM100 * TWOM100; } - /* Check for overflow. */ - else if (isgreaterequal (x, (float) FLT_MAX_EXP)) - return huge * huge; - /* And underflow (including -inf). */ - else if (isless (x, (float) (FLT_MIN_EXP - FLT_MANT_DIG))) - return TWOM100 * TWOM100; - /* Maybe the result needs to be a denormalised number... */ - else if (!isnan (x)) - return __ieee754_exp2f (x + 100.0) * TWOM100; - else /* isnan(x) */ - return x + x; + else + /* Return x, if x is a NaN or Inf; or overflow, otherwise. */ + return TWO127*x; } |