Mercurial > sdl-ios-xcode
view src/thread/pth/SDL_sysmutex.c @ 2752:edd2839b36f7
http://sources.redhat.com/ml/newlib/2002/msg00230.html
Stephen L Moshier wrote:
>
> pow(x,y) returns 0 when x is very close to -1.0 and y is very large.
> The following test program prints
>
> pow(1.0000000000000002e+00 4.5035996273704970e+15) = 2.7182818284590455e+00
> pow(-1.0000000000000002e+00 4.5035996273704970e+15) =0.0000000000000000e+00
> pow(9.9999999999999978e-01 4.5035996273704970e+15) = 3.6787944117144222e-01
> pow(-9.9999999999999978e-01 4.5035996273704970e+15) = 0.0000000000000000e+00
>
> which is incorrect for the negative arguments raised to an odd integer
> power.
>
> -----
> double pow (double, double);
>
> int
> main ()
> {
> double x, y, z;
>
> x = 1.0 + pow (2.0, -52.0);
> y = 1.0 + pow (2.0, 52.0);
> z = pow (x, y);
> printf ("pow(%.16e %.16e) = %.16e\n", x, y, z);
> x = -x;
> z = pow (x, y);
> printf ("pow(%.16e %.16e) = %.16e\n", x, y, z);
> x = 1.0 - pow (2.0, -52.0);
> z = pow (x, y);
> printf ("pow(%.16e %.16e) = %.16e\n", x, y, z);
> x = -x;
> z = pow (x, y);
> printf ("pow(%.16e %.16e) = %.16e\n", x, y, z);
> }
> -----
>
> Here is a patch for newlib/libm/math/epow.c:
Patch checked in and duplicated for ef_pow.c. Thanks.
-- Jeff J.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Mon, 15 Sep 2008 04:31:30 +0000 |
parents | c121d94672cb |
children | 99210400e8b9 |
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/* SDL - Simple DirectMedia Layer Copyright (C) 1997-2006 Sam Lantinga This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Sam Lantinga slouken@libsdl.org */ #include "SDL_config.h" /* * GNU pth mutexes * * Patrice Mandin */ #include <pth.h> #include "SDL_mutex.h" #include "SDL_sysmutex_c.h" /* Create a mutex */ SDL_mutex * SDL_CreateMutex(void) { SDL_mutex *mutex; /* Allocate mutex memory */ mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex)); if (mutex) { /* Create the mutex, with initial value signaled */ if (!pth_mutex_init(&(mutex->mutexpth_p))) { SDL_SetError("Couldn't create mutex"); SDL_free(mutex); mutex = NULL; } } else { SDL_OutOfMemory(); } return (mutex); } /* Free the mutex */ void SDL_DestroyMutex(SDL_mutex * mutex) { if (mutex) { SDL_free(mutex); } } /* Lock the mutex */ int SDL_mutexP(SDL_mutex * mutex) { if (mutex == NULL) { SDL_SetError("Passed a NULL mutex"); return -1; } pth_mutex_acquire(&(mutex->mutexpth_p), FALSE, NULL); return (0); } /* Unlock the mutex */ int SDL_mutexV(SDL_mutex * mutex) { if (mutex == NULL) { SDL_SetError("Passed a NULL mutex"); return -1; } pth_mutex_release(&(mutex->mutexpth_p)); return (0); } /* vi: set ts=4 sw=4 expandtab: */