diff options
Diffstat (limited to '')
| -rw-r--r-- | Makefile | 2 | ||||
| -rw-r--r-- | libred.h | 7 | ||||
| -rw-r--r-- | libred.h.0 | 4 | ||||
| -rw-r--r-- | libred_check_timetravel.3 | 36 | ||||
| -rw-r--r-- | solar.c | 141 |
5 files changed, 79 insertions, 111 deletions
@@ -22,7 +22,7 @@ OBJ =\ LOBJ = $(OBJ:.o=.lo) MAN0 = libred.h.0 -MAN3 = libred_check_timetravel.3 libred_get_colour.3 libred_solar_elevation.3 +MAN3 = libred_get_colour.3 libred_solar_elevation.3 MAN7 = libred.7 @@ -147,10 +147,11 @@ double libred_solar_elevation(double, double, double *); /** - * Exit if time the is before year 0 in J2000 - * - * @return 0 on success, -1 on error + * This function is obsolete */ +#if defined(__GNUC__) +__attribute__((__deprecated__("libred_check_timetravel is not needed"), __const__)) +#endif int libred_check_timetravel(void); @@ -119,12 +119,8 @@ This header defines the following functions: .BR libred_solar_elevation (3) .TP * -.BR libred_check_timetravel (3) -.TP -* .BR libred_get_colour (3) .SH SEE ALSO .BR libred (7), .BR libred_solar_elevation (3), -.BR libred_check_timetravel (3), .BR libred_get_colour (3) diff --git a/libred_check_timetravel.3 b/libred_check_timetravel.3 deleted file mode 100644 index cf79cd2..0000000 --- a/libred_check_timetravel.3 +++ /dev/null @@ -1,36 +0,0 @@ -.TH LIBRED_CHECK_TIMETRAVEL 3 LIBRED -.SH NAME -libred_check_timetravel \- Exit the process if the clock is too far in the past -.SH SYNOPSIS -.nf -#include <libred.h> - -int \fBlibred_check_timetravel\fP(void); -.fi -.PP -Link with -.IR -lred . -.SH DESCRIPTION -The -.BR libred_check_timetravel () -function exits the process if -.B libred -is not compiled to support the current time, which is the case -if it was compiled without -.I \-DTIMETRAVELLER -and the clock is before year 2000.5 in the Julian calendar. Before -exiting, the function will print an informative error message to -standard error. -.SH RETURN VALUE -Upon successful completion, without time incompatibility, the function -.BR libred_check_timetravel () -returns 0. On failure, the function returns -1 and sets -.I errno -to indicate the error. -.SH ERRORS -The function may fail for any reason specified for -.BR clock_gettime (3). -.SH SEE ALSO -.BR libred.h (0), -.BR libred (7), -.BR libred_solar_elevation (3) @@ -3,6 +3,7 @@ #include <math.h> #include <time.h> #include <errno.h> +#include <stdint.h> #include <stdio.h> #include <stdlib.h> @@ -21,58 +22,78 @@ /** - * Get current Julian Centuries time (100 Julian days since J2000) + * Get current Julian Centuries time (100 Julian Days since J2000) + * and Julian Day time * - * @param nowp Output parameter for the current Julian Centuries time - * @return 0 on success, -1 on failure - * @throws Any error specified for clock_gettime(3) on error + * @param tc_out Output parameter for the current Julian Centuries time + * @param td_out Output parameter for the current Julian Day time + * @return 0 on success, -1 on failure + * @throws Any error specified for clock_gettime(3) on error */ static int -julian_centuries(double *nowp) +julian_time(double *tc_out, double *td_out) { struct timespec now; + double tu; if (clock_gettime(CLOCK_REALTIME_COARSE, &now)) return -1; - *nowp = (double)(now.tv_nsec) / 1000000000.0 + (double)(now.tv_sec); - *nowp = (*nowp / 86400.0 + 2440587.5 - 2451545.0) / 36525.0; + tu = fma((double)now.tv_nsec, 0.000000001, (double)now.tv_sec); + *td_out = tu / 86400.0 + 2440587.5; + *tc_out = (*td_out - 2451545.0) / 36525.0; return 0; } + /** - * Convert a Julian Centuries timestamp to a Julian Day timestamp + * Convert an angle (or otherwise) from degrees to radians * - * @param t The time in Julian Centuries - * @return The time in Julian Days + * @param deg The angle in degrees + * @param The angle in radians */ static double -julian_centuries_to_julian_day(double t) +radians(double deg) { - return 36525.0 * t + 2451545.0; + return (double)M_PI / 180.0 * deg; } +/** + * Convert an angle (or otherwise) from radians to degrees + * + * @param rad The angle in radians + * @param The angle in degrees + */ +static double +degrees(double rad) +{ + return 180.0 / (double)M_PI * rad; +} /** * Convert an angle (or otherwise) from degrees to radians + * and, using fused multply–add, add some number of degrees * * @param deg The angle in degrees - * @param The angle in radians + * @param aug The number of radians to add + * @param The angle in radians, plus `aug` */ static double -radians(double deg) +radians_plus(double deg, double aug) { - return deg * (double)M_PI / 180.0; + return fma((double)M_PI / 180.0, deg, aug); } /** * Convert an angle (or otherwise) from radians to degrees + * and, using fused multply–add, add some number of degrees * * @param rad The angle in radians - * @param The angle in degrees + * @param aug The number of degrees to add + * @param The angle in degrees, plus `aug` */ static double -degrees(double rad) +degrees_plus(double rad, double aug) { - return rad * 180.0 / (double)M_PI; + return fma(180.0 / (double)M_PI, rad, aug); } @@ -88,10 +109,11 @@ degrees(double rad) static double elevation_from_hour_angle(double latitude, double declination, double hour_angle) { - double r = cos(radians(latitude)); - r *= cos(hour_angle) * cos(declination); - r += sin(radians(latitude)) * sin(declination); - return asin(r); + double c, s; + latitude = radians(latitude); + c = cos(latitude) * cos(declination); + s = sin(latitude) * sin(declination); + return asin(fma(c, cos(hour_angle), s)); } /** @@ -103,11 +125,7 @@ elevation_from_hour_angle(double latitude, double declination, double hour_angle static double sun_geometric_mean_longitude(double t) { - double r = fmod(pow(0.0003032 * t, 2.0) + 36000.76983 * t + 280.46646, 360.0); -#if defined(TIMETRAVELLER) - r = r < 0.0 ? (r + 360.0) : r; -#endif - return radians(r); + return radians(fmod(fma(fma(0.0003032, t, 36000.76983), t, 280.46646), 360.0)); } /** @@ -119,7 +137,7 @@ sun_geometric_mean_longitude(double t) static double sun_geometric_mean_anomaly(double t) { - return radians(pow(-0.0001537 * t, 2.0) + 35999.05029 * t + 357.52911); + return radians(fmod(fma(fma(-0.0001537, t, 35999.05029), t, 357.52911), 360.0)); } /** @@ -131,7 +149,7 @@ sun_geometric_mean_anomaly(double t) static double earth_orbit_eccentricity(double t) { - return pow(-0.0000001267 * t, 2.0) - 0.000042037 * t + 0.016708634; + return fma(fma(-0.0000001267, t, -0.000042037), t, 0.016708634); } /** @@ -145,9 +163,9 @@ static double sun_equation_of_centre(double t) { double a = sun_geometric_mean_anomaly(t), r; - r = sin(1.0 * a) * (pow(-0.000014 * t, 2.0) - 0.004817 * t + 1.914602); - r += sin(2.0 * a) * (-0.000101 * t + 0.019993); - r += sin(3.0 * a) * 0.000289; + r = sin(1.0 * a) * fma(fma(-0.000014, t, 0.004817), t, 1.914602); + r = fma(sin(2.0 * a), fma(-0.000101, t, 0.019993), r); + r = fma(sin(3.0 * a), 0.000289, r); return radians(r); } @@ -172,8 +190,9 @@ sun_real_longitude(double t) static double sun_apparent_longitude(double t) { - double r = degrees(sun_real_longitude(t)) - 0.00569; - return radians(r - 0.00478 * sin(radians(-1934.136 * t + 125.04))); + double r = degrees_plus(sun_real_longitude(t), -0.00569); + double a = radians(fma(-1934.136, t, 125.04)); + return radians(fma(-0.00478, sin(a), r)); } /** @@ -186,7 +205,7 @@ sun_apparent_longitude(double t) static double mean_ecliptic_obliquity(double t) { - double r = pow(0.001813 * t, 3.0) - pow(0.00059 * t, 2.0) - 46.815 * t + 21.448; + double r = fma(fma(fma(0.001813, t, -0.00059), t, -46.815), t, 21.448); return radians(23.0 + (26.0 + r / 60.0) / 60.0); } @@ -200,8 +219,8 @@ mean_ecliptic_obliquity(double t) static double corrected_mean_ecliptic_obliquity(double t) { - double r = 0.00256 * cos(radians(-1934.136 * t + 125.04)); - return radians(r + degrees(mean_ecliptic_obliquity(t))); + double r = cos(radians(fma(-1934.136, t, 125.04))); + return radians_plus(0.00256 * r, mean_ecliptic_obliquity(t)); } /** @@ -231,10 +250,12 @@ equation_of_time(double t) double e = earth_orbit_eccentricity(t); double m = sun_geometric_mean_anomaly(t); double y = pow(tan(corrected_mean_ecliptic_obliquity(t) / 2.0), 2.0); - double r = y * sin(2.0 * l); - r += (4.0 * y * cos(2.0 * l) - 2.0) * e * sin(m); - r -= pow(0.5 * y, 2.0) * sin(4.0 * l); - r -= pow(1.25 * e, 2.0) * sin(2.0 * m); + double r, c, s; + s = y * sin(2.0 * l); + c = y * cos(2.0 * l); + r = fma(fma(4.0, c, -2.0), e * sin(m), s); + r = fma(pow(0.50 * y, 2.0), sin(-4.0 * l), r); + r = fma(pow(1.25 * e, 2.0), sin(-2.0 * m), r); return 4.0 * degrees(r); } @@ -242,7 +263,8 @@ equation_of_time(double t) * Calculates the Sun's elevation as apparent * from a geographical position * - * @param t The time in Julian Centuries + * @param tc The time in Julian Centuries + * @param td The time in Julian Days * @param latitude The latitude in degrees northwards from * the equator, negative for southwards * @param longitude The longitude in degrees eastwards from @@ -251,13 +273,13 @@ equation_of_time(double t) * from the specified position, measured in radians */ static double -solar_elevation_from_time(double t, double latitude, double longitude) +solar_elevation_from_time(double tc, double td, double latitude, double longitude) { - double a = julian_centuries_to_julian_day(t); - a = (a - round(a) - 0.5) * 1440; - a = 720.0 - a - equation_of_time(t); - a = radians(a / 4.0 - longitude); - return elevation_from_hour_angle(latitude, solar_declination(t), a); + double r; + td = td - round(td); + r = fma(1440, td - 1, -equation_of_time(tc)); + r = radians(fma(0.25, r, -longitude)); + return elevation_from_hour_angle(latitude, solar_declination(tc), r); } /** @@ -277,33 +299,18 @@ solar_elevation_from_time(double t, double latitude, double longitude) double libred_solar_elevation(double latitude, double longitude, double *elevation) { - double t; - if (julian_centuries(&t)) + double tc, td; + if (julian_time(&tc, &td)) return -1; - *elevation = degrees(solar_elevation_from_time(t, latitude, longitude)); + *elevation = degrees(solar_elevation_from_time(tc, td, latitude, longitude)); return 0; } /** - * Exit if time the is before year 0 in J2000 - * - * @return 0 on success, -1 on error + * This function is obsolete */ int libred_check_timetravel(void) { -#if !defined(TIMETRAVELLER) - struct timespec now; - if (clock_gettime(CLOCK_REALTIME, &now)) - return -1; - if (now.tv_sec < (time_t)946728000L) { - fprintf(stderr, - "We have detected that you are a time-traveller" - "(or your clock is not configured correctly.)" - "Please recompile libred with -DTIMETRAVELLER" - "(or correct your clock.)"); - exit(1); - } -#endif return 0; } |