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cd4c8c9ec5
test on 4-core-4-hyperthread i5 and 2-core-4-hyperthread i5, the speed of generating lunar calendar almost doubled.
132 lines
3.5 KiB
C
132 lines
3.5 KiB
C
/*
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copyright 2014, Chen Wei <weichen302@gmail.com>
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version 0.0.3
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Implement astronomical algorithms for finding solar terms and moon phases.
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Truncated LEA-406 for calculate Moon's apparent longitude;
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Reference:
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LEA-406: S. M. Kudryavtsev (2007) "Long-term harmonic development of
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lunar ephemeris", Astronomy and Astrophysics 471, 1069-1075
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include <pthread.h>
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#include <assert.h>
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#include "astro.h"
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#include "lea406-full.h"
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static double vlea406[MAX_THREADS];
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static int num_threads = 0; /* number of threads for compute lea406-full */
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static int nelems_per_thread; /* number of elements assigned to a thread */
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/* count logical CPU by parsing /proc/cpuinfo */
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int cpucount(void)
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{
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FILE *fp;
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int logic_cpu;
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char *s;
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char buf[MAX_CPUINFO_LEN];
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fp = fopen("/proc/cpuinfo", "rb");
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logic_cpu = 0;
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while ((s = fgets(buf, MAX_CPUINFO_LEN, fp)) != NULL) {
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if (s == strstr(buf, "processor"))
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logic_cpu += 1;
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}
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logic_cpu = (logic_cpu > MAX_THREADS) ? MAX_THREADS : logic_cpu;
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return logic_cpu;
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}
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/* the thread worker for lea406 */
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void *lea406worker(void *args)
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{
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int tid, i, start, end;
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double t, tm, tm2, V, arg;
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tid = ((struct worker_param *) args)->tid;
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t = ((struct worker_param *) args)->tc;
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tm = t / 10.0;
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tm2 = tm * tm;
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start = tid * nelems_per_thread;
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end = start + nelems_per_thread;
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end = (end > LEA406TERMS) ? LEA406TERMS : end;
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V = 0.0;
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for (i = start; i < end; i++) {
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arg = (M_ARG[i][0] + t * (M_ARG[i][1] + M_ARG[i][2] * t)) * ASEC2RAD;
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V += M_AP[i][0] * sin(arg + M_AP[i][3] * DEG2RAD)
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+ M_AP[i][1] * sin(arg + M_AP[i][4] * DEG2RAD) * tm
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+ M_AP[i][2] * sin(arg + M_AP[i][5] * DEG2RAD) * tm2;
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}
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vlea406[tid] = V;
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return NULL;
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}
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/*
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* LEA-406 Moon Solution
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*
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* Reference:
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* Long-term harmonic development of lunar ephemeris.
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* Kudryavtsev S.M. <Astron. Astrophys. 471, 1069 (2007)>
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*
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*/
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/* compute moon ecliptic longitude using lea406 */
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double lea406(double jd, int ignorenutation) {
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int rc, i;
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double t, V;
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t = (jd - J2000) / 36525.0;
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/* set number of threads number of logical CPU */
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num_threads = (num_threads) ? num_threads : cpucount();
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pthread_t threads[num_threads];
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struct worker_param *tmp;
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struct worker_param *thread_args[num_threads];
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/* init thread args */
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for (i = 0; i < num_threads; i++) {
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tmp = (struct worker_param *) malloc(sizeof(struct worker_param));
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tmp->tc = (jd - J2000) / 36525.0;
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tmp->tid = i;
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thread_args[i] = tmp;
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}
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nelems_per_thread = LEA406TERMS / num_threads;
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for (i = 0; i < num_threads; i++) {
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rc = pthread_create(&threads[i], NULL, lea406worker, thread_args[i]);
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assert(0 == rc);
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}
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V = FRM[0] + (((FRM[4] * t + FRM[3]) * t + FRM[2]) * t + FRM[1]) * t;
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for (i = 0; i < num_threads; i++) {
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rc = pthread_join(threads[i], NULL);
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assert(0 == rc);
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}
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for (i = 0; i < num_threads; i++) {
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V += vlea406[i];
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}
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V *= ASEC2RAD;
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if (!ignorenutation) {
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V += nutation(jd);
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/* printf("debug lea406, nutation been adjusted"); */
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}
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return V;
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}
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/* calculate the apparent position of the Moon, it is an alias to the
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* lea406 function
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*/
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double apparentmoon(double jd, int ignorenutation)
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{
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return lea406(jd, ignorenutation);
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}
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