3rd,円周率を「米粒を敷き詰めて計算」する方法【C言語】

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正方形を敷き詰めるやり方。

このやり方では正解より必ず小さな値に成る。

pai.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>


void now(void)
{
	time_t t = time(NULL);
	struct tm *local = localtime(&t);
/*
	printf("%04d/", local->tm_year + 1900);
	printf("%02d/", local->tm_mon + 1);
	printf("%02d", local->tm_mday);

	printf(" ");
*/
	printf("%02d:", local->tm_hour);
	printf("%02d:", local->tm_min);
	printf("%02d\n", local->tm_sec);
	fflush(stdout);
}

int main(int argc,char *argv[])
{
			double  n=1000.0f ;

	if(argc > 1 )
	{
		n=atof( argv[1] ) ;		
	}
    double x,y,xx,yy;
	long long i;

	now();
	//--- --- --- ---
		do{
				double hen = 2.0f / n ;
				double henf = hen / 2.0f ;
				double sum = hen * hen ; // 面積
				double len = 0.0f;
				for(x=henf ; x <= 1.0f -henf ; x+= hen)
				{
						xx = x + henf ;
						xx *= xx ;
						for(y=henf ; y <= 1.0f-henf ;y+=hen)
						{
								yy = y + henf ;
								yy *= yy ;
								if(xx + yy <= 1.0f) len += 1.0f ;
						}
				}
				printf("%1.15f log10(%.3f)分割 ",4.0f * len * sum ,log10(n));
				now();
				n *= 1.03f;
		}while(1);
	return 0;
}

---

出力結果.

3.141512401600000 log10(5.000)分割 11:54:09
3.141514585306505 log10(5.013)分割 11:54:22
3.141516901724735 log10(5.026)分割 11:54:35
3.141519624956707 log10(5.039)分割 11:54:50
3.141521733419711 log10(5.051)分割 11:55:07
3.141523616809169 log10(5.064)分割 11:55:23
3.141525718581799 log10(5.077)分割 11:55:40
3.141527528977863 log10(5.090)分割 11:55:59
3.141529637102726 log10(5.103)分割 11:56:18
3.141531361794161 log10(5.116)分割 11:56:39
3.141532997960393 log10(5.128)分割 11:57:02
3.141534862594533 log10(5.141)分割 11:57:25