SQRT Problem.

[sergioms]

long DesvioPadrao(long pesos[100], u16_t tamanho)
{
	double ld_raiz;
	long total = 0;
	long media;
	long ll_resultado;
	int iCont;

	char strTexto[100];

	for(iCont=0; iCont<tamanho; iCont++)
		total += pesos[iCont];

	media = total / tamanho;
	total = 0;

	for(iCont=0; iCont<tamanho; iCont++)
	{
		ll_resultado = pesos[iCont] - media;
		total = total + (ll_resultado * ll_resultado);
	}

	total = (long) total / (tamanho - 1);

       /*
       here total = 10
       */
	ld_raiz = sqrt(total);

	total = (long)ld_raiz;
	return total;
}

My function return 528062108, when i call SQRT function passing value 10 like argument, and cast (or no cast) to long.

[Fader_Berg]

sqrt takes a double as argument, not long.

ld_raiz = sqrt((double) total);

[sergioms]

sqrt takes a double as argument, not long.

ld_raiz = sqrt((double) total);

The problems continue..

[laserlight]

Post the smallest and simplest compilable program that demonstrates the problem. Also, post your input, expected output and actual output.

[anduril462]

sqrt takes a double as argument, not long.

ld_raiz = sqrt((double) total);

Type promotion should happily convert the long value to a double before making the call, so nothing to worry about there.

[sergioms]

Maybe, my enviroment get an error...
a simple sqrt(2); showed in "%d" on a printf get same error.

[laserlight]

What is the error? Are you sure you are compiling as C?

[Fader_Berg]

Maybe, my enviroment get an error...
a simple sqrt(2); showed in "%d" on a printf get same error.

You can't print doubles with %d [printf("%d", sqrt(2))], you must use %lf.

[sergioms]

Yes, i'm compiling by GCC ARM using Yargato lib.
YAGARTO - Yet another GNU ARM toolchain

[Adak]

QUOTE=Fader_Berg; You can't print doubles with %d [printf("%d", sqrt(2))], you must use %lf.

[sergioms]

QUOTE=Fader_Berg; You can't print doubles with %d [printf("%d", sqrt(2))], you must use %lf.

erros continue...

[Fader_Berg]

printf("%lf", sqrt(2))

...doesn't give you the right answer?

[sergioms]

unsigned long isqrt(const unsigned long n);

/*-- isqrt -----------------------------------------------------------------*/

unsigned long isqrt(unsigned long n) {
  unsigned long s, t;

#define sqrtBit(k) \
  t = s+(1UL<<(k-1)); t <<= k+1; if (n >= t) { n -= t; s |= 1UL<<k; }

  s = 0UL;
#ifdef __alpha
  if (n >= 1UL<<62) { n -= 1UL<<62; s = 1UL<<31; }
  sqrtBit(30); sqrtBit(29); sqrtBit(28); sqrtBit(27); sqrtBit(26);
  sqrtBit(25); sqrtBit(24); sqrtBit(23); sqrtBit(22); sqrtBit(21);
  sqrtBit(20); sqrtBit(19); sqrtBit(18); sqrtBit(17); sqrtBit(16);
  sqrtBit(15);
#else
  if (n >= 1UL<<30) { n -= 1UL<<30; s = 1UL<<15; }
#endif
  sqrtBit(14); sqrtBit(13); sqrtBit(12); sqrtBit(11); sqrtBit(10);
  sqrtBit(9); sqrtBit(8); sqrtBit(7); sqrtBit(6); sqrtBit(5);
  sqrtBit(4); sqrtBit(3); sqrtBit(2); sqrtBit(1);
  if (n > s<<1) s |= 1UL;

#undef sqrtBit

  return s;
}