2007/6/9, Dann Corbit <[EMAIL PROTECTED]>:
#include <math.h>
double log10nfactorialestimate(unsigned n)
{
unsigned i;
double estimate = 0;
for (i = 1; i < n; i++)
estimate += log10(n);
return estimate;
}
#ifdef UNIT_TEST
#include <stdio.h>
#include <time.h>
int main(void)
{
clock_t start,
end;
double answer;
start = clock();
end = clock();
answer = log10nfactorialestimate(92838278);
printf("log 10 of 92838278! is pretty close to %g and took %g
seconds\n",
answer, (end - start) / (1.0 * CLOCKS_PER_SEC));
return 0;
}
#endif
/*
C:\tmp>cl /W4 /Ox /DUNIT_TEST log10EST.C
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 14.00.50727.42
for 80x86
Copyright (C) Microsoft Corporation. All rights reserved.
log10EST.C
Microsoft (R) Incremental Linker Version 8.00.50727.42
Copyright (C) Microsoft Corporation. All rights reserved.
/out:log10EST.exe
log10EST.obj
C:\tmp>log10est
log 10 of 92838278! is pretty close to 7.3971e+008 and took 0 seconds
*/
Hum... I think there is a little improvement: when n is too large,(say
n>10, 000) we can use Stirling's formula to get the estimated value of
n! :-)
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