I am referring to using MPIR with gcc in the MinGW shell (outside Matlab).
First question (of two):
In MPIR, is it possible to declare / define a function with return type
mpf_t (for example, or mpz_t)? My calculation of exp(x) via the function
exp_calc(mpf_t x, int NN) works with type void, but when I declare it to be
void , gcc complains:
“exp_calc.h:2:7: error: 'exp_calc' declared as function returning an array
mpf_t exp_calc(mpf_t x, int NN);
testest.c: In function 'main': testest.c:27:8: error: incompatible types
when assigning exp_a = exp_calc(a, num_exp_terms); In file included from
exp_calc.c:2:0:
exp_calc.h:2:7: error: 'exp_calc' declared as function mpf_t exp_calc(mpf_t
x, int NN);
Here is the beginning and end of exp_calc.c :
#include "mpir.h"
#include "exp_calc.h"
mpf_t exp_calc(mpf_t x, int NN) {
mpf_t denominator, numerator, frac_val, outvalue;
mpz_t fac_value;
[…calculations via the Taylor sum representation of exp …]
return outvalue;
}
Second question (regarding the accuracy of exp(-0.01) ):
In my current (naive?) working implementation of the calculation of
exp(-0.01) (and smaller negative numbers), which uses the type void for the
function, the result does not seem to be correct to more than 15 digits in
MPIR, when using mp_bitcnt_t bct = 2000; and NN = 1000 terms in the Taylor
sum for exp (I've compared it to Matlab vpa and Wolfram alpha, who agree in
the result (to at least 100 digits)).
Any ideas what to change? I will post the code upon request. Thanks again!
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