On 21 June 2015 at 19:57, <highcalcula...@gmail.com> wrote:
> 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)?
>
No. You would have to use C++ for this sort of thing. It's not possible in
C.
> 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)).
>
I can only imagine there is a bug in your code for computing exp.
Bill.
> Any ideas what to change? I will post the code upon request. Thanks again!
>
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