/cln-1.3.2/src/float/transcendental/cl_LF_ratseries_p.cc
C++ | 91 lines | 66 code | 10 blank | 15 comment | 7 complexity | 34d1e48c8dfc0898cd88edc3f5a1d3e7 MD5 | raw file
Possible License(s): GPL-2.0
- // eval_rational_series().
- // General includes.
- #include "base/cl_sysdep.h"
- // Specification.
- #include "float/transcendental/cl_LF_tran.h"
- // Implementation.
- #include "cln/lfloat.h"
- #include "cln/integer.h"
- #include "cln/exception.h"
- #include "float/lfloat/cl_LF.h"
- namespace cln {
- // Subroutine.
- // Evaluates S = sum(N1 <= n < N2, a(n)/b(n) * (p(N1)...p(n))/(q(N1)...q(n)))
- // and returns P = p(N1)...p(N2-1), Q = q(N1)...q(N2-1), B = B(N1)...B(N2-1)
- // and T = B*Q*S (all integers). On entry N1 < N2.
- // P will not be computed if a NULL pointer is passed.
- static void eval_p_series_aux (uintC N1, uintC N2,
- const cl_p_series& args,
- cl_I* P, cl_I* T)
- {
- switch (N2 - N1) {
- case 0:
- throw runtime_exception(); break;
- case 1:
- if (P) { *P = args.pv[N1]; }
- *T = args.pv[N1];
- break;
- case 2: {
- var cl_I p01 = args.pv[N1] * args.pv[N1+1];
- if (P) { *P = p01; }
- *T = args.pv[N1]
- + p01;
- break;
- }
- case 3: {
- var cl_I p01 = args.pv[N1] * args.pv[N1+1];
- var cl_I p012 = p01 * args.pv[N1+2];
- if (P) { *P = p012; }
- *T = args.pv[N1]
- + p01
- + p012;
- break;
- }
- case 4: {
- var cl_I p01 = args.pv[N1] * args.pv[N1+1];
- var cl_I p012 = p01 * args.pv[N1+2];
- var cl_I p0123 = p012 * args.pv[N1+3];
- if (P) { *P = p0123; }
- *T = args.pv[N1]
- + p01
- + p012
- + p0123;
- break;
- }
- default: {
- var uintC Nm = (N1+N2)/2; // midpoint
- // Compute left part.
- var cl_I LP, LT;
- eval_p_series_aux(N1,Nm,args,&LP,<);
- // Compute right part.
- var cl_I RP, RT;
- eval_p_series_aux(Nm,N2,args,(P?&RP:(cl_I*)0),&RT);
- // Put together partial results.
- if (P) { *P = LP*RP; }
- // S = LS + LP * RS, so T = LT + LP*RT.
- *T = LT + LP*RT;
- break;
- }
- }
- }
- const cl_LF eval_rational_series (uintC N, const cl_p_series& args, uintC len)
- {
- if (N==0)
- return cl_I_to_LF(0,len);
- var cl_I T;
- eval_p_series_aux(0,N,args,NULL,&T);
- return cl_I_to_LF(T,len);
- }
- // Bit complexity (if p(n), q(n), a(n), b(n) have length O(log(n))):
- // O(log(N)^2*M(N)).
- } // namespace cln