From: Stefan Weinzierl <weinzierl@uni-mainz.de>
Date: Tue, 4 Jun 2019 08:21:10 +0000 (+0200)
Subject: Fix slow numerical computation of zeta({7,3}).
X-Git-Tag: release_1-7-7~10
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=b16d5b34f40c9dcd6bd4f9e1fdeeb65cb1612db3;ds=sidebyside

Fix slow numerical computation of zeta({7,3}).

The bug was reported by Vitaly Magerya <vmagerya@gmail.com>, see
<https://www.ginac.de/pipermail/ginac-list/2019-May/002265.html>.
---

diff --git a/ginac/inifcns_nstdsums.cpp b/ginac/inifcns_nstdsums.cpp
index 0a60d780..f040e8ad 100644
--- a/ginac/inifcns_nstdsums.cpp
+++ b/ginac/inifcns_nstdsums.cpp
@@ -3882,17 +3882,21 @@ static ex zeta1_evalf(const ex& x)
 		const int count = x.nops();
 		const lst& xlst = ex_to<lst>(x);
 		std::vector<int> r(count);
+		std::vector<int> si(count);
 
 		// check parameters and convert them
 		auto it1 = xlst.begin();
 		auto it2 = r.begin();
+		auto it_swrite = si.begin();
 		do {
 			if (!(*it1).info(info_flags::posint)) {
 				return zeta(x).hold();
 			}
 			*it2 = ex_to<numeric>(*it1).to_int();
+			*it_swrite = 1;
 			it1++;
 			it2++;
+			it_swrite++;
 		} while (it2 != r.end());
 
 		// check for divergence
@@ -3900,6 +3904,10 @@ static ex zeta1_evalf(const ex& x)
 			return zeta(x).hold();
 		}
 
+		// use Hoelder convolution if Digits is large
+		if (Digits>50)
+			return numeric(zeta_do_Hoelder_convolution(r, si));
+
 		// decide on summation algorithm
 		// this is still a bit clumsy
 		int limit = (Digits>17) ? 10 : 6;