From a49b41a74b37db35562efb298c91ff0dcc8bd954 Mon Sep 17 00:00:00 2001
From: "Joachim Wuttke (o)" <j.wuttke@fz-juelich.de>
Date: Mon, 31 Jul 2017 17:22:12 +0200
Subject: [PATCH] Extra precautions to prevent rounding error or excessive
precision in tack values.
---
pub/plot/axis.cpp | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/pub/plot/axis.cpp b/pub/plot/axis.cpp
index 4ebe1d6f..01a50438 100644
--- a/pub/plot/axis.cpp
+++ b/pub/plot/axis.cpp
@@ -362,10 +362,21 @@ void CAxis::calc_lintacks(vector<double>& Tacks, int& ntpt, double& dtack) const
dtack = .25 * pow(10., ir);
ntpt = 5;
}
+ // Sets tack vector, taking extra precaution to avoid rounding errors.
Tacks.clear();
- for (double d = dtack * (floor(inf/dtack)-1); d <= dtack * (ceil(sup/dtack)+1); d += dtack)
+ double dlow = dtack * (floor(inf/dtack)-1);
+ double dhig = dtack * (ceil(sup/dtack)+1);
+ double drange = dhig-dlow;
+ int nTacks = drange/dtack + 1.5;
+ if (nTacks<2)
+ throw "BUG: calc_lintacks -> nTacks<2";
+ for (int i=0; i<nTacks; ++i) {
+ double d = (i*dhig + (nTacks-1-i)*dlow)/(nTacks-1);
+ if (std::abs(d)<1e-15*drange)
+ d = 0;
if (inf-1e-4*range <= d && d <= sup+1e-4*range)
Tacks.push_back(d);
+ }
}
--
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