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DM-21697 Fix SpanSet Creation from large circles #514

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DM-21697 Fix SpanSet Creation from large circles #514

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10 changes: 7 additions & 3 deletions src/geom/SpanSet.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -691,9 +691,13 @@ std::shared_ptr<SpanSet> SpanSet::fromShape(int r, Stencil s, lsst::geom::Point2
tempVec.reserve(2 * r + 1);
switch (s) {
case Stencil::CIRCLE:
for (auto dy = -r; dy <= r; ++dy) {
int dx = static_cast<int>(sqrt(r * r - dy * dy));
tempVec.emplace_back(dy + offset.getY(), -dx + offset.getX(), dx + offset.getX());
{
double dr = static_cast<double>(r);
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@gpdf gpdf Feb 6, 2020

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I think a comment is necessary to clarify what problem is being avoided by the parallel increment of the integer and the double. And I might name the variable that holds "r-squared" something like r_sq.

dr *= dr;
for (auto dy = std::make_pair<int, double>(-r, -r); dy.first <= r; ++dy.first, ++dy.second) {
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@gpdf gpdf Feb 6, 2020

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Some C++ style guides frown on applying the increment/decrement operators to floating-point values. However, I don't think the LSST style guide mentions this.

Still, dy.second += 1.0 might help the reader understand the nature of the parallelism a bit more.

int dx = static_cast<int>(sqrt(dr-(dy.second*dy.second)));
tempVec.emplace_back(dy.first + offset.getY(), -dx + offset.getX(), dx + offset.getX());
}
}
break;
case Stencil::MANHATTAN:
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