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bug #698: rewrite LinSpaced for integer scalar types to avoid overflow and guarantee an even spacing when possible.

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Otherwise, the "high" bound is implicitly lowered to the largest value allowing for an even distribution.
This changeset also disable vectorization for this integer path.
This commit is contained in:
Gael Guennebaud
2016-10-24 15:50:27 +02:00
parent e8e56c7642
commit 53c77061f0
4 changed files with 62 additions and 31 deletions
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38
test/nullary.cpp
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@@ -57,23 +57,31 @@ void testVectorType(const VectorType& base)
VERIFY_IS_APPROX(m,n);
}
VectorType n(size);
for (int i=0; i<size; ++i)
n(i) = size==1 ? low : (low + ((high-low)*Scalar(i))/(size-1));
VERIFY_IS_APPROX(m,n);
if((!NumTraits<Scalar>::IsInteger) || ((high-low)>=size && (Index(high-low)%(size-1))==0) || (Index(high-low+1)<size && (size%Index(high-low+1))==0))
{
VectorType n(size);
if((!NumTraits<Scalar>::IsInteger) || (high-low>=size))
for (int i=0; i<size; ++i)
n(i) = size==1 ? low : (low + ((high-low)*Scalar(i))/(size-1));
else
for (int i=0; i<size; ++i)
n(i) = size==1 ? low : low + Scalar((double(high-low+1)*double(i))/double(size));
VERIFY_IS_APPROX(m,n);
// random access version
m = VectorType::LinSpaced(size,low,high);
VERIFY_IS_APPROX(m,n);
// random access version
m = VectorType::LinSpaced(size,low,high);
VERIFY_IS_APPROX(m,n);
VERIFY( internal::isApprox(m(m.size()-1),high) );
VERIFY( size==1 || internal::isApprox(m(0),low) );
VERIFY( internal::isApprox(m(m.size()-1),high) );
VERIFY( size==1 || internal::isApprox(m(0),low) );
// sequential access version
m = VectorType::LinSpaced(Sequential,size,low,high);
VERIFY_IS_APPROX(m,n);
VERIFY( internal::isApprox(m(m.size()-1),high) );
}
// sequential access version
m = VectorType::LinSpaced(Sequential,size,low,high);
VERIFY_IS_APPROX(m,n);
VERIFY( internal::isApprox(m(m.size()-1),high) );
Scalar tol_factor = (high>=0) ? (1+NumTraits<Scalar>::dummy_precision()) : (1-NumTraits<Scalar>::dummy_precision());
VERIFY( m(m.size()-1) <= high*tol_factor );
VERIFY( size==1 || internal::isApprox(m(0),low) );
// check whether everything works with row and col major vectors
@@ -96,7 +104,7 @@ void testVectorType(const VectorType& base)
VERIFY_IS_APPROX( ScalarMatrix::LinSpaced(1,low,high), ScalarMatrix::Constant(high) );
// regression test for bug 526 (linear vectorized transversal)
if (size > 1) {
if (size > 1 && (!NumTraits<Scalar>::IsInteger)) {
m.tail(size-1).setLinSpaced(low, high);
VERIFY_IS_APPROX(m(size-1), high);
}