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Library: extend text coverage for util::floorwrap

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These two helpers ''just happen to work'' in the full domain, and also for unsigned types.
I can not recall that I actually was aware of that, but it's nice.

Thus add some test cases to cover the bounds of the domain
This commit is contained in:
Fischlurch 2026-09-14 16:34:15 +02:00
parent 77257c5653
commit 29a39a0f7f
1 changed files with 53 additions and 4 deletions
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57
tests/lib/util-floordiv-test.cpp
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@ -30,7 +30,7 @@
using ::Test;
using util::isnil;
using util::_Fmt;
using std::integral;
namespace util {
namespace test {
@ -42,6 +42,13 @@ namespace test {
const uint NUM_ELMS_PERFORMANCE_TEST = 50000000;
const uint NUMBER_LIMIT = 1 << 30;
template<typename NUM>
constexpr NUM _MAX = std::numeric_limits<NUM>::max();
template<typename NUM>
constexpr NUM _MIN = std::numeric_limits<NUM>::lowest();
typedef std::vector<int> VecI;
VecI
@ -108,7 +115,7 @@ namespace test {
{
seedRand();
verifyBehaviour ();
verifyBehaviour();
verifyIntegerTypes<int>();
verifyIntegerTypes<long>();
@ -116,6 +123,8 @@ namespace test {
verifyIntegerTypes<int64_t>();
verifyIntegerTypes<llong>();
verifyBounds();
if (not isnil (arg))
runPerformanceTest();
}
@ -154,7 +163,7 @@ namespace test {
template<typename I>
void
verifyIntegerTypes ()
verifyIntegerTypes()
{
I n,d,expectedRes;
@ -168,11 +177,51 @@ namespace test {
}
void
verifyBounds()
{
auto verify = []<integral I>(I num, I den, I expect_quot, I expect_rem)
{
auto res = floorwrap (num,den);
CHECK (res.quot == expect_quot, "quotient mismatch");
CHECK (res.rem == expect_rem , "remainder mismatch");
CHECK (res.quot == floordiv (num,den), "floordiv diverges");
};
//----- num | den | quotient | remainder
verify (_MAX<int>, 1, _MAX<int> , 0);
verify (_MAX<int>, 2, _MAX<int>/2 , 1);
verify (_MAX<int>, 5, _MAX<int>/5 , 2);
verify (_MIN<int>, 1, _MIN<int> , 0);
verify (_MIN<int>, 2, _MIN<int>/2 , 0);
verify (_MIN<int>, 5, _MIN<int>/5 -1, 2); // _MIN<int> ≡ -2147483648 /5 ≡ -429496729 -1 step ≡ -429496730 · 5 ≡ -2147483650 ⟹ Δ = +2
verify (_MAX<int>,-1, -_MAX<int> , 0);
verify (_MAX<int>,-2, -_MAX<int>/2 -1,-1);
verify (_MAX<int>,-5, -_MAX<int>/5 -1,-3); // Δ ≡ -3 here since -_MAX<int> ≡ _MIN<int> + 1
verify (_MAX<uint>, 1u, _MAX<uint> ,0u);
verify (_MAX<uint>, 2u, _MAX<uint>/2 ,1u);
verify (_MAX<uint>, 5u, _MAX<uint>/5 ,0u);
verify (_MIN<int64_t>, int64_t(1), _MIN<int64_t> , int64_t(0));
verify (_MIN<int64_t>, int64_t(2), _MIN<int64_t>/2 , int64_t(0));
verify (_MIN<int64_t>, int64_t(5), _MIN<int64_t>/5 -1, int64_t(2)); // 2^63 / 5 ≡ 1844674407370955161.6 ; 1844674407370955162 · 5 ⟹ Δ = +2
verify (_MIN<int8_t>, int8_t(1), int8_t(-128) , int8_t(0));
verify (_MIN<int8_t>, int8_t(2), int8_t(-64 ) , int8_t(0));
verify (_MIN<int8_t>, int8_t(5), int8_t(-26 ) , int8_t(2)); // 2^7 / 5 ≡ 25.6 ; 26 · 5 ≡ 130 ⟹ Δ = +2
verify (_MAX<int8_t>, int8_t(5), int8_t( 25 ) , int8_t(2)); // (2^7-1) / 5 ≡ 25.4 ; 25 · 5 ≡ 125 ⟹ Δ = +2
}
/** @test timing measurements to compare implementation details.
* This test uses a sequence of random integers, where the values
* used as denominator are ensured not to be zero.
*
*
* \par measurement results
* My experiments (AMD Athlon-64 4200 X2) gave me
* the following timing measurements in nanoseconds: