[BUG] Unexpected return value for `sign` of some 4-element `uint64` array

[stemann]

sign for a some (randomly generated) 4-element uint64 array does not return the expected return value (an array of 0x0000000000000001), but instead returns an array of 0xffffffffffffffff.

The following test fails:

    array x_uint64({uint64_t(0xa11cc311cb6acd70), uint64_t(0x7a375ac3ebb533f3), uint64_t(0x734969adf9d7190c), uint64_t(0xb400515a4f673424)});
    array expected({uint64_t(0x0000000000000001), uint64_t(0x0000000000000001), uint64_t(0x0000000000000001), uint64_t(0x0000000000000001)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

To Reproduce

// fails
    array x_uint64({uint64_t(0xa11cc311cb6acd70), uint64_t(0x7a375ac3ebb533f3), uint64_t(0x734969adf9d7190c), uint64_t(0xb400515a4f673424)});
    array expected({uint64_t(0x0000000000000001), uint64_t(0x0000000000000001), uint64_t(0x0000000000000001), uint64_t(0x0000000000000001)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

// succeeds, wrong return value
    x_uint64 = array({uint64_t(0xa11cc311cb6acd70), uint64_t(0x7a375ac3ebb533f3), uint64_t(0x734969adf9d7190c), uint64_t(0xb400515a4f673424)});
    expected = array({uint64_t(0xffffffffffffffff), uint64_t(0xffffffffffffffff), uint64_t(0xffffffffffffffff), uint64_t(0xffffffffffffffff)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

// succeeds, the first three elements
    x_uint64 = array({uint64_t(0xa11cc311cb6acd70), uint64_t(0x7a375ac3ebb533f3), uint64_t(0x734969adf9d7190c)});
    expected = array({uint64_t(0x0000000000000001), uint64_t(0x0000000000000001), uint64_t(0x0000000000000001)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

// succeeds, the first two elements
    x_uint64 = array({uint64_t(0xa11cc311cb6acd70), uint64_t(0x7a375ac3ebb533f3)});
    expected = array({uint64_t(0x0000000000000001), uint64_t(0x0000000000000001)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

// succeeds, the first element
    x_uint64 = array({uint64_t(0xa11cc311cb6acd70)});
    expected = array({uint64_t(0x0000000000000001)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

// succeeds, 0xffffffffffffffff
    x_uint64 = array({uint64_t(0xffffffffffffffff)});
    expected = array({uint64_t(0x0000000000000001)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

// succeeds, 0x0000000000000001
    x_uint64 = array({uint64_t(0x0000000000000001)});
    expected = array({uint64_t(0x0000000000000001)});
    CHECK(array_equal(sign(x_uint64), expected).item<bool>());

Expected behavior

    array x_uint64({uint64_t(0xa11cc311cb6acd70), uint64_t(0x7a375ac3ebb533f3), uint64_t(0x734969adf9d7190c), uint64_t(0xb400515a4f673424)});
    array expected({uint64_t(0x0000000000000001), uint64_t(0x0000000000000001), uint64_t(0x0000000000000001), uint64_t(0x0000000000000001)});

Desktop (please complete the following information):

• OS Version: MacOS 14.4.1 (Intel, x86_64)
• Version master @ 13b2677 (post v0.24.1)

Additional context

Discovered in relation to implementing unary ops for Julia - and checking equivalence of unary ops wrt. Julia implementations: stemann/MLX.jl#14

[angeloskath]

Fixed in #2024 thanks for finding and reporting it!