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Fixes issue with truncating implicitly rounding in some cases #600

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merged 2 commits into from
Jul 17, 2023
Merged

Fixes issue with truncating implicitly rounding in some cases #600

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1cab271
Fixes issue with truncating implicitly rounding in some cases
paupino Jul 16, 2023
fd7d96e
Merge branch 'master' into issue/599
paupino Jul 16, 2023
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30 changes: 8 additions & 22 deletions src/ops/array.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,13 @@ use crate::constants::{MAX_PRECISION_U32, POWERS_10, U32_MASK};

/// Rescales the given decimal to new scale.
/// e.g. with 1.23 and new scale 3 rescale the value to 1.230
#[inline(always)]
#[inline]
pub(crate) fn rescale_internal(value: &mut [u32; 3], value_scale: &mut u32, new_scale: u32) {
rescale::<true>(value, value_scale, new_scale);
}

#[inline(always)]
fn rescale<const ROUND: bool>(value: &mut [u32; 3], value_scale: &mut u32, new_scale: u32) {
if *value_scale == new_scale {
// Nothing to do
return;
Expand Down Expand Up @@ -32,7 +37,7 @@ pub(crate) fn rescale_internal(value: &mut [u32; 3], value_scale: &mut u32, new_
// Any remainder is discarded if diff > 0 still (i.e. lost precision)
remainder = div_by_u32(value, 10);
}
if remainder >= 5 {
if ROUND && remainder >= 5 {
for part in value.iter_mut() {
let digit = u64::from(*part) + 1u64;
remainder = if digit > U32_MASK { 1 } else { 0 };
Expand Down Expand Up @@ -60,26 +65,7 @@ pub(crate) fn rescale_internal(value: &mut [u32; 3], value_scale: &mut u32, new_

#[inline]
pub(crate) fn truncate_internal(value: &mut [u32; 3], value_scale: &mut u32, desired_scale: u32) {
if *value_scale <= desired_scale {
// Nothing to do, we're already at the desired scale (or less)
return;
}
if is_all_zero(value) {
*value_scale = desired_scale;
return;
}
while *value_scale > desired_scale {
// We're removing precision, so we don't care about handling the remainder
if *value_scale < 10 {
let adjustment = *value_scale - desired_scale;
div_by_u32(value, POWERS_10[adjustment as usize]);
*value_scale = desired_scale;
} else {
div_by_u32(value, POWERS_10[9]);
// Only 9 as this array starts with 1
*value_scale -= 9;
}
}
rescale::<false>(value, value_scale, desired_scale);
}

#[cfg(feature = "legacy-ops")]
Expand Down
86 changes: 70 additions & 16 deletions tests/decimal_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2674,24 +2674,78 @@ fn it_can_trunc() {
#[test]
fn it_can_trunc_with_scale() {
let cmp = Decimal::from_str("1.2345").unwrap();
assert_eq!(Decimal::from_str("1.23450").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("1.234500001").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("1.23451").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("1.23454").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("1.23455").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("1.23456").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("1.23459").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("1.234599999").unwrap().trunc_with_scale(4), cmp);
let tests = [
"1.23450",
"1.234500001",
"1.23451",
"1.23454",
"1.23455",
"1.23456",
"1.23459",
"1.234599999",
];
for test in tests {
assert_eq!(
Decimal::from_str(test).unwrap().trunc_with_scale(4),
cmp,
"Original: {}",
test
);
}

let cmp = Decimal::from_str("-1.2345").unwrap();
assert_eq!(Decimal::from_str("-1.23450").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("-1.234500001").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("-1.23451").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("-1.23454").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("-1.23455").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("-1.23456").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("-1.23459").unwrap().trunc_with_scale(4), cmp);
assert_eq!(Decimal::from_str("-1.234599999").unwrap().trunc_with_scale(4), cmp);
let tests = [
"-1.23450",
"-1.234500001",
"-1.23451",
"-1.23454",
"-1.23455",
"-1.23456",
"-1.23459",
"-1.234599999",
];
for test in tests {
assert_eq!(
Decimal::from_str(test).unwrap().trunc_with_scale(4),
cmp,
"Original: {}",
test
);
}

// Complex cases
let cmp = Decimal::from_str("0.5156").unwrap();
let tests = [
"0.51560089",
"0.515600893",
"0.5156008936",
"0.51560089369",
"0.515600893691",
"0.5156008936910",
"0.51560089369101",
"0.515600893691016",
"0.5156008936910161",
"0.51560089369101613",
"0.515600893691016134",
"0.5156008936910161349",
"0.51560089369101613494",
"0.515600893691016134941",
"0.5156008936910161349411",
"0.51560089369101613494115",
"0.515600893691016134941151",
"0.5156008936910161349411515",
"0.51560089369101613494115158",
"0.515600893691016134941151581",
"0.5156008936910161349411515818",
];
for test in tests {
assert_eq!(
Decimal::from_str(test).unwrap().trunc_with_scale(4),
cmp,
"Original: {}",
test
);
}
}

#[test]
Expand Down