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Fix exp function to actually work #43

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Fix exp function to actually work #43

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1 change: 1 addition & 0 deletions decTest/exp.decTest
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Original file line number Diff line number Diff line change
Expand Up @@ -540,6 +540,7 @@ expx1200 exp 1 -> 2.718281828459045235360287471352662 Inexact Rounded
Precision: 34
maxExponent: 6144
minExponent: -6143
clamp: 1
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@alkis alkis Jan 3, 2018

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Why do we need this? This test should not change at all.

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@djrodgerspryor djrodgerspryor Jan 6, 2018 •
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Because of these lines in the run-test script:

    let d128_env = Environment {
        precision: Some(34),
        rounding: Some(Rounding::HalfEven),
        max_exponent: Some(6144),
        min_exponent: Some(-6143),
        extended: true,
        clamp: true,
    };

    if *env != d128_env {
        return TestResult::Ignored(test);
    }

Without that change, the tests were silently skipped (and none of the other matched either).

Maybe I should have gone in the other direction and defined a different Environment just for these tests? I assume that the check is there to make sure that it only runs applicable tests, but since the exp tests pass with the different clamping mode, I assume that all of those test cases are still valid with the different clamping mode.

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@alkis alkis Jan 7, 2018

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Is it possible to change run_test() to run ops with the specified environment which will make this change unnecessary and increase test coverage?

expx1201 exp 309.5948855821510212996700645087188 -> 2.853319692901387521201738015050724E+134 Inexact Rounded
expx1202 exp 9.936543068706211420422803962680164 -> 20672.15839203171877476511093276022 Inexact Rounded
expx1203 exp 6.307870323881505684429839491707908 -> 548.8747777054637296137277391754665 Inexact Rounded
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1 change: 1 addition & 0 deletions src/bin/run-test.rs
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Expand Up @@ -494,6 +494,7 @@ fn run_test<'a>(env: &Environment, test: Test<'a>) -> TestResult<'a> {
&test);
}
Op::Divide(a, b) => simple_op!(test, value = div(a, b)),
Op::Exp(a) => simple_op!(test, value = exp(a)),
Op::Fma(a, b, c) => simple_op!(test, value = mul_add(a, b, c)),
Op::Invert(a) => simple_op!(test, value = not(a)),
Op::LogB(a) => simple_op!(test, value = logb(a)),
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12 changes: 7 additions & 5 deletions src/dec128.rs
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Expand Up @@ -617,13 +617,11 @@ impl d128 {
/// respectively). Inexact results will almost always be correctly rounded, but may be up to 1
/// ulp (unit in last place) in error in rare cases. This is a mathematical function; the
/// 10<sup>6</sup> restrictions on precision and range apply as described above.
pub fn exp<O: AsRef<d128>>(mut self, exp: O) -> d128 {
pub fn exp(mut self) -> d128 {
d128::with_context(|ctx| unsafe {
let mut num_self: decNumber = uninitialized();
let mut num_exp: decNumber = uninitialized();
decimal128ToNumber(&self, &mut num_self);
decimal128ToNumber(exp.as_ref(), &mut num_exp);
decNumberExp(&mut num_self, &num_self, &num_exp, ctx);
decNumberExp(&mut num_self, &num_self, ctx);
*decimal128FromNumber(&mut self, &num_self, ctx)
})
}
Expand Down Expand Up @@ -948,7 +946,6 @@ extern "C" {
ctx: *mut Context)
-> *mut decNumber;
fn decNumberExp(res: *mut decNumber,
lhs: *const decNumber,
rhs: *const decNumber,
ctx: *mut Context)
-> *mut decNumber;
Expand Down Expand Up @@ -1093,4 +1090,9 @@ mod tests {
assert_eq!(d128::from_str(&(::std::u64::MIN).to_string()).unwrap(),
d128::from(::std::u64::MIN));
}

#[test]
fn math_op() {
assert_eq!(d128!(1), d128!(1).ln().exp());
}
}