Differentiation functions with Box<dyn Trait> args fails

[motabbara]

Please see https://fwd.gymni.ch/eTJnUQ

Fail on "Attempting to call an indirect active function whose runtime value is inactive".

#![feature(autodiff)]
use std::autodiff::autodiff;
use std::fmt;

#[derive(Debug)]
struct Foo {
    pub test: f64
}

pub trait Cool: fmt::Debug {
    fn gen(&self) -> f64;
}

impl Cool for Foo {
    fn gen(&self) -> f64 {
        self.test * self.test
    }
}


#[autodiff(dsquare, Reverse, Duplicated, Duplicated)]
pub fn square(num: &Foo, result: &mut f64) {
    *result = num.gen()
}

#[autodiff(dsquare2, Reverse, Duplicated, Duplicated)]
pub fn square2(num: &Box<dyn Cool>, result: &mut f64) {
    *result = num.gen()
}

Incidentally, generic functions fail to differentiate even without the box e.g,.,

#[autodiff(dsquare3, Reverse, Duplicated, Duplicated)]
pub fn square3<U: Cool>(num: &U, result: &mut f64) {
    *result = num.gen()
}

[motabbara]

@ZuseZ4, any recommendations about where in the codebase to look to examine calling traits through Box? Happy to attempt to try something myself with some pointers.

[ZuseZ4]

I'm currently traveling, but I'll be back at my laptop on the 23rd, then I can look closer at the runtime inactivity. In the meantime, if you have a local build, can you run cargo +expand and post the ad macro expansions? Otherwise there might be flags to get the output from the explorer.

Support for Generics should be easy to add, we had support in an earlier implementation. You need to adjust the frontend to not error on generics, and adjust the autodiff function body to call the generic primal function. I will look up the two locations in my frontend pr that you'd need to modify for that.

[motabbara]

Here it is:

#![feature(prelude_import)]
#![feature(autodiff)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;
use std::autodiff::autodiff;
use std::fmt;
struct Foo {
    pub test: f64,
}
#[automatically_derived]
impl ::core::fmt::Debug for Foo {
    #[inline]
    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
        ::core::fmt::Formatter::debug_struct_field1_finish(f, "Foo", "test", &&self.test)
    }
}
pub trait Cool: fmt::Debug {
    fn gen(&self) -> f64;
}
impl Cool for Foo {
    fn gen(&self) -> f64 {
        self.test * self.test
    }
}
#[rustc_autodiff]
#[inline(never)]
pub fn square(num: &Foo, result: &mut f64) {
    *result = num.gen();
}
#[rustc_autodiff(Reverse, Duplicated, Duplicated, None)]
#[inline(never)]
pub fn dsquare(num: &Foo, dnum: &mut Foo, result: &mut f64, dresult: &mut f64) {
    unsafe {
        asm!("NOP", options(pure, nomem));
    };
    ::core::hint::black_box(square(num, result));
    ::core::hint::black_box((dnum, dresult));
}
#[rustc_autodiff]
#[inline(never)]
pub fn square2(num: &Box<dyn Cool>, result: &mut f64) {
    *result = num.gen();
}
#[rustc_autodiff(Reverse, Duplicated, Duplicated, None)]
#[inline(never)]
pub fn dsquare2(
    num: &Box<dyn Cool>,
    dnum: &mut Box<dyn Cool>,
    result: &mut f64,
    dresult: &mut f64,
) {
    unsafe {
        asm!("NOP", options(pure, nomem));
    };
    ::core::hint::black_box(square2(num, result));
    ::core::hint::black_box((dnum, dresult));
}
fn main() {
    for i in 0..5 {
        let mut d_foo = Foo { test: 0.0 };
        let f = Foo { test: i as f64 };
        let mut c = 0.0;
        let mut d_c = 1.0;
        let r = dsquare(&f, &mut d_foo, &mut c, &mut d_c);
        {
            ::std::io::_print(format_args!("d_foo {0:?}\n", d_foo));
        };
        let mut d_foo: Box<dyn Cool> = Box::new(Foo { test: 0.0 });
        let f: Box<dyn Cool> = Box::new(Foo { test: i as f64 });
        let r = dsquare2(&f, &mut d_foo, &mut c, &mut d_c);
        {
            ::std::io::_print(format_args!("d_foo {0:?}\n", d_foo));
        };
    }
}