Error "cannot sample empty range" on very basic ParticleSwarm

[sffc]

Repro:

    #[test]
    fn test_simple_particle_swarm() {
        struct CostFn;
        impl CostFunction for CostFn {
            type Param = f64;
            type Output = f64;
            fn cost(&self, param: &f64) -> Result<f64, Error> {
                Ok(*param)
            }
        }
        let solver = ParticleSwarm::new((-5.0, 5.0), 15);
        let res = Executor::new(CostFn, solver)
            .configure(|state| state.max_iters(10))
            .run()
            .unwrap();
        println!("{res}");
    }

When I run this code, it immediately fails with the message

thread 'cal::chinese_internal::simple::test::test_simple_particle_swarm' panicked at /Users/sffc/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand-0.8.5/src/rng.rs:134:9:
cannot sample empty range
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/panicking.rs:75:14
   2: core::panicking::panic
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/panicking.rs:145:5
   3: rand::rng::Rng::gen_range
             at /Users/sffc/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rand-0.8.5/src/rng.rs:134:9
   4: argmin_math::primitives::random::<impl argmin_math::ArgminRandom for f64>::rand_from_range
             at /Users/sffc/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/argmin-math-0.4.0/src/primitives/random.rs:16:21
   5: <argmin::solver::particleswarm::ParticleSwarm<P,F,R> as argmin::core::solver::Solver<O,argmin::core::state::populationstate::PopulationState<argmin::solver::particleswarm::Particle<P,F>,F>>>::next_iter::{{closure}}
             at /Users/sffc/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/argmin-0.10.0/src/solver/particleswarm/mod.rs:364:21
   6: core::iter::adapters::map::map_fold::{{closure}}
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/iter/adapters/map.rs:88:28
   7: <core::slice::iter::IterMut<T> as core::iter::traits::iterator::Iterator>::fold
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/slice/iter/macros.rs:255:27
   8: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/iter/adapters/map.rs:128:19
   9: core::iter::traits::iterator::Iterator::for_each
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/iter/traits/iterator.rs:827:14
  10: alloc::vec::Vec<T,A>::extend_trusted
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/alloc/src/vec/mod.rs:3774:26
  11: <alloc::vec::Vec<T,A> as alloc::vec::spec_extend::SpecExtend<T,I>>::spec_extend
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/alloc/src/vec/spec_extend.rs:29:14
  12: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/alloc/src/vec/spec_from_iter_nested.rs:62:16
  13: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/alloc/src/vec/spec_from_iter.rs:34:9
  14: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/alloc/src/vec/mod.rs:3633:9
  15: core::iter::traits::iterator::Iterator::collect
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/iter/traits/iterator.rs:2027:9
  16: <argmin::solver::particleswarm::ParticleSwarm<P,F,R> as argmin::core::solver::Solver<O,argmin::core::state::populationstate::PopulationState<argmin::solver::particleswarm::Particle<P,F>,F>>>::next_iter
             at /Users/sffc/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/argmin-0.10.0/src/solver/particleswarm/mod.rs:380:14
  17: argmin::core::executor::Executor<O,S,I>::run
             at /Users/sffc/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/argmin-0.10.0/src/core/executor.rs:221:45
  18: icu_calendar::cal::chinese_internal::simple::test::test_simple_particle_swarm
             at ./src/cal/chinese/simple.rs:237:14
  19: icu_calendar::cal::chinese_internal::simple::test::test_simple_particle_swarm::{{closure}}
             at ./src/cal/chinese/simple.rs:225:36
  20: core::ops::function::FnOnce::call_once
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/ops/function.rs:253:5
  21: core::ops::function::FnOnce::call_once
             at /rustc/1159e78c4747b02ef996e55082b704c09b970588/library/core/src/ops/function.rs:253:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[stefan-k]

I suspect your Param needs to be of type Vec<f64> instead of f64.

[ElGreenoProgramador]

Hello! I've found the same problem but you can simulate the 1D behaviour using Vector1 from nalgebra (or equivalent structure).
A bit counterintuitive but it works ahahah
Tested with version 0.11.0