faiss 0.13.0

High-level bindings for Faiss, the vector similarity search engine
Documentation 
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use std::ffi;

use super::*;

/// Uses a-priori knowledge on the Faiss indexes to extract tunable parameters.
pub struct ParameterSpace {
    inner: *mut FaissParameterSpace,
}

impl ParameterSpace {
    /// Create a new instance
    pub fn new() -> Result<Self> {
        unsafe {
            let mut inner = ptr::null_mut();
            faiss_try(faiss_ParameterSpace_new(&mut inner))?;

            Ok(ParameterSpace { inner })
        }
    }

    /// Set one of the parameters
    pub fn set_index_parameter<I, V>(&self, index: &I, name: &str, value: V) -> Result<()>
    where
        I: NativeIndex<Inner = FaissIndex>,
        V: Into<f64>,
    {
        unsafe {
            let name_param = ffi::CString::new(name).map_err(|_| Error::ParameterName)?;
            let index_ptr = index.inner_ptr();
            let v = value.into();
            faiss_try(faiss_ParameterSpace_set_index_parameter(
                self.inner,
                index_ptr,
                name_param.as_ptr(),
                v,
            ))?;

            Ok(())
        }
    }

    /// Print a description on stdout
    pub fn display(&self) {
        unsafe {
            faiss_ParameterSpace_display(self.inner);
        }
    }

    /// nb of combinations, = product of values sizes
    pub fn n_combinations(&self) -> usize {
        unsafe { faiss_ParameterSpace_n_combinations(self.inner) }
    }
}

/// Supports only version >= 1.6.4
impl Drop for ParameterSpace {
    fn drop(&mut self) {
        unsafe {
            faiss_ParameterSpace_free(self.inner);
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::index::autotune::ParameterSpace;
    use crate::index::index_factory;
    use crate::metric::MetricType;

    #[test]
    fn set_nprobe_in_flat() {
        let mut index = index_factory(64, "IVF8,Flat", MetricType::L2).unwrap();

        let ps = ParameterSpace::new().unwrap();
        let name = "nprobe";

        ps.set_index_parameter(&mut index, &name, 5.0).unwrap();

        let actual_nprobe = unsafe {
            let index_ivf = faiss_sys::faiss_IndexIVF_cast(index.inner_ptr());

            faiss_sys::faiss_IndexIVF_nprobe(index_ivf)
        };

        assert_eq!(actual_nprobe, 5usize);
    }
}