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Rust language bindings for Faiss

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faiss_ParameterSpace_set_index_parameters usage

guskovd opened this issue · comments

commented

I want to change the parameter "nprobe" in the index.

According to https://github.com/facebookresearch/faiss/wiki/FAQ you need to use the set_index_parameter function (I found faiss_ParameterSpace_set_index_parameters)

But I do not understand how to create an instance of FaissParameterSpace and how to work with it

commented

I'm afraid that the high-level bindings do not expose setting index parameters once the index was already constructed. I have managed to make do without this, apparently.

In the low-level API, the constructor function to the parameter space object is faiss_ParameterSpace_new.

FaissParameterSpace* params = NULL;
int err = faiss_ParameterSpace_new(&params);

Nevertheless, if you'd like to try and extend the safe API with parameter space setting, please let me know, so I can then provide better guidance.

commented

I seem to have succeeded

	    let param = "nprobe".to_string();
	    let mut param_vec: Vec<*mut faiss_sys::FaissParameterSpace> = vec![std::ptr::null::<*mut faiss_sys::FaissParameterSpace>() as *mut _];
	    faiss_sys::faiss_ParameterSpace_new(param_vec.as_mut_ptr());
	    faiss_sys::faiss_ParameterSpace_set_index_parameter(*param_vec.as_mut_ptr(), self.inner_ptr(), param.as_ptr() as *const _, 2.0 );
	    let nprobe = faiss_sys::faiss_IndexIVF_nprobe(self.inner_ptr());
	    println!("{:?}", nprobe);
2
commented

Good to know! I'll leave this open in the event that we or someone else would be interested in making it part of the high level API.

commented

@ava57r The function

extern "C" {
    pub fn faiss_ParameterSpace_new(space: *mut *mut FaissParameterSpace) -> ::std::os::raw::c_int;

Is the translation of the C function

int faiss_ParameterSpace_new(ParameterSpace** p_space);

Where to *p_space is assigned the output of constructing a ParameterSpace object via new. Using it would be something like this:

let mut p_space = std::ptr::null_mut();
let e = faiss_ParameterSpace_new(&mut p_space);
commented

faiss_ParameterSpace_free function exists only versions >= 1.6.4

fix free parameterspace (#1243)

commented

This seems to have been resolved by #14.