Panic when no GPUs

[cogciprocate]

Panic when no GPUs

[jekirl]

This occurs whenever ocl::core:: get_device_ids does not receive CL_SUCCESS as a result of the ffi call to clGetDeviceIDs.

I see two options, either to change the return type to Result<Vec<Device>> or to replace the expect with unwrap_or(vec![])

[c0gent]

I agree. Try out the device_result branch and let me know how that looks to you two.

[c0gent]

@yongqli @J-e-k

I'm hesitant to add too many convenience functions but would the following be a useful Device method?:

    /// Returns a list of devices exactly as `::list` does but unwraps any
    /// error and returns an empty `Vec` in the event that the error is a
    /// `CL_DEVICE_NOT_FOUND` variant.
    ///
    /// This is a convenience function.
    ///
    ///
    /// ### Panics
    ///
    /// Panics upon any OpenCL error other than `CL_DEVICE_NOT_FOUND` or any
    /// other type of error.
    ///
    pub fn list_or_empty(platform: &Platform, device_types: Option<DeviceType>)
                -> Vec<Device> {
        match Device::list(platform, device_types) {
            Ok(vec) => vec,
            Err(err) => match err.status() {
                Some(s) => match s {
                    Status::CL_DEVICE_NOT_FOUND => Vec::with_capacity(0),
                    _ => panic!("{}", err),
                },
                None => panic!("{}", err),
            },
        }
    }

[jekirl]

Thanks for the fast fix. I don't think list_or_empty is particularly necessary (for my use case at least). Using result as you did in #40 is 👍

[c0gent]

Alright. If @yongqli is satisfied I'll merge and close this.

[yongqli]

@c0gent Thanks, but I don't feel the convenience function is particularly necessary either.

[c0gent]

Good enough. Thanks guys.