Function verify 

pub fn verify(
    client: &Client,
    sample: impl Fn(usize) -> Duration,
    written: &Handle,
) -> Result<(), ThroughputError>

Runs one pass and confirms it wrote written, before any pass is timed.

A launch that fails leaves its failure on the buffers it never wrote, and sync answers Ok regardless. A sample has no way to say so, and would time the launch overhead and report it as bandwidth.

Errors

ThroughputError::Launch when the pass did not run. The cause is logged by the device where it happened.