# IInt8LegacyCalibrator¶

class tensorrt.IInt8LegacyCalibrator(self: tensorrt.tensorrt.IInt8LegacyCalibrator) → None

Extends the IInt8Calibrator class. This calibrator requires user parameterization, and is provided as a fallback option if the other calibrators yield poor results.

Variables
• quantilefloat The quantile (between 0 and 1) that will be used to select the region maximum when the quantile method is in use. See the user guide for more details on how the quantile is used.

• regression_cutofffloat The fraction (between 0 and 1) of the maximum used to define the regression cutoff when using regression to determine the region maximum. See the user guide for more details on how the regression cutoff is used

get_algorithm(self: tensorrt.tensorrt.IInt8LegacyCalibrator) → tensorrt.tensorrt.CalibrationAlgoType

Signals that this is the legacy calibrator.

Returns

CalibrationAlgoType.LEGACY_CALIBRATION

get_batch(self: tensorrt.tensorrt.IInt8LegacyCalibrator, names: List[str]) → List[int]

Get a batch of input for calibration. The batch size of the input must match the batch size returned by get_batch_size() .

A possible implementation may look like this:

def get_batch(names):
try:
# Assume self.batches is a generator that provides batch data.
data = next(self.batches)
# Assume that self.device_input is a device buffer allocated by the constructor.
cuda.memcpy_htod(self.device_input, data)
return [int(self.device_input)]
except StopIteration:
# When we're out of batches, we return either [] or None.
# This signals to TensorRT that there is no calibration data remaining.
return None

Parameters

names – The names of the network inputs for each object in the bindings array.

Returns

A list of device memory pointers set to the memory containing each network input data, or an empty list if there are no more batches for calibration. You can allocate these device buffers with pycuda, for example, and then cast them to int to retrieve the pointer.

get_batch_size(self: tensorrt.tensorrt.IInt8LegacyCalibrator) → int

Get the batch size used for calibration batches.

Returns

The batch size.

read_calibration_cache(self: tensorrt.tensorrt.IInt8LegacyCalibrator) → buffer

Calibration is potentially expensive, so it can be useful to generate the calibration data once, then use it on subsequent builds of the network. The cache includes the regression cutoff and quantile values used to generate it, and will not be used if these do not match the settings of the current calibrator. However, the network should also be recalibrated if its structure changes, or the input data set changes, and it is the responsibility of the application to ensure this.

Reading a cache is just like reading any other file in Python. For example, one possible implementation is:

def read_calibration_cache(self):
# If there is a cache, use it instead of calibrating again. Otherwise, implicitly return None.
if os.path.exists(self.cache_file):
with open(self.cache_file, "rb") as f:

Returns

A cache object or None if there is no data.

write_calibration_cache(self: tensorrt.tensorrt.IInt8LegacyCalibrator, cache: buffer) → None

Save a calibration cache.

Writing a cache is just like writing any other buffer in Python. For example, one possible implementation is:

def write_calibration_cache(self, cache):
with open(self.cache_file, "wb") as f:
f.write(cache)

Parameters

cache – The calibration cache to write.