[Apache TVM Discuss] [Questions] Using tvm quantize model is too slower than not quantize

[wangbingjia via Apache TVM Discuss]

**My target is "cuda",  and I use the first way to quantize 
model**(https://tvm.apache.org/docs/how_to/deploy_models/deploy_quantized.html#sphx-glr-how-to-deploy-models-deploy-quantized-py)
![image|690x208](upload://9L806XQ1UCjaUQG2SAy6XbI6cMn.png) 

**and then inference speed is very slow, Why does this happen？Did i do 
something wrong？？**

the code is:
```
# ------------get test preprocess data----------------
class Reid_date:
    def __init__(self, root_path, transforms):
        self.transforms = transforms
        self.root_path = root_path
        self.images = self.get_images()

    
    def get_images(self):
        if os.path.exists(self.root_path) == True:
            images = ['{}/{}'.format(self.root_path, i) for i in 
os.listdir(self.root_path)]
        else:
            raise ValueError("the img path is not exit,please check out!")
        return images
    
    def __getitem__(self, item):
        path = self.images[item]
        img = Image.open(path).convert('RGB')
        img = self.transforms(img)
        return img, path

    def __len__(self):
        return len(self.images)

class Data:
    def __init__(self, data_path):
        self.batchsize = args.batchsize
        self.data_path = data_path
        test_transforms = transforms.Compose([
            transforms.Resize((args.height, args.width)),
            transforms.ToTensor(),
            transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[ 0.229, 
0.224, 0.225])
        ])
        self.testset = Reid_date(self.data_path, test_transforms)
        self.test_loader = dataloader.DataLoader(self.testset, 
batch_size=self.batchsize, num_workers=0)


# ------------define quantize data and return mod-----------
def calibrate_dataset():
    val_data = Data(args.quantize_data_path)
    for i, data in enumerate(val_data.test_loader):
        if i * 32 >= 512:
            break
        data_temp = data[0].numpy()
        yield {"data": data_temp}

def quantize(mod, params, data_aware):
    if data_aware:
        with relay.quantize.qconfig(calibrate_mode="kl_divergence", 
weight_scale="max"):
            mod = relay.quantize.quantize(mod, params, 
dataset=calibrate_dataset())
    else:
        with relay.quantize.qconfig(calibrate_mode="global_scale", 
global_scale=8.0):
            mod = relay.quantize.quantize(mod, params)
    return mod

# evaluate code
def evaluate(lib, ctx, input_shape):
        module = runtime.GraphModule(lib["default"](ctx))
        input_auto_schedule = 
tvm.nd.array((np.random.uniform(size=input_shape)).astype("float32"))
        module.set_input("input0", input_auto_schedule)

        # evaluate
        print("**Evaluate inference time cost...**")
        print(module.benchmark(ctx, number=2 ,repeat=2))


# main function
if args.use_quantize:
    mod = quantize(mod, params, data_aware=True)
    with tvm.transform.PassContext(opt_level=3):
        lib = relay.build(mod, args.target, params=params)

        # evaluate time 
        evaluate(lib, ctx, input_shape)
# unquantize result
# Execution time summary:
# mean (ms)   median (ms)    max (ms)     min (ms)     std (ms)  
# 172.6577     171.1886         175.1060     169.2712    0.3174  

# quantize result
# Execution time summary:
# mean (ms)   median (ms)    max (ms)     min (ms)     std (ms)  
# 15192.1886   15192.1886   15298.1060   15086.2712    105.9174  
```





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