utils.py

import numpy as np
import torch
from torch import nn
import torch.nn.functional as F
from model_class import CharRNN

train_on_gpu = torch.cuda.is_available()

def get_model():
    model = torch.load('./model/model.pt', map_location=torch.device('cpu'))
    return model

def predict(net, char, h=None, top_k=None):
        ''' Given a character, predict the next character.
            Returns the predicted character and the hidden state.
        '''
        
        # tensor inputs
        x = np.array([[net.char2int[char]]])
        x = one_hot_encode(x, len(net.chars))
        inputs = torch.from_numpy(x)
        
        if(train_on_gpu):
            inputs = inputs.cuda()
        
        # detach hidden state from history
        h = tuple([each.data for each in h])
        # get the output of the model
        out, h = net(inputs, h)

        # get the character probabilities
        p = F.softmax(out, dim=1).data
        if(train_on_gpu):
            p = p.cpu() # move to cpu
        
        # get top characters
        if top_k is None:
            top_ch = np.arange(len(net.chars))
        else:
            p, top_ch = p.topk(top_k)
            top_ch = top_ch.numpy().squeeze()
        
        # select the likely next character with some element of randomness
        p = p.numpy().squeeze()
        char = np.random.choice(top_ch, p=p/p.sum())
        
        # return the encoded value of the predicted char and the hidden state
        return net.int2char[char], h

def PlotGenerate(net, size, prime='The', top_k=None):
        
    if(train_on_gpu):
        net.cuda()
    else:
        net.cpu()
    
    net.eval() # eval mode
    
    # First off, run through the prime characters
    chars = [ch for ch in prime]
    h = net.init_hidden(1)
    for ch in prime:
        char, h = predict(net, ch, h, top_k=top_k)

    chars.append(char)
    
    # Now pass in the previous character and get a new one
    for ii in range(size):
        char, h = predict(net, chars[-1], h, top_k=top_k)
        chars.append(char)

    return ''.join(chars)

def one_hot_encode(arr, n_labels):
    
    # Initialize the the encoded array
    one_hot = np.zeros((arr.size, n_labels), dtype=np.float32)
    
    # Fill the appropriate elements with ones
    one_hot[np.arange(one_hot.shape[0]), arr.flatten()] = 1
    
    # Finally reshape it to get back to the original array
    one_hot = one_hot.reshape((*arr.shape, n_labels))
    
    return one_hot