theano學習筆記(1)—代數

theano教程：http://deeplearning.net/software/theano/tutorial/adding.html

兩個標量相加

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from theano import function
import theano.tensor as T

# 第1步：定義兩個變量及其類型
x = T.dscalar('x')  # 雙精度浮點型的0-維數組（也就是標量）
y = T.dscalar('y')

# 第2步：構建表達式
z = x + y

# 構造函數f，輸入[x, y]，輸出是一個0維的numpy.ndarray
f = function([x, y], z)

print f(2, 3)  # 使用函數

兩個矩陣相加

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import numpy
from theano import function
import theano.tensor as T

x = T.dmatrix('x')
y = T.dmatrix('y')
z = x + y
f = function([x, y], z)

print f([[1, 2], [3, 4]], [[10, 20], [30, 40]])
print f(numpy.array([[1, 2], [3, 4]]), numpy.array([[10, 20], [30, 40]]))

練習

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from theano import function
import theano.tensor as T

a = T.vector()  # 向量
b = T.vector() 
out = a ** 2 + b ** 2 + 2 * a * b
f = function([a, b], out)
print f([0, 1], [1, 2])

>>>[ 1.  9.]