Protobuf has a hard limit of 2GB. And 2^22*256 floats are 4GB. Your problem is, that you are going to embed the initial value into the graph-proto by
import tensorflow as tf
import numpy as np
w_init = np.random.randn(2**22, 256).astype(np.float32)
w = tf.Variable(tf.convert_to_tensor(w_init))
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print sess.run(tf.reduce_sum(w))
causing
ValueError: Cannot create a tensor proto whose content is larger than 2GB.
This graph definition above is basically saying: "The graph has a variable occupying 4GB and here are the exact values: ..."
Instead, you should write
import tensorflow as tf
import numpy as np
w_init = np.random.randn(2**22, 256).astype(np.float32)
w_plhdr = tf.placeholder(dtype=tf.float32, shape=[2**22, 256])
w = tf.get_variable('w', [2**22, 256])
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
sess.run(w.assign(w_plhdr), {w_plhdr: w_init})
print sess.run(tf.reduce_sum(w))
This way, your variable holds 4GB of value but the graph only has the knowledge: "Hey, there is a variable of size 4 GB. Just don't care about the exact values within the graph definition. Because there is an operation to overwrite these values anyway later.".