CODEWITHSUNDEEP
tensorflow
user1506145
user1506145

Reputation: 5286

Tensorflow can not run integer matrix multiplication on GPU

Take a look at this example, where I attempt to multiple two tf.int32 matrices using my GPU.

import tensorflow as tf
matrix1 = tf.constant([[3,3]])
matrix2 = tf.constant([[2],[2]])

with tf.device("/gpu:0"):
    product = tf.matmul(matrix1,matrix2)

with tf.Session() as sess:
    result = sess.run(product)
    print(result)

It is similar to the example found on https://www.tensorflow.org/versions/r0.10/get_started/basic_usage.html

I get the output:

...
I tensorflow/core/common_runtime/gpu/gpu_init.cc:102] Found device 0 with properties: 
name: GeForce GTX 1080
major: 6 minor: 1 memoryClockRate (GHz) 1.7715
pciBusID 0000:03:00.0
Total memory: 7.92GiB
Free memory: 213.62MiB
I tensorflow/core/common_runtime/gpu/gpu_init.cc:126] DMA: 0 
I tensorflow/core/common_runtime/gpu/gpu_init.cc:136] 0:   Y 
I tensorflow/core/common_runtime/gpu/gpu_device.cc:839] Creating TensorFlow device (/gpu:0) -> (device: 0, name: GeForce GTX 1080, pci bus id: 0000:03:00.0)
E tensorflow/core/client/tensor_c_api.cc:485] Cannot assign a device to node 'MatMul': Could not satisfy explicit device specification '/device:GPU:0' because no supported kernel for GPU devices is available.
     [[Node: MatMul = MatMul[T=DT_INT32, transpose_a=false, transpose_b=false, _device="/device:GPU:0"](Const, Const_1)]]

Why can't I perform a matrix multiplication on the GPU? I can fix this by using allow_soft_placement = True, but I would like to do this on the GPU..

Upvotes: 0

Views: 1240

Answers (1)

mrry
mrry

Reputation: 126154

Integer multiplication is currently not implemented for the GPU in TensorFlow, and your matrices matrix1 and matrix2 have type tf.int32. (It turns out that it is easy to implement but, for various reasons discussed in this answer, TensorFlow doesn't include op registrations for tf.int32 on GPU devices.)

Assuming you are actually interested in multiplying (much larger) floating-point matrices, you can change your program to:

import tensorflow as tf
matrix1 = tf.constant([[3., 3.]])
matrix2 = tf.constant([[2.], [2.]])

with tf.device("/gpu:0"):
    product = tf.matmul(matrix1,matrix2)

with tf.Session() as sess:
    result = sess.run(product)
    print(result)

...and the multiplication will execute on your GPU.

Upvotes: 2

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