Update README.md

Author: goldsborough

README.md

@@ -9,7 +9,8 @@ There are a few "sights" you can metaphorically visit in this repository:
 - Build C++ and/or CUDA extensions by going into the `cpp/` or `cuda/` folder and executing `python setup.py install`,
 - JIT-compile C++ and/or CUDA extensions by going into the `cpp/` or `cuda/` folder and calling `python jit.py`, which will JIT-compile the extension and load it,
 - Benchmark Python vs. C++ vs. CUDA by running `python benchmark.py {py, cpp, cuda} [--cuda]`,
-- Run gradient-checks on the code by running `python grad_check.py {py, cpp, cuda}`.
+- Run gradient checks on the code by running `python grad_check.py {py, cpp, cuda} [--cuda]`.
+- Run output checks on the code by running `python check.py {forward, backward} [--cuda]`.
 
 ## Authors
 

check.py

@@ -24,6 +24,11 @@ def check_equal(first, second, verbose):
         np.testing.assert_allclose(x, y, err_msg="Index: {}".format(i))
 
 
+def zero_grad(variables):
+    for variable in variables:
+        variable.grad.zero_()
+
+
 def check_forward(variables, with_cuda, verbose):
     baseline_values = python.lltm_baseline.LLTMFunction.apply(*variables)
     cpp_values = cpp.lltm.LLTMFunction.apply(*variables)
@@ -44,6 +49,8 @@ def check_backward(variables, with_cuda, verbose):
     (baseline_values[0] + baseline_values[1]).sum().backward()
     grad_baseline = [var.grad for var in variables]
 
+    zero_grad(variables)
+
     cpp_values = cpp.lltm.LLTMFunction.apply(*variables)
     (cpp_values[0] + cpp_values[1]).sum().backward()
     grad_cpp = [var.grad for var in variables]
@@ -53,6 +60,7 @@ def check_backward(variables, with_cuda, verbose):
     print('Ok')
 
     if with_cuda:
+        zero_grad(variables)
         cuda_values = cuda.lltm.LLTMFunction.apply(*variables)
         (cuda_values[0] + cuda_values[1]).sum().backward()
         grad_cuda = [var.grad for var in variables]