Add matmul driver example for floopy

examples/fortran/matmul-driver.py

+import numpy as np
+import numpy.linalg as la
+import pyopencl as cl
+import pyopencl.array
+import pyopencl.clrandom
+import loopy as lp
+
+
+def main():
+    fn = "matmul.floopy"
+    with open(fn, "r") as inf:
+        source = inf.read()
+
+    dgemm, = lp.parse_transformed_fortran(source, filename=fn)
+
+    ctx = cl.create_some_context()
+    queue = cl.CommandQueue(ctx)
+
+    n = 2048
+    a = cl.array.empty(queue, (n, n), dtype=np.float64, order="F")
+    b = cl.array.empty(queue, (n, n), dtype=np.float64, order="F")
+    c = cl.array.zeros(queue, (n, n), dtype=np.float64, order="F")
+    cl.clrandom.fill_rand(a)
+    cl.clrandom.fill_rand(b)
+
+    dgemm = lp.set_options(dgemm, write_code=True)
+
+    dgemm(queue, a=a, b=b, alpha=1, c=c)
+
+    c_ref = (a.get() @ b.get())
+    assert la.norm(c_ref - c.get())/la.norm(c_ref) < 1e-10
+
+
+if __name__ == "__main__":
+    main()