parallelize matmul via openmp

Author: andrewkchan

src/infer.cpp

@@ -7,6 +7,7 @@
 static void matmul(float* xout, float* x, float* w, int n, int d) {
 	// W (d,n) @ x (n,) -> xout (d,)
 	int i;
+#pragma omp parallel for private(i)
 	for (i = 0; i < d; i++) {
 		float val = 0.0f;
 		for (int j = 0; j < n; j++) {