py bindings -- improve autotuner by using multiple of 64 input
py bindings -- improve autotuner by using multiple of 64 input


Former-commit-id: 11153c72791cb14dc84c91ff2adb08838da41b28
Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide