| import cupy | |
| from cupy import _core | |
| _piecewise_krnl = _core.ElementwiseKernel( | |
| 'bool cond, T value', | |
| 'T y', | |
| 'if (cond) y = value', | |
| 'cupy_piecewise_kernel' | |
| ) | |
| def piecewise(x, condlist, funclist): | |
| """Evaluate a piecewise-defined function. | |
| Args: | |
| x (cupy.ndarray): input domain | |
| condlist (list of cupy.ndarray): | |
| Each boolean array/ scalar corresponds to a function | |
| in funclist. Length of funclist is equal to that of | |
| condlist. If one extra function is given, it is used | |
| as the default value when the otherwise condition is met | |
| funclist (list of scalars): list of scalar functions. | |
| Returns: | |
| cupy.ndarray: the scalar values in funclist on portions of x | |
| defined by condlist. | |
| .. warning:: | |
| This function currently doesn't support callable functions, | |
| args and kw parameters. | |
| .. seealso:: :func:`numpy.piecewise` | |
| """ | |
| if cupy.isscalar(condlist): | |
| condlist = [condlist] | |
| condlen = len(condlist) | |
| funclen = len(funclist) | |
| if condlen == funclen: | |
| out = cupy.zeros(x.shape, x.dtype) | |
| elif condlen + 1 == funclen: | |
| func = funclist[-1] | |
| funclist = funclist[:-1] | |
| if callable(func): | |
| raise NotImplementedError( | |
| 'Callable functions are not supported currently') | |
| out = cupy.full(x.shape, func, x.dtype) | |
| else: | |
| raise ValueError('with {} condition(s), either {} or {} functions' | |
| ' are expected'.format(condlen, condlen, condlen + 1)) | |
| for condition, func in zip(condlist, funclist): | |
| if callable(func): | |
| raise NotImplementedError( | |
| 'Callable functions are not supported currently') | |
| if isinstance(func, cupy.ndarray): | |
| func = func.astype(x.dtype) | |
| _piecewise_krnl(condition, func, out) | |
| return out | |