get magnitudes in cython for less memory consumption (#946)

src/urh/cythonext/util.pyx

@@ -9,7 +9,7 @@ import numpy as np
 from libc.stdint cimport uint8_t, uint16_t, uint32_t, uint64_t, int64_t
 from libc.stdlib cimport malloc, calloc, free
 from cython.parallel import prange
-from libc.math cimport log10,pow
+from libc.math cimport log10,pow,sqrt
 from libcpp cimport bool
 
 from cpython cimport array
@@ -124,6 +124,17 @@ cpdef uint64_t crc(uint8_t[:] inpt, uint8_t[:] polynomial, uint8_t[:] start_valu
 
     return crc & crc_mask
 
+
+cpdef np.ndarray[np.double_t, ndim=1] get_magnitudes(IQ arr):
+    cdef uint64_t i, n = len(arr)
+
+    cdef np.ndarray[np.double_t, ndim=1] result = np.zeros(n, dtype = np.double)
+
+    for i in range(0, n):
+        result[i] = sqrt(arr[i][0] * arr[i][0] + arr[i][1] * arr[i][1])
+
+    return result
+
 cpdef np.ndarray[np.uint64_t, ndim=1] calculate_cache(uint8_t[:] polynomial, bool reverse_polynomial=False, uint8_t bits=8):
     cdef uint8_t j, poly_order = len(polynomial)
     cdef uint64_t crc_mask = <uint64_t> pow(2, poly_order - 1) - 1

src/urh/signalprocessing/IQArray.py

@@ -5,6 +5,8 @@
 
 import numpy as np
 
+from urh.cythonext.util import get_magnitudes
+
 
 class IQArray(object):
     def __init__(self, data: np.ndarray, dtype=None, n=None, skip_conversion=False):
@@ -75,13 +77,9 @@ def imag(self):
     def imag(self, value):
         self.__data[:, 1] = value
 
-    @property
-    def magnitudes_squared(self):
-        return self.real**2.0 + self.imag**2.0
-
     @property
     def magnitudes(self):
-        return np.sqrt(self.magnitudes_squared)
+        return get_magnitudes(self.__data)
 
     @property
     def magnitudes_normalized(self):