执行每个语句后，请考虑以下代码的内存使用情况：
import numpy
import scipy.signal
import gc
# memory at this point is ~35mb
a = numpy.ones(10**7)
b = numpy.ones(10**7)
# memory at this point is ~187mb
c = scipy.signal.fftconvolve(a, numpy.flipud(b), mode="full")
# memory usage at this point is 645mb
# given that a,b,c take up about 305mb in total, this is much
# larger than expected
# If we delete a,b,c and garbage collect...
del a,b,c
gc.collect()
# ...the memory usage drops to ~340mb which is a drop of 305mb
# (as expected since that is the size of what we deleted)
# but the remaining memory usage is still 340mb
# which is much larger than the starting value of 35 mb
为什么这个过程使用了这么多额外的内存。 fftconvolve函数是否有泄漏，还是有其他解释？
平台：