In [16]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*2).dtype Out[16]: dtype('uint64')
In [17]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*n).dtype Out[17]: dtype('float64')
In [18]: type(n) Out[18]: <type 'int'>
Now that's just strange. What's going on?
On Fri, May 1, 2009 at 1:02 PM, Neal Becker ndbecker2@gmail.com wrote:
In [16]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*2).dtype Out[16]: dtype('uint64')
In [17]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*n).dtype Out[17]: dtype('float64')
In [18]: type(n) Out[18]: <type 'int'>
Now that's just strange. What's going on?
The n is signed, uint64 is unsigned. So a signed type that can hold uint64 is needed. There ain't no such integer, so float64 is used. I think the logic here is a bit goofy myself since float64 doesn't have the needed 64 bit precision and the conversion from int kind to float kind is confusing. I think it would be better to raise a NotAvailable error or some such. Lest you think this is an isolated oddity, sometimes numeric arrays can be converted to object arrays.
Chuck
Charles R Harris wrote:
On Fri, May 1, 2009 at 1:02 PM, Neal Becker ndbecker2@gmail.com wrote:
In [16]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*2).dtype Out[16]: dtype('uint64')
In [17]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*n).dtype Out[17]: dtype('float64')
In [18]: type(n) Out[18]: <type 'int'>
Now that's just strange. What's going on?
The n is signed, uint64 is unsigned. So a signed type that can hold uint64 is needed. There ain't no such integer, so float64 is used. I think the logic here is a bit goofy myself since float64 doesn't have the needed 64 bit precision and the conversion from int kind to float kind is confusing. I think it would be better to raise a NotAvailable error or some such. Lest you think this is an isolated oddity, sometimes numeric arrays can be converted to object arrays.
Chuck
I don't think that any type of integer arithmetic should ever be automatically promoted to float.
Besides that, what about the first example? There, I used '2' rather than 'n'. Is not '2' also an int?
On Fri, May 1, 2009 at 7:24 PM, Neal Becker ndbecker2@gmail.com wrote:
Charles R Harris wrote:
On Fri, May 1, 2009 at 1:02 PM, Neal Becker ndbecker2@gmail.com wrote:
In [16]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*2).dtype Out[16]: dtype('uint64')
In [17]: (np.linspace (0, len (x)-1, len(x)).astype (np.uint64)*n).dtype Out[17]: dtype('float64')
In [18]: type(n) Out[18]: <type 'int'>
Now that's just strange. What's going on?
The n is signed, uint64 is unsigned. So a signed type that can hold uint64 is needed. There ain't no such integer, so float64 is used. I
think
the logic here is a bit goofy myself since float64 doesn't have the
needed
64 bit precision and the conversion from int kind to float kind is confusing. I think it would be better to raise a NotAvailable error or some such. Lest you think this is an isolated oddity, sometimes numeric arrays can be converted to object arrays.
Chuck
I don't think that any type of integer arithmetic should ever be automatically promoted to float.
Besides that, what about the first example? There, I used '2' rather than 'n'. Is not '2' also an int?
What version of numpy are you using?
Chuck
On Fri, May 1, 2009 at 7:39 PM, Charles R Harris charlesr.harris@gmail.comwrote:
On Fri, May 1, 2009 at 7:24 PM, Neal Becker ndbecker2@gmail.com wrote:
Charles R Harris wrote:
On Fri, May 1, 2009 at 1:02 PM, Neal Becker ndbecker2@gmail.com
wrote:
In [16]: (np.linspace (0, len (x)-1, len(x)).astype
(np.uint64)*2).dtype
Out[16]: dtype('uint64')
In [17]: (np.linspace (0, len (x)-1, len(x)).astype
(np.uint64)*n).dtype
Out[17]: dtype('float64')
In [18]: type(n) Out[18]: <type 'int'>
Now that's just strange. What's going on?
The n is signed, uint64 is unsigned. So a signed type that can hold uint64 is needed. There ain't no such integer, so float64 is used. I
think
the logic here is a bit goofy myself since float64 doesn't have the
needed
64 bit precision and the conversion from int kind to float kind is confusing. I think it would be better to raise a NotAvailable error or some such. Lest you think this is an isolated oddity, sometimes numeric arrays can be converted to object arrays.
Chuck
I don't think that any type of integer arithmetic should ever be automatically promoted to float.
Besides that, what about the first example? There, I used '2' rather than 'n'. Is not '2' also an int?
What version of numpy are you using?
And what is the value of n?
Chuck
Charles R Harris wrote:
On Fri, May 1, 2009 at 7:39 PM, Charles R Harris charlesr.harris@gmail.comwrote:
On Fri, May 1, 2009 at 7:24 PM, Neal Becker ndbecker2@gmail.com wrote:
Charles R Harris wrote:
On Fri, May 1, 2009 at 1:02 PM, Neal Becker ndbecker2@gmail.com
wrote:
In [16]: (np.linspace (0, len (x)-1, len(x)).astype
(np.uint64)*2).dtype
Out[16]: dtype('uint64')
In [17]: (np.linspace (0, len (x)-1, len(x)).astype
(np.uint64)*n).dtype
Out[17]: dtype('float64')
In [18]: type(n) Out[18]: <type 'int'>
Now that's just strange. What's going on?
The n is signed, uint64 is unsigned. So a signed type that can hold uint64 is needed. There ain't no such integer, so float64 is used. I
think
the logic here is a bit goofy myself since float64 doesn't have the
needed
64 bit precision and the conversion from int kind to float kind is confusing. I think it would be better to raise a NotAvailable error or some such. Lest you think this is an isolated oddity, sometimes numeric arrays can be converted to object arrays.
Chuck
I don't think that any type of integer arithmetic should ever be automatically promoted to float.
Besides that, what about the first example? There, I used '2' rather than 'n'. Is not '2' also an int?
What version of numpy are you using?
And what is the value of n?
Chuck
np.version.version Out[5]: '1.3.0' (I think the previous test was on 1.2.0 and did the same thing)
(np.linspace (0, 1023,1024).astype(np.uint64)*2).dtype Out[2]: dtype('uint64')
In [3]: n=-7
In [4]: (np.linspace (0, 1023,1024).astype(np.uint64)*n).dtype Out[4]: dtype('float64')
Neal Becker wrote:
Charles R Harris wrote:
On Fri, May 1, 2009 at 7:39 PM, Charles R Harris charlesr.harris@gmail.comwrote:
On Fri, May 1, 2009 at 7:24 PM, Neal Becker ndbecker2@gmail.com wrote:
Charles R Harris wrote:
On Fri, May 1, 2009 at 1:02 PM, Neal Becker ndbecker2@gmail.com
wrote:
In [16]: (np.linspace (0, len (x)-1, len(x)).astype
(np.uint64)*2).dtype
Out[16]: dtype('uint64')
In [17]: (np.linspace (0, len (x)-1, len(x)).astype
(np.uint64)*n).dtype
Out[17]: dtype('float64')
In [18]: type(n) Out[18]: <type 'int'>
Now that's just strange. What's going on?
The n is signed, uint64 is unsigned. So a signed type that can hold uint64 is needed. There ain't no such integer, so float64 is used. I
think
the logic here is a bit goofy myself since float64 doesn't have the
needed
64 bit precision and the conversion from int kind to float kind is confusing. I think it would be better to raise a NotAvailable error or some such. Lest you think this is an isolated oddity, sometimes numeric arrays can be converted to object arrays.
Chuck
I don't think that any type of integer arithmetic should ever be automatically promoted to float.
Besides that, what about the first example? There, I used '2' rather than 'n'. Is not '2' also an int?
What version of numpy are you using?
And what is the value of n?
Chuck
np.version.version Out[5]: '1.3.0' (I think the previous test was on 1.2.0 and did the same thing)
(np.linspace (0, 1023,1024).astype(np.uint64)*2).dtype Out[2]: dtype('uint64')
In [3]: n=-7
In [4]: (np.linspace (0, 1023,1024).astype(np.uint64)*n).dtype Out[4]: dtype('float64')
Numpy-discussion mailing list Numpy-discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Hi, //I think this behavior has been raised before. IIRC, Numpy is trying to do the operation that is requested by converting the dtype into floats since this is a generic solution that will avoid overflow with any ints not just unsigned ints.
Note that you get a different result if you use subtraction than multiplication.
np.linspace (0, 1023,1024)
array([ 0.00000000e+00, 1.00000000e+00, 2.00000000e+00, ..., 1.02100000e+03, 1.02200000e+03, 1.02300000e+03])
np.linspace (0, 1023,1024).astype(np.uint64)*-7
array([ -0.00000000e+00, -7.00000000e+00, -1.40000000e+01, ..., -7.14700000e+03, -7.15400000e+03, -7.16100000e+03])
np.linspace (0, 1023,1024).astype(np.uint64)-7
array([18446744073709551609, 18446744073709551610, 18446744073709551611, ..., 1014, 1015, 1016], dtype=uint64)
Bruce
Neal Becker wrote:
In [3]: n=-7
In [4]: (np.linspace (0, 1023,1024).astype(np.uint64)*n).dtype Out[4]: dtype('float64')
what would you like (expect) to happen when you multiply an unsigned type by a negative number?
-Chris
participants (4)
-
Bruce Southey -
Charles R Harris -
Christopher Barker -
Neal Becker