[phenixbb] Speeding direct summation ?

Pavel Afonine pafonine at lbl.gov
Fri Nov 2 09:40:24 PDT 2018


I agree, the difference is likely something else than "FFT vs direct 
summation"!
Pavel

On 11/3/18 00:19, Tim Gruene wrote:
> Dear Clement,
>
> as far as I understand, SHELXL is compiled against the Intel FFT
> library. Before, SHELXL used direct summation. If there was any
> noticeable difference, I am sure George Sheldrich would not have taken
> this step, as he would have had to expect a flood of complaints. My
> guess is that the difference is not because of the difference between
> FFT and SHELXL.
>
> Best regards,
> Tim
>
> On 11/02/2018 05:01 PM, Clement Degut wrote:
>> Hi,
>> I have (very) high resolution data, for which direct summation method
>> seems to give significantly better map than FFT (i.e. visible hydrogen
>> vs not).
>> My main problem is that refinement got from quite slow, to barely not
>> really possible to handle slow.
>> I have 2 question from that :
>> Am I looking at an artifact ? Meaning should at this resolution (0.84A
>> for CC1/2 at 30% and good overall statistics) see extreme difference
>> between map quality with direct summation vs FFT ?
>> And if yes, can I speed the process compiling phenix with openMP on our
>> cluster ? Or shoul I just become patient ?
>>
>> Many thanks
>>
>> Clément
>>
>>
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>
>
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