[DAMD-13] Change pfsFiberTrace description to persist trace-function coefficients as double Created: 17/Nov/16  Updated: 20/Dec/16  Resolved: 20/Dec/16

Status: Won't Fix
Project: Data Model
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Story Priority: Major
Reporter: aritter Assignee: Unassigned
Resolution: Won't Fix Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Blocks
blocks PIPE2D-98 Add test to confirm that a FiberTrace... Done
Relates
relates to PIPE2D-98 Add test to confirm that a FiberTrace... Done
Story Points: 0.25

 Description   

As shown in PIPE2D-98, the lack of precision in the trace-function coefficients due to only persisting floats is responsible for the difference between the stored FiberTraces and the reconstructed ones. This means that we will have to change the datamodel to persist the trace-function coefficients as double values.

 Comments   
Comment by rhl [ 17/Nov/16 ]

Hmm, I am suspicious about needing doubles. The description of this ticket says, "As shown in PIPE2D-98", but I do not see any such demonstration in that ticket, just a comment from swinbank that this might be a problem.

What basis functions are you using? Polynomials? What is the maximum value of the basis functions (probably 1 as I think you're normalising the range into +-1)? Is there some delicate cancellation? Please investigate why you are losing so much precision as to need doubles before implementing this ticket.

Comment by swinbank [ 20/Dec/16 ]

Obsoleted by work on PIPE2D-98.

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