Project

General

Profile

Bug #1705

examples/charm++/kmeans occasionally loops forever, seen on uth-linux-x86_64

Added by Phil Miller almost 2 years ago. Updated almost 2 years ago.

Status:
Merged
Priority:
Normal
Assignee:
Category:
-
Target version:
Start date:
10/05/2017
Due date:
% Done:

0%


Description

We've seen this failure a few times, but never debugged it. I've added some prints and after a dozen or so runs, got this:

Iteration 36937
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36938
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36939
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36940
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36941
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36942
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36943
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36944
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36945
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36946
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36947
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36948
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36949
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36950
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01
Iteration 36951
i 3, x'-x 5.794072e-01, y'-y 5.794072e-01

History

#1 Updated by Phil Miller almost 2 years ago

Looks like a floating point associativity failure in the use of the sum_double reduction:

(gdb) p means[3]
$26 = {x = 0.57940721684981966, y = 0.37208395089429952}
(gdb) p oldMeans[3]         XX
$27 = {x = 0.57940721684981955, y = 0.37208395089429952}
                            ^^

#2 Updated by Phil Miller almost 2 years ago

  • Status changed from New to Implemented

#3 Updated by Phil Miller almost 2 years ago

  • Target version set to 6.8.1
  • Status changed from Implemented to Merged

Also available in: Atom PDF