Re^4: RE on lines read from in-memory scalar is very slow

[Anonymous Monk]

FWIW, Win10 & Strawberry:

v5.32.1
tempfile.txt is size 29 Mb
0.115239 read lines from disk and do RE (32571 matches).
0.676642 read lines from in-memory file and do RE (32571 matches).

v5.38.0
tempfile.txt is size 29 Mb
0.156708 read lines from disk and do RE (32571 matches).
0.628221 read lines from in-memory file and do RE (32571 matches).

v5.26.3
tempfile.txt is size 29 Mb
0.122374 read lines from disk and do RE (32571 matches).
0.671405 read lines from in-memory file and do RE (32571 matches).

v5.16.3
tempfile.txt is size 28 Mb
0.119628 read lines from disk and do RE (32760 matches).
0.057724 read lines from in-memory file and do RE (32760 matches).

[Anonymous Monk]

Couple other additions to assortment of facts:

• if loops are changed to

  while(my $s = <$fh>) {
    $s =~ /^ ?Query/ && $match_count1++;
  }
  

  then deterioration gets significantly worse (compare to parent node):

  v5.32.1
  tempfile.txt is size 29 Mb
  0.121957 read lines from disk and do RE (32571 matches).
  9.511288 read lines from in-memory file and do RE (32571 matches).
  

• if loops are changed to

  while(my $s = <$fh>) {
    index( $s, 'Query' ) != -1 && $match_count1++;;
  }
  

  (the same without the "$s") then using in-memory string is (of course) faster:

  v5.32.1
  tempfile.txt is size 29 Mb
  0.092390 read lines from disk and do RE (32571 matches).
  0.051797 read lines from in-memory file and do RE (32571 matches).
  

[afoken]

if loops

if is no loop.

Alexander

[hippo]

Read as "if the loops are changed to XYZ then ...". HTH.