completed filtering section

rsa250/README.md

@@ -246,6 +246,25 @@ for the estimates in previous sections, and extrapolate.
 
 ## Reproducing the filtering results
 
+Several filtering experiments were done during the sieving phase.
+The final one can be reproduced as follows, with revision f59dcf48f:
+```
+purge -out purged3.gz -nrels 6132671469 -keep 160 -col-min-index 0 -col-max-index 8460769956 -t 56 -required_excess 0.0 files
+```
+where `files` is the list of files with unique relations (output of `dup2`).
+This took about 9.3 hours on the machine wurst, with 138GB of peak memory.
+
+The merge step can be reproduced as follows (revision eaeb2053d):
+```
+merge -out history5 -t 112 -target_density 250 -mat purged3.gz -skip 32
+```
+and took about 3 hours on the machine wurst, with a peak memory of 1500GB.
+
+Finally the replay step can be reproduced as follows:
+```
+replay -purged purged3.gz -his history5 -out rsa250.matrix.250.bin
+```
+
 ## Estimating linear algebra time more precisely, and choosing parameters
 
 ## Reproducing the linear algebra results