Add an example of using multiple threads for DNS lookups.

diff --git a/doc/man1/hath.1 b/doc/man1/hath.1
index b72896a543708c72eab258c57e134430e34970b3..6e7a618c61adbaaf7ac2cf9ccd0abb85dec56264 100644 (file)
--- a/doc/man1/hath.1
+++ b/doc/man1/hath.1
@@ -109,6 +109,19 @@ the given CIDRs.
 198.41.0.7:
 .fi
 .P
+The DNS lookups are usually the bottleneck for this mode, but we can
+perform them in parallel. Simply pass the number of threads to the GHC
+runtime on the command line; for example, the following will perform
+25 lookups in parallel:
+.P
+.nf
+.I $ hath reversed +RTS -N25 <<< \(dq198.41.0.4/24\(dq
+198.41.0.4: a.root-servers.net.
+198.41.0.5:
+198.41.0.6: rs.internic.net.
+\(pc\(pc\(pc
+.fi
+.P
 Each of the modes also supports a present-tense flavor; the following
 are equivalent to their counterparts: \fBregex\fR, \fBreduce\fR,
 \fBdupe\fR, \fBdiff\fR, \fBlist\fR, \fBreverse\fR.

diff --git a/hath.cabal b/hath.cabal
index e6f53955df5171fc884c5f847d921f11e1ba2164..8eb569f410238a9c8ab9aed7c632f5e41e353d32 100644 (file)
--- a/hath.cabal
+++ b/hath.cabal
@@ -93,6 +93,19 @@ description:
   198.41.0.6: rs.internic.net.
   198.41.0.7:
   @
+  .
+  The DNS lookups are usually the bottleneck for this mode, but we can
+  perform them in parallel. Simply pass the number of threads to the
+  GHC runtime on the command line; for example, the following will
+  perform 25 lookups in parallel:
+  .
+  @
+  hath reversed +RTS -N25 <<< \"198.41.0.4\/24\"
+  198.41.0.4: a.root-servers.net.
+  198.41.0.5:
+  198.41.0.6: rs.internic.net.
+  ...
+  @
 
 executable hath
   build-depends: