I add exponential distribution random generator (and little bit
refactoring:) ).
I use inverse transform method to create its distribution.  It's very
simple method that is
created by - log (rand()). We can control slope of distribution using
threshold parameter.
It is same as gaussian threshold.

usage example
  pgbench --exponential=NUM -S

Attached graph is created with exponential threshold = 5. We can see
distribution in the graphs. It supports -S, -N options and custom script.
So we set
"¥setexponential [var] [min] [max] [threshold]" in a transaction pattern
it appear distribution we want.

We have no time to fix its very much... But I think almost part of patch
have been completed.

Mitsumasa KONDO
NTT Open Source Software Center

Attachment: gaussian_and_exponential_pgbench_v6.patch
Description: Binary data

<<attachment: exponential=5.png>>

Attachment: gnuplot.sh
Description: Bourne shell script

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