fact3 is a recur based function.
fact4 is a reduce based function.
They are compared calculating 1000!


criterium.core=> (bench (user/fact3 1000) :verbose)
amd64 Linux 2.6.36-gentoo-r5 4 cpu(s)
OpenJDK 64-Bit Server VM 19.0-b09
Runtime arguments: -Xms512m -Xmx512m -Denclojure/projectDirectory=/home/odyssomay/NetBeansProjects/Test -DCOMMONS_EXEC_DEBUG=true -Xrunjdwp:transport=dt_socket,server=y,suspend=n
Evaluation count             : 92580
Execution time mean          : 661.882881 us  95.0% CI: (661.740419 us, 662.048539 us)
Execution time std-deviation : 770.738685 us  95.0% CI: (767.065606 us, 774.673540 us)

Found 1 outliers in 60 samples (1.6667 %)
	low-severe	 1 (1.6667 %)
 Variance from outliers : 17.3373 % Variance is moderately inflated by outliers
nil

criterium.core=> (bench (user/fact4 1000) :verbose)
amd64 Linux 2.6.36-gentoo-r5 4 cpu(s)
OpenJDK 64-Bit Server VM 19.0-b09
Runtime arguments: -Xms512m -Xmx512m -Denclojure/projectDirectory=/home/odyssomay/NetBeansProjects/Test -DCOMMONS_EXEC_DEBUG=true -Xrunjdwp:transport=dt_socket,server=y,suspend=n
Evaluation count             : 28440
Execution time mean          : 2.151680 ms  95.0% CI: (2.151251 ms, 2.152173 ms)
Execution time std-deviation : 1.131510 ms  95.0% CI: (1.124378 ms, 1.137222 ms)

Found 1 outliers in 60 samples (1.6667 %)
	low-severe	 1 (1.6667 %)
 Variance from outliers : 12.5398 % Variance is moderately inflated by outliers
nil