gmpbench -- how to utilize all CPU cores?

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http://gmplib.org/gmpbench.html

Good open source benchmark, but if I run it, it uses only one CPU core.
Is it possible to use all CPU cores?

My results for fun and info ("model name    : Intel(R) Core(TM)2 Duo
CPU     T5450  @ 1.66GHz")

    gmpbench-0.2$ ./runbench
    ***** GMPbench version 0.2 *****
    Using default CFLAGS = "-O3 -fomit-frame-pointer"
    Using default CC = "gcc"
    Using default LIBS = "-static -lgmp"
    Using compilation command: gcc -O3 -fomit-frame-pointer foo.c -o foo
    -static -lgmp
    You may want to override CC, CFLAGS, and LIBS
    Using gmp version: 5.1.2
    Compiling benchmarks
    Running benchmarks (propagated score accuracy exceeds printed
    intermediates)
      Category base
        Program multiply (weight=1)
          GMPbench.base.multiply(128)                        1.448e+07
          GMPbench.base.multiply(512)                          2.4e+06
          GMPbench.base.multiply(8192)                        2.37e+04
          GMPbench.base.multiply(131072)                           505
          GMPbench.base.multiply(2097152)                         18.5
          GMPbench.base.multiply(128,128)                    1.036e+07
          GMPbench.base.multiply(512,512)                    1.592e+06
          GMPbench.base.multiply(8192,8192)                  1.694e+04
          GMPbench.base.multiply(131072,131072)                    358
          GMPbench.base.multiply(2097152,2097152)                 12.6
          GMPbench.base.multiply(15000,10000)                     8551
          GMPbench.base.multiply(20000,10000)                     6989
          GMPbench.base.multiply(30000,10000)                     4383
          GMPbench.base.multiply(16777216,512)                    44.7
          GMPbench.base.multiply(16777216,262144)                 3.01
        GMPbench.base.multiply                        5873.6
        Program divide (weight=1)
          GMPbench.base.divide(8192,32)                      3.055e+05
          GMPbench.base.divide(8192,64)                      2.332e+05
          GMPbench.base.divide(8192,128)                      1.09e+05
          GMPbench.base.divide(8192,4096)                    3.065e+04
          GMPbench.base.divide(131072,65536)                       448
          GMPbench.base.divide(8388608,4194304)                   2.59
          GMPbench.base.divide(8192,8064)                    3.026e+06
          GMPbench.base.divide(16777216,262144)                   1.56
        GMPbench.base.divide                          5812.8
        Program gcd (weight=0.5)
          GMPbench.base.gcd(128,128)                         6.351e+05
          GMPbench.base.gcd(512,512)                         9.725e+04
          GMPbench.base.gcd(8192,8192)                            1661
          GMPbench.base.gcd(131072,131072)                        23.7
          GMPbench.base.gcd(1048576,1048576)                      1.31
        GMPbench.base.gcd                             1260.7
        Program gcdext (weight=0.5)
          GMPbench.base.gcdext(128,128)                      4.373e+05
          GMPbench.base.gcdext(512,512)                      7.215e+04
          GMPbench.base.gcdext(8192,8192)                         1073
          GMPbench.base.gcdext(131072,131072)                     16.4
          GMPbench.base.gcdext(1048576,1048576)                  0.816
        GMPbench.base.gcdext                          853.54
      GMPbench.base                           3284
      Category app
        Program rsa (weight=1)
          GMPbench.app.rsa(512)                                   3824
          GMPbench.app.rsa(1024)                                   675
          GMPbench.app.rsa(2048)                                  98.5
        GMPbench.app.rsa                              633.51
        Program pi (weight=1)
          GMPbench.app.pi(10000)                                   163
          GMPbench.app.pi(100000)                                 7.26
          GMPbench.app.pi(1000000)                               0.379
        GMPbench.app.pi                               7.6546
      GMPbench.app                          69.636
    GMPbench:         478.21

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