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建成後:GSL和環境變量
$ gcc generator.c -lm -lgsl -lgslcblas -lm
代碼:
#include <stdio.h>
#include <gsl/gsl_rng.h>
gsl_rng * r;
/* global generator */
int main (void)
{
const gsl_rng_type * T;
gsl_rng_env_setup();
T = gsl_rng_default;
r = gsl_rng_alloc (T);
printf ("generator type: %s\n", gsl_rng_name (r));
printf ("seed = %lu\n", gsl_rng_default_seed);
printf ("first value = %lu\n", gsl_rng_get (r));
gsl_rng_free (r);
return 0;
}
然後在方式運行:
$ ./a.out
我得到:
generator type: mt19937
seed = 0
first value = 4293858116
如果我做的:
$ GSL_RNG_SEED=1 GSL_RNG_TYPE="taus" ./a.out
我得到:
GSL_RNG_TYPE=taus
GSL_RNG_SEED=1
generator type: taus
seed = 1
first value = 802792108
但這樣做後:
$ GSL_RNG_SEED=1
$ GSL_RNG_TYPE="taus"
$ ./a.out
我得到相同的輸出作爲第一次:
generator type: mt19937
seed = 0
first value = 4293858116
爲什麼可執行文件沒有得到th e最後一種環境變量值(GSL_RNG_SEED = 1和GSL_RNG_TYPE =「taus」)?