/*

  This program is part of the TACLeBench benchmark suite.
  Version V 2.0

  Name: st

  Author: unknown

  Function: st is a statistics program.
    This program computes for two arrays of numbers the sum, the mean,
    the variance, and standard deviation. It then determines the
    correlation coefficient between the two arrays.

  Source: MRTC
          http://www.mrtc.mdh.se/projects/wcet/wcet_bench/st/st.c

  Changes: No major functional changes.

  License: May be used, modified, and re-distributed freely

*/

/*
  Forward declaration of functions
*/

// Wasm loop bounds

__attribute__((import_module("__pragma"), import_name("loopbound"))) extern void
__pragma_loopbound(unsigned int min_bound, unsigned int max_bound);

void st_initSeed(void);
long st_randomInteger();
void st_initialize(float *);
void st_init(void);
int st_return(void);
float st_fabs(float);
float st_sqrtf(float);
float st_square(float);
void st_calc_Sum_Mean(float *, float *, float *);
void st_calc_Var_Stddev(float *, float, float *, float *);
void st_calc_LinCorrCoef(float *, float *, float, float, float *);
__attribute__((noinline)) __attribute__((export_name("entrypoint"))) void
st_main(void);
__attribute__((noinline)) __attribute__((export_name("main"))) int main(void);

/*
  Declaration of global variables
*/

volatile int st_seed;
float st_arrayA[1000], st_arrayB[1000];
float st_sumA, st_sumB;
float st_meanA, st_meanB, st_varA, st_varB, st_stddevA, st_stddevB, st_coef;

/*
  Initialization- and return-value-related functions
*/

/*
  st_initSeed initializes the seed used in the "random" number generator.
*/
void
st_initSeed() {
    st_seed = 0;
}

/*
  st_RandomInteger generates random integers between 0 and 8094.
*/
long
st_randomInteger() {
    st_seed = ((st_seed * 133) + 81) % 8095;
    return (st_seed);
}

void
st_initialize(float *array) {
    register int i;

    __pragma_loopbound(1000, 1000);
    for (i = 0; i < 1000; i++)
        array[i] = i + st_randomInteger();
}

void
st_init() {
    st_initSeed();
    st_initialize(st_arrayA);
    st_initialize(st_arrayB);
}

int
st_return() {
    float checksum = st_meanA + st_meanB + st_stddevA + st_stddevB + st_coef;
    /* allow rounding errors for the checksum */
    checksum -= 13695.986328;
    return ((checksum < 0.000001 && checksum > -0.000001) ? 0 : -1);
}

/*
  Arithmetic math functions
*/

float
st_fabs(float n) {
    float f;

    if (n >= 0)
        f = n;
    else
        f = -n;

    return (f);
}

float
st_sqrtf(float val) {
    float x = val / 10;
    float dx;
    float diff;
    float min_tol = 0.00001f;

    int i, flag = 0;

    if (val == 0)
        x = 0;
    else {
        __pragma_loopbound(19, 19);
        for (i = 1; i < 20; i++) {
            if (!flag) {
                dx = (val - (x * x)) / (2.0f * x);
                x = x + dx;
                diff = val - (x * x);

                if (st_fabs(diff) <= min_tol)
                    flag = 1;
            }
        }
    }

    return (x);
}

float
st_square(float x) {
    return (x * x);
}

/*
  Algorithm core functions
*/

void
st_calc_Sum_Mean(float *array, float *sum, float *mean) {
    int i;

    *sum = 0;

    __pragma_loopbound(1000, 1000);
    for (i = 0; i < 1000; i++)
        *sum += array[i];
    *mean = *sum / 1000;
}

void
st_calc_Var_Stddev(float *array, float mean, float *var, float *stddev) {
    int i;
    float diffs = 0.0f;

    __pragma_loopbound(1000, 1000);
    for (i = 0; i < 1000; i++)
        diffs += st_square(array[i] - mean);

    *var = diffs / 1000;
    *stddev = st_sqrtf(*var);
}

void
st_calc_LinCorrCoef(float *arrayA, float *arrayB, float meanA, float meanB,
                    float *coef) {
    int i;
    float numerator = 0.0f, Aterm = 0.0f, Bterm = 0.0f;

    __pragma_loopbound(1000, 1000);
    for (i = 0; i < 1000; i++) {
        numerator += (arrayA[i] - meanA) * (arrayB[i] - meanB);
        Aterm += st_square(arrayA[i] - meanA);
        Bterm += st_square(arrayB[i] - meanB);
    }

    *coef = numerator / (st_sqrtf(Aterm) * st_sqrtf(Bterm));
}

/*
  Main functions
*/

__attribute__((noinline)) __attribute__((export_name("entrypoint"))) void
st_main(void) {
    st_calc_Sum_Mean(st_arrayA, &st_sumA, &st_meanA);
    st_calc_Var_Stddev(st_arrayA, st_meanA, &st_varA, &st_stddevA);

    st_calc_Sum_Mean(st_arrayB, &st_sumB, &st_meanB);
    st_calc_Var_Stddev(st_arrayB, st_meanB, &st_varB, &st_stddevB);

    st_calc_LinCorrCoef(st_arrayA, st_arrayB, st_meanA, st_meanB, &st_coef);
}

__attribute__((noinline)) __attribute__((export_name("main"))) int
main(void) {
    st_init();
    st_main();

    return (st_return());
}