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/*
! Content:
! A simple example of single-precision real-to-complex out-of-place 2D
! FFT using Intel(R) MKL DFTI
!
!****************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <float.h>
#include "mkl_service.h"
#include "mkl_dfti.h"

static void init_r(float *x, int N1, int N2, int H1, int H2);
static void init_c(MKL_Complex8 *x, int N1, int N2, int H1, int H2);
static int verify_c(MKL_Complex8 *x, int N1, int N2, int H1, int H2);
static int verify_r(float *x, int N1, int N2, int H1, int H2);

/* Define the format to printf MKL_LONG values */
#if !defined(MKL_ILP64)
#define LI "%li"
#else
#define LI "%lli"
#endif

int main(void)
{
    /* Size of 2D transform */
    int N1 = 4, N2 = 5;

    /* Arbitrary harmonic used to verify FFT */
    int H1 = -1, H2 = 2;

    /* Execution status */
    MKL_LONG status = 0;

    /* Pointers to input and output data */
    float *x_real = 0;
    MKL_Complex8 *x_cmplx = 0;

    DFTI_DESCRIPTOR_HANDLE hand = 0;

    char version[DFTI_VERSION_LENGTH];

    DftiGetValue(0, DFTI_VERSION, version);
    printf("%s\n", version);

    printf("Example basic_sp_real_dft_2d\n");
    printf("Forward-Backward single-precision 2D real out-of-place FFT\n");
    printf("Configuration parameters:\n");
    printf(" DFTI_PRECISION                = DFTI_SINGLE\n");
    printf(" DFTI_FORWARD_DOMAIN           = DFTI_REAL\n");
    printf(" DFTI_DIMENSION                = 2\n");
    printf(" DFTI_LENGTHS                  = {%i, %i}\n", N1, N2);
    printf(" DFTI_PLACEMENT                = DFTI_NOT_INPLACE\n");
    printf(" DFTI_CONJUGATE_EVEN_STORAGE   = DFTI_COMPLEX_COMPLEX\n");
    /*printf(" DFTI_PACKED_FORMAT            = DFTI_CCE_FORMAT\n");*/

    printf("Create DFTI descriptor\n");
    {
        MKL_LONG N[2];  N[0] = N1;  N[1] = N2;
        status = DftiCreateDescriptor(&hand, DFTI_SINGLE, DFTI_REAL, 2, N);
        if (0 != status) goto failed;
    }

    printf("Set configuration: out-of-place\n");
    status = DftiSetValue(hand, DFTI_PLACEMENT, DFTI_NOT_INPLACE);
    if (0 != status) goto failed;

    printf("Set configuration: CCE storage\n");
    status = DftiSetValue(hand, DFTI_CONJUGATE_EVEN_STORAGE,
                          DFTI_COMPLEX_COMPLEX);
    if (0 != status) goto failed;

    /* This is not needed for DFTI_COMPLEX_COMPLEX storage */
    /* status = DftiSetValue(hand, DFTI_PACKED_FORMAT, DFTI_CCE_FORMAT); */
    /* if (0 != status) goto failed; */

    printf("Set input  strides = ");
    {
        MKL_LONG rs[3]; rs[0] = 0; rs[1] = N2; rs[2] = 1;
        printf("{"LI", "LI", "LI"}\n", rs[0],rs[1],rs[2]);
        status = DftiSetValue(hand, DFTI_INPUT_STRIDES, rs);
        if (0 != status) goto failed;
    }

    printf("Set output strides = ");
    {
        MKL_LONG cs[3]; cs[0] = 0; cs[1] = N2/2+1; cs[2] = 1;
        printf("{"LI", "LI", "LI"}\n", cs[0],cs[1],cs[2]);
        status = DftiSetValue(hand, DFTI_OUTPUT_STRIDES, cs);
        if (0 != status) goto failed;
    }

    printf("Commit the descriptor\n");
    status = DftiCommitDescriptor(hand);
    if (0 != status) goto failed;

    printf("Allocate data arrays\n");
    x_real = (float *)mkl_malloc(N1*N2*sizeof(float), 64);
    if (0 == x_real) goto failed;
    x_cmplx = (MKL_Complex8*)mkl_malloc(N1*(N2/2+1)*sizeof(MKL_Complex8), 64);
    if (0 == x_cmplx) goto failed;

    printf("Initialize data for r2c transform\n");
    init_r(x_real, N1, N2, H1, H2);

    printf("Compute real-to-complex transform\n");
    status = DftiComputeForward(hand, x_real, x_cmplx);
    if (0 != status) goto failed;

    printf("Verify the result\n");
    status = verify_c(x_cmplx, N1, N2, H1, H2);
    if (0 != status) goto failed;

    printf("Reconfigure DFTI descriptor for backward transform\n");

    printf("Set input  strides = ");
    {
        MKL_LONG cs[3]; cs[0] = 0; cs[1] = N2/2+1; cs[2] = 1;
        printf("{"LI", "LI", "LI"}\n", cs[0],cs[1],cs[2]);
        status = DftiSetValue(hand, DFTI_INPUT_STRIDES, cs);
        if (0 != status) goto failed;
    }

    printf("Set output strides = ");
    {
        MKL_LONG rs[3]; rs[0] = 0; rs[1] = N2; rs[2] = 1;
        printf("{"LI", "LI", "LI"}\n", rs[0],rs[1],rs[2]);
        status = DftiSetValue(hand, DFTI_OUTPUT_STRIDES, rs);
        if (0 != status) goto failed;
    }

    printf("Commit the descriptor\n");
    status = DftiCommitDescriptor(hand);
    if (0 != status) goto failed;

    printf("Initialize data for c2r transform\n");
    init_c(x_cmplx, N1, N2, H1, H2);

    printf("Compute backward transform\n");
    status = DftiComputeBackward(hand, x_cmplx, x_real);
    if (0 != status) goto failed;

    printf("Verify the result of the backward transform\n");
    status = verify_r(x_real, N1, N2, H1, H2);
    if (0 != status) goto failed;

 cleanup:

    printf("Free DFTI descriptor\n");
    DftiFreeDescriptor(&hand);

    printf("Free data arrays\n");
    mkl_free(x_real);
    mkl_free(x_cmplx);

    printf("TEST %s\n",0==status ? "PASSED" : "FAILED");
    return status;

 failed:
    printf(" ERROR, status = "LI"\n", status);
    status = 1;
    goto cleanup;
}

/* Compute (K*L)%M accurately */
static float moda(int K, int L, int M)
{
    return (float)(((long long)K * L) % M);
}

/* Initialize array x(N) to produce unit peaks at x(H) and x(N-H) */
static void init_r(float *x, int N1, int N2, int H1, int H2)
{
    float TWOPI = 6.2831853071795864769f, phase, factor;
    int n1, n2, S1, S2, index;

    /* Generalized strides for row-major addressing of x */
    S2 = 1;
    S1 = N2;

    factor = (2*(N1-H1)%N1==0 && 2*(N2-H2)%N2==0) ? 1.0f : 2.0f;
    for (n1 = 0; n1 < N1; n1++)
    {
        for (n2 = 0; n2 < N2; n2++)
        {
            phase  = moda(n1,H1,N1) / N1;
            phase += moda(n2,H2,N2) / N2;
            index = n1*S1 + n2*S2;
            x[index] = factor * cosf( TWOPI * phase ) / (N1*N2);
        }
    }
}

/* Verify that x has unit peak at H */
static int verify_c(MKL_Complex8 *x, int N1, int N2, int H1, int H2)
{
    float err, errthr, maxerr;
    int n1, n2, S1, S2, index;

    /* Generalized strides for row-major addressing of x */
    S2 = 1;
    S1 = N2/2+1;

    /*
     * Note, this simple error bound doesn't take into account error of
     * input data
     */
    errthr = 2.5f * logf( (float)N1*N2 ) / logf(2.0f) * FLT_EPSILON;
    printf(" Check if err is below errthr %.3lg\n", errthr);

    maxerr = 0;
    for (n1 = 0; n1 < N1; n1++)
    {
        for (n2 = 0; n2 < N2/2+1; n2++)
        {
            float re_exp = 0.0f, im_exp = 0.0f, re_got, im_got;

            if ((( n1-H1)%N1==0 && ( n2-H2)%N2==0) ||
                ((-n1-H1)%N1==0 && (-n2-H2)%N2==0))
            {
                re_exp = 1;
            }

            index = n1*S1 + n2*S2;
            re_got = x[index].real;
            im_got = x[index].imag;
            err  = fabsf(re_got - re_exp) + fabsf(im_got - im_exp);
            if (err > maxerr) maxerr = err;
            if (!(err < errthr))
            {
                printf(" x[%i][%i]: ",n1,n2);
                printf(" expected (%.7g,%.7g), ",re_exp,im_exp);
                printf(" got (%.7g,%.7g), ",re_got,im_got);
                printf(" err %.3lg\n", err);
                printf(" Verification FAILED\n");
                return 1;
            }
        }
    }
    printf(" Verified,  maximum error was %.3lg\n", maxerr);
    return 0;
}

/* Initialize array x(N) to produce unit peak at x(H) */
static void init_c(MKL_Complex8 *x, int N1, int N2, int H1, int H2)
{
    float TWOPI = 6.2831853071795864769f, phase;
    int n1, n2, S1, S2, index;

    /* Generalized strides for row-major addressing of x */
    S2 = 1;
    S1 = N2/2+1;

    for (n1 = 0; n1 < N1; n1++)
    {
        for (n2 = 0; n2 < N2/2+1; n2++)
        {
            phase  = moda(n1,H1,N1) / N1;
            phase += moda(n2,H2,N2) / N2;
            index = n1*S1 + n2*S2;
            x[index].real =  cosf( TWOPI * phase ) / (N1*N2);
            x[index].imag = -sinf( TWOPI * phase ) / (N1*N2);
        }
    }
}

/* Verify that x has unit peak at H */
static int verify_r(float *x, int N1, int N2, int H1, int H2)
{
    float err, errthr, maxerr;
    int n1, n2, S1, S2, index;

    /* Generalized strides for row-major addressing of x */
    S2 = 1;
    S1 = N2;

    /*
     * Note, this simple error bound doesn't take into account error of
     * input data
     */
    errthr = 2.5f * logf( (float)N1*N2 ) / logf(2.0f) * FLT_EPSILON;
    printf(" Check if err is below errthr %.3lg\n", errthr);

    maxerr = 0;
    for (n1 = 0; n1 < N1; n1++)
    {
        for (n2 = 0; n2 < N2; n2++)
        {
            float re_exp = 0.0f, re_got;

            if ((n1-H1)%N1==0 && (n2-H2)%N2==0)
            {
                re_exp = 1;
            }

            index = n1*S1 + n2*S2;
            re_got = x[index];
            err  = fabsf(re_got - re_exp);
            if (err > maxerr) maxerr = err;
            if (!(err < errthr))
            {
                printf(" x[%i][%i]: ",n1,n2);
                printf(" expected %.7g, ",re_exp);
                printf(" got %.7g, ",re_got);
                printf(" err %.3lg\n", err);
                printf(" Verification FAILED\n");
                return 1;
            }
        }
    }
    printf(" Verified,  maximum error was %.3lg\n", maxerr);
    return 0;
}