JNI double arrays problems

[hana amiri]

I am new to NDK. Lately, i ve been trying to use a C library to perform convolution on two double arrays extracted from wav files.

I made some changes to the code, so that one native function (convolution) will call several other usual C functions (fft, ifft,..).

I don't know what the problem is, i get this error

invalid use of void expression

Here's the code:

#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <jni.h>
#include <android/log.h>
// Private function prototypes
#define SIZE_MAX ((size_t)-1)



int  transform(double real[], double imag[], size_t n) {
    if (n == 0)
        return 1;

    else  // More complicated algorithm for arbitrary sizes
    {
        return transform_bluestein(real, imag, n);
        __android_log_print(ANDROID_LOG_VERBOSE, "log", "inside transform ", 1);
    }
}


int inverse_transform(double real[], double imag[], size_t n) {
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "inside ifft ", 1);
    return transform(imag, real, n);
}



int transform_bluestein(double real[], double imag[], size_t n) {
    // Variables
    int status = 0;
    double *cos_table, *sin_table;
    double *areal, *aimag;
    double *breal, *bimag;
    double *creal, *cimag;
    size_t m;
    size_t size_n, size_m;
    size_t i;

    __android_log_print(ANDROID_LOG_VERBOSE, "log", "start bluestein ", 1);
    // Find a power-of-2 convolution length m such that m >= n * 2 + 1
    {
        size_t target;
        if (n > (SIZE_MAX - 1) / 2)
        {
            __android_log_print(ANDROID_LOG_VERBOSE, "log", "return zero ", 1);
            return 0;
        }
        target = n * 2 + 1;
        for (m = 1; m < target; m *= 2) {
            if (SIZE_MAX / 2 < m)
            {
                __android_log_print(ANDROID_LOG_VERBOSE, "log", "return 0", 1);
                return 0;
            }
        }
    }

    // Allocate memory
    if (SIZE_MAX / sizeof(double) < n || SIZE_MAX / sizeof(double) < m)
        return 0;
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "allocate ", 1);
    size_n = n * sizeof(double);
    size_m = m * sizeof(double);
    cos_table = malloc(size_n);
    sin_table = malloc(size_n);
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "inside allocate ", 1);
    areal = calloc(m, sizeof(double));
    aimag = calloc(m, sizeof(double));
    breal = calloc(m, sizeof(double));
    bimag = calloc(m, sizeof(double));
    creal = malloc(size_m);
    cimag = malloc(size_m);
    if (cos_table == NULL || sin_table == NULL
            || areal == NULL || aimag == NULL
            || breal == NULL || bimag == NULL
            || creal == NULL || cimag == NULL)
        goto cleanup;
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "finished allocation", 1);

    // Trignometric tables

    for (i = 0; i < n; i++) {
        double temp = M_PI * (size_t)((unsigned long long)i * i % ((unsigned long long)n * 2)) / n;
        // Less accurate version if long long is unavailable: double temp = M_PI * i * i / n;
        cos_table[i] = cos(temp);
        sin_table[i] = sin(temp);
        //        __android_log_print(ANDROID_LOG_VERBOSE, "log", "inside for %d ", i);
    }

    // Temporary vectors and preprocessing
    for (i = 0; i < n; i++) {
        areal[i] =  real[i] * cos_table[i] + imag[i] * sin_table[i];
        aimag[i] = -real[i] * sin_table[i] + imag[i] * cos_table[i];
        //        __android_log_print(ANDROID_LOG_VERBOSE, "log", "inside for %d ", i);

    }
    breal[0] = cos_table[0];
    bimag[0] = sin_table[0];
    for (i = 1; i < n; i++) {
        breal[i] = breal[m - i] = cos_table[i];
        bimag[i] = bimag[m - i] = sin_table[i];
        //        __android_log_print(ANDROID_LOG_VERBOSE, "log", "inside for %d ", i);

    }
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "before postprocessing ", i);

    //    // Convolution
    //    if (!Java_com_example_convolution_MainActivity_convolution(env, obj, areal, aimag, breal, bimag, creal, cimag, m))
    //        goto cleanup;

    // Postprocessing
    for (i = 0; i < n; i++) {
        real[i] =  creal[i] * cos_table[i] + cimag[i] * sin_table[i];//------------------- (problem starts here)
        imag[i] = -creal[i] * sin_table[i] + cimag[i] * cos_table[i];
        //    __android_log_print(ANDROID_LOG_VERBOSE, "log", "inside for %d ", i);
    }
    status = 1;

    // Deallocation
    cleanup:
    free(cimag);
    free(creal);
    free(bimag);
    free(breal);
    free(aimag);
    free(areal);
    free(sin_table);
    free(cos_table);
    return status;
}




JNIEXPORT jint JNICALL Java_com_example_convolution_MainActivity_convolution (JNIEnv *env, jobject obj, jdoubleArray xreal, jdoubleArray ximag, jdoubleArray yreal, jdoubleArray yimag, jdoubleArray outreal, jdoubleArray outimag, jsize n)
{
    jint status = 0;
    jsize size;
    jsize i;
    jdouble *xr, *xi, *yr, *yi;
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "start of convolution ", 1);

    if (SIZE_MAX / sizeof(jdouble) < n)
        return 0;

    size = n * sizeof(jdouble);

    xr = (*env)->GetDoubleArrayElements(env, xreal, 0);

    xi = (*env)->GetDoubleArrayElements(env, ximag, 0);

    yr = (*env)->GetDoubleArrayElements(env, yreal, 0);

    yi = (*env)->GetDoubleArrayElements(env, yimag, 0);

    outr = (*env)->GetDoubleArrayElements(env, outreal, 0);

    outim = (*env)->GetDoubleArrayElements(env, outim, 0);

    if (xr == NULL || xi == NULL || yr == NULL || yi == NULL)
    {
        goto cleanup;
        __android_log_print(ANDROID_LOG_VERBOSE, "log",  "one of the arrays is null ", 1);

    }
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "after allocation ", 1);

    transform(xr,xi,n);
    transform(yr,yi,n);

    if (!transform(xr, xi, n))
    {
        goto cleanup;
        __android_log_print(ANDROID_LOG_VERBOSE, "log", "transform(xr,xi,n) not performed ", 1);

    }

    if (!transform(yr, yi, n))
    {
        goto cleanup;
        __android_log_print(ANDROID_LOG_VERBOSE, "log", "transform(yr,yi,n) not performed ", 1);
    }
    __android_log_print(ANDROID_LOG_VERBOSE, "log", "after fft ", 1);//------------------------not showing

    for (i = 0; i < n; i++) {

        jdouble temp = xr[i] * yr[i] - xi[i] * yi[i];
        xi[i] = xi[i] * yr[i] + xr[i] * yi[i];
        xr[i] = temp;
        //__android_log_print(ANDROID_LOG_VERBOSE, "log", "inside for convolution", 1);//---------------------not showing

    }
    inverse_transform(xr,xi,n);

    if (!inverse_transform(xr, xi, n))
    {
        goto cleanup;
        __android_log_print(ANDROID_LOG_VERBOSE, "log", "inverse_transform(xr,xi,n) not performed ", 1);
    }

        for (i = 0; i < n; i++) {  // Scaling (because this FFT implementation omits it)
            outr[i] = xr[i] / n;
            outim[i] = xi[i] / n;
        }
       
    status = 1;

    cleanup:

    //free(yi);
    (*env)->ReleaseDoubleArrayElements(env, yimag, yi, 0);

    //free(yr);
    (*env)->ReleaseDoubleArrayElements(env, yreal, yr, 0);

    //free(xi);
    (*env)->ReleaseDoubleArrayElements(env, ximag, xi, 0);

    //free(xr);
    (*env)->ReleaseDoubleArrayElements(env, xreal, xr, 0);

    return status;
}

Can anyone help me ?

[RagsSuper!]

Hi Hana,

Some of the instances where this error can occur is,

a. Use sizeof(void) or sizeof(void *).
b. Prototype a function as void and assign it to a variable of type int, float etc.

I don't see above in your code. But, can you provide details of which line in the code you are seeing this error?
Also, I hope you have run Javah on the class file and included the Java_com_example_convolution_MainActivity_convolution.h file in the 'C' code?

...

[hana amiri]

The error is shown here:

outr[i] = xr[i] / n;
outim[i] = xi[i] / n;

I dont have a returning void function.

[RagsSuper!]

Hi Hana,

Couple of things.

1. I don't see outr and outim variables declared. Am I missing anything? I think they should be declared as jdouble.

2. In the below code,

    outr = (*env)->GetDoubleArrayElements(env, outreal, 0);

    outim = (*env)->GetDoubleArrayElements(env, outim, 0);



I think outimag should be passed instead of outim in the second statement. Hope this helps.

Thanks and Regards,
Raghunand.