// Schmidhuber's neural bucket brigade
struct Incomming {
	int n;
	int *idxArr;
};

struct Ctx {
	float lamda;

	float *xtm1;
	float **wtm1; // by index i index j

	float *xtm2;
	float **wtm2; // by index i index j

	Incomming **incomming; // by index j
};

// calc c_ij for t
float ctm0(Ctx *ctx, int i, int j) {
	return ctx->xtm1[i]*ctx->wtm1[i][j];
}

// calc c_ij for t-1
float ctm1(Ctx *ctx, int i, int j) {
	return ctx->xtm2[i]*ctx->wtm2[i][j];
}


float deltaW(Ctx *ctx, int i, int j) {
	float cDivSum = 0.0f;

	Incomming *incommingByJ = ctx->incomming[j];

	for( int k = 0; k < incommingByJ->n; k++ ) {
		int i2 = incommingByJ->idxArr[k];

		cDivSum += ctm1(ctx, i2, j);
	}

	float res = (ctm1(ctx, i, j) / cDivSum);

	// TODO< multiply by sum of kwins >

	res += (-ctx->lamda*ctm0(ctx, i, j));

	// TODO< add ext >

	return res;
}