Global shear as in Snoopy

The Snoopy code has an option WITH_SHEAR for global shear (see also TIME_DEPENDANT_SHEAR).

There are 3 variables kxt, k2t and ik2t depending on time used to compute the operators.

void kvolve(const double tremap) {
	int i, j, k;
	for( i = 0; i < NX_COMPLEX/NPROC; i++) {
		for( j = 0; j < NY_COMPLEX; j++) {
			for( k = 0; k < NZ_COMPLEX; k++) {
				kxt[ IDX3D ] = kx[ IDX3D ] + tremap * param.shear * ky[ IDX3D ];

tremap is a time related to the shear.

From time to time, the fields has to be "remaped" with something like:

void remap(double complex qi[]) {
	int i, j, k;
	int nx, ny, nxtarget;

	for( i = 0; i < NX_COMPLEX; i++) {
		nx = fmod( i + (NX_COMPLEX / 2) ,  NX_COMPLEX ) - NX_COMPLEX / 2 ;
		for( j = 0; j < NY_COMPLEX; j++) {
			ny = fmod( j + (NY_COMPLEX / 2) ,  NY_COMPLEX ) - NY_COMPLEX / 2 ;
			
			nxtarget = nx + ny;		// We have a negative shear, hence nx plus ny
			
			if( (nxtarget > -NX_COMPLEX / 2) & (nxtarget < NX_COMPLEX/2)) {
			
				if ( nxtarget <0 ) nxtarget = nxtarget + NX_COMPLEX;
			
				for( k = 0; k < NZ_COMPLEX; k++) {
					w1[k + NZ_COMPLEX * j + NZ_COMPLEX * NY_COMPLEX * nxtarget] = qi[ IDX3D ];
				
				}
			}
		}
	}