diff --git a/maxwell/src/lib.rs b/maxwell/src/lib.rs
index 1c72ead..ba2f46d 100644
--- a/maxwell/src/lib.rs
+++ b/maxwell/src/lib.rs
@@ -104,7 +104,7 @@ impl<SBP: SbpOperator2d> System<SBP> {
         let metrics = grid.metrics(&op).unwrap();
 
         #[cfg(feature = "sparse")]
-        let rhs = sparse::rhs_matrix(&op, ny, nx);
+        let rhs = sparse::rhs_matrix(&op, &grid).rhs;
 
         #[cfg(feature = "sparse")]
         let lhs = sparse::implicit_matrix(rhs.view(), 0.2 / std::cmp::max(ny, nx) as Float);
@@ -160,6 +160,7 @@ impl<SBP: SbpOperator2d> System<SBP> {
     #[cfg(feature = "sparse")]
     pub fn advance_sparse(&mut self, dt: Float) {
         let rhs = self.rhs.view();
+        //let lhs = self.explicit.view();
         let rhs_f = |next: &mut Field, now: &Field, _t: Float| {
             next.fill(0.0);
             sprs::prod::mul_acc_mat_vec_csr(
@@ -167,6 +168,7 @@ impl<SBP: SbpOperator2d> System<SBP> {
                 now.as_slice().unwrap(),
                 next.as_slice_mut().unwrap(),
             );
+            // sprs::lingalg::dsolve(..)
         };
         sbp::integrate::integrate::<sbp::integrate::Rk4, _, _>(
             rhs_f,
diff --git a/maxwell/src/sparse.rs b/maxwell/src/sparse.rs
index 6234fea..e34eeef 100644
--- a/maxwell/src/sparse.rs
+++ b/maxwell/src/sparse.rs
@@ -14,14 +14,31 @@ pub fn implicit_matrix(rhs: sprs::CsMatView<Float>, dt: Float) -> sprs::CsMat<Fl
     &eye(n) - &f
 }
 
-/// Assumes self boundaries
-pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<Float> {
-    let fluxes = {
-        let d1_x = op.op_eta().diff_matrix(nx);
-        let d1_y = op.op_xi().diff_matrix(ny);
+fn diagonal(values: &[Float]) -> sprs::CsMat<Float> {
+    let values = values.to_vec();
+    let indptr = (0..values.len() + 1).collect();
+    let indices = (0..values.len()).collect();
 
-        let dx = kronecker_product(eye(ny).view(), d1_x.view());
-        let dy = kronecker_product(d1_y.view(), eye(nx).view());
+    sprs::CsMat::new((values.len(), values.len()), indptr, indices, values)
+}
+
+pub struct Implicit {
+    pub(crate) rhs: sprs::CsMat<Float>,
+    /// Diagonal matrix
+    pub(crate) lhs: sprs::CsMat<Float>,
+}
+
+/// Assumes self boundaries
+pub fn rhs_matrix(op: &dyn SbpOperator2d, grid: &super::Grid) -> Implicit {
+    let metrics = grid.metrics(op).unwrap();
+    let nx = grid.nx();
+    let ny = grid.ny();
+    let fluxes = {
+        let d1_xi = op.op_eta().diff_matrix(nx);
+        let d1_eta = op.op_xi().diff_matrix(ny);
+
+        let d1_xi = kronecker_product(eye(ny).view(), d1_xi.view());
+        let d1_eta = kronecker_product(d1_eta.view(), eye(nx).view());
 
         let mut a_flux = sprs::CsMat::zero((3, 3));
         a_flux.insert(1, 2, -1.0);
@@ -31,29 +48,82 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
         b_flux.insert(0, 1, 1.0);
         b_flux.insert(1, 0, 1.0);
 
-        &kronecker_product(a_flux.view(), dx.view()) + &kronecker_product(b_flux.view(), dy.view())
+        let detj_dxi_dx = diagonal(metrics.detj_dxi_dx().as_slice().unwrap());
+        let detj_dxi_dx = &d1_xi * &detj_dxi_dx;
+        // Can multiply with the constant matrix after differentiation
+        let f_flux_dxi = kronecker_product(a_flux.view(), detj_dxi_dx.view());
+
+        let detj_dxi_dy = diagonal(metrics.detj_dxi_dy().as_slice().unwrap());
+        let detj_dxi_dy = &d1_xi * &detj_dxi_dy;
+        let f_flux_deta = kronecker_product(b_flux.view(), detj_dxi_dy.view());
+
+        let detj_deta_dx = diagonal(metrics.detj_deta_dx().as_slice().unwrap());
+        let detj_deta_dx = &d1_eta * &detj_deta_dx;
+        let g_flux_dxi = kronecker_product(a_flux.view(), detj_deta_dx.view());
+
+        let detj_deta_dy = diagonal(metrics.detj_deta_dy().as_slice().unwrap());
+        let detj_deta_dy = &d1_eta * &detj_deta_dy;
+        let g_flux_deta = kronecker_product(b_flux.view(), detj_deta_dy.view());
+
+        let f_flux = &f_flux_dxi + &f_flux_deta;
+        let g_flux = &g_flux_dxi + &g_flux_deta;
+
+        &f_flux + &g_flux
+    };
+
+    fn flux_matrix(
+        kx: ndarray::ArrayView2<Float>,
+        ky: ndarray::ArrayView2<Float>,
+        positive: bool,
+    ) -> sprs::CsMat<Float> {
+        let mut r = &(&kx * &kx) + &(&ky * &ky);
+        r.map_inplace(|v| *v = v.sqrt());
+        let a00 = if positive {
+            &ky * &ky / (2.0 * &r)
+        } else {
+            -&ky * &ky / (2.0 * &r)
+        };
+        let a00 = diagonal(a00.as_slice().unwrap());
+        let a01 = &ky / 2.0;
+        let a01 = diagonal(a01.as_slice().unwrap());
+        let a02 = &kx * &ky / (2.0 * &r);
+        let a02 = diagonal(a02.as_slice().unwrap());
+        let a10 = &a01;
+        let a11 = if positive { &r / 2.0 } else { -&r / 2.0 };
+        let a11 = diagonal(a11.as_slice().unwrap());
+        let a12 = -&kx / 2.0;
+        let a12 = diagonal(a12.as_slice().unwrap());
+        let a20 = &a02;
+        let a21 = &a12;
+        let a22 = if positive {
+            &kx * &kx / (2.0 * &r)
+        } else {
+            -&kx * &kx / (2.0 * &r)
+        };
+        let a22 = diagonal(a22.as_slice().unwrap());
+
+        sprs::bmat(&[
+            [Some(a00.view()), Some(a01.view()), Some(a02.view())],
+            [Some(a10.view()), Some(a11.view()), Some(a12.view())],
+            [Some(a20.view()), Some(a21.view()), Some(a22.view())],
+        ])
+    }
+
+    let e0 = |n| {
+        let mut e0 = sprs::CsMat::zero((n, 1));
+        e0.insert(0, 0, 1.0);
+        e0
+    };
+    let en = |n| {
+        let mut en = sprs::CsMat::zero((n, 1));
+        en.insert(n - 1, 0, 1.0);
+        en
     };
 
     let sat_west = {
         // West boundary
-        let aminus = {
-            let mut aminus = sprs::CsMat::zero((3, 3));
-            aminus.insert(1, 1, -0.5);
-            aminus.insert(1, 2, -0.5);
-            aminus.insert(2, 1, -0.5);
-            aminus.insert(2, 2, -0.5);
-            aminus
-        };
-        let e0 = {
-            let mut e0 = sprs::CsMat::zero((nx, 1));
-            e0.insert(0, 0, 1.0);
-            e0
-        };
-        let en = {
-            let mut en = sprs::CsMat::zero((nx, 1));
-            en.insert(nx - 1, 0, 1.0);
-            en
-        };
+        let e0 = e0(nx);
+        let en = en(nx);
 
         // Periodic => (e_0 - e_n)q => 0
         let p = &e0 - &en;
@@ -66,7 +136,8 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
         // Upscaling to (nx * ny, nx * ny)
         let mat = kronecker_product(eye(ny).view(), mat.view());
 
-        let mut sat = kronecker_product(aminus.view(), mat.view());
+        let aminus = flux_matrix(metrics.detj_dxi_dx(), metrics.detj_dxi_dy(), false);
+        let mut sat = &aminus * &kronecker_product(eye(3).view(), mat.view());
 
         let tau = 1.0;
         // Scaling by tau
@@ -76,24 +147,8 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
 
     let sat_east = {
         // East boundary
-        let aminus = {
-            let mut aplus = sprs::CsMat::zero((3, 3));
-            aplus.insert(1, 1, 0.5);
-            aplus.insert(1, 2, -0.5);
-            aplus.insert(2, 1, -0.5);
-            aplus.insert(2, 2, 0.5);
-            aplus
-        };
-        let e0 = {
-            let mut e0 = sprs::CsMat::zero((nx, 1));
-            e0.insert(0, 0, 1.0);
-            e0
-        };
-        let en = {
-            let mut en = sprs::CsMat::zero((nx, 1));
-            en.insert(nx - 1, 0, 1.0);
-            en
-        };
+        let e0 = e0(nx);
+        let en = en(nx);
 
         // Periodic => (e_0 - e_n) => 0
         let p = &en - &e0;
@@ -106,7 +161,9 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
         // Upscaling to (nx * ny, nx * ny)
         let mat = kronecker_product(eye(ny).view(), mat.view());
 
-        let mut sat = kronecker_product(aminus.view(), mat.view());
+        let aplus = flux_matrix(metrics.detj_dxi_dx(), metrics.detj_dxi_dy(), true);
+
+        let mut sat = &aplus * &kronecker_product(eye(3).view(), mat.view());
 
         let tau = -1.0;
         // Scaling by tau
@@ -116,24 +173,8 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
 
     let sat_south = {
         // South boundary
-        let bminus = {
-            let mut bminus = sprs::CsMat::zero((3, 3));
-            bminus.insert(0, 0, -0.5);
-            bminus.insert(0, 1, 0.5);
-            bminus.insert(1, 0, 0.5);
-            bminus.insert(1, 1, -0.5);
-            bminus
-        };
-        let e0 = {
-            let mut e0 = sprs::CsMat::zero((ny, 1));
-            e0.insert(0, 0, 1.0);
-            e0
-        };
-        let en = {
-            let mut en = sprs::CsMat::zero((ny, 1));
-            en.insert(ny - 1, 0, 1.0);
-            en
-        };
+        let e0 = e0(ny);
+        let en = en(ny);
 
         // Periodic => (e_0 - e_n) => 0
         let p = &e0 - &en;
@@ -146,7 +187,9 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
         // Upscaling to (nx * ny, nx * ny)
         let mat = kronecker_product(mat.view(), eye(nx).view());
 
-        let mut sat = kronecker_product(bminus.view(), mat.view());
+        let bminus = flux_matrix(metrics.detj_deta_dx(), metrics.detj_deta_dy(), false);
+
+        let mut sat = &bminus * &kronecker_product(eye(3).view(), mat.view());
 
         let tau = 1.0;
         // Scaling by tau
@@ -156,24 +199,8 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
 
     let sat_north = {
         // North boundary
-        let bplus = {
-            let mut bplus = sprs::CsMat::zero((3, 3));
-            bplus.insert(0, 0, 0.5);
-            bplus.insert(0, 1, 0.5);
-            bplus.insert(1, 0, 0.5);
-            bplus.insert(1, 1, 0.5);
-            bplus
-        };
-        let e0 = {
-            let mut e0 = sprs::CsMat::zero((ny, 1));
-            e0.insert(0, 0, 1.0);
-            e0
-        };
-        let en = {
-            let mut en = sprs::CsMat::zero((ny, 1));
-            en.insert(ny - 1, 0, 1.0);
-            en
-        };
+        let e0 = e0(ny);
+        let en = en(ny);
 
         // Periodic => (e_0 - e_n) => 0
         let p = &en - &e0;
@@ -186,7 +213,9 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
         // Upscaling to (nx * ny, nx * ny)
         let mat = kronecker_product(mat.view(), eye(nx).view());
 
-        let mut sat = kronecker_product(bplus.view(), mat.view());
+        let bminus = flux_matrix(metrics.detj_deta_dx(), metrics.detj_deta_dy(), true);
+
+        let mut sat = &bminus * &kronecker_product(eye(3).view(), mat.view());
 
         let tau = -1.0;
         // Scaling by tau
@@ -194,49 +223,74 @@ pub fn rhs_matrix(op: &dyn SbpOperator2d, ny: usize, nx: usize) -> sprs::CsMat<F
         sat
     };
 
-    &fluxes + &(&(&sat_west + &sat_east) + &(&sat_north + &sat_south))
+    let rhs = &fluxes + &(&(&sat_west + &sat_east) + &(&sat_north + &sat_south));
+
+    Implicit {
+        rhs,
+        lhs: kronecker_product(
+            sprs::CsMat::eye(3).view(),
+            diagonal(metrics.detj().as_slice().unwrap()).view(),
+        ),
+    }
 }
 
 /// RHS with some additional dissipation from the upwind operator
 pub fn rhs_matrix_with_upwind_dissipation(
     op: &dyn UpwindOperator2d,
-    ny: usize,
-    nx: usize,
+    grid: &super::Grid,
 ) -> sprs::CsMat<Float> {
-    let rhs = rhs_matrix(op.as_sbp(), ny, nx);
+    let rhs = rhs_matrix(op.as_sbp(), grid).rhs;
+    let metrics = grid.metrics(op.as_sbp()).unwrap();
+    let nx = grid.nx();
+    let ny = grid.ny();
+
+    let diss = |kx: ndarray::ArrayView2<Float>, ky: ndarray::ArrayView2<Float>| {
+        let r = &kx * &kx + &ky * &ky;
+        let s00 = &ky * &ky / &r;
+        let s00 = diagonal(s00.as_slice().unwrap());
+        let s02 = -&kx * &ky / &r;
+        let s02 = diagonal(s02.as_slice().unwrap());
+        let s11 = diagonal(r.as_slice().unwrap());
+        let s20 = &s02;
+        let s22 = &kx * &kx / &r;
+        let s22 = diagonal(s22.as_slice().unwrap());
+        sprs::bmat(&[
+            [Some(s00.view()), None, Some(s02.view())],
+            [None, Some(s11.view()), None],
+            [Some(s20.view()), None, Some(s22.view())],
+        ])
+    };
 
     let diss_x = {
         let diss_x = UpwindOperator2d::op_xi(op).diss_matrix(nx);
         let diss_x = kronecker_product(eye(ny).view(), diss_x.view());
-        let sa = {
-            let mut sa = sprs::CsMat::zero((3, 3));
-            sa.insert(1, 1, 1.0);
-            sa.insert(2, 2, 1.0);
-            sa
-        };
-        kronecker_product(sa.view(), diss_x.view())
+        let met = diss(metrics.detj_dxi_dx(), metrics.detj_dxi_dy());
+        &met * &kronecker_product(eye(3).view(), diss_x.view())
     };
 
     let diss_y = {
         let diss_y = UpwindOperator2d::op_eta(op).diss_matrix(ny);
         let diss_y = kronecker_product(diss_y.view(), eye(nx).view());
-        let sa = {
-            let mut sa = sprs::CsMat::zero((3, 3));
-            sa.insert(0, 0, 1.0);
-            sa.insert(1, 1, 1.0);
-            sa
-        };
-        kronecker_product(sa.view(), diss_y.view())
+        let met = diss(metrics.detj_deta_dx(), metrics.detj_deta_dy());
+        &met * &kronecker_product(eye(3).view(), diss_y.view())
     };
 
     &rhs + &(&diss_x + &diss_y)
 }
 
 #[test]
-fn dummy() {
+fn creation() {
     let ny = 16;
-    let nx = 17;
+    let nx = 170;
 
-    let rhs = rhs_matrix(&sbp::operators::Upwind4, ny, nx);
-    let _lhs = implicit_matrix(rhs.view(), 1e-2);
+    let x = ndarray::Array::from_shape_fn((ny, nx), |(_j, i)| i as Float / (nx - 1) as Float);
+    let y = ndarray::Array::from_shape_fn((ny, nx), |(j, _i)| j as Float / (ny - 1) as Float);
+
+    let op = &sbp::operators::Upwind4;
+
+    let grid = sbp::grid::Grid::new(x, y).unwrap();
+
+    let _rhs = rhs_matrix(op, &grid);
+    // let _lhs = implicit_matrix(rhs.view(), 1e-2);
+    let _rhs_upwind = rhs_matrix_with_upwind_dissipation(op, &grid);
 }
diff --git a/sbp/src/grid.rs b/sbp/src/grid.rs
index 66b3149..cb9c9d4 100644
--- a/sbp/src/grid.rs
+++ b/sbp/src/grid.rs
@@ -114,6 +114,12 @@ impl Metrics {
             detj_deta_dy,
         })
     }
+    pub fn nx(&self) -> usize {
+        self.detj.shape()[1]
+    }
+    pub fn ny(&self) -> usize {
+        self.detj.shape()[0]
+    }
 }
 
 impl Metrics {