minor

fem/bounds.cpp

@@ -41,9 +41,14 @@ void PLBound::Setup(const int nb_i, const int ncp_i,
    tol = tol_i;
    lbound.SetSize(ncp, nb);
    ubound.SetSize(ncp, nb);
+   lbound_t.SetSize(nb, ncp);
+   ubound_t.SetSize(nb, ncp);
    nodes.SetSize(nb);
    weights.SetSize(nb);
    control_points.SetSize(ncp);
+   xhat.SetSize(nb);
+   what.SetSize(nb);
+   cphat.SetSize(ncp);
 
    auto scalenodes = [](const Vector &in, const real_t a, const real_t b) -> Vector
    {
@@ -90,6 +95,10 @@ void PLBound::Setup(const int nb_i, const int ncp_i,
       MFEM_ABORT("Unsupported interval points. Use [0,1].\n");
    }
    control_points = scalenodes(control_points, 0.0, 1.0); // rescale to [0,1]
+   for (int i = 0; i < ncp; i++)
+   {
+      cphat(i) = 2.0*control_points(i) - 1.0;
+   }
 
    Poly_1D::Basis &basis1d(poly1d.GetBasis(nb-1, b_type));
 
@@ -145,6 +154,8 @@ void PLBound::Setup(const int nb_i, const int ncp_i,
                lbound(j,i) = std::max(lbound(j,i),0_r);
             }
          }
+         lbound_t(i,j) = lbound(j,i);
+         ubound_t(i,j) = ubound(j,i);
       }
    }
 
@@ -176,6 +187,11 @@ void PLBound::Setup(const int nb_i, const int ncp_i,
          nodes(i) = irule.IntPoint(i).x;
       }
    }
+   for (int i = 0; i < nb; i++)
+   {
+      xhat(i) = 2.0*nodes(i) - 1.0;
+      what(i) = 2.0*weights(i);
+   }
 
    if (b_type == 2)
    {
@@ -755,4 +771,4 @@ void PLBound::Print(std::ostream &outp) const
    ubound.Print(outp);
 }
 
-}
+}

fem/bounds.hpp

@@ -13,6 +13,7 @@
 #define MFEM_BOUNDS
 
 #include "../config/config.hpp"
+#include "../general/forall.hpp"
 #include "fespace.hpp"
 
 namespace mfem
@@ -60,7 +61,9 @@ private:
    bool proj = true; // Use linear projection to compute bounds.
    real_t tol = 0.0; // offset bounds to avoid round-off errors
    Vector nodes, weights, control_points;
+   Vector xhat, what, cphat;
    DenseMatrix lbound, ubound; // ncp x nb matrices with bounds of all bases
+   DenseMatrix lbound_t, ubound_t; // nb x ncp transposes for device kernel
    // Some auxillary storage for computing the bounds with Bernstein
    DenseMatrix basisMatNodes; // Bernstein bases at equispaced nodes
    DenseMatrix basisMatInt;   // Bernstein bases at GLL nodes
@@ -113,7 +116,10 @@ public:
     *  @details This projection increases the computational cost but results in
     *  tighter bounds.
     */
-   void SetProjectionFlagForBounding(bool proj_) { proj = proj_; }
+   void SetProjectionFlagForBounding(bool proj_)
+   {
+      proj = proj_;
+   }
 
    /** @brief Compute piecewise linear bounds for the lexicographically-ordered
     *  nodal coefficients in @a coeff in 1D/2D/3D.
@@ -137,9 +143,23 @@ public:
    /// Get number of control points used to compute the bounds.
    int GetNControlPoints() const { return ncp; }
 
+   /// Get the underlying 1D basis type.
+   int GetBasisType() const { return b_type; }
+
    /// Get 1D control point locations (lexicographic order) in [0,1].
    const Vector &GetControlPoints() const { return control_points; }
 
+   /** @brief Compute element-wise bounds from a lexicographic E-vector.
+    *
+    *  @details The expected layout of @a e_vec is `ND x VDIM x NE`, where
+    *  `ND = nb^rdim`, `VDIM = fes_vdim`, and `NE` is the number of elements.
+    *  The output layout matches GridFunction::GetElementBounds:
+    *  `NE x active_vdim`, with the element index varying fastest.
+    */
+   void GetElementBoundsKernel(const int rdim, const int fes_vdim,
+                               const Vector &e_vec, Vector &lower,
+                               Vector &upper, const int vdim = 0) const;
+
    /** @brief Get lower and upper bounding matrix (ncp^dim x nb^dim)
     *
     *  @details The matrices can be used to compute the bounds at control points
@@ -183,6 +203,600 @@ private:
               const int cp_type_i, const real_t tol_i);
 };
 
+namespace internal
+{
+
+struct PLBoundDeviceData
+{
+   int nb;
+   int ncp;
+   const real_t *xhat;
+   const real_t *what;
+   const real_t *cphat;
+   const real_t *lbound;
+   const real_t *ubound;
+};
+
+template<int T_NB = 0, bool T_PROJ = true>
+inline void GetElementBoundsKernel1D(const PLBoundDeviceData &data,
+                                     const int fes_vdim,
+                                     const int ne,
+                                     const Vector &e_vec,
+                                     Vector &lower,
+                                     Vector &upper,
+                                     const int comp0,
+                                     const int ncomp)
+{
+   constexpr int GENERIC_MAX_ND = 32;
+   constexpr int MAX_ND = T_NB ? T_NB : GENERIC_MAX_ND;
+   constexpr int BLOCK_X = 2*MAX_ND;
+
+   const int nd = T_NB ? T_NB : data.nb;
+   MFEM_VERIFY(nd <= MAX_ND,
+               "Device element bounds kernel supports up to 32 "
+               "1D degrees of freedom.");
+
+   const auto E = Reshape(e_vec.Read(), nd, fes_vdim, ne);
+   auto L = Reshape(lower.Write(), ne, ncomp);
+   auto U = Reshape(upper.Write(), ne, ncomp);
+
+   mfem::forall_2D<BLOCK_X>(ne*ncomp, BLOCK_X, 1,
+                            [=] MFEM_HOST_DEVICE (int ec)
+   {
+      const int e = ec % ne;
+      const int c = ec / ne;
+      const int vc = comp0 + c;
+      const real_t *coeff = &E(0, vc, e);
+      const int tid = MFEM_THREAD_ID(x);
+
+      MFEM_SHARED real_t sproj[MAX_ND];
+      MFEM_SHARED real_t ssum0[MAX_ND];
+      MFEM_SHARED real_t ssum1[MAX_ND];
+      MFEM_SHARED real_t smin[BLOCK_X];
+      MFEM_SHARED real_t smax[BLOCK_X];
+      MFEM_SHARED real_t sa0;
+      MFEM_SHARED real_t sa1;
+
+      MFEM_FOREACH_THREAD(i, x, nd)
+      {
+         if constexpr (T_PROJ)
+         {
+            const real_t x = data.xhat[i];
+            const real_t w = data.what[i];
+            ssum0[i] = 0.5*coeff[i]*w;
+            ssum1[i] = 1.5*coeff[i]*w*x;
+         }
+         else
+         {
+            ssum0[i] = 0.0;
+            ssum1[i] = 0.0;
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      MFEM_FOREACH_THREAD(ii, x, 1)
+      {
+         sa0 = 0.0;
+         sa1 = 0.0;
+         for (int i = 0; i < nd; i++)
+         {
+            sa0 += ssum0[i];
+            sa1 += ssum1[i];
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      MFEM_FOREACH_THREAD(i, x, nd)
+      {
+         if constexpr (T_PROJ)
+         {
+            const real_t x = data.xhat[i];
+            sproj[i] = coeff[i] - sa0 - sa1*x;
+         }
+         else
+         {
+            sproj[i] = coeff[i];
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      real_t lower_local = HUGE_VAL;
+      real_t upper_local = -HUGE_VAL;
+      MFEM_FOREACH_THREAD(j, x, data.ncp)
+      {
+         real_t lo = 0.0;
+         real_t hi = 0.0;
+         if constexpr (T_PROJ)
+         {
+            const real_t xcp = data.cphat[j];
+            lo = sa0 + sa1*xcp;
+            hi = lo;
+         }
+
+         for (int i = 0; i < nd; i++)
+         {
+            const real_t val = sproj[i];
+            const real_t lv = data.lbound[j + i*data.ncp]*val;
+            const real_t uv = data.ubound[j + i*data.ncp]*val;
+            lo += lv < uv ? lv : uv;
+            hi += lv > uv ? lv : uv;
+         }
+         lower_local = lower_local < lo ? lower_local : lo;
+         upper_local = upper_local > hi ? upper_local : hi;
+      }
+
+      smin[tid] = lower_local;
+      smax[tid] = upper_local;
+      MFEM_SYNC_THREAD;
+
+      MFEM_FOREACH_THREAD(ii, x, 1)
+      {
+         real_t lower_ec = smin[0];
+         real_t upper_ec = smax[0];
+         const int nthreads = MFEM_THREAD_SIZE(x);
+         const int nactive = data.ncp < nthreads ? data.ncp : nthreads;
+         for (int t = 1; t < nactive; t++)
+         {
+            lower_ec = lower_ec < smin[t] ? lower_ec : smin[t];
+            upper_ec = upper_ec > smax[t] ? upper_ec : smax[t];
+         }
+         L(e, c) = lower_ec;
+         U(e, c) = upper_ec;
+      }
+   });
+}
+
+template<int T_NB = 0, int T_NCP = 0, bool T_PROJ = true>
+inline void GetElementBoundsKernel2D(const PLBoundDeviceData &data,
+                                     const int fes_vdim,
+                                     const int ne,
+                                     const Vector &e_vec,
+                                     Vector &lower,
+                                     Vector &upper,
+                                     const int comp0,
+                                     const int ncomp)
+{
+   constexpr int DEFAULT_MAX_NB = 8;
+   constexpr int DEFAULT_MAX_CP = 3*DEFAULT_MAX_NB;
+   constexpr int MAX_NB = T_NB ? T_NB : DEFAULT_MAX_NB;
+   constexpr int MAX_CP = T_NCP ? T_NCP : DEFAULT_MAX_CP;
+   constexpr int MAX_THREADS = MAX_CP*MAX_CP;
+
+   const int nb = data.nb;
+   const int ncp = data.ncp;
+   const int nd = nb*nb;
+   MFEM_VERIFY(nb <= MAX_NB,
+               "Device 2D element bounds kernel exceeds its compile-time "
+               "1D degree bound.");
+   MFEM_VERIFY(ncp <= MAX_CP,
+               "Device 2D element bounds kernel exceeds its compile-time "
+               "control-point bound.");
+   MFEM_VERIFY(ncp*ncp <= MAX_THREADS,
+               "Device 2D element bounds kernel exceeds its compile-time "
+               "thread-block bound.");
+
+   const auto E = Reshape(e_vec.Read(), nd, fes_vdim, ne);
+   auto L = Reshape(lower.Write(), ne, ncomp);
+   auto U = Reshape(upper.Write(), ne, ncomp);
+
+   mfem::forall_2D<MAX_THREADS>(ne*ncomp, ncp, ncp,
+                                [=] MFEM_HOST_DEVICE (int ec)
+   {
+      const int e = ec % ne;
+      const int c = ec / ne;
+      const int vc = comp0 + c;
+      const real_t *coeff = &E(0, vc, e);
+      const int tx = MFEM_THREAD_ID(x);
+      const int ty = MFEM_THREAD_ID(y);
+
+      MFEM_SHARED real_t sproj[MAX_NB*MAX_NB];
+      MFEM_SHARED real_t srow_min[MAX_NB*MAX_CP];
+      MFEM_SHARED real_t srow_max[MAX_NB*MAX_CP];
+      MFEM_SHARED real_t srow_a0[MAX_NB];
+      MFEM_SHARED real_t srow_a1[MAX_NB];
+      MFEM_SHARED real_t sa0[MAX_CP];
+      MFEM_SHARED real_t sa1[MAX_CP];
+      MFEM_SHARED real_t smin[MAX_THREADS];
+      MFEM_SHARED real_t smax[MAX_THREADS];
+
+      // Stage 1a: for each nodal row, form the per-node contributions to the
+      // row-wise linear fit used by the first 1D bounding solve.
+      MFEM_FOREACH_THREAD(jrow, y, nb)
+      {
+         const real_t *row_coeff = coeff + jrow*nb;
+         const int row_ncp_off = jrow*MAX_CP;
+         MFEM_FOREACH_THREAD(i, x, nb)
+         {
+            if constexpr (T_PROJ)
+            {
+               const real_t x = data.xhat[i];
+               const real_t w = data.what[i];
+               srow_min[row_ncp_off + i] = 0.5*row_coeff[i]*w;
+               srow_max[row_ncp_off + i] = 1.5*row_coeff[i]*w*x;
+            }
+            else
+            {
+               srow_min[row_ncp_off + i] = 0.0;
+               srow_max[row_ncp_off + i] = 0.0;
+            }
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      // Stage 1b: reduce the row-wise projection coefficients a0/a1.
+      if constexpr (T_PROJ)
+      {
+         MFEM_FOREACH_THREAD(jrow, y, nb)
+         {
+            const int row_ncp_off = jrow*MAX_CP;
+            real_t a0 = 0.0;
+            real_t a1 = 0.0;
+            MFEM_FOREACH_THREAD(ii, x, 1)
+            {
+               for (int i = 0; i < nb; i++)
+               {
+                  a0 += srow_min[row_ncp_off + i];
+                  a1 += srow_max[row_ncp_off + i];
+               }
+               srow_a0[jrow] = a0;
+               srow_a1[jrow] = a1;
+            }
+         }
+         MFEM_SYNC_THREAD;
+      }
+
+      // Stage 1c: subtract the row-wise linear fit once and cache the
+      // projected row coefficients for reuse across all x-control points.
+      MFEM_FOREACH_THREAD(jrow, y, nb)
+      {
+         const real_t *row_coeff = coeff + jrow*nb;
+         MFEM_FOREACH_THREAD(i, x, nb)
+         {
+            if constexpr (T_PROJ)
+            {
+               const real_t x = data.xhat[i];
+               sproj[jrow*MAX_NB + i] = row_coeff[i]
+                                        - srow_a0[jrow] - srow_a1[jrow]*x;
+            }
+            else
+            {
+               sproj[jrow*MAX_NB + i] = row_coeff[i];
+            }
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      // Stage 1d: solve the first 1D bounding problem along each nodal row and
+      // store bounds at every x-direction control point.
+      MFEM_FOREACH_THREAD(icp, x, ncp)
+      {
+         MFEM_FOREACH_THREAD(jrow, y, nb)
+         {
+            const int row_cp_off = jrow*ncp;
+            real_t lo = 0.0;
+            real_t hi = 0.0;
+            if constexpr (T_PROJ)
+            {
+               const real_t xcp = data.cphat[icp];
+               lo = srow_a0[jrow] + srow_a1[jrow]*xcp;
+               hi = lo;
+            }
+            for (int i = 0; i < nb; i++)
+            {
+               const real_t val = sproj[jrow*MAX_NB + i];
+               const real_t lv = data.lbound[icp + i*data.ncp]*val;
+               const real_t uv = data.ubound[icp + i*data.ncp]*val;
+               lo += lv < uv ? lv : uv;
+               hi += lv > uv ? lv : uv;
+            }
+            srow_min[row_cp_off + icp] = lo;
+            srow_max[row_cp_off + icp] = hi;
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      // Stage 2a: from the row bounds, form the per-row contributions to the
+      // second 1D projection solve in the y-direction.
+      MFEM_FOREACH_THREAD(icp, x, ncp)
+      {
+         MFEM_FOREACH_THREAD(jrow, y, nb)
+         {
+            const int row_cp_off = jrow*ncp;
+            if constexpr (T_PROJ)
+            {
+               const real_t x = data.xhat[jrow];
+               const real_t w = data.what[jrow];
+               const real_t t = 0.5*(srow_min[row_cp_off + icp] +
+                                     srow_max[row_cp_off + icp]);
+               smin[row_cp_off + icp] = 0.5*t*w;
+               smax[row_cp_off + icp] = 1.5*t*w*x;
+            }
+            else
+            {
+               smin[row_cp_off + icp] = 0.0;
+               smax[row_cp_off + icp] = 0.0;
+            }
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      // Stage 2b: reduce the y-direction projection coefficients for each
+      // x-control-point column.
+      MFEM_FOREACH_THREAD(jj, y, 1)
+      {
+         MFEM_FOREACH_THREAD(icp, x, ncp)
+         {
+            real_t a0 = 0.0;
+            real_t a1 = 0.0;
+            for (int jrow = 0; jrow < nb; jrow++)
+            {
+               a0 += smin[jrow*ncp + icp];
+               a1 += smax[jrow*ncp + icp];
+            }
+            sa0[icp] = a0;
+            sa1[icp] = a1;
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      // Stage 2c: subtract the y-direction linear fit from the intermediate
+      // row bounds so the final tensor-product bound uses the perturbation.
+      if constexpr (T_PROJ)
+      {
+         MFEM_FOREACH_THREAD(icp, x, ncp)
+         {
+            MFEM_FOREACH_THREAD(jrow, y, nb)
+            {
+               const int row_cp_off = jrow*ncp;
+               const real_t x = data.xhat[jrow];
+               const real_t t = sa0[icp] + sa1[icp]*x;
+               srow_min[row_cp_off + icp] -= t;
+               srow_max[row_cp_off + icp] -= t;
+            }
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      // Stage 3: each thread now owns one 2D control point (icp, kcp) and
+      // accumulates its final lower/upper bound from the row-bound data.
+      MFEM_FOREACH_THREAD(icp, x, ncp)
+      {
+         MFEM_FOREACH_THREAD(kcp, y, ncp)
+         {
+            real_t lo = 0.0;
+            real_t hi = 0.0;
+            if constexpr (T_PROJ)
+            {
+               const real_t xcp = data.cphat[kcp];
+               lo = sa0[icp] + sa1[icp]*xcp;
+               hi = lo;
+            }
+            for (int jrow = 0; jrow < nb; jrow++)
+            {
+               const real_t w0 = srow_min[jrow*ncp + icp];
+               const real_t w1 = srow_max[jrow*ncp + icp];
+               const real_t lb = data.lbound[kcp + jrow*data.ncp];
+               const real_t ub = data.ubound[kcp + jrow*data.ncp];
+               const real_t v0 = lb*w0;
+               const real_t v1 = ub*w0;
+               const real_t v2 = lb*w1;
+               const real_t v3 = ub*w1;
+               real_t vlo = v0 < v1 ? v0 : v1;
+               real_t vhi = v0 > v1 ? v0 : v1;
+               vlo = vlo < v2 ? vlo : v2;
+               vlo = vlo < v3 ? vlo : v3;
+               vhi = vhi > v2 ? vhi : v2;
+               vhi = vhi > v3 ? vhi : v3;
+               lo += vlo;
+               hi += vhi;
+            }
+            const int slot = kcp*ncp + icp;
+            smin[slot] = lo;
+            smax[slot] = hi;
+         }
+      }
+      MFEM_SYNC_THREAD;
+
+      const int lane = ty*ncp + tx;
+      const int nactive = ncp*ncp;
+      const int nthreads = MFEM_THREAD_SIZE(x)*MFEM_THREAD_SIZE(y);
+
+      // Reduce all 2D control-point bounds to one lower/upper pair per
+      // (element, component).
+      if (nthreads == 1)
+      {
+         if (tx == 0 && ty == 0)
+         {
+            real_t lower_ec = smin[0];
+            real_t upper_ec = smax[0];
+            for (int t = 1; t < nactive; t++)
+            {
+               lower_ec = lower_ec < smin[t] ? lower_ec : smin[t];
+               upper_ec = upper_ec > smax[t] ? upper_ec : smax[t];
+            }
+            L(e, c) = lower_ec;
+            U(e, c) = upper_ec;
+         }
+      }
+      else
+      {
+         for (int stride = (nactive + 1)/2; stride > 0;
+              stride = (stride + 1)/2)
+         {
+            if (lane < stride && lane + stride < nactive)
+            {
+               smin[lane] = smin[lane] < smin[lane + stride] ?
+                            smin[lane] : smin[lane + stride];
+               smax[lane] = smax[lane] > smax[lane + stride] ?
+                            smax[lane] : smax[lane + stride];
+            }
+            MFEM_SYNC_THREAD;
+            if (stride == 1) { break; }
+         }
+
+         if (lane == 0)
+         {
+            L(e, c) = smin[0];
+            U(e, c) = smax[0];
+         }
+      }
+   });
+}
+
+} // namespace internal
+
+inline void PLBound::GetElementBoundsKernel(const int rdim, const int fes_vdim,
+                                            const Vector &e_vec,
+                                            Vector &lower, Vector &upper,
+                                            const int vdim) const
+{
+   MFEM_VERIFY(b_type != BasisType::Positive,
+               "Bernstein device bounds are not implemented.");
+   if (rdim == 3)
+   {
+      MFEM_ABORT("Device element bounds kernel currently only supports 1D/2D.");
+   }
+   MFEM_VERIFY(rdim == 1 || rdim == 2, "Invalid element dimension.");
+   MFEM_VERIFY(vdim >= -1 && vdim <= fes_vdim, "Invalid vector component.");
+   const int nd = static_cast<int>(std::pow(nb, rdim));
+   const int ne = e_vec.Size()/(nd*fes_vdim);
+   const int ncomp = (vdim > 0) ? 1 : fes_vdim;
+
+   lower.SetSize(ne*ncomp, e_vec);
+   upper.SetSize(ne*ncomp, e_vec);
+   lower.UseDevice(true);
+   upper.UseDevice(true);
+
+   if (!proj)
+   {
+      MFEM_ABORT("Device element bounds kernel currently requires projection "
+                 "enabled.");
+   }
+
+   const real_t *dxhat = xhat.Read();
+   const real_t *dwhat = what.Read();
+   const real_t *dcphat = cphat.Read();
+   const real_t *dlbound = lbound.Read();
+   const real_t *dubound = ubound.Read();
+
+   internal::PLBoundDeviceData data
+   {
+      nb,
+      ncp,
+      dxhat,
+      dwhat,
+      dcphat,
+      dlbound,
+      dubound
+   };
+
+   const int comp0 = (vdim > 0) ? (vdim - 1) : 0;
+
+   if (rdim == 1)
+   {
+      switch (nb)
+      {
+         case 2: return internal::GetElementBoundsKernel1D<2, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 3: return internal::GetElementBoundsKernel1D<3, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 4: return internal::GetElementBoundsKernel1D<4, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 5: return internal::GetElementBoundsKernel1D<5, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 6: return internal::GetElementBoundsKernel1D<6, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 7: return internal::GetElementBoundsKernel1D<7, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 8: return internal::GetElementBoundsKernel1D<8, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 9: return internal::GetElementBoundsKernel1D<9, true>(data, fes_vdim, ne,
+                                                                     e_vec, lower, upper,
+                                                                     comp0, ncomp);
+         case 10: return internal::GetElementBoundsKernel1D<10, true>(data, fes_vdim, ne,
+                                                                       e_vec, lower, upper,
+                                                                       comp0, ncomp);
+         default: return internal::GetElementBoundsKernel1D<0, true>(data, fes_vdim, ne,
+                                                                      e_vec, lower, upper,
+                                                                      comp0, ncomp);
+      }
+   }
+#define MFEM_PLBOUND_2D_DISPATCH(NB, NCP) \
+   return internal::GetElementBoundsKernel2D<NB, NCP, true>(data, fes_vdim, ne, \
+                                                            e_vec, lower, upper, \
+                                                            comp0, ncomp)
+   switch (nb)
+   {
+      case 2:
+         switch (ncp)
+         {
+            case 4: MFEM_PLBOUND_2D_DISPATCH(2, 4);
+            case 6: MFEM_PLBOUND_2D_DISPATCH(2, 6);
+            case 8: MFEM_PLBOUND_2D_DISPATCH(2, 8);
+         }
+         break;
+      case 3:
+         switch (ncp)
+         {
+            case 6: MFEM_PLBOUND_2D_DISPATCH(3, 6);
+            case 9: MFEM_PLBOUND_2D_DISPATCH(3, 9);
+            case 12: MFEM_PLBOUND_2D_DISPATCH(3, 12);
+         }
+         break;
+      case 4:
+         switch (ncp)
+         {
+            case 8: MFEM_PLBOUND_2D_DISPATCH(4, 8);
+            case 12: MFEM_PLBOUND_2D_DISPATCH(4, 12);
+            case 16: MFEM_PLBOUND_2D_DISPATCH(4, 16);
+         }
+         break;
+      case 5:
+         switch (ncp)
+         {
+            case 10: MFEM_PLBOUND_2D_DISPATCH(5, 10);
+            case 15: MFEM_PLBOUND_2D_DISPATCH(5, 15);
+            case 20: MFEM_PLBOUND_2D_DISPATCH(5, 20);
+         }
+         break;
+      case 6:
+         switch (ncp)
+         {
+            case 12: MFEM_PLBOUND_2D_DISPATCH(6, 12);
+            case 18: MFEM_PLBOUND_2D_DISPATCH(6, 18);
+            case 24: MFEM_PLBOUND_2D_DISPATCH(6, 24);
+         }
+         break;
+      case 7:
+         switch (ncp)
+         {
+            case 14: MFEM_PLBOUND_2D_DISPATCH(7, 14);
+            case 21: MFEM_PLBOUND_2D_DISPATCH(7, 21);
+            case 28: MFEM_PLBOUND_2D_DISPATCH(7, 28);
+         }
+         break;
+      case 8:
+         switch (ncp)
+         {
+            case 16: MFEM_PLBOUND_2D_DISPATCH(8, 16);
+            case 24: MFEM_PLBOUND_2D_DISPATCH(8, 24);
+            case 32: MFEM_PLBOUND_2D_DISPATCH(8, 32);
+         }
+         break;
+   }
+#undef MFEM_PLBOUND_2D_DISPATCH
+   return internal::GetElementBoundsKernel2D<0, 0, true>(data, fes_vdim, ne,
+                                                         e_vec, lower, upper,
+                                                         comp0, ncomp);
+}
+
 } // namespace mfem
 
 #endif // MFEM_BOUNDS

fem/gridfunc.cpp

@@ -5252,6 +5252,30 @@ void GridFunction::GetElementBounds(const PLBound &plb,
                                     Vector &lower, Vector &upper,
                                     const int vdim) const
 {
+   if (UseDevice() && Device::Allows(Backend::DEVICE_MASK) &&
+       plb.GetBasisType() != BasisType::Positive &&
+       UsesTensorBasis(*fes))
+   {
+      const FiniteElement &fe = *fes->GetTypicalFE();
+      const int rdim = fe.GetDim();
+      const int fes_dim = fes->GetVDim();
+      const int nel = fes->GetNE();
+      const int nd = fe.GetDof();
+
+      Vector e_vec(nd*fes_dim*nel, Device::GetDeviceMemoryType());
+      e_vec.UseDevice(true);
+      const ElementRestrictionOperator *elem_restr =
+         fes->GetElementRestriction(ElementDofOrdering::LEXICOGRAPHIC);
+      MFEM_VERIFY(elem_restr != nullptr,
+                  "Element restriction is required for device bounds.");
+      elem_restr->Mult(*this, e_vec);
+
+      plb.GetElementBoundsKernel(rdim, fes_dim, e_vec, lower, upper, vdim);
+      lower.HostRead();
+      upper.HostRead();
+      return;
+   }
+
    int nel  = fes->GetNE();
    int fes_dim  = fes->GetVDim();
    lower.SetSize(nel*(vdim > 0 ? 1 :fes_dim));

miniapps/tools/CMakeLists.txt

@@ -61,6 +61,10 @@ if (MFEM_USE_MPI)
       LIBRARIES mfem-common)
       add_dependencies(gridfunction-bounds copy_miniapps_tools_data)
 
+    add_mfem_miniapp(random-gridfunction-bounds
+      MAIN random-gridfunction-bounds.cpp
+      LIBRARIES mfem)
+
     add_mfem_miniapp(plor-transfer
       MAIN plor-transfer.cpp LIBRARIES mfem)
 

miniapps/tools/makefile

@@ -23,7 +23,8 @@ MFEM_LIB_FILE = mfem_is_not_built
 SEQ_MINIAPPS = display-basis load-dc convert-dc get-values lor-transfer \
 	tmop-check-metric tmop-metric-magnitude compare-dc
 
-PAR_MINIAPPS = nodal-transfer plor-transfer gridfunction-bounds
+PAR_MINIAPPS = nodal-transfer plor-transfer gridfunction-bounds \
+	random-gridfunction-bounds
 
 ifeq ($(MFEM_USE_MPI),NO)
    MINIAPPS = $(SEQ_MINIAPPS)
@@ -79,7 +80,7 @@ RUN_MPI = $(MFEM_MPIEXEC) $(MFEM_MPIEXEC_NP) $(MFEM_MPI_NP)
 # Do not test: display-basis, load-dc, convert-dc, get-values, lor-transfer, plor-transfer
 NO_TEST_APPS = display-basis load-dc convert-dc get-values lor-transfer \
 	plor-transfer tmop-check-metric tmop-metric-magnitude gridfunction-bounds \
-	compare-dc
+	random-gridfunction-bounds compare-dc
 $(foreach app,$(NO_TEST_APPS),$(app)-test-seq $(app)-test-par):
 	@true
 

miniapps/tools/random-gridfunction-bounds.cpp

@@ -0,0 +1,263 @@
+// Copyright (c) 2010-2025, Lawrence Livermore National Security, LLC. Produced
+// at the Lawrence Livermore National Laboratory. All Rights reserved. See files
+// LICENSE and NOTICE for details. LLNL-CODE-806117.
+//
+// This file is part of the MFEM library. For more information and source code
+// availability visit https://mfem.org.
+//
+// MFEM is free software; you can redistribute it and/or modify it under the
+// terms of the BSD-3 license. We welcome feedback and contributions, see file
+// CONTRIBUTING.md for details.
+//
+//    ---------------------------------------------------------------------
+//     Compute bounds of a random grid function on a generated tensor mesh
+//    ---------------------------------------------------------------------
+//
+// This miniapp generates a 1D segment mesh or 2D quad mesh, builds a random
+// discontinuous grid function, computes element-wise piecewise linear bounds,
+// and visualizes the input field together with the lower and upper bounds.
+//
+// Compile with: make random-gridfunction-bounds
+//
+// Sample runs:
+//   mpirun -np 4 random-gridfunction-bounds
+//   mpirun -np 4 random-gridfunction-bounds -nx 64 -o 6 -ref 3 -d hip
+
+#include "mfem.hpp"
+
+#include <algorithm>
+#include <type_traits>
+
+using namespace mfem;
+using namespace std;
+
+void VisualizeField(ParMesh &pmesh, ParGridFunction &input,
+                    char *title, int pos_x, int pos_y);
+
+int main(int argc, char *argv[])
+{
+   Mpi::Init(argc, argv);
+   Hypre::Init();
+
+   int dim = 2;
+   int nx = 16;
+   int order = 4;
+   int num_comp = 2;
+   int ref = 2;
+   int niter = 1000;
+   int seed = 12345;
+   bool kernel_only = true;
+   bool visualization = false;
+   const char *device_config = "cpu";
+
+   OptionsParser args(argc, argv);
+   args.AddOption(&dim, "-dim", "--dimension",
+                  "Dimension of the generated tensor-product mesh (1 or 2).");
+   args.AddOption(&nx, "-nx", "--num-elements",
+                  "Number of elements in each mesh direction.");
+   args.AddOption(&order, "-o", "--order",
+                  "Polynomial degree of the random discontinuous field.");
+   args.AddOption(&num_comp, "-nc", "--num-components",
+                  "Number of vector components in the ParFiniteElementSpace.");
+   args.AddOption(&ref, "-ref", "--piecewise-linear-ref-factor",
+                  "Scaling factor for the resolution of the piecewise linear "
+                  "bounds. If less than 2, the resolution is picked "
+                  "automatically.");
+   args.AddOption(&niter, "-ni", "--num-iters",
+                  "Number of times to evaluate the bounds.");
+   args.AddOption(&seed, "-rs", "--random-seed",
+                  "Random seed used to initialize the field.");
+   args.AddOption(&device_config, "-d", "--device",
+                  "Device configuration string, see Device::Configure().");
+   args.AddOption(&kernel_only, "-ko", "--kernel-only",
+                  "-no-ko", "--no-kernel-only",
+                  "Run only PLBound::GetElementBoundsKernel on a prebuilt "
+                  "element E-vector.");
+   args.AddOption(&visualization, "-vis", "--visualization", "-no-vis",
+                  "--no-visualization",
+                  "Enable or disable GLVis visualization.");
+   args.ParseCheck();
+
+   MFEM_VERIFY(dim == 1 || dim == 2, "dim must be 1 or 2.");
+   MFEM_VERIFY(nx > 0, "nx must be positive.");
+   MFEM_VERIFY(order >= 0, "order must be non-negative.");
+   MFEM_VERIFY(num_comp > 0, "num_comp must be positive.");
+   MFEM_VERIFY(niter > 0, "niter must be positive.");
+
+   Device device(device_config);
+   if (Mpi::Root()) { device.Print(); }
+
+   Mesh mesh = (dim == 1) ?
+               Mesh::MakeCartesian1D(nx, 1.0) :
+               Mesh::MakeCartesian2D(nx, nx, Element::QUADRILATERAL, true,
+                                     1.0, 1.0);
+   ParMesh pmesh(MPI_COMM_WORLD, mesh);
+
+   const int mesh_dim = pmesh.Dimension();
+   L2_FECollection fec(order, mesh_dim, BasisType::GaussLobatto);
+   ParFiniteElementSpace fes(&pmesh, &fec, num_comp, Ordering::byNODES);
+   ParGridFunction input(&fes);
+   input.Randomize(seed + Mpi::WorldRank());
+   input.UseDevice(true);
+
+   L2_FECollection fec_pc(0, mesh_dim);
+   ParFiniteElementSpace fes_pc(&pmesh, &fec_pc, num_comp, Ordering::byNODES);
+   ParGridFunction lowerb(&fes_pc), upperb(&fes_pc);
+   Vector lower_vec, upper_vec;
+
+   PLBound plb(&fes, ref*(fes.GetMaxElementOrder() + 1));
+   if (kernel_only)
+   {
+      const FiniteElement &fe = *fes.GetTypicalFE();
+      const int rdim = fe.GetDim();
+      const int nd = fe.GetDof();
+      const int fes_dim = fes.GetVDim();
+      Vector e_vec(nd*fes_dim*fes.GetNE(), Device::GetDeviceMemoryType());
+      e_vec.UseDevice(true);
+
+      const ElementRestrictionOperator *elem_restr =
+         fes.GetElementRestriction(ElementDofOrdering::LEXICOGRAPHIC);
+      MFEM_VERIFY(elem_restr != nullptr,
+                  "Element restriction is required for kernel-only mode.");
+      elem_restr->Mult(input, e_vec);
+
+      for (int i = 0; i < niter; i++)
+      {
+         plb.GetElementBoundsKernel(rdim, fes_dim, e_vec, lower_vec, upper_vec);
+      }
+   }
+   else
+   {
+      for (int i = 0; i < niter; i++)
+      {
+         input.GetElementBounds(plb, lower_vec, upper_vec);
+      }
+   }
+
+   const real_t *lower_data = lower_vec.HostRead();
+   const real_t *upper_data = upper_vec.HostRead();
+
+   // Build a host reference from the lexicographic E-vector and the scalar
+   // PLBound::GetNDBounds path to avoid re-entering the device dispatch.
+   const bool use_dev = input.UseDevice();
+   PLBound plb_host(&fes, ref*(fes.GetMaxElementOrder() + 1));
+   Vector lower_ref, upper_ref;
+   const FiniteElement &fe = *fes.GetTypicalFE();
+   const int rdim = fe.GetDim();
+   const int nd = fe.GetDof();
+   const int nel = fes.GetNE();
+   const int fes_dim = fes.GetVDim();
+   Vector e_vec_ref(nd*fes_dim*nel);
+   lower_ref.SetSize(nel*fes_dim);
+   upper_ref.SetSize(nel*fes_dim);
+   const ElementRestrictionOperator *elem_restr =
+      fes.GetElementRestriction(ElementDofOrdering::LEXICOGRAPHIC);
+   MFEM_VERIFY(elem_restr != nullptr,
+               "Element restriction is required for host reference.");
+   input.UseDevice(false);
+   input.HostRead();
+   elem_restr->Mult(input, e_vec_ref);
+   input.UseDevice(use_dev);
+   const real_t *e_ref_data = e_vec_ref.HostRead();
+
+   for (int d = 0; d < fes_dim; d++)
+   {
+      for (int e = 0; e < nel; e++)
+      {
+         Vector coeff(nd);
+         for (int i = 0; i < nd; i++)
+         {
+            coeff(i) = e_ref_data[i + nd*(d + fes_dim*e)];
+         }
+         Vector lower_c, upper_c;
+         plb_host.GetNDBounds(rdim, coeff, lower_c, upper_c);
+         lower_ref(e + d*nel) = lower_c.Min();
+         upper_ref(e + d*nel) = upper_c.Max();
+      }
+   }
+   const real_t *lower_ref_data = lower_ref.HostRead();
+   const real_t *upper_ref_data = upper_ref.HostRead();
+
+   MFEM_VERIFY(lower_vec.Size() == lower_ref.Size() &&
+               upper_vec.Size() == upper_ref.Size(),
+               "Reference element-bound vectors have inconsistent sizes.");
+
+   real_t lower_diff = 0.0;
+   real_t upper_diff = 0.0;
+   for (int i = 0; i < lower_vec.Size(); i++)
+   {
+      lower_diff = std::max(lower_diff,
+                            std::abs(lower_data[i] - lower_ref_data[i]));
+   }
+   for (int i = 0; i < upper_vec.Size(); i++)
+   {
+      upper_diff = std::max(upper_diff,
+                            std::abs(upper_data[i] - upper_ref_data[i]));
+   }
+   MPI_Allreduce(MPI_IN_PLACE, &lower_diff, 1, MPITypeMap<real_t>::mpi_type,
+                 MPI_MAX, pmesh.GetComm());
+   MPI_Allreduce(MPI_IN_PLACE, &upper_diff, 1, MPITypeMap<real_t>::mpi_type,
+                 MPI_MAX, pmesh.GetComm());
+
+   const real_t verify_tol = std::is_same<real_t, float>::value ?
+                             real_t(1.0e-5) : real_t(1.0e-12);
+   MFEM_VERIFY(lower_diff <= verify_tol && upper_diff <= verify_tol,
+               "Device element bounds do not match host reference.");
+
+   lowerb = lower_vec;
+   upperb = upper_vec;
+
+   real_t lower_min = lowerb.Min();
+   real_t upper_max = upperb.Max();
+   MPI_Allreduce(MPI_IN_PLACE, &lower_min, 1, MPITypeMap<real_t>::mpi_type,
+                 MPI_MIN, pmesh.GetComm());
+   MPI_Allreduce(MPI_IN_PLACE, &upper_max, 1, MPITypeMap<real_t>::mpi_type,
+                 MPI_MAX, pmesh.GetComm());
+
+   if (Mpi::Root())
+   {
+      cout << "dim: " << mesh_dim << '\n'
+           << "nx: " << nx << '\n'
+           << "order: " << order << '\n'
+           << "num components: " << num_comp << '\n'
+           << "PL bound control-point factor: " << ref << '\n'
+           << "iterations: " << niter << '\n'
+           << "kernel-only mode: " << (kernel_only ? "yes" : "no") << '\n'
+           << "host/device lower max diff: " << lower_diff << '\n'
+           << "host/device upper max diff: " << upper_diff << '\n'
+           << "global lower bound minimum: " << lower_min << '\n'
+           << "global upper bound maximum: " << upper_max << endl;
+   }
+
+   if (visualization)
+   {
+      char title1[] = "Random input gridfunction";
+      char title2[] = "Element-wise lower bound";
+      char title3[] = "Element-wise upper bound";
+      VisualizeField(pmesh, input, title1, 0, 0);
+      VisualizeField(pmesh, lowerb, title2, 450, 0);
+      VisualizeField(pmesh, upperb, title3, 900, 0);
+   }
+
+   return 0;
+}
+
+void VisualizeField(ParMesh &pmesh, ParGridFunction &input,
+                    char *title, int pos_x, int pos_y)
+{
+   socketstream sock;
+   if (pmesh.GetMyRank() == 0)
+   {
+      sock.open("localhost", 19916);
+      sock << "solution\n";
+   }
+   pmesh.PrintAsOne(sock);
+   input.SaveAsOne(sock);
+   if (pmesh.GetMyRank() == 0)
+   {
+      sock << "window_title '" << title << "'\n"
+           << "window_geometry "
+           << pos_x << " " << pos_y << " " << 400 << " " << 400 << "\n"
+           << "keys jRmclApppppppppppp//]]]]]]]]" << endl;
+   }
+}