Starts working on the 1D version of Helpmholtz operator

src/operators/HelmholtzOperator1d.cpp

@@ -0,0 +1,80 @@
+/*
+ * MRCPP, a numerical library based on multiresolution analysis and
+ * the multiwavelet basis which provide low-scaling algorithms as well as
+ * rigorous error control in numerical computations.
+ * Copyright (C) 2021 Stig Rune Jensen, Jonas Juselius, Luca Frediani and contributors.
+ *
+ * This file is part of MRCPP.
+ *
+ * MRCPP is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * MRCPP is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with MRCPP.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * For information on the complete list of contributors to MRCPP, see:
+ * <https://mrcpp.readthedocs.io/>
+ */
+
+#include "HelmholtzOperator1d.h"
+#include "HelmholtzKernel.h"
+#include "utils/Printer.h"
+
+namespace mrcpp {
+
+/** @returns New HelmholtzOperator object
+ *  @param[in] mra: Which MRA the operator is defined
+ *  @param[in] m: Exponential parameter of the operator
+ *  @param[in] pr: Build precision, closeness to exp(-mu*r)/r
+ *  @details This will construct a gaussian expansion to approximate
+ *  exp(-mu*r)/r, and project each term into a one-dimensional MW operator.
+ *  Subsequent application of this operator will apply each of the terms to
+ *  the input function in all Cartesian directions.
+ */
+HelmholtzOperator::HelmholtzOperator(const MultiResolutionAnalysis<3> &mra, double mu, double prec)
+        : ConvolutionOperator<3>(mra) {
+    int oldlevel = Printer::setPrintLevel(0);
+
+    this->setBuildPrec(prec);
+    double o_prec = prec;
+    double k_prec = prec / 10.0;
+    double r_min = this->MRA.calcMinDistance(k_prec);
+    double r_max = this->MRA.calcMaxDistance();
+
+    HelmholtzKernel kernel(mu, k_prec, r_min, r_max);
+    initialize(kernel, k_prec, o_prec);
+    this->initOperExp(kernel.size());
+
+    Printer::setPrintLevel(oldlevel);
+}
+
+HelmholtzOperator::HelmholtzOperator(const MultiResolutionAnalysis<3> &mra, double mu, double prec, int root, int reach)
+        : ConvolutionOperator<3>(mra, root, reach) {
+    int oldlevel = Printer::setPrintLevel(0);
+
+    this->setBuildPrec(prec);
+    double o_prec = prec;
+    double k_prec = prec / 100.0;
+    double r_min = this->MRA.calcMinDistance(k_prec);
+    double r_max = this->MRA.calcMaxDistance();
+
+    // Adjust r_max for periodic world
+    auto rel_root = this->oper_root - this->MRA.getRootScale();
+    r_max *= std::pow(2.0, -rel_root);
+    r_max *= (2.0 * this->oper_reach) + 1.0;
+
+    HelmholtzKernel kernel(mu, k_prec, r_min, r_max);
+    initialize(kernel, k_prec, o_prec);
+    this->initOperExp(kernel.size());
+
+    Printer::setPrintLevel(oldlevel);
+}
+
+} // namespace mrcpp

src/operators/HelmholtzOperator1d.h

@@ -0,0 +1,51 @@
+/*
+ * MRCPP, a numerical library based on multiresolution analysis and
+ * the multiwavelet basis which provide low-scaling algorithms as well as
+ * rigorous error control in numerical computations.
+ * Copyright (C) 2021 Stig Rune Jensen, Jonas Juselius, Luca Frediani and contributors.
+ *
+ * This file is part of MRCPP.
+ *
+ * MRCPP is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * MRCPP is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with MRCPP.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * For information on the complete list of contributors to MRCPP, see:
+ * <https://mrcpp.readthedocs.io/>
+ */
+
+#pragma once
+
+#include "ConvolutionOperator.h"
+
+namespace mrcpp {
+
+/** @class HelmholtzOperator1d
+ *
+ * @brief Convolution with the Helmholtz Green's function kernel for the one-dimensional case
+ *
+ * @details The 1d Helmholtz kernel is a single Slater-type function
+ * 
+ * \f$ H(r-r') = \frac{1}{2k} e^{-k}{|x-x'|} \f$
+ */
+
+
+class HelmholtzOperator1d final : public ConvolutionOperator<3> {
+public:
+    HelmholtzOperator1d(const MultiResolutionAnalysis<3> &mra, double k, double prec);
+    HelmholtzOperator1d(const MultiResolutionAnalysis<3> &mra, double k, double prec, int root, int reach = 1);
+    HelmholtzOperator1d(const HelmholtzOperator1d &oper) = delete;
+    HelmholtzOperator1d &operator=(const HelmholtzOperator1d &oper) = delete;
+};
+
+} // namespace mrcpp
+