[arrayfire] 136/248: Port shallow water eq example from 2.1

[Ghislain Vaillant]

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ghisvail-guest pushed a commit to branch dfsg-clean
in repository arrayfire.

commit c23e49bb53a26d4945ec3749672a884d2d70cc66
Author: Umar Arshad <umar at arrayfire.com>
Date:   Mon Oct 19 16:53:11 2015 -0400

    Port shallow water eq example from 2.1
---
 examples/common/progress.h |  2 +-
 examples/pde/swe.cpp       | 86 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 1 deletion(-)

diff --git a/examples/common/progress.h b/examples/common/progress.h
index debb511..6452aa2 100644
--- a/examples/common/progress.h
+++ b/examples/common/progress.h
@@ -36,7 +36,7 @@ static bool progress(unsigned iter_curr, af::timer t, double time_total)
 
     if (time_curr < time_total) return true;
 
-    printf(" ### vortex %f iterations per second (max)\n", max_rate);
+    printf(" ### %f iterations per second (max)\n", max_rate);
     return false;
 }
 
diff --git a/examples/pde/swe.cpp b/examples/pde/swe.cpp
new file mode 100644
index 0000000..84ce1ff
--- /dev/null
+++ b/examples/pde/swe.cpp
@@ -0,0 +1,86 @@
+#include <math.h>
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+#include <arrayfire.h>
+#include "../common/progress.h"
+
+using namespace af;
+
+Window *win;
+
+array normalize(array a, float max)
+{
+    float mx = max * 0.5;
+    float mn = -max * 0.5;
+    return (a-mn)/(mx-mn);
+}
+
+static void swe(bool console)
+{
+    double time_total = 20; // run for N seconds
+    // Grid length, number and spacing
+    const unsigned Lx = 512, nx = Lx + 1;
+    const unsigned Ly = 512, ny = Ly + 1;
+    const float dx = Lx / (nx - 1);
+    const float dy = Ly / (ny - 1);
+
+    array ZERO = constant(0, nx, ny);
+    array um = ZERO, vm = ZERO;
+    unsigned io = (unsigned)floor(Lx  / 5.0f),
+             jo = (unsigned)floor(Ly / 5.0f),
+             k = 20;
+    array x = tile(moddims(seq(nx),nx,1), 1,ny);
+    array y = tile(moddims(seq(ny),1,ny), nx,1);
+
+    // Initial condition
+    array etam = 0.01f * exp((-((x - io) * (x - io) + (y - jo) * (y - jo))) / (k * k));
+    float m_eta = max<float>(etam);
+    array eta = etam;
+    float dt = 0.5;
+
+    // conv kernels
+    float h_diff_kernel[] = {9.81f * (dt / dx), 0, -9.81f * (dt / dx)};
+    float h_lap_kernel[] = {0, 1, 0, 1, -4, 1, 0, 1, 0};
+
+    array h_diff_kernel_arr(3, h_diff_kernel);
+    array h_lap_kernel_arr(3, 3, h_lap_kernel);
+
+    if(!console) {
+        win = new Window(512, 512,"Shallow Water Equations");
+        win->setColorMap(AF_COLORMAP_MOOD);
+    }
+
+    timer t = timer::start();
+    unsigned iter = 0;
+    while (progress(iter, t, time_total)) {
+        // compute
+        array up = um + convolve(eta, h_diff_kernel_arr);
+        array vp = um + convolve(eta, h_diff_kernel_arr.T());
+        array e = convolve(eta, h_lap_kernel_arr);
+        array etap = 2 * eta - etam + (2 * dt * dt) / (dx * dy) * e;
+
+        etam = eta;
+        eta = etap;
+        if (!console) {
+            win->image(normalize(eta, m_eta));
+            // viz
+        } else eval(eta, up, vp);
+        iter++;
+    }
+}
+int main(int argc, char* argv[])
+{
+    int device = argc > 1 ? atoi(argv[1]) : 0;
+    bool console = argc > 2 ? argv[2][0] == '-' : false;
+    try {
+        af::setDevice(device);
+        af::info();
+        printf("Simulation of shallow water equations\n");
+        swe(console);
+    } catch (af::exception& e) {
+        fprintf(stderr, "%s\n", e.what());
+        throw;
+    }
+    return 0;
+}

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