Add new example with implementation of Perlin Noise

~4.2x speedup versus serial on OSX / gcc.
~2.9x speedup versus serial on Windows / MSVC.

examples/noise/noise.cpp

@@ -0,0 +1,150 @@
+/*
+  Copyright (c) 2010-2011, Intel Corporation
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are
+  met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+
+    * Neither the name of Intel Corporation nor the names of its
+      contributors may be used to endorse or promote products derived from
+      this software without specific prior written permission.
+
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
+*/
+
+#ifdef _MSC_VER
+#define _CRT_SECURE_NO_WARNINGS
+#define NOMINMAX
+#pragma warning (disable: 4244)
+#pragma warning (disable: 4305)
+#endif
+
+#include <stdio.h>
+#include <algorithm>
+#include "../timing.h"
+#include "../cpuid.h"
+#include "noise_ispc.h"
+using namespace ispc;
+
+extern void noise_serial(float x0, float y0, float x1, float y1,
+                         int width, int height, float output[]);
+
+/* Write a PPM image file with the image */
+static void
+writePPM(float *buf, int width, int height, const char *fn) {
+    FILE *fp = fopen(fn, "wb");
+    fprintf(fp, "P6\n");
+    fprintf(fp, "%d %d\n", width, height);
+    fprintf(fp, "255\n");
+    for (int i = 0; i < width*height; ++i) {
+        float v = buf[i] * 255.f;
+        if (v < 0) v = 0;
+        if (v > 255) v = 255;
+        for (int j = 0; j < 3; ++j)
+            fputc((char)v, fp);
+    }
+    fclose(fp);
+}
+
+
+// Make sure that the vector ISA used during compilation is supported by
+// the processor.  The ISPC_TARGET_* macro is set in the ispc-generated
+// header file that we include above.
+static void
+ensureTargetISAIsSupported() {
+#if defined(ISPC_TARGET_SSE2)
+    bool isaSupported = CPUSupportsSSE2();
+    const char *target = "SSE2";
+#elif defined(ISPC_TARGET_SSE4)
+    bool isaSupported = CPUSupportsSSE4();
+    const char *target = "SSE4";
+#elif defined(ISPC_TARGET_AVX)
+    bool isaSupported = CPUSupportsAVX();
+    const char *target = "AVX";
+#else
+#error "Unknown ISPC_TARGET_* value"
+#endif
+    if (!isaSupported) {
+        fprintf(stderr, "***\n*** Error: the ispc-compiled code uses the %s instruction "
+                "set, which isn't\n***        supported by this computer's CPU!\n", target);
+        fprintf(stderr, "***\n***        Please modify the "
+#ifdef _MSC_VER
+                "MSVC project file "
+#else
+                "Makefile "
+#endif
+                "to select another target (e.g. sse2)\n***\n");
+        exit(1);
+    }
+}
+
+
+int main() {
+    unsigned int width = 768;
+    unsigned int height = 768;
+    float x0 = -10;
+    float x1 = 10;
+    float y0 = -10;
+    float y1 = 10;
+
+    float *buf = new float[width*height];
+
+    ensureTargetISAIsSupported();
+
+    //
+    // Compute the image using the ispc implementation; report the minimum
+    // time of three runs.
+    //
+    double minISPC = 1e30;
+    for (int i = 0; i < 3; ++i) {
+        reset_and_start_timer();
+        noise_ispc(x0, y0, x1, y1, width, height, buf);
+        double dt = get_elapsed_mcycles();
+        minISPC = std::min(minISPC, dt);
+    }
+
+    printf("[noise ispc]:\t\t\t[%.3f] million cycles\n", minISPC);
+    writePPM(buf, width, height, "noise-ispc.ppm");
+
+    // Clear out the buffer
+    for (unsigned int i = 0; i < width * height; ++i)
+        buf[i] = 0;
+
+    // 
+    // And run the serial implementation 3 times, again reporting the
+    // minimum time.
+    //
+    double minSerial = 1e30;
+    for (int i = 0; i < 3; ++i) {
+        reset_and_start_timer();
+        noise_serial(x0, y0, x1, y1, width, height, buf);
+        double dt = get_elapsed_mcycles();
+        minSerial = std::min(minSerial, dt);
+    }
+
+    printf("[noise serial]:\t\t\t[%.3f] millon cycles\n", minSerial);
+    writePPM(buf, width, height, "noise-serial.ppm");
+
+    printf("\t\t\t\t(%.2fx speedup from ISPC)\n", minSerial/minISPC);
+
+    return 0;
+}