improve built-in function "sinpi"

"sinpi" was calculated as "sin(pi * x)".
But that was not a quite-good way.
This patch improved the function, also included a test case.

v2: fix compiling warning

Signed-off-by: Homer Hsing <homer.xing@intel.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/utests/builtin_sinpi.cpp b/utests/builtin_sinpi.cpp
new file mode 100644
index 00000000..0e11a0d7
--- /dev/null
+++ b/utests/builtin_sinpi.cpp
@@ -0,0 +1,104 @@
+#include <cmath>
+#include "utest_helper.hpp"
+
+static int as_int(float x) {
+  union {float f; int i;} u;
+  u.f = x;
+  return u.i;
+}
+
+static float sinpi(float x) {
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+  float y, z;
+  int n = 0, ix;
+  const float pi = 3.1415927410e+00f;
+
+  ix = as_int(x) & 0x7fffffff;
+
+  if (ix < 0x3e800000)
+    return sinf(pi * x);
+  y = -x;
+  z = floorf(y);
+  if (z != y) {
+    y *= 0.5f;
+    y = 2.f * (y - floorf(y));
+    n = y * 4.f;
+  } else {
+    if (ix >= 0x4b800000) {
+      y = 0;
+      n = 0;
+    } else {
+      if (ix < 0x4b000000)
+        z = y + 8.3886080000e+06f;
+      int n = as_int(z);
+      n &= 1;
+      y = n;
+      n <<= 2;
+    }
+  }
+  switch (n) {
+  case 0:
+    y = sinf(pi * y);
+    break;
+  case 1:
+  case 2:
+    y = cosf(pi * ((float) 0.5 - y));
+    break;
+  case 3:
+  case 4:
+    y = sinf(pi * (1.f - y));
+    break;
+  case 5:
+  case 6:
+    y = -cosf(pi * (y - (float) 1.5));
+    break;
+  default:
+    y = sinf(pi * (y - (float) 2.0));
+    break;
+  }
+  return -y;
+}
+
+void builtin_sinpi(void)
+{
+  const int n = 1024;
+  float src[n];
+
+  // Setup kernel and buffers
+  OCL_CREATE_KERNEL("builtin_sinpi");
+  OCL_CREATE_BUFFER(buf[0], 0, n * sizeof(float), NULL);
+  OCL_CREATE_BUFFER(buf[1], 0, n * sizeof(float), NULL);
+  OCL_SET_ARG(0, sizeof(cl_mem), &buf[0]);
+  OCL_SET_ARG(1, sizeof(cl_mem), &buf[1]);
+  globals[0] = n;
+  locals[0] = 16;
+
+  for (int j = 0; j < 1000; j ++) {
+    OCL_MAP_BUFFER(0);
+    for (int i = 0; i < n; ++i) {
+      src[i] = ((float*)buf_data[0])[i] = (j*n + i) * 0.01f;
+    }
+    OCL_UNMAP_BUFFER(0);
+
+    OCL_NDRANGE(1);
+
+    OCL_MAP_BUFFER(1);
+    float *dst = (float*)buf_data[1];
+    for (int i = 0; i < n; ++i) {
+      float cpu = sinpi(src[i]);
+      OCL_ASSERT (fabsf(cpu - dst[i]) < 1e-4);
+    }
+    OCL_UNMAP_BUFFER(1);
+  }
+}
+
+MAKE_UTEST_FROM_FUNCTION(builtin_sinpi);