Sync from v0.13

csrc/cpu/float_convert.hpp

@@ -0,0 +1,106 @@
+
+static float bf16_to_float(uint16_t bf16) {
+  uint32_t bits = static_cast<uint32_t>(bf16) << 16;
+  float fp32;
+  std::memcpy(&fp32, &bits, sizeof(fp32));
+  return fp32;
+}
+
+static uint16_t float_to_bf16(float fp32) {
+  uint32_t bits;
+  std::memcpy(&bits, &fp32, sizeof(fp32));
+  return static_cast<uint16_t>(bits >> 16);
+}
+
+/************************************************
+ * Copyright (c) 2015 Princeton Vision Group
+ * Licensed under the MIT license.
+ * Codes below copied from
+ * https://github.com/PrincetonVision/marvin/tree/master/tools/tensorIO_matlab
+ *************************************************/
+static uint16_t float_to_fp16(float fp32) {
+  uint16_t fp16;
+
+  unsigned x;
+  unsigned u, remainder, shift, lsb, lsb_s1, lsb_m1;
+  unsigned sign, exponent, mantissa;
+
+  std::memcpy(&x, &fp32, sizeof(fp32));
+  u = (x & 0x7fffffff);
+
+  // Get rid of +NaN/-NaN case first.
+  if (u > 0x7f800000) {
+    fp16 = 0x7fffU;
+    return fp16;
+  }
+
+  sign = ((x >> 16) & 0x8000);
+
+  // Get rid of +Inf/-Inf, +0/-0.
+  if (u > 0x477fefff) {
+    fp16 = sign | 0x7c00U;
+    return fp16;
+  }
+  if (u < 0x33000001) {
+    fp16 = (sign | 0x0000);
+    return fp16;
+  }
+
+  exponent = ((u >> 23) & 0xff);
+  mantissa = (u & 0x7fffff);
+
+  if (exponent > 0x70) {
+    shift = 13;
+    exponent -= 0x70;
+  } else {
+    shift = 0x7e - exponent;
+    exponent = 0;
+    mantissa |= 0x800000;
+  }
+  lsb = (1 << shift);
+  lsb_s1 = (lsb >> 1);
+  lsb_m1 = (lsb - 1);
+
+  // Round to nearest even.
+  remainder = (mantissa & lsb_m1);
+  mantissa >>= shift;
+  if (remainder > lsb_s1 || (remainder == lsb_s1 && (mantissa & 0x1))) {
+    ++mantissa;
+    if (!(mantissa & 0x3ff)) {
+      ++exponent;
+      mantissa = 0;
+    }
+  }
+
+  fp16 = (sign | (exponent << 10) | mantissa);
+
+  return fp16;
+}
+
+static float fp16_to_float(uint16_t fp16) {
+  unsigned sign = ((fp16 >> 15) & 1);
+  unsigned exponent = ((fp16 >> 10) & 0x1f);
+  unsigned mantissa = ((fp16 & 0x3ff) << 13);
+  int temp;
+  float fp32;
+  if (exponent == 0x1f) { /* NaN or Inf */
+    mantissa = (mantissa ? (sign = 0, 0x7fffff) : 0);
+    exponent = 0xff;
+  } else if (!exponent) { /* Denorm or Zero */
+    if (mantissa) {
+      unsigned int msb;
+      exponent = 0x71;
+      do {
+        msb = (mantissa & 0x400000);
+        mantissa <<= 1; /* normalize */
+        --exponent;
+      } while (!msb);
+      mantissa &= 0x7fffff; /* 1.mantissa is implicit */
+    }
+  } else {
+    exponent += 0x70;
+  }
+  temp = ((sign << 31) | (exponent << 23) | mantissa);
+  std::memcpy(&fp32, &temp, sizeof(temp));
+  return fp32;
+}