1 files changed, 232 insertions, 0 deletions
diff --git a/tesseract/src/lstm/functions.h b/tesseract/src/lstm/functions.h
new file mode 100644
index 00000000..9cc447da
--- /dev/null
+++ b/tesseract/src/lstm/functions.h
@@ -0,0 +1,232 @@
+///////////////////////////////////////////////////////////////////////
+// File:        functions.h
+// Description: Collection of function-objects used by the network layers.
+// Author:      Ray Smith
+//
+// (C) Copyright 2014, Google Inc.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+///////////////////////////////////////////////////////////////////////
+
+#ifndef TESSERACT_LSTM_FUNCTIONS_H_
+#define TESSERACT_LSTM_FUNCTIONS_H_
+
+#include "helpers.h"
+
+// Setting this to 1 or more causes massive dumps of debug data: weights,
+// updates, internal calculations etc, and reduces the number of test iterations
+// to a small number, so outputs can be diffed.
+#define DEBUG_DETAIL 0
+#if DEBUG_DETAIL > 0
+#undef _OPENMP  // Disable open mp to get the outputs in sync.
+#endif
+
+namespace tesseract {
+
+// Size of static tables.
+constexpr int kTableSize = 4096;
+// Scale factor for float arg to int index.
+constexpr double kScaleFactor = 256.0;
+
+// Generated lookup tables.
+extern const double TanhTable[];
+extern const double LogisticTable[];
+
+// Non-linearity (sigmoid) functions with cache tables and clipping.
+inline double Tanh(double x) {
+  if (x < 0.0) return -Tanh(-x);
+  x *= kScaleFactor;
+  unsigned index = static_cast<unsigned>(x);
+  if (index >= (kTableSize - 1)) return 1.0;
+  double tanh_i0 = TanhTable[index];
+  double tanh_i1 = TanhTable[index + 1];
+  // Linear interpolation.
+  return tanh_i0 + (tanh_i1 - tanh_i0) * (x - index);
+}
+
+inline double Logistic(double x) {
+  if (x < 0.0) return 1.0 - Logistic(-x);
+  x *= kScaleFactor;
+  unsigned index = static_cast<unsigned>(x);
+  if (index >= (kTableSize - 1)) return 1.0;
+  double l0 = LogisticTable[index];
+  double l1 = LogisticTable[index + 1];
+  // Linear interpolation.
+  return l0 + (l1 - l0) * (x - index);
+}
+
+// Non-linearity (sigmoid) functions and their derivatives.
+struct FFunc {
+  inline double operator()(double x) const { return Logistic(x); }
+};
+struct FPrime {
+  inline double operator()(double y) const { return y * (1.0 - y); }
+};
+struct ClipFFunc {
+  inline double operator()(double x) const {
+    if (x <= 0.0) return 0.0;
+    if (x >= 1.0) return 1.0;
+    return x;
+  }
+};
+struct ClipFPrime {
+  inline double operator()(double y) const {
+    return 0.0 < y && y < 1.0 ? 1.0 : 0.0;
+  }
+};
+struct Relu {
+  inline double operator()(double x) const {
+    if (x <= 0.0) return 0.0;
+    return x;
+  }
+};
+struct ReluPrime {
+  inline double operator()(double y) const { return 0.0 < y ? 1.0 : 0.0; }
+};
+struct GFunc {
+  inline double operator()(double x) const { return Tanh(x); }
+};
+struct GPrime {
+  inline double operator()(double y) const { return 1.0 - y * y; }
+};
+struct ClipGFunc {
+  inline double operator()(double x) const {
+    if (x <= -1.0) return -1.0;
+    if (x >= 1.0) return 1.0;
+    return x;
+  }
+};
+struct ClipGPrime {
+  inline double operator()(double y) const {
+    return -1.0 < y && y < 1.0 ? 1.0 : 0.0;
+  }
+};
+struct HFunc {
+  inline double operator()(double x) const { return Tanh(x); }
+};
+struct HPrime {
+  inline double operator()(double y) const {
+    double u = Tanh(y);
+    return 1.0 - u * u;
+  }
+};
+struct UnityFunc {
+  inline double operator()(double /*x*/) const { return 1.0; }
+};
+struct IdentityFunc {
+  inline double operator()(double x) const { return x; }
+};
+
+// Applies Func in-place to inout, of size n.
+template <class Func>
+inline void FuncInplace(int n, double* inout) {
+  Func f;
+  for (int i = 0; i < n; ++i) {
+    inout[i] = f(inout[i]);
+  }
+}
+// Applies Func to u and multiplies the result by v component-wise,
+// putting the product in out, all of size n.
+template <class Func>
+inline void FuncMultiply(const double* u, const double* v, int n, double* out) {
+  Func f;
+  for (int i = 0; i < n; ++i) {
+    out[i] = f(u[i]) * v[i];
+  }
+}
+// Applies the Softmax function in-place to inout, of size n.
+template <typename T>
+inline void SoftmaxInPlace(int n, T* inout) {
+  if (n <= 0) return;
+  // A limit on the negative range input to exp to guarantee non-zero output.
+  const T kMaxSoftmaxActivation = 86.0f;
+
+  T max_output = inout[0];
+  for (int i = 1; i < n; i++) {
+    T output = inout[i];
+    if (output > max_output) max_output = output;
+  }
+  T prob_total = 0.0;
+  for (int i = 0; i < n; i++) {
+    T prob = inout[i] - max_output;
+    prob = exp(ClipToRange(prob, -kMaxSoftmaxActivation, static_cast<T>(0)));
+    prob_total += prob;
+    inout[i] = prob;
+  }
+  if (prob_total > 0.0) {
+    for (int i = 0; i < n; i++) inout[i] /= prob_total;
+  }
+}
+
+// Copies n values of the given src vector to dest.
+inline void CopyVector(int n, const double* src, double* dest) {
+  memcpy(dest, src, n * sizeof(dest[0]));
+}
+
+// Adds n values of the given src vector to dest.
+inline void AccumulateVector(int n, const double* src, double* dest) {
+  for (int i = 0; i < n; ++i) dest[i] += src[i];
+}
+
+// Multiplies n values of inout in-place element-wise by the given src vector.
+inline void MultiplyVectorsInPlace(int n, const double* src, double* inout) {
+  for (int i = 0; i < n; ++i) inout[i] *= src[i];
+}
+
+// Multiplies n values of u by v, element-wise, accumulating to out.
+inline void MultiplyAccumulate(int n, const double* u, const double* v,
+                               double* out) {
+  for (int i = 0; i < n; i++) {
+    out[i] += u[i] * v[i];
+  }
+}
+
+// Sums the given 5 n-vectors putting the result into sum.
+inline void SumVectors(int n, const double* v1, const double* v2,
+                       const double* v3, const double* v4, const double* v5,
+                       double* sum) {
+  for (int i = 0; i < n; ++i) {
+    sum[i] = v1[i] + v2[i] + v3[i] + v4[i] + v5[i];
+  }
+}
+
+// Sets the given n-vector vec to 0.
+template <typename T>
+inline void ZeroVector(int n, T* vec) {
+  memset(vec, 0, n * sizeof(*vec));
+}
+
+// Clips the given vector vec, of size n to [lower, upper].
+template <typename T>
+inline void ClipVector(int n, T lower, T upper, T* vec) {
+  for (int i = 0; i < n; ++i) vec[i] = ClipToRange(vec[i], lower, upper);
+}
+
+// Converts the given n-vector to a binary encoding of the maximum value,
+// encoded as vector of nf binary values.
+inline void CodeInBinary(int n, int nf, double* vec) {
+  if (nf <= 0 || n < nf) return;
+  int index = 0;
+  double best_score = vec[0];
+  for (int i = 1; i < n; ++i) {
+    if (vec[i] > best_score) {
+      best_score = vec[i];
+      index = i;
+    }
+  }
+  int mask = 1;
+  for (int i = 0; i < nf; ++i, mask *= 2) {
+    vec[i] = (index & mask) ? 1.0 : 0.0;
+  }
+}
+
+}  // namespace tesseract.
+
+#endif  // TESSERACT_LSTM_FUNCTIONS_H_