Use std:: qualified math functions to avoid float-to-double promotion (#5088)

Summary:

Fix 4 `performance-type-promotion-in-math-fn` lint warnings by using `std::floor`, `std::fabs`, and `std::pow` instead of the unqualified C versions. The unqualified versions promote `float` arguments to `double`, causing unnecessary precision loss and performance overhead. Also added missing `#include <cmath>` in `IndexIVFSpectralHash.cpp`.

Differential Revision: D100576274

Author: junjieqi

faiss/IndexIVFSpectralHash.cpp

@@ -10,6 +10,7 @@
 #include <faiss/IndexIVFSpectralHash.h>
 
 #include <algorithm>
+#include <cmath>
 #include <cstdint>
 #include <memory>
 
@@ -159,7 +160,7 @@ void binarize_with_freq(
     memset(codes, 0, (nbit + 7) / 8);
     for (size_t i = 0; i < nbit; i++) {
         float xf = (x[i] - c[i]);
-        int64_t xi = int64_t(floor(xf * freq));
+        int64_t xi = int64_t(std::floor(xf * freq));
         int64_t bit = xi & 1;
         codes[i >> 3] |= bit << (i & 7);
     }

faiss/VectorTransform.cpp

@@ -279,7 +279,7 @@ void LinearTransform::set_is_orthonormal() {
                 float v = ATA[i + j * d_out];
                 if (i == j)
                     v -= 1;
-                if (fabs(v) > eps) {
+                if (std::fabs(v) > eps) {
                     is_orthonormal = false;
                 }
             }
@@ -773,7 +773,7 @@ void PCAMatrix::prepare_Ab() {
         if (eigen_power != 0) {
             float* ai = A.data();
             for (int i = 0; i < d_out; i++) {
-                float factor = pow(eigenvalues[i] + epsilon, eigen_power);
+                float factor = std::pow(eigenvalues[i] + epsilon, eigen_power);
                 for (int j = 0; j < d_in; j++)
                     *ai++ *= factor;
             }