Fix ES kernel for ns=2 sigma=2

Author: DiamonDinoia

src/finufft_core.cpp

@@ -569,8 +569,8 @@ template<typename TF> void FINUFFT_PLAN_T<TF>::precompute_horner_coeffs() {
     // coeffs[0] is highest degree.
     int used = 0;
     for (size_t k = 0; k < coeffs.size(); ++k) {
-      if (std::abs(coeffs[k]) >= tol * 0.50) { // divide tol by 5 otherwise it fails in
-                                               // some cases
+      if (std::abs(coeffs[k]) >= tol * 0.5) { // divide tol by 2 otherwise it fails in
+                                              // some cases
         used = static_cast<int>(coeffs.size() - k);
         break;
       }

src/spreadinterp.cpp

@@ -2057,6 +2057,8 @@ int setup_spreader(finufft_spread_opts &opts, T eps, double upsampfac, int kerev
   }
   // Compute ns (kernel width) using central helper; caller handles clipping.
   ns = compute_kernel_ns(upsampfac, (double)eps, kernel_type, opts);
+  // ns == 2 breaks for float with upsampfact = 2.00
+  if (std::is_same_v<T, float> && upsampfac == 2.00) ns = std::max(ns, 3);
   if (ns > MAX_NSPREAD) {
     // clip to fit allocated arrays, Horner rules
     if (showwarn)

test/CMakeLists.txt

@@ -46,14 +46,7 @@ if(NOT FINUFFT_USE_DUCC0 AND FINUFFT_USE_OPENMP)
 endif()
 
 # Add ctest definitions that run at both precisions...
-function(
-    add_tests_with_prec
-    PREC
-    REQ_TOL
-    CHECK_TOL
-    SUFFIX
-    MAX_DIGITS
-)
+function(add_tests_with_prec PREC REQ_TOL CHECK_TOL SUFFIX)
     # All of the following should be run at OMP_NUM_THREADS=4 or something small,
     # as in makefile. This prevents them taking a huge time on a, say, 128-core
     # Rome node. ... but I don't know platform-indep way to do that! Does anyone?
@@ -111,5 +104,5 @@ endfunction()
 
 # use above function to actually add the tests, with certain requested and check
 # tols
-add_tests_with_prec(float 1e-5 2e-4 f 5)
-add_tests_with_prec(double 1e-12 1e-11 "" 15)
+add_tests_with_prec(float 1e-5 2e-4 f)
+add_tests_with_prec(double 1e-12 1e-11 "")