added simd_exp2 func and test

Geolm · Jan 19, 2024 · 4105129 · 4105129
1 parent bd33677
commit 4105129
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diff --git a/extra/simd_math.c b/extra/simd_math.c
@@ -174,6 +174,33 @@ simd_vector simd_exp(simd_vector x)
     return y;
 }
 
+//----------------------------------------------------------------------------------------------------------------------
+// based on https://github.com/jeremybarnes/cephes/blob/master/single/exp2f.c
+simd_vector simd_exp2(simd_vector x)
+{
+    // clamp values
+    x = simd_clamp(x, simd_splat(-127.f), simd_splat(127.f));
+    simd_vector equal_to_zero = simd_cmp_eq(x, simd_splat_zero());
+
+    simd_vector i0 = simd_floor(x);
+    x = simd_sub(x, i0);
+
+    simd_vector above_half = simd_cmp_gt(x, simd_splat(.5f));
+    simd_vector one = simd_splat(1.f);
+    i0 = simd_select(i0, simd_add(i0, one), above_half);
+    x = simd_select(x, simd_sub(x, one), above_half);
+
+    simd_vector px = simd_fmad(x, simd_splat(1.535336188319500E-004f), simd_splat(1.339887440266574E-003f));
+    px = simd_fmad(px, x, simd_splat(9.618437357674640E-003f));
+    px = simd_fmad(px, x, simd_splat(5.550332471162809E-002f));
+    px = simd_fmad(px, x, simd_splat(2.402264791363012E-001f));
+    px = simd_fmad(px, x, simd_splat(6.931472028550421E-001f));
+    px = simd_fmad(px, x,  one);
+    px = simd_ldexp(px, i0);
+
+    return simd_select(px, one, equal_to_zero);
+}
+
 //----------------------------------------------------------------------------------------------------------------------
 // based on http://gruntthepeon.free.fr/ssemath/
 void simd_sincos(simd_vector x, simd_vector* s, simd_vector* c)

diff --git a/extra/simd_math.h b/extra/simd_math.h
@@ -45,6 +45,9 @@ simd_vector simd_log2(simd_vector x);
 // max error : 1.108270880e-07
 simd_vector simd_exp(simd_vector x);
 
+// max error : 1.042427087e-07
+simd_vector simd_exp2(simd_vector x);
+
 // max error : 4.768371582e-07
 simd_vector simd_cbrt(simd_vector x);
 

diff --git a/tests/test_simd_math.h b/tests/test_simd_math.h
@@ -157,6 +157,7 @@ SUITE(exponentiation)
     RUN_TESTp(generic_test, logf, simd_log, FLT_EPSILON, 1000.f, 1.e-06f, true, "simd_log");
     RUN_TESTp(generic_test, log2f, simd_log2, FLT_EPSILON, 1.e20f, 3.e-07f, true, "simd_log2");
     RUN_TESTp(generic_test, expf, simd_exp, -87.f, 87.f, 1.e-06f, true, "simd_exp");
+    RUN_TESTp(generic_test, exp2f, simd_exp2, -126.f, 126.f, 2.e-07f, true, "simd_exp2");
     RUN_TESTp(generic_test, expf, simd_approx_exp, -87.f, 87.f, 2.e-03f, true, "simd_approx_exp");
     RUN_TESTp(generic_test, cbrtf, simd_cbrt, -100.f, 100.f, 2.e-07f, true, "simd_cbrt");
 }