Add sqrt tests from assignment 1

tests_ispcpp/sqrt.ispc

@@ -0,0 +1,62 @@
+
+static const float kThreshold = 0.00001f;
+
+export void sqrt_ispc(uniform int N,
+                      uniform floating initialGuess,
+                      uniform floating values[],
+                      uniform floating output[])
+{
+    foreach (i = 0 ... N) {
+
+        floating x = values[i];
+        floating guess = initialGuess;
+
+        floating pred = abs(guess * guess * x - 1.f);
+
+        while (pred > kThreshold) {
+            guess = (3.f * guess - x * guess * guess * guess) * 0.5f;
+            pred = abs(guess * guess * x - 1.f);
+        }
+
+        output[i] = x * guess;
+
+    }
+}
+
+task void sqrt_ispc_task(uniform int N,
+                         uniform int span,
+                         uniform floating initialGuess,
+                         uniform floating values[],
+                         uniform floating output[])
+{
+
+    uniform int indexStart = taskIndex * span;
+    uniform int indexEnd = min(N, indexStart + span);
+
+    foreach (i = indexStart ... indexEnd) {
+
+        floating x = values[i];
+        floating guess = initialGuess;
+
+        floating pred = abs(guess * guess * x - 1.f);
+
+        while (pred > kThreshold) {
+            guess = (3.f * guess - x * guess * guess * guess) * 0.5f;
+            pred = abs(guess * guess * x - 1.f);
+        }
+
+        output[i] = x * guess;
+
+    }
+}
+
+export void sqrt_ispc_withtasks(uniform int N,
+                                uniform floating initialGuess,
+                                uniform floating values[],
+                                uniform floating output[])
+{
+
+    uniform int span = N / 64;  // 64 tasks
+
+    launch[N/span] sqrt_ispc_task(N, span, initialGuess, values, output);
+}